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The Classic Bike Thread


Nigel Clark
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BFG Pete and I have been taking classic bikes with one or two others on the 'While we can't go out...' thread. I fear we may be subverting the original thread as we're chatting about going out on our bikes!

Perhaps we need a new thread for classic bikes, so here goes.

My two wheel Triumph is back on the road after a lengthy layup. More news will follow as I cover more miles.

Please add anything and everything relevant to classic bikes here. This is my Tiger 650, back after recommissioning.

Nigel

 

20201111_191517.thumb.jpg.69ee280f28e6fa9445ae9864bdaf0088.jpg

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How do you like this one a Moto Guzzi 175cc of the early 50's now finished and belonging to one of our local club members. His brother in law in the UK found it for him and shipped it to OZ after removing ALL asbestos (brakes, clutch, electricals) in case the Aussie Customs decided to be difficult re asbestos, which can cost tens of thousands in strip downs specialist asbestos removal and subsequent rebuilds! The potential asbestos items were then shipped by std post and arrived untested! as said bike now finished but only ridden very locally, he just always wanted one!

In return our member has shipped a very early small wheel Moke back to his BIL in the UK, as well as recently a very sound and original BRG Mayflower, which I believe will be repainted in black and silver.

 

Moto Guzzi.jpg

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37 minutes ago, poppyman said:

I thought this forum was for classic cars not bikes??

That's elitist... or exclusive... or whatever... :)

You'll be telling me we're not allowed thread drift or jokes next.

(I was just about to say that if it's got the name 'Triumph' on it it's welcome, but then someone will start up an underwear thread...)

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Here goes with some more of the classic bikes I've owned over the last decade or so. All but one were Triumphs.

The 200cc Tiger Cub was a fun little thing. Bought for £950, ridden hard (that's the only way with such a small engine) for a year, until the big end went so badly the engine seized on the way to its MoT test. I pushed it into the workshop, the test was performed and it passed! I sold it on as a project for £1,100. Classic bike inflation was rampant 10 years ago.

The Tiger 90 is a 350. It was nice, zippy little bike and because of the small capacity quite smooth for a parallel twin.

Next comes the T100SS 500. Smaller and smoother than my Tiger 650 and almost as fast because it was lighter. I really liked this bike but it always felt a bit too small for my 6 foot frame.

The last bike here is a BSA A65 650. My Triumph 650 (pictured at the start of this thread) is my favourite from all the bikes I've had since my teens but I just had to try the opposition's 650cc offering. By comparison, I found the BSA heavier and therefore slower, and under-braked for its weight. On the plus side, it was much easier to keep the oil on the inside the BSA engine.

Nigel

cub1.JPG

SAM_1405.JPG

SAM_1567.JPG

SAM_1654.JPG

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Evening All. 

Following on from the topic "While we can't go out"  ..where all the policemen are working from home :P so let's bring a little sunshine into our homes and get on with our classic bike thread-drift.,  and my last post on Thursday   "... while the oil was hot from the run - I decided to drain it today, in readiness of dropping the sump tomorrow."

Well, that never happened "tomorrow" ..but it did yesterday / on Saturday.  Not at all good news, but then it could have been far worse. . .

  P1370729s.jpg.a2de5ff7306ad52ae649175c47829e78.jpg

^ After 443 running-in miles this is what I found.  The dirty colour of the oil reflects the amount of carbon deposit (soot) from the combustion chambers before the piston rings have bedded in (..there's more blow-by than there will be ..once that running-in is complete).  You can see here lumps of metal withing the folds of the paper element filter and also two pieces laying in the bottom (just under the filter). There's also a couple of flakes, one may be seen at the end of the central rib) which look like a flake of varnish or shellak.  

NB. replacing the original wire-mesh gauze filter with the paper-element is a modification I do to my engines.  All have been done but for Katie which had a new finer gauze fitted. I did however give the bike's new owner the special parts to convert it should he so choose.

P1370754s.jpg.148b36c1bff73dbc079a09a1cc940beb.jpg

^ nothing amiss can be seen up inside there.

P1370738s.thumb.jpg.dd2abc850d2db3abf04012d93c0ec08a.jpg

^ in close up this is what I found (..after being rinsed in petrol / laid out on a piece of kitchen paper-towel). 

The shellak-like flakes I've never seen before ; they're brittle/hard and transparently thin.  First thought was - it must surely be a smear of gasket sealant that's flaked off somewhere.  But where it could have come from is a mystery, particularly as there are no signs of gasket-card fibres nor of cork. They are too large to have gone through any of the oil-ways,  and in any case - I'm really careful not to apply too much gasket sealant ..in avoidance of creating squeezed out beads.  I was using Wellseal  gasket sealant but have recently been trying a similar product in tube form, it's of thicker consistency and from Loctite.  Wellseal doesn't go hard and the tubed stuff is only supposed to go tacky.  Whatever they are must have flaked off a relatively flat almost-shiny surface.  But what and where.?  

After sleeping on the question, I think I might have an answer : Loctite yes, but not the gasket sealant. :huh:  No, I'm thinking it must be the wicking Loctite I used to seal around the leaky cylinder sleeve (as fitted by sloppy professional) < here >.  And in the process some of it has run through the crack, and all the way down the outside of the sleeve.  It has then hardened, not in the crack but around the bottom rim of the cylinder liner where it projects just a little into the crankcase.  The engine-running splash of oil from the crankshaft has in effect jet-washed it loose, and it's then been washed into the sump with the returning oil. 

 

I'm happy with that explanation so let's now look at the metal bits ; they are non-ferrous and judging by their hardness and sheen are more likely to be aluminium than white-metal (from the rear-main bearing).  The almost 4mm long piece is a turn-and-a-half scroll, or thought of another way - like a shaving.  Other pieces of the metal found are also very thin shaving with torn edges.  Again in context of a running engine, it seizing and otherwise vibrating far more that it should, I was bewildered - where on earth have they come from ? 

If they are indeed white-metal from the rear-main bearing - well., there's nothing there to scrape or shave the metal.   If it were the aluminium of the piston seizing, then.., I've never seen one which has been 'shaved into a scroll '  nor can I envisage how a 4mm length of metal shaving can get passed the piston's skirt and its bottom ring..?  

There are actually very few moving parts within these engines that are aluminium.  The pistons & con-rods are, but with a chain-driven overhead-camshaft design .. that's about it.  Still, I had two scenarios to consider.,  1. is that moving aluminium parts have scrapes along an edge of steel, or 2. moving steel parts have scraped along the insides of the aluminium cases or a cover.  In time, I considered the fact that I hadn't replaced the cylinder liner myself, and perhaps that the skirt of it is shaped to clear the con-rod as it swings around to 90 degrees ??  The scraping then would be off the side of the aluminium con-rod.  

Surely not., no I think., the sleeves are flat bottomed and although there may be an inside chamfer, that is ..I'm sure is all the way around, so there's no 'right orientation' to fit the sleeves ..but for the cutouts in their top rim which to clear opened valves.  I would have seen and noted such clearances when I had the engine inverted on the bench. 

Hang on.. The sleeve fitted to the rear cylinder of this engine was replaced (..by aforementioned said professional) and its dowel hole didn't align  and had to be re-drilled.  Judging by its original dowel location - the sleeve was probably from a front cylinder and so is rotated.  Well perhaps then., those dowels also locate the rotation of the sleeve ..whereby cutout / scallops in its skirt are there to clear the con-rod's throw.?  

I couldn't think of anything else that might scrape, so I left the matter to be further investigated.  I could do that by visually inspecting up the sump more closely, or perhaps from previous rebuild and assembly photos.  After sleeping on it, or rather waking early and thinking about it - I might now have realised the source of those metal bits.. 

Aluminium ? yes.  Engine case ?  possibly yes.  From < here > doing this ..after the engine was rebuilt and during installation . . 

P1340701s.thumb.jpg.4d2b94b4e49b6a7b9c1150f20c24c6b0.jpg

Moments before this photo was taken ; the hole was drilled. Being non-ferrous I couldn't use a magnet to catch any bits, so instead I had layers of sticky gaffer and masking tape with plastic packed-in behind the hole.  Still, at the time, I suspected some bits might find their way into the sump but knowing that I was using a fine oil-filter, which is situated before the pump and/or bearings - I accepted the risk (..rather than dismantling everything) ..baring in mind that this was my own bike's engine and not a customers.

Drilling and tapping the aluminium case might well have created the scroll like shaving and other particles.  And even if they had been caught in the stickiness of the layers of tape, they might have easily been dropped again just as I pulled that tape out of the timing chain's chimney. 

Shoddy workmanship on my part, but I think that is the mystery solved. 

I don't know about the black round ball seen in the photo, either what it is nor where it came from, perhaps it's a bit of shot used to blast this engine's cases that had hidden away in some dark corner until washed out by the engine oil ?  ( NB.. I did extensively jet wash these cases inside and out, and also washed out the cases with petrol, but one cannot be 101% be sure that a piece might have been tucked away withing a rough sand casting).        

In conclusion, the bits found in the sump and filter are a sad reflection on my skills &/or carelessness in rebuilding this engine.  But my choosing to modify / replace the original gauze oil-filter with a very much finer paper element type has proven its worth. 

Regarding this engine repeatedly seizing - I'm still assuming it is the end-float against the rear-main bearing being too tight.  In the future I'll use the recommended 0.004" as the very minimum. David Holyoaks - Engineer and experience re-builder of these bikes ..and who once own Stewart Engineering, had advised me that it wasn't critical if a little too tight, but perhaps this engine demonstrates the old adage "if it possibly can go wrong - it will".

 

Moving on., the sump and magnets was cleaned out, and is back now on again, with a new filter of course.  The oil was a little dirty but I didn't think too bad for the next five hundred miles - when it and the filter will be changed again.. subject of course to no great disaster happening in the meantime.  At least with dirty oil I can see, and therefore address, any oil leaks !

P1370746s.jpg.059dd792bedc979092242dd52365bbba.jpg

 

Yesterday, I also changed the engine's leaky front crankshaft oil-seal.   I don't know what happened there, because the dynamo's journal (that the seal works against is fine, and there's no way without being totally ham-fisted I could have damaged it, but still it didn't seal 100%.  It's easy to change, simply by removing the dynamo, prising the old seal out with a couple of screwdrivers and then gently and squarely tapping the new one into place.

P1370763s.thumb.jpg.3ea3385b4c3d5b78b5bfa683f55ad6a8.jpg

^ the new NAK replacement seal.  The one previously fitted was a different brand and is much harder ..Perhaps it was old stock and the rubber had gone hard.  Anyway it was consigned to the bin.

P1370757as.thumb.jpg.124398c826b0baf4bb50fedb63cbc0da.jpg

^ weepy oil dribbling down and being blown back along the engine fins is just a mess and possibly conceals any other places that may also have an oil weep.  Wiped clean so that I can monitor anywhere that doesn't remain dry.  As before, I added a smear of silicon grease to the lips before fitting it.  Fortunately the drain hole in the bottom of dynamo's casing had been cleared before I fitted it, and so any oil drained well enough away and no damage was done to the windings or contacts.  However., with mud on the road and the bike being 'garaged' in a farmer's yard that hole was all but blocked again. Good job I checked it now and cleaned it out again. as a flood of oil in the dynamo will cause it to short out.   I used to have a rubber mud flap on the mudguard of this bike.  I can't remember taking it off but there's no sign of it so I guess I must have.  Time again to fit one &/or else a local cover over the dynamo's hole, so it might still drain, but the mud from the front tyre cannot splatter over and block it. 

Well that's it for yet another today. I have a couple more jobs to do before I ride very far including a recently failed headlamp-dip bulb.  Hey ho., the riding is good. 

Bidding you a pleasant Sunday evening.

Pete.    

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I don't have any bikes at the moment but i want to restore a yamaha rd350lc after the gt6 is done.

I used to race a yam tz250b and honda nc30/vfr400, i got so fed up with people building me engines that went bang to quick, that i started building my own 2 and 4 stroke engines.

 

paul

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14 hours ago, ludwig113 said:

I don't have any bikes at the moment but i want to restore a yamaha rd350lc after the gt6 is done.

I used to race a yam tz250b and honda nc30/vfr400, i got so fed up with people building me engines that went bang to quick, that i started building my own 2 and 4 stroke engines.

 

paul

Hi Paul,

Have you got any photos of you previous bikes?

Nigel

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16 hours ago, Bfg said:

Evening All. 

Following on from the topic "While we can't go out"  ..where all the policemen are working from home :P so let's bring a little sunshine into our homes and get on with our classic bike thread-drift.,  and my last post on Thursday   "... while the oil was hot from the run - I decided to drain it today, in readiness of dropping the sump tomorrow."

Well, that never happened "tomorrow" ..but it did yesterday / on Saturday.  Not at all good news, but then it could have been far worse. . .

  P1370729s.jpg.a2de5ff7306ad52ae649175c47829e78.jpg

^ After 443 running-in miles this is what I found.  The dirty colour of the oil reflects the amount of carbon deposit (soot) from the combustion chambers before the piston rings have bedded in (..there's more blow-by than there will be ..once that running-in is complete).  You can see here lumps of metal withing the folds of the paper element filter and also two pieces laying in the bottom (just under the filter). There's also a couple of flakes, one may be seen at the end of the central rib) which look like a flake of varnish or shellak.  

NB. replacing the original wire-mesh gauze filter with the paper-element is a modification I do to my engines.  All have been done but for Katie which had a new finer gauze fitted. I did however give the bike's new owner the special parts to convert it should he so choose.

P1370754s.jpg.148b36c1bff73dbc079a09a1cc940beb.jpg

^ nothing amiss can be seen up inside there.

P1370738s.thumb.jpg.dd2abc850d2db3abf04012d93c0ec08a.jpg

^ in close up this is what I found (..after being rinsed in petrol / laid out on a piece of kitchen paper-towel). 

The shellak-like flakes I've never seen before ; they're brittle/hard and transparently thin.  First thought was - it must surely be a smear of gasket sealant that's flaked off somewhere.  But where it could have come from is a mystery, particularly as there are no signs of gasket-card fibres nor of cork. They are too large to have gone through any of the oil-ways,  and in any case - I'm really careful not to apply too much gasket sealant ..in avoidance of creating squeezed out beads.  I was using Wellseal  gasket sealant but have recently been trying a similar product in tube form, it's of thicker consistency and from Loctite.  Wellseal doesn't go hard and the tubed stuff is only supposed to go tacky.  Whatever they are must have flaked off a relatively flat almost-shiny surface.  But what and where.?  

After sleeping on the question, I think I might have an answer : Loctite yes, but not the gasket sealant. :huh:  No, I'm thinking it must be the wicking Loctite I used to seal around the leaky cylinder sleeve (as fitted by sloppy professional) < here >.  And in the process some of it has run through the crack, and all the way down the outside of the sleeve.  It has then hardened, not in the crack but around the bottom rim of the cylinder liner where it projects just a little into the crankcase.  The engine-running splash of oil from the crankshaft has in effect jet-washed it loose, and it's then been washed into the sump with the returning oil. 

 

I'm happy with that explanation so let's now look at the metal bits ; they are non-ferrous and judging by their hardness and sheen are more likely to be aluminium than white-metal (from the rear-main bearing).  The almost 4mm long piece is a turn-and-a-half scroll, or thought of another way - like a shaving.  Other pieces of the metal found are also very thin shaving with torn edges.  Again in context of a running engine, it seizing and otherwise vibrating far more that it should, I was bewildered - where on earth have they come from ? 

If they are indeed white-metal from the rear-main bearing - well., there's nothing there to scrape or shave the metal.   If it were the aluminium of the piston seizing, then.., I've never seen one which has been 'shaved into a scroll '  nor can I envisage how a 4mm length of metal shaving can get passed the piston's skirt and its bottom ring..?  

There are actually very few moving parts within these engines that are aluminium.  The pistons & con-rods are, but with a chain-driven overhead-camshaft design .. that's about it.  Still, I had two scenarios to consider.,  1. is that moving aluminium parts have scrapes along an edge of steel, or 2. moving steel parts have scraped along the insides of the aluminium cases or a cover.  In time, I considered the fact that I hadn't replaced the cylinder liner myself, and perhaps that the skirt of it is shaped to clear the con-rod as it swings around to 90 degrees ??  The scraping then would be off the side of the aluminium con-rod.  

Surely not., no I think., the sleeves are flat bottomed and although there may be an inside chamfer, that is ..I'm sure is all the way around, so there's no 'right orientation' to fit the sleeves ..but for the cutouts in their top rim which to clear opened valves.  I would have seen and noted such clearances when I had the engine inverted on the bench. 

Hang on.. The sleeve fitted to the rear cylinder of this engine was replaced (..by aforementioned said professional) and its dowel hole didn't align  and had to be re-drilled.  Judging by its original dowel location - the sleeve was probably from a front cylinder and so is rotated.  Well perhaps then., those dowels also locate the rotation of the sleeve ..whereby cutout / scallops in its skirt are there to clear the con-rod's throw.?  

I couldn't think of anything else that might scrape, so I left the matter to be further investigated.  I could do that by visually inspecting up the sump more closely, or perhaps from previous rebuild and assembly photos.  After sleeping on it, or rather waking early and thinking about it - I might now have realised the source of those metal bits.. 

Aluminium ? yes.  Engine case ?  possibly yes.  From < here > doing this ..after the engine was rebuilt and during installation . . 

P1340701s.thumb.jpg.4d2b94b4e49b6a7b9c1150f20c24c6b0.jpg

Moments before this photo was taken ; the hole was drilled. Being non-ferrous I couldn't use a magnet to catch any bits, so instead I had layers of sticky gaffer and masking tape with plastic packed-in behind the hole.  Still, at the time, I suspected some bits might find their way into the sump but knowing that I was using a fine oil-filter, which is situated before the pump and/or bearings - I accepted the risk (..rather than dismantling everything) ..baring in mind that this was my own bike's engine and not a customers.

Drilling and tapping the aluminium case might well have created the scroll like shaving and other particles.  And even if they had been caught in the stickiness of the layers of tape, they might have easily been dropped again just as I pulled that tape out of the timing chain's chimney. 

Shoddy workmanship on my part, but I think that is the mystery solved. 

I don't know about the black round ball seen in the photo, either what it is nor where it came from, perhaps it's a bit of shot used to blast this engine's cases that had hidden away in some dark corner until washed out by the engine oil ?  ( NB.. I did extensively jet wash these cases inside and out, and also washed out the cases with petrol, but one cannot be 101% be sure that a piece might have been tucked away withing a rough sand casting).        

In conclusion, the bits found in the sump and filter are a sad reflection on my skills &/or carelessness in rebuilding this engine.  But my choosing to modify / replace the original gauze oil-filter with a very much finer paper element type has proven its worth. 

Regarding this engine repeatedly seizing - I'm still assuming it is the end-float against the rear-main bearing being too tight.  In the future I'll use the recommended 0.004" as the very minimum. David Holyoaks - Engineer and experience re-builder of these bikes ..and who once own Stewart Engineering, had advised me that it wasn't critical if a little too tight, but perhaps this engine demonstrates the old adage "if it possibly can go wrong - it will".

 

Moving on., the sump and magnets was cleaned out, and is back now on again, with a new filter of course.  The oil was a little dirty but I didn't think too bad for the next five hundred miles - when it and the filter will be changed again.. subject of course to no great disaster happening in the meantime.  At least with dirty oil I can see, and therefore address, any oil leaks !

P1370746s.jpg.059dd792bedc979092242dd52365bbba.jpg

 

Yesterday, I also changed the engine's leaky front crankshaft oil-seal.   I don't know what happened there, because the dynamo's journal (that the seal works against is fine, and there's no way without being totally ham-fisted I could have damaged it, but still it didn't seal 100%.  It's easy to change, simply by removing the dynamo, prising the old seal out with a couple of screwdrivers and then gently and squarely tapping the new one into place.

P1370763s.thumb.jpg.3ea3385b4c3d5b78b5bfa683f55ad6a8.jpg

^ the new NAK replacement seal.  The one previously fitted was a different brand and is much harder ..Perhaps it was old stock and the rubber had gone hard.  Anyway it was consigned to the bin.

P1370757as.thumb.jpg.124398c826b0baf4bb50fedb63cbc0da.jpg

^ weepy oil dribbling down and being blown back along the engine fins is just a mess and possibly conceals any other places that may also have an oil weep.  Wiped clean so that I can monitor anywhere that doesn't remain dry.  As before, I added a smear of silicon grease to the lips before fitting it.  Fortunately the drain hole in the bottom of dynamo's casing had been cleared before I fitted it, and so any oil drained well enough away and no damage was done to the windings or contacts.  However., with mud on the road and the bike being 'garaged' in a farmer's yard that hole was all but blocked again. Good job I checked it now and cleaned it out again. as a flood of oil in the dynamo will cause it to short out.   I used to have a rubber mud flap on the mudguard of this bike.  I can't remember taking it off but there's no sign of it so I guess I must have.  Time again to fit one &/or else a local cover over the dynamo's hole, so it might still drain, but the mud from the front tyre cannot splatter over and block it. 

Well that's it for yet another today. I have a couple more jobs to do before I ride very far including a recently failed headlamp-dip bulb.  Hey ho., the riding is good. 

Bidding you a pleasant Sunday evening.

Pete.    

Hi Pete,

That's some feat of engineering forensics, good to know you're identifying the root causes of the debris in the oil filter, none of which sound too serious given the effectiveness of your paper filter element modification. I hope you can start enjoying the ride more as the running process progresses.

I got my Triumph 650 out for a few miles in the autumn sun yesterday, a great 30 miles of country lanes, B-roads and a few miles of A-road. Sitting at home I sometimes think I might fancy getting a Trident 750 triple, then I get out on the 650 twin and it reminds me that it really is just the right bike for me. The smooth power delivery and three cylinder exhaust note might be nice to have by I wouldn't want the extra weight. A Trident weighs almost 40% more than my 650.

Nigel

Here, for no particular reason is Trident photo, from the Triumph Owners Motorcycle Club's website. It's a T150V with disc front brake and 5 speed gears:

?width=960&hq=1

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I never got into motorbikes as my sister and I were mentally scarred by travelling to Sennen Cove in Cornwall from Bury St Edmunds each year for our holiday. Mother was pillion and we were in the sidecar . The motor bike registered in 1934 was an AJS 1000 with gear change on the tank. From memory the plugs needed cleaning every 60 miles !
 

The pic was taken in the mid 50’s 

 5E0987FB-CEDE-447B-AB44-94F11BD897CC.thumb.jpeg.59b6965fd3f72611de5c769ea6aac3b1.jpeg

Paul

 

 

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A Classic. And a "not so classic". The Shooting Star, was rebuilt from a "kit of parts" in a North Sea Ferry Engine Room Work shop. Naked originally, the fairing and "Rodark" Steel panniers where fitted for a touring trip to the IOM which never materialised. The "Beemer" was last of what I regard as the "real" ones. (`83 build).

SS-2.jpg

SS-1.jpg

BMW.jpg

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Never got into motor cycles , most apprentices had broken legs or arms  so 4 wheels always  had more appeal as a 17 year old 

having said that My father had a 700cc N U T  and later  pre WW2   a racing BSA which he got fined 5 shillings in Porlock for making too much noise and 

the following day the side car broke its mounts on Porlock hill after some one stalled in front of them the brakes worked the sidecar didnt 

his first bike had acetylene lamps  and the rubber bulb off the horn often used to suck water from where ever they could 

hence  its 4 wheels for me 

Pete

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Having got the baffle tube and a tube of black silicon in stock, I took the opportunity this afternoon to test the ideas I have.  Here's a pictorial report . . .

P1370765s.jpg.2710c44f7bce6ec302e0156fe1cfa635.jpg

1/2 metre of 32.5mm OD perforated tube in stainless steel.  

P1370766s.jpg.395f9074507a17c20f089644e4410ebf.jpg

32.5mm was actually closer to 31.5mm and the ID of the stainless tube fitted into this silencer is perhaps 35.5mm ..so the baffle's fit was a little slack. Nevertheless - better than being too tight to go in !

P1370774s.jpg.cac6b59467ebca576135f23c31f1f185.jpg

^ The felt pen mark on the silencer is to where its end pipe extends into the casting.  And the felt pen marks on the perforated tube are at 100, 150, and 200mm. The baffle tube pushed into the silencer to just short of the 200mm mark, before its end fouled on the inside curvature of the aluminium casting.  That doesn't leave a whole lot of length of baffle to do its job.  But as that was expected - I had an idea to improve on that. . .

P1370776s.jpg.ddc505fb82b6802f2a7418c5374c2ee4.jpg

^ four slots cut into the end ..each at approximately 90 degrees to the next

 P1370778as.thumb.jpg.b0f8d5ca54788dd4178b3e6cb01e441c.jpg

^ the top and bottom quadrants (between the slots) was biffed in ..and then the two sides were similarly formed around those to shape its end into an almost-closed (..aside from the perforations of course) cone shape.  The now tapered baffle pushes into the silencer by another 50mm.  

The concept being ; the pulses of exhaust gasses will be forced through the perforations, and although a very short length of baffle - this re direction of their high-pressure wave-fronts will happen progressively  ..as the cone gets tighter.  Likewise the sound's wave-front will progressively dissipate and loose its bark ..which (previously) uncurbed resonated around in the cast-metal chamber.   Silencer baffle theory talks about sound waves cancelling each other out, whereas I tend to think of this baffle as progressively shaving the magnitude from each shock wave.  

I took this experiment one stage further. . .

P1370784as.thumb.jpg.692162770d829c118639a62d47b99d40.jpg

^ Having cut across the pipe (across just three perforations) I then used a solid round bar, hammered at an angle into the tube - to invert the curved shape of the perforated tube.

P1370786s.jpg.506d9b5a1a4d2587c919d29c0589ebd5.jpg

^ the blue felt pen mark indicates where the inside end of the silencer's front end-pipe finishes.  The 'flutes' I've shaped (one from either side) are from the hacksaw cuts made at 3/4" and 1-1/2" from that mark. 

Again my understanding of the theory is ; the exhaust gasses will have to snake passed these indentations with induced swirl and turbulence ..and in doing so the sound's wave-front is part reflected and part deflected, so broken up.  An analogy might be the energy of a seaside ocean wave being progressively dissipated as it crosses and is part reflected, part deflected by diagonal breakers ..rather than the wave crashing hard and square against a sea wall.   

P1370795s.jpg.c624a26b9f58f174b6e816b4b9e10c4f.jpg

P1370793s.jpg.ef83517f783f866d8a5f433bfeeb041d.jpg

^ The perforated tube within the end pipe does nothing as a baffle, so it was cut short ..leaving just enough for the baffle to be glued in place. 

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^ cleaning the inside of the end pipe took just as long as making the baffle.  Fitting the baffle inside was then a sticky job.

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^ Job done.  The silencer will now sit undisturbed for a day or two to allow the silicon goo to set (during this cold weather).

I've never made silencer baffles before - so it will be interesting to see if it works, and of course how effectively.?  I'll refit the silencer and try it as it is now ..which ought to give me a clue as to whether I ought to do similar with the rear end pipe. 

 

That's it..  lots of pictures, not too many words. But I hope it has been of interest.  Your feedback is welcomed. 

Pete.

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Really interesting stuff. There are a few classic cars that would benefit from such baffles in the exhaust!

I will be interested to know how effective this process to be. One thought though... Will the silicone be sufficiently heat resistant to last? No doubt it can soak up the engine's vibration but I wonder about heat.

Nigel

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Silicon, although horrible slimy stuff, is good with temperatures. Certainly over 100 degrees C is no problem, and any gasket sealant would specified to withstand engine-oil temperatures, so 250 degrees would be usual spec.  And I reckon (..can't say more than that)  that it'll be good for an exhaust silencer.

 

Edit :  looking up the spec., it says . . .

Visbella Silicone Engine Repair High Temperature Gasket Seal Maker (black)

  • Typical applications: Rear main bearing cap split line, damper keyway sealing, differential cover, intake end seals, intake manifolds, OHC cap, oil pan corner seals, oil pan gasket, side cover plate, thermostat housing, timing cover, transmission pan, valve cover gasket, vibration damper, water pump cover gasket, exhaust manifold & connection points
  • High Temperature & Heat Resistant from -80ºF to 500ºF
  • Product Features: -- Heat resistant & flexible from -80°F to +500°F (-62°C to +260°C) -- Excellent bonding to wide range of applications -- Forms to any shape instantly -- Resists cracking, shrinking and migration caused by thermal cycling -- Resistance to oil, water & toxic chemicals -- Pressure resistant --- Makes air tight & leak proof gaskets in seconds ***Please read instructions carefully before use***

 

 

PS..  personally I do NOT use silicon sealants for engine gaskets on any  of my vehicles, nor would I.  I've rebuilt customer's engines and replaced camshafts because beads of it have blocked oil ways.  It's an invaluable product for a whole lot of jobs, but imo it's not safe to use it in engines, or gearboxes with oil ways. 

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