Finished engine rebuild

Swell

Swell

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Hi all, just finished an engine rebuild on an R100 airhead 1980 and replaced the rings and removed and cleaned up the valves. On starting I noticed that the left hand exhaust is expelling gas stronger than the right when you put your hands to the ends of the pipes. The difference isn’t massive but still noticeable. Any thoughts as whether this is a normal airhead trait or have I got something wrong on the rebuild. The valve clearances were checked and all good and it starts fine with no unusual noises from the heads.
Thanks in advance for any info.
 
Have you checked the carb diaphragms and sync'd the idle stops / throttle butterflys ?
 
I tried with both hands on different exhausts and the result was the same. The bike has dellorto carbs so no diaphragm but I’ll check the vacuum and balance to see if that’s the issue. The only other causes I can think of are: the exhaust valve not opening sufficiently enough, the new rings failing or the bore is scored but, that would increase crank pressure as gas slips past the rings. I’ll drink a few glasses of red and think it over. Thanks for the info.
 
My experience tells me that holding your hand at the exhausts is notoriously inaccurate and doesn't really tell you a great deal, unless the difference is large due to some mechanical failure/issue. Unless you have blueprinted the tits off this engine, induction system and exhaust system, variation between the cylinders is inevitable (it is, effectively, 2 separate single cylinder engines that just happen to share a common crank and camshaft).

As you have rebuilt the engine, I would do some basic checks (valve clearances COLD, compression test with butterflies/slides open, carb tune/balance etc) to make sure all is well and it isn't about to destruct itself, run it in, then go from there- it will change during and after the run in (which is why you run them in).
 
One muffler might be slightly more restrictive than the other, perhaps due to past fouling of some sort, or, if your bike uses them, the gaskets between the pipe and the header ending up in the muffler.
If you have to recheck valve clearances it it best done by feel on a hot motor, running at tickover.
You should be able to fell the same clearance on all valves, and FWIW the change from cold to hot is surprisingly minor, and within the degree of accuracy when setting, so little need to wait for a cold motor if you have to reset them.
 
Sorted. The carbs were massively out of synch due in part to me tightening the throttle cable at the carbs too much when rebuilding. Once they were loosened and the carbs balanced it’s all sweet. Just get to get it through MOT and the old girl is good for a bit of arsing around in the sun.
Thanks for all the help gentlemen.
 
Twelve measly quid, you tight arse. The help offered so far is worth that alone. Think how much joy this forum will bring to your life for the rest of the year.

Go on, you know you want to.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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