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Spit 1500 jets


Luke Remon
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Hello everyone,

I have a 1977 Spitfire 1500 and have been wondering how to make it run less terribly. Basically I'm 18 and have no experience so its all a learning curve. Since I've had the car I've never managed to get it running right.I have been reading that the likely cause is the wrong needles however I do not have the money to be buying vast quantities of needles until one works. It has a standard exhaust and standard air filters and airbag because apparently that makes a difference. Electronic ignition, sports coil - I'll be honest I don't know if what I'm listing is of any relevance but here we are. I haven't had the car long enough to take it to any club meetings, oh and also I have no idea how to even set the idle mixture. Really i'm just hoping that there's someone in the East Sussex area that can show me what I'm doing regarding the carbs because I've spent many hours fiddling with them and just made it worse ( after the coronavirus obviously). But if anyone thinks they can help remotely and give me some really straightforward step by step instructions on how to 'make it work', or recommendations on what jets to put in it I would be very grateful.

Thank you in advance 

Luke

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This might help.  

standard needles should be fine if the engine is standard . 
balance the carbs, twelve flats down on the needles and a turn and a half (I think it is) on the idle screws should get it running close  

you could have other issues though  - inlet manifold leak if it’s idling too high  for example 

 

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there is a good chance you have wax stat jets  

the larger of the two shown here

image.jpeg.a80157e77438beb23808afd718676595.jpeg

these can cause lots or reliability snags and can be easily resolved by remove the jet and  un crimp  the base cap and swap the wax plug with two 1p pennies

you must retain the small metal spacer , refit the cap and then reset the jet heights

there are jet conversion kits around for silly £££ss and they dont fit well 

i would take the air piston cover and piston off , and wind the jet up till level with the bridge, then refit the piston and top cover 

undo the big nut on the jet holder 1/2 turn and give it a tap. the air piston should fall with a clunk  no sticking if its free nip the big nut and then drop the jet adjuster 12 flats (3 turns) 

next pull the choke and return it, give the jet a light press with finger it should be up against the  big nut  but if not the choke levers ( rather crude linkage)

is sticking somewhere and needs a look see,  its very common on SU that chokes stick holding the jet down  and you never can set the mixture 

use engine oil in the dashpots 

have a look see what you can tell us 

Pete

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you mention needles   early 1500 has ABT    Later  ADN    for those with std exh and filters 

to read this you need to remove the air piston and  loosen the screw that holds the needle holder  , pull it out and the needle spec is stamped on its end its not visible till removed 

 the top of the needle  will be sprung , dont loose it , on refit the needle holder is set level with the base of the air piston  the holder only fits in one position 

to align the fixing screw .

 

Pete

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13 hours ago, Luke Remon said:

Hello everyone,

I have a 1977 Spitfire 1500 and have been wondering how to make it run less terribly. Basically I'm 18 and have no experience so its all a learning curve. Since I've had the car I've never managed to get it running right.I have been reading that the likely cause is the wrong needles however I do not have the money to be buying vast quantities of needles until one works. It has a standard exhaust and standard air filters and airbag because apparently that makes a difference. Electronic ignition, sports coil - I'll be honest I don't know if what I'm listing is of any relevance but here we are. I haven't had the car long enough to take it to any club meetings, oh and also I have no idea how to even set the idle mixture. Really i'm just hoping that there's someone in the East Sussex area that can show me what I'm doing regarding the carbs because I've spent many hours fiddling with them and just made it worse ( after the coronavirus obviously). But if anyone thinks they can help remotely and give me some really straightforward step by step instructions on how to 'make it work', or recommendations on what jets to put in it I would be very grateful.

Thank you in advance 

Luke

Hi Luke! You can get a 1500 on twin hs4 running really nicely without everything having to be 100% spot on, you just have to work through things carefully. Once it's running "well" you can look at finessing it to "Great".
First thing is first, before you try and tune the carbs, the ignition side of things needs to be in good shape. Do you have (or have access to) a timing light?
Set the timing, make sure the plugs are clean, in good condition and that the gaps are about 25thou. (Feeler gauge, plug spanner/socket required) 
Good move going for the electronic ignition, if it starts and runs then that's probably ok.

Check which carb needles you have. Regardless of (minor) mods the car will run pretty well on standard or something "mildly modified" like AAQ or AAT. Are the needles in good condition? No need to buy loads of different ones, just check yours are in good shape.

Take the top (dome) off the carb (3 screws each) and carefully remove the pistons - pistons are matched to domes, don''t mix them up.
After turning the car over but not starting, pull the choke cable as you stand by the engine and look down the "jets" (the bit the needle slots into) and look for the height of the fuel in the jet. 3/8" to 1/2" is fine. Much higher - might have flooding/rich running issues, much lower it might run lean. Anywhere in that range is fine. 

Turn the LOWER hex on the base of the carb until the jet is level with the bridge (no choke etc.) then turn them back down 12 flats or 2 complete turns - this is your starting point for tuning.

Operate both the choke and the throttle and CAREFULLY watch the mechanisms - the 2 carbs should move in unison and by the same amounts. Watch for anything sticking or jamming.
Check that at full pedal movement the throttle butterflys are fully open (about horizontal) 
Check that with the choke full in the cam that pushes the throttle when choke is "on" isn't touching the bolt head that it acts on. Should be a small gap and roughly the same on both carbs. Also check that the jets return smoothly to the default position when they choke is off.
Before you refit the pistons springs and domes check that the needles are fitted evenly into the pistons, both the "holders" should be flush with the piston bottom. When you refit them make sure you put oil in the damper (engine oil is fine)

Once refitted, push them up and let them drop together, you should feel even resistance/damping pushing them up, and they should drop together and land with a nice metally "clonk".

At this point... start it up, let it come to temp (don't try tuning unless it's at the middle on the gauge) Once it's warmed up and no choke it's time to tune! There are loads of great guides to tuning SU HS series carbs out there, so I won't repeat it all here.

Sorry for the essay...
Cheers, Sam

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13 minutes ago, Luke Remon said:

Thank you everyone for the quick response. So, should I purchase a colour tune and some kind of vacuum test thing to balance the carbs?

Many thanks,

Luke

Never had much luck with a colourtune on my Triumphs, by the su guide and by ear always seems to be better (although I had great success with it on land rovers oddly)

A flow meter type thing is very handy for balancing the carbs and will give you a bit more confidence than the old tube+ear method if you are new to this stuff. I managed for years with the cheaper gunsons jobby before getting a nice snail shell type.

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3 minutes ago, Luke Remon said:

So what am I listening for then after ive balanced the carbs?

How smooth it runs, how it revs up, does it misfire, stutter or back fire. It's kinda hard to describe, listen for the "goodness of the running" 🙂 Sorry.

I highly recommend reading through this set of pages on adjustment and tuning: http://sucarb.co.uk/technical-hs-type-carburetter-tuning-general

A bit of care and following that lot will get you to a really nice state of running if nothing is wrong/faulty.

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The best way to check ignition timing is with a strobe light, ideally one with a "delay" function that allows you to dial in the correct advance and get the strobe at TDC, because not all engines have the graduated scale for setting other angles.

The book timing is specified at idle with no vacuum advance, so disconnect (and plug) the little vacuum pipe from the carbs to the distributor. You don't want to cause a leak at the carb, so it needs plugging, but the disi end can be left open. Get the engine warm and let it idle. Put the strobe pickup around the front plug lead and point the strobe at the pulley.

It's normally very hard to see the mark on the pulley unless you put a dob of white paint (or Tippex) on it first. The TDC pointer on the timing cover is more obvious but again, a bit of white paint helps.

Once you have the idle advance correct, rev the engine up a bit with the strobe still on to confirm that the timing changes (advances) as the revs increase. You're not looking to measure how much, just confirm the mechanism isn't stuck.

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balancers and colour tunes ...not  really needed  

most carbs were supplied with the idle screw pre set  for on line engine assy on production , no faffing around with balancers 

 so loosen the connecting rod clamp and back the idle screws off,  turn to just touch the the spindle lever , turn in 1.5 turns on each carb then the throttles are mechanically set to the same position , this will be quite close enough for now .

colour tune    use your ears  , you can tell if you are making improvements or worse ,  by the sounds and feels of the idle .

timing get a small pea bub on some wire connect to coil dizzy lead terminal and earth , remove HT lead from coil ,  turn engine with ignition on as the elecy unit or points break the bulb will light,   so you turn the crank slowly till no 1 approaches firing and nudge the crank till the bulb lights  ...look at the timing marks on the pulley and see what you have 

you are looking for 10 deg BTDC  for a UK 1500

Pete

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Dicks on the case    you need to get a manual  Hanyes gives some good clues  more in depth from original reprints of the triumph workshop manuals,

if you are a club member club shop needs you to log in to get the member prices its a different log in/register than what you use on forum

these manuals give you all the basics and pictures of what to do 

reckon you have a long learning curve , we can all help but   just now  need to reset all the clocks and get some breaky in 

Pete

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not 1500 but covers most things spitfire http://vitessesteve.co.uk/Servicemanuals

bulb  small like a panel light bulb , 2watts   bigger bulbs will stay on all the time 

pulley  the crankshaft front pulley, on its rim will be timing marks, may need a clean and a wipe of white paint to read it and you need to turn it to see where it is 

to adjust timing  you need to set the points gap to the correct gap   0.015"  for lucas   0.018" delco   the heel of the points must be on the top of the dizzy cam lobe

to change timing undo the dizzy clamp bolt and you can turn the body to  make change 

if you get this far ask what next  

Pete

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spanner on the crank front nut , or   put in 4th gear and push slowly /rock the front tyre whilst looking at the pulley ,  

the marks come round twice for each firing it does  NOT   matter if you set timing on number 1 or Number 4 compression strokes 

you can tell what youre on look at the dizzy rotor , see which HT wire its pointing at on the cap ( with cap off)

always when  pushing in gear that you  imobilise the HT by pulling a coil HT lead or you may start it up in gear and run yourself over  !!!! if the ignition is ON 

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I think the spanner required is 1 13/16" or 36mm  - a socket can be too deep and catch the radiator - I bought a set of large spanners as it was cheaper to get the one I wanted in the set compared to a singleton. 

But Pete's method works very well - but you must ensure you take it out of gear before you start the car! And/or take the socket/spanner off the pulley too.......

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Right I've had a look and I'm way put of my depth. After this coronavirous thing I'm gonna have to get someone to show me because I haven't a clue really. I'm pretty sure it is wrong though. Managed to check the vacuum advance thing - I think that works. I don't really want to run it though - it sounds dodgy and I don't want to cause any damage to the engine.

Luke

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Luke just when you need a local area to get some help they lock us all down 

bit too far for me to run out even for a bacon buttie ,  but live in hope the lock down will be over by ???????  whenever and normality starts to return 

should be a runner by..................christmas   

Pete

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4 hours ago, Luke Remon said:

it sounds dodgy

Worry not, we all started where you are, or earlier, and most of us many decades ago.  A light mechanical/metallic sound (tappets?)/ heavy metallic/ misfiring/  backfiring/what do the plugs look like?  If you go back to the very basics (logically) and set things as they should be one step at a time you may be a on a roll.

Dick

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