a10 plunger, one exhaust cooler than other

[allenbrighton]

hi guys

i have re-built an a10  [ thoroughly]  and a roughly tuned the carb [new one ] ------went on a long test run ----found that it behaved like a constipated horse [ as expected due to a rough tune ] now i have it behaving its self --except on tickover one of the exhausts is substancialy cooler than the other , it ticks over forever --very smooth--throttling is good , havent run it on the road yet to see if it mis-fires yet

am i worrying too much or can you give me a clue b4 i dig too deeply into it

many thanks

allen

mod edit: title edited (forum rule in tech boards: must show topic subject)

[Greybeard]

My thoughts about the exhaust pipe temperature is that piston rings on one side might a bit tight. Do you feel like taking the top off to check the rings and bore? If not, run the bike a bit longer and hopefully things will settle down.

When I rebuilt my bike the downpipes quickly blued up. I reckon I allowed the engine to get too hot while the rings were bedding in. Since then the engine doesn't overheat.

[allenbrighton]

hi many thanks for your reply --its actualy the exhaust gas temp i was concerned [ with your hand over the pipe one feels cooler than the other on tickover  ] not actualy had any bluing yet

thanks for your reply --i was concidering a duff plug or overtightened tappets , but as you say it may need more running in ,

many thanks for your suggestion

regards

allen

[Greybeard]

hi many thanks for your reply --its actualy the exhaust gas temp i was concerned [ with your hand over the pipe one feels cooler than the other on tickover  ] not actualy had any bluing yet

thanks for your reply --i was concidering a duff plug or overtightened tappets , but as you say it may need more running in ,

many thanks for your suggestion

regards

allen

So, are you saying one side is relatively cool rather than too hot?
Is the engine running evenly?

[allenbrighton]

hi--yes on tickover --very constant -smoothe the exhaust gas on one cylinder appears hotter than the other --almost as if 1 cylinder isnt fireing although it appears to be --very strange

i thought just to be an easy option change the plugs , if one  only works under load --albeit i have heard of one cylinder getting more fuel than the other  as there is only 1 carb , i will go out tomorrow and test it --do you have a plug that you have found to be better than the other --i originaly had 9-1 pistons in it but i couldnt turn it over --with the standard pistons this is a challenge  [ with age my mind makes promises my body cant keep

stay safe

regards

allen

[Swarfcut]

With the engine running I'd cautiously remove the plug cap of the hot side. That will give an indication whether or not the cold side is actually doing any work. If the motor falters appreciably then  the cold side is performing poorly and it's a case of magneto pick up, plug lead, cap, plug,  tappets, valves, compression.. All or any can contribute to poor running. Doing the same to the cold side gives a comparison on how each cylinder is working. You should hear a spark jump from the cap to the plug as the cap is removed. If the engine runs better with the cap slightly off, spark jumping, the fault is in the plug. This external spark gap was the basis of so called spark booster devices, typically found on two stroke outboard motors. They would work to clear a fouled plug.

 Swarfy

[allenbrighton]

many thanks --i`ll give it a go today --i fitted a thorspark unit ---the magneto was re-built --but couldnt give it a powerful enough kick --but so far the thorspark unit seems ok  [ who knows

stay safe

regards

allen

[Swarfcut]

 With  this electronic ignition system the coil should produce sparks of equal intensity on each  bare plug lead. Any difference is down to  something within the coil or lead  If this checks out OK, its back to basics, plugs, caps, mechanical or an obscure fuel problem. A double ended  coil /dead spark system with a single trigger will generate simultaneous sparks on each lead, so try simply swapping over the plug leads if this is the case. If the fault also swaps sides, time for a warranty claim for a new coil.

 Swarfy

[BSA_54A10]

Could also be some thing as simple as induction bias
Some bikes it was a problem & on others it was not a problem
But it is worse at idle

For my money I would polish the piper then go for a spirited ride .
When returning shut down the instant you are back then have a close look at the blueing on the pipes

[Jules]

I reckon its just the carb bias, one cylinder richer than the other, particularly as its a smooth idle, no misfire - whether thats an issue for you or not depends on driving. I'd give it a good run and if it behaves/drives well, leave well alone. if you are still concerned at this point though, immediately check the colour of both plugs upon return, I suspect one will show a bit blacker than the other, thats all....
Its actually quite surprising how a little extra fuel cools the combustion, very important at high speed/load...

[allenbrighton]

hi guys --many thanks ---think that i have found it --somehow ---dont know ---but the exhaust rocker was set at 008  doh!!!  seems ok now , but i still have a tuning issue --i`v e removed the thorspark unit and gone back to magneto , the engine hunts  and still wont rev --i noticed in the float bowl i have two settings --it was set on the lower setting --as it was new i didnt check this --just the needles etc   so i have put it on the higher setting in the vague hope that this will sort the issue --it really misses as though it was running out of petrol , i didnt worry when i was running in as i didnt rev it that high ---still we live in hope and die in despair

stay safe

allen

[morris]

A Colortune is a great piece of kit for this. I had a similar issue on my plunger. The Colortune showed the left hand cylinder much richer on tick over. A bit of fiddling with the carb settings made a nice blue flame in both cylinders