Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
plugs 2 and 3 share the same ignition system,points,coils,and capacitor,can you swop the plug leads over? are the long enough? and then see if the trouble still stays on 3, that make it a carb issue,and/or exhaust BTW does the 3 exhaust silencer/tailpipe got hot ?or the same as the others ?
Was it running before the rebore? If so, what was it like?Getting to more obscure stuff, have you checked the tdc mark against actual tdc with a wire down cylinder 1 or 4.
Just looked back at the thread from beginning, the problem you said was with no2 plug sooting up, you changed the caps over from 2 and 3 to see if it transfered, that's what you have now. Do you have two new caps that you can put on those two cylinders?Are you using the same caps for both the boyer and the points system by transferring them onto the lead sets?Also, I think, you get an opposite effect it some circumstances. One coil fires two plugs, if the resistance fails on one side then that route to earth will fire more easily as it has least resistance to impede it. But the good side with normal resistance may fail to fire at all if all the coil's energy is dissipated via the path of least resistance. So the failure exists of one side but the observable fault is effectively in the "wrong" position.
I've had a similar issue a long time ago, found one valve rocker eventually discoulored from heat so assumed the valve must be sticking so that engine got pulled, do you have another set of pipes to try, and possibly try new O rings on the inlet manifolds, or a spare set of inlet manifolds and rubbers. I'm just wondering if something is leaking air only when hot and leaning the mixture out on the inlet side, maybe smear silicon over everything - spraying wd40 doesn't always find inlet leaks. Were both sets of carbs overhauled by the same person? Possible if unlikely that perhaps something has been misplaced in a similar way on both sets of carbs, or a partially blocked tap on one fuel line starving one pot of fuel in preference to its neighbour. I've found on the sidevalve motors I'e been working on recently I was getting counter initiative plug fouling and backfires when it was actually too lean ( air leak in the manifold and head bolts not properly tight, ran perfectly til worked hard then no power and backfires, left for 15 minutes it ran fine again. Whether engine was hot the head bolts needed a good 1/2 turn to feel about right, they felt tight when it arrived. ) Its a bit baffling on your bike, it seems you have covered most of the bases, is the battery and wiring good? Last time my 500 was in regular use it had a few issues with not revving out and with not charging, swapping 're then rec units from spares that worked fine when last used didn't resolve it, sadly neither did parking it in a shed.
just seen this thread http://www.sohc.co.uk/index.php?topic=9583.msg67421;topicseen#new his bike wouldn't runn above 4K see if anything helps
It sounds like you've brought it quite a long way already Jon and hopefully you'll get this problem sorted as well.Just a couple more things to throw in the pot, have you tried it with the air filter removed from the air box?Also, a really odd one. Years ago a friend had a bike doing something similar revs wise, turned out that it had a twist grip that was incorrect fitted into the bike's original switchgear that wouldn't open the carbs more that about half way, it wasn't until looking for something else in carbs that it was spotted.
Genuine or replica pipes?