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Solex B30 PSE1 Cover Screw Specs


Colin

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Hi Team ! (sorry) ūüėĎ

Working back up the line and following my recent fuel system debacle, I note that at some point (did I drop the originals somewhere??!), two of the flat headed screws seem to have turned into thin wing nutted fixings! 

Perfectly adequate, but I'm in a position to replace them properly now and wondered what their spec is, screws and nuts being v complicated.

These days, Mthis and Mthat sizes are the norm, and I think an M5 might be close to the size but I think the thread may be not quite right!!

Any ideas?? ūü§Ē

Best, 

C

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Well, they shouldn't be metric, if original UK carbs from the pre-decimal days. One USA site I've just checked claims M4 is correct, but they may have been metric from the word go; I know Solex carbs for other European cars such as VW all used metric.

If no-one has come up with the correct size I'll dig one out and measure over the next few days; in the meantime replacement screws are available over the water, and bound to be here too:

https://www.carburetion.com/screws.asp

http://www.gowerlee.dircon.co.uk/PSEItype.html

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Thanks chaps.

I hold a small stock of M size screws. 

M4 slips through, M6 is too fat.

I would imagine if I got hold of M5's, the threads would not match.

The 3/16 option sounds like one I should pursue via the 'net.

Cheers and best,

Colin W

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in uk metric wasnt invented in the auto industry and SU being an older design could well be older than unf 

i got a few from Canley last year   checking some old ones   they are  pitch 24  dia 0.1825  which looks like whitworth  !!!  or    3/16"UNF apart from the dia ought to be 0.1875"

both similar apart from thread angles 

senior moment syndrome    this is for a B30 solex    and im waffling SU  ...Grrrr   where the pills  ????

 

Mick dolphin lists  503273 at 10P  no site seem to x ref to thread sizes 

Pete

 

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Peter,

That's also good, specific info., too.

Many thanks,

Best,

C.

Just for info folks, the missing screws I replaced long ago with flat head screws and wing nuts on thr bottom. 

They tighten up nicely and I have never had a problem with the carb as a result! But original, they certainly are not!!

The carb has a casting date stamp of 1963 on my 1970 Herald! ūüėĀ

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Peter,

That's also good, specific info., too.

Many thanks,

Best,

C.

Just for info folks, the missing screws I replaced long ago with flat head screws and wing nuts on thr bottom. 

They tighten up nicely and I have never had a problem with the carb as a result! But original, they certainly are not!!

The carb has a casting date stamp of 1963 on my 1970 Herald! 

Pimp my Vit :- Thanks! Those outer two screws in the lower left set deffo look the part. Not sure about the other two! ūüėä

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mick is  goldmine of useful new old stock  the shop is old school  so its e mail phone etc but you can be amazed at just what he has listed

you do need a triumph part number to find anything , easy as most other mainstream retailers use triumph part numbers if you dont have a parts list

get one on your wish list from club shop 

Pete

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  • 2 years later...

Did anyone get to the bottom of this? My Solex B30 has a couple of stripped threads and Gower and Lee suggested Helicoils. Helicoils are available in a number of Imperial threads as well as metric, so if it's possible to keep the originals it would save on head scratching later. I called Mick Dolphin today, and he has a few of the screws in stock, but is a self-confessed tyro when it comes to thread identification so can't help beyond agreeing the part number. I went through all my thread gauges and micrometer measurements of the major diameter and have not yet made a decision. The pitch is a very good match for M0.75, but the thread would then have to be M4.5 and the major diameter is almost 5mm, or about 3/16". An old Starrett gauge says 34TPI which is not a thread that exists (I wonder why they bothered to include one in the set), and while I got a reasonable result on a Whitworth gauge I haven't any of the right nuts, taps or dies to test that hypothesis. I couldn't get a good match on UNF, UNC, BA or BSF.

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Hi Morgana.

Confession time:- I did not contact Mick D - on the basis that (some of) the original screws seem to have stripped the thread in the carb body (must be very soft steel and I must've been over zealous in my tightenings during previous dismantling and subsequent assemblies. At the time I was out of country and inclined to use anything which would do the job (e.g. hold the two parts together tightly) and I used some bolts close to the screw size which had butterfly nuts in the stripped thread holes. These have done the job all these years! Were I to purchase a set from the part numbers given above, I'd still find I couldn't tighten in at least two of the thread, so a bit pointless. As I recall, the screws were viable still (not with mullered thread), but had clearly cleaned out the threaded body. So, what does one do . . . ? I'm sure the  more capable mechanic engineers here will say cut a new thread in the lower carb body and match with a suitable screw. I'm not that au fait with such practices & have always worked round such things!

Let us know how you get on!! At .10p each, a set from M Dolphin can't be a bad thing to have??

Best,

C.

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as said earlier  they certainly wont be any metric thread  but far older  from the days of BSF BSW   vintage and pre UNF/UNC

no reason why you cant drill and tap with any oversize you fancy

and helicoil only works if you know what thread/pitch you want to end up with

tap to a coarse  M6 should work ok 

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Yes, I could go to Screwfix and get an off the shelf M5 or 6 Helicoil set but since they're available in a variety of Imperial sizes then it should be possible to get a Helicoil set of the original thread and use the 'right' screws. Like you Colin, there are also a couple of holes that have odd screws and nuts on! All well and good, but getting the nuts on with all the projecting bits of the carburettor and cables is quite the fiddle, and I don't want to take the whole thing off each time I need to check the float chamber. As there's still something funny going on with the fuelling it's been on and off a number of times this week. It's a real fuss trying to do a repair and finding the fixings one takes off are metric so don't match the parts book or the spares one has to hand!

Thinking out loud, if we discount metric then it's going to be 3/16" (0.1875") or gauge 12 (0.1890") - my Presto booklet is unclear about the distinction between gauges 10 and 12. Elsewhere it appears to be 10 at 0.190".

3/16" could be BSW at 24TPI; BSF at 32TPI or "special" Unified threads at 24 to 32TPI. Gauge 12 could be NC 24TPI, NF 28TPI. Gauge 10 is approximately 2BA. Also UNC/NC 24TPI; UNF/NF 32TPI, or NS 30TPI.

It can be seen in the attached picture that 24TPI BSW is far too coarse. The 34TPI of the Starrett No. 6 gauge fits well. A Metric 0.75 pitch results in...33.9TPI, bringing us back to M4.5.

One can see from this table of threads that there's not anything close for the required TPI and major diameter except M4.5. Alas, the major diameter is rather too large for that!

BSW at 24TPI would seem to be a much better thread for alloy than the one they used, since it's significantly coarser.

IMG_20230216_185952.jpg

IMG_20230216_185817.jpg

IMG_20230216_185736.jpg

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