GT250 Misfire

[A100man]

Odd one..

Was running OK last summer, first ride this year - misfire onto one pot then none. short walk/push home...

Tried new plugs.. nope but noticed spark was weak.. so got some new coils. NIce fat spark, great but not the solution.. It starts and runs on two but after 20-30 second starts to misfire and then drops onto one and teh plug oils up. New condensors last year.. points cleaned to no avail..

Thoughts?
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[stinkwheel]

Crank seal drawing gearbox oil?
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[bypass2]

Old petrol. when you put the new coils on do you get new HT leads and plug caps. petrol tap working ok

[A100man]

[A100man]

One other thing..about it the only part of the ignition that hasn't been replaced (yet) is the RHS points they were slightly pitted but better after a sanding clean and gap set..
____________________
Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[stinkwheel]

Battery in good order?
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[B1N]

Float needles sticking maybe?
Are you running the oil pump or premix?

[A100man]

Battery at 12.7 so good I reckon, new last year also.
Running oil pump premix not advisable on these CCI motors

Also remember that i added some baffle wrap which wasn't there last year.. I wonder if it's strangling the motor.. easy enough to check, Then I'll try some new points ..
____________________
Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[A100man]

[stinkwheel]

Maybe worth giving the points a blast of contact cleaner too in case they've got oil on? I once cleaned mine with brake cleaner and it turns out that their claim to leave no residue is a blatant lie, it apparently does leave a residue and furthermore, that residue is non-conductive.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[B1N]

If you have an OK spark I would be looking at carburation.
It could be one sticky float valve, (needle valve), tap your float bowls with the handle of a screwdriver, or better still take the carbs off and have a look, it could even be a punctured float.
Also check inlet rubbers for air leaks.

Do your float valves, have rubber tips, could be ethanol swelling the rubber?
I drain my float bowls over the winter, which is easy to do on my bike.

[blurredman]

New coils don't necessarily mean good coils.. I've had them bad out of the box...


Swap the coil and spark plug over? Clean those points! File them down a bit perhaps, then re-adjust gap width to compensate. Two condensers? Swap them over?


Sorry, just recently been messing with this sort of thing myself.
____________________
CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S.
Current: 1973 MZ ES250/2 - 17k. , 1979 Suzuki TS185ER - 9k, 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (295cc) - 38k, 1989 MZ ETZ251 - 49k

[jeffyjeff]

Maybe try one of those inline spark testers to see if you have a degrade in spark after 20-30 seconds. Misfire (to me) suggests intermittent ignition system issue. Fuel system issues would be apparent all the time.
____________________
History shows again and again how nature points out the folly of men - BOC

[B1N]

Yeah you could be right, difficult to diagnose without being there but personally I'd change the plugs first thing of course and if I see a good spark I don't waste time looking for more spark, check other things first then come back to ignition later if needed.
Go for the low hanging fruit first, spray a bit of carb cleaner around the inlet rubbers while it's running, if the engine increases RPM then it is sucking in air.
We all have our own way of doing things.

[stinkwheel]

[B1N]

I gave up the fags 21 years ago.

[A100man]

small update..

Took out the baffle on the offending side (no difference) then changed the plug (again!) it ran ok for a minute or two but was too loud to continue (for the neighbours). I couldn't then get the unwrapped baffle back in cos the internals of teh exhaust had collapsed..

.. I have spare (pattern) exhaust for that side will now fit and then try a road run.
____________________
Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600