650 poor/not running

[callyboy]

Or I can sell you a brand new 650 tank for £250 posted..lol

Got to admire your persistence Rob

Pete

[Soichiro]

I'm alright for tanks thanks.

[Soichiro]

Bought an ultrasonic cleaner, cleaned the carbs, there wasn't much shite in the carbs but that's been eliminated. New jets etc. Robbed the HT caps off the reliable Honda. New petrol. Used a remote tank rather than the bike tank. Checked for sparks - loads of them.
After 20 mins of cranking it begrudgingly started up for a short time. Pot 1 is hot, others aren't. I must be missing something but can't think what. I think I'll wheel the bastard round to the bike shop and spoil their day. Its spoilt enough of mine.

I won't join the club yet because if I get any more shit from it I'll break it for spares.

[johnr]

ok, have you checked compression? have you chacked valve clearances? im not really worrried about the clearances being too big and rattling, but it they are too small then the valves might not fully close leaving you with low compression and poor running. also, when the engine gets warm, the expansion of metal might make things worse causing it to run worse when its getting warm. these are shim engines not tappets, so if there is wear in the valve seats then the clearances wil tighten and go quieter not slacken and get noisy.

[Soichiro]

I haven't checked the compression for two reasons; it does run (when it decides to). If there were low compression, it wouldn't run at all. Secondly, I've loaned my tester out and not had it back.
I think it's a fuel issue. I'll clean the tank out, take off the fuel tap and clean that up. The other thing to check is whether the slides in the carbs lift with the vacuum. I'll have to remove the airbox to see what's happening there.

[johnr]

but if it runs when cold and doesnt when hot, and its not ignition related, then it might be that your valve clearances are zero when cold and slightly open when hot, as everything expands. which would explain the poor running as it lost compression as the valves were held open.

[Doc44]

Watching this with interest as I have a very similar problem which I thought until recently was fuel but now considering the possibility of valves.

[fossie]

When johnr bought my 250,000 mile 650 it started ,ran smoked a touch......but started fine ...ran better over 3000rpm. When he took the head off , number 3 exhaust valve was so coked up it didn't move , but the thing ran ok..

For my money I would look at coil connections . They earth through the mounting bolts on to clean metal.

[Soichiro]

Do the coils even need an earth?
The primary is fed 12V via the kill switch and switched to earth to induce a back EMF in the secondary. E = -L dI dt if memory serves.
I really can't see the valves causing it because it ran absolutely fine. I'll have a go on the weekend, should have my compression tester back by then.

[sparki]

i've had not dissimalar symptoms where the dyna s on another motor was breaking down after 5-10 minutes of running or xx miles up the road... swapped it out for oem ignition and all ok... obviously they are an "all in one" setup but i'd try to swap out the pickups and see if the issue is there... maybe a wire has a break as they do get pretty brittle :-/