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Suffolk super punch

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Mole Tue, 12/05/2020

Hi posted this question before but due to not being very good with forums cant seem to find it so apologies for starting a new thread.

I have a Suffolk super punch 17" with a cast engine I haven't got the plate with the info on all I have is the number cast in to the block z22282. The trouble I'm having is its smoking loads and trying to find out where its pulling it from, is it likely to be pulling it from the sump past the rings or maybe past the valve guides?

In terms of starting and running it's great starts first pull before you run out of cord idles well and has loads of power just a bit stuck as what to do now any help would be greatly appreciated 

Thank carl

Forums

Jonson Wed, 13/05/2020

Hi. In my experience it's usually worn piston rings causing this, replacements are still available.
Have you changed the oil recently?
Also might be worth checking the crankcase breather filter isn't blocked, but this is unlikely to cause lots of smoke.
If you plan on ordering new rings you'll need to determine if you have the 75cc or 98cc engine. If you post a couple more pics of the entire engine it's easy enough to tell.

wristpin Wed, 13/05/2020

Before you go tearing things apart.

Check that it’s not over filled with oil

If you are not already useing a straight SAE 30 oil switch to that, regardless of what any book may say.

It’s unusual for the crankcase breather in the valve chest to be gummed up but on an old engine, not so unusual for the little alloy base and “ paxolin” valve disc to be worn and not sealing , Sometimes, just turning over the disc to present an unworn face to the base will bring about an improvement. Also, it’s not unknown for the fibre washer under the valve base to have gone missing.

Mole Thu, 14/05/2020

Thank you both for your replys after some digging I read about the breather it's all intact so will turn the disk over and try and replace the fiber washer altho it's intact and give that ago I had a feeling it's the rings so have gone ahead and stripped it and found the top ring to have a .032 thou gap and the middle ring to have a .028 thou gap this seems pretty large do you know what they should be and the tolerance is ??

wristpin Thu, 14/05/2020

Those are very large gaps - I'll have a look for a specification, but I've just looked through several manuals and the one bit of information that is missing from all is ring gaps.,  the oil control ring is the bottom one. As a rough guess I would say 8 thou is the max for the top two and may be 20 for the oil control.

Bear in mind bore wear  - both parallelism and ovality. New rings in a worn bore are at the best a compromise and will loose some of their effectiveness as they have e to bed to the worn bore. 

Mole Fri, 15/05/2020

Thank you very much it seems to be one of the hardest bits of info to find. I have measured the bore and it appears to be a good 2" with a vernirer but If i remember I'll bring a bore mic home from work and check it

Jonson Fri, 15/05/2020

If it starts, idles and runs well but smokes a lot then it's likely the bore should be generally ok.
Your engine is one of the earlier 75cc units, with the larger flywheel and better sounding exhaust.
After fitting new rings its often a good idea to lubricate the bore well prior to its first start.

Mole Fri, 15/05/2020

Hi thanks that's given me some confidence iv gone the right way. Yes the exhaust dose have quite a nice note to it.

When you say earilyer models would you have a rough idea of a date ?

villiers98 Sat, 16/05/2020

Large flywheels engines seemed to end about 1967 - 8 . Has dipstick in plastic bung and recoil starter so post 1959. Between that quite difficult to be more exact . Does it still have the Suffolk Iron Foundry plate on the front of the cylinder cowling as thisshould have a model number  like 75G14  mark 2A which can help