Trouble starting...

[jim.cox]

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ok, now I'm completely stumped!! I've checked spark to each cylinder and that's fine, I've triple checked the wiring and they're all firing in the right order, I've had the carbs off again and put them back together with the manual and checked everything there. So there's spark to each cylinder, there's fuel getting in there (I can smell it from the exhaust) but it just refuses to kick into life, not even the slightest hint of one cylinder firing. I'm sure it's something to do with the work I've done, which is all spark and carbs, but I've checked them over thoroughly and I still can't get life out of the damned thing! Any ideas are gratefully received at this point!

Spark has to occur at the right time - check the timing - I've seen motors set up 180 degress out

[magicmonkey]

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Spark has to occur at the right time - check the timing - I've seen motors set up 180 degress out

yup, I have thought about looking at the timing but I'm a bit weary of that as it would work fine before I played around with the carbs and spark, I know it's not out far enough to actually prevent it from firing ...

[magicmonkey]

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OK.
We all know an engine needs 3 things to go...but each must be present in the right quantities/time etc. The higher performance an engine is, the more critical those factors.You prolly need an 'expert' there with the bike. And maybe, some starting rollers like a few of the racers use...

yup, I get what your saying, I'm just completely stumped as it seems that everything is where it should be. I di wonder if maybe one of the vacum lines is blocked or something, would that be able to cause this problem?

[Grasshopperus]

OK, I'm out of ideas too.

Crash start it. Ride the shit out of it for 30 mins, red line once per minute, show it who's boss. That'll learn it.

[magicmonkey]

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OK, I'm out of ideas too.

Crash start it. Ride the shit out of it for 30 mins, red line once per minute, show it who's boss. That'll learn it.

lol, at the moment I'm seriously considering doing something like that, only thing stopping me is that I haven't got a trailer of a tow bar to get it back up the hill

[T.W.R]

When you say you've got spark to all cylinders is it a good spark ie: pale blue or a pissy yellow spark?
going back over some of your earlier posts about what had happened and what you had encountered I'd be inclined to think you've got too much fuel getting to the cylinders ie: drowning the spark.

A good spark should be able to jump a 8mm gap on a tester

[magicmonkey]

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When you say you've got spark to all cylinders is it a good spark ie: pale blue or a pissy yellow spark?
going back over some of your earlier posts about what had happened and what you had encountered I'd be inclined to think you've got too much fuel getting to the cylinders ie: drowning the spark.

A good spark should be able to jump a 8mm gap on a tester

The spark was pissy and weak, now it's a nice strong one and can jump about a 1cm gap to the engine block (approximated by eye, hardly scientific but I'm fairly confident in it)

I am wondering af there might be petrol that's refusing to come out of the cylinders for some reason but I can't see the plugs being wet at all when I pop them out. I'll get those plugs out again and double check later tonight though.

[T.W.R]

another thought is the electrolisis cleaning bent you went on with the carbs...when you finished doing that did you actually thoroughly clean the carbs out afterwards??? doing that does leave a scale type deposit in confined spaces and if you hadn't removed the emulsion tubes etc you're bound to have blocked galleries with the carbs & possibly partially blocked primary & main jets.
it's always easier & safer to just clean carbs with actual fuel rather than foriegn materials especially water as foriegn materials contribute to the majority of carb problems

[MSTRS:Me]

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... but I can't see the plugs being wet at all when I pop them out....

There's a clue. Got the tank tap set to prime?

[magicmonkey]

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another thought is the electrolisis cleaning bent you went on with the carbs...when you finished doing that did you actually thoroughly clean the carbs out afterwards??? doing that does leave a scale type deposit in confined spaces and if you hadn't removed the emulsion tubes etc you're bound to have blocked galleries with the carbs & possibly partially blocked primary & main jets.
it's always easier & safer to just clean carbs with actual fuel rather than foriegn materials especially water as foriegn materials contribute to the majority of carb problems

I did make sure to remove everything I could from the carbs (including the jets but excluding the pilot screws) and gave them a good scrub down with carb cleaner and a toothbrush when they came out, it's also been running since I did that. I must confess I've been thinking about trying to source another set of carbs if I can get them for a reasonable price though as I do wonder if the amount of work I've done on them has blinded me to any glaring problems ...

[magicmonkey]

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There's a clue. Got the tank tap set to prime?

I've drained the carbs that much recently that I have a routine in place at the moment! I usually out the tank on prime when I put it back on the bike, go and have a smoke and then pop it onto 'on' although I have played around with the positions to see if they help starting at all (also played around with having the tank cap open when starting to eliminate a blockage in the vacum tube)

[magicmonkey]

last night I just popped the spark plugs out and i've left them on the bench so that any fuel in the cylinders can evaporate, later tonight I'm going to check the float levels and then put a squirt of 'start ya bastard' into the cylinders before putting the plugs back in. Hopefully I'll get a vroom out of the engine and that'll just confirm that the spark is working properly. Then I can focus all my attention on the carbs, joy!

[renegade master]

I think you might just have to call a mech aye

[bogan]

don't call a mech, you've come this far! have you checked the compression on each cylinder?

[magicmonkey]

I'm hoping to sort it out myself, I know it's just a pissy little problem but the kind of thing that will cost hundreds in labour for a mech to sort out (they won'tknow exactly what work I've done so they'll have to diagnose it from scratch).

I haven't checked the compression beyond making sure the rear wheel locks in first although getting a compression tester is on the cards if I can't get it running pretty soon as I've checked just about everything so far ...