Right, having given up on the injection for my engine and gone back to carbs (which I feel much happier about, since I don't know a huge amount
about injection set ups yet) I'm still having problems. The engine turns over fine, and tries to fire on number 3 and 4 cylinders only. It's
not the coils, as I changed them over and it's still the same. The only thing I can find is that the plugs on 3 and 4 come out wet. Could it be
over fuelling on these two, and under on the others? The sparks are fine, all 4 plugs are firing. I had taken the carbs apart to clean them, as they
hadn't been used in years. Is there something I could've missed?
Your thoughts please gents!
Oh, is there anyone near me with a compression tester I could borrow, just in case this could be a related issue?
yes - have you checked the needle valve in the float chamber is sealing?
it wouldn't surprise me if thius is stuck partailly open after a time of non use to allow too much fuel in, but then again, it may not be but is
simple eunough to check.
Are the plugs definitely firing when under compression? Wet plugs won't always fire properly and plugs will sometimes fire when @ atmospheric
pressure but fail to fire when compressed @ 10:1!! Have you tried swapping the plugs over to see if it makes any difference.... I've found that
(particularly with bike plugs for some reason) once they get saturated and wet they're permanently shagged despite many different attempts to dry
them out and revive them....
Colourtune is your friend in a case like this. You'll be able to see if its definitely firing (and if it is what the spark looks like) and by
looking at the flame work out whether the plugs are wet because the mixture is rich or because they're not firing and just getting coated...
A compression test is a sensible precaution when it comes to chasing down problems like this though...
Edited to say I've got a comp tester and a colortune I can lend but it's probably a bit too far....
[Edited on 8/8/07 by BenB]
Check timing and HT leads in the right place!
I would suspect timing as well. 90% of starting problems are ignition-related rather than induction-related, in my experience. If there's spark there, and fuel & compression, the only thing left is timing...
Not many bike engines have adjustable timing without power commanders or similar electronic equipment. Bike plugs don't like flooding so I'd invest in a new set of plugs and a carb inspection before you try starting it.
look down the carbs as you try to start it
is the end carbs flooding in as opossed to spraying it in
Right, had a look and the two that are trying to fire are leaking fuel into the engine! The other two plugs are coming out dry, so I suspect these two
aren't getting any/enough fuel.
The timing isn't adjustable on the bird lump, so there's not a lot I can do. As said, the coils have been changed over and the leads too.
All that does is blow back through the carbs! I'll give the crabs a more complete clean and see what happens.
quote:
Originally posted by DIY Si
I'll give the crabs a more complete clean and see what happens.