Re-occuring Ignition fault

[smartiedarkblue]

hi all,

HELP PLEASE....................

I have had this nightmare problem now for months and can't find the fault, i put a new set of plugs in and thought i had cured the fault but its back with vengance.

Symptons are: The bike can be running fine then there is a series of backfires up through the carb bodies. Then she can drop a cylinder, I have had the carbs off and checked, no problems found apart from a sticking plunger but that was sooted up so i cleaned and put back.

When turning over without the carbs on i could see one of the plugs sparking when the inlet valves were still open and she was on her inlet stroke. only every now and again not every time.

This is only happening on the rear unit, The rear coil has been loose for some time and has been rattling around for a while, could this now be damaged and letting the plugs spark when they want???

Any help would be greatly appreciated.

cheers
ed

[odie]

As the coil is supposed to be bolted up and not rattle around wouldn't it be a good idea to bolt it up, it don't matter if its not the cause or not, its not supposed to be loose!
As for the problem, what have you done to the bike before the problem started, people always don't give a full history, i.e what was done before the problem started and 9 times out of ten its the cause.
With it backfiring up through the carbs that says to me that the timing is out, now if it was cam timing your engine would not run, so it is pointing towards the ignition timing.
Have you had the right hand engine cover off?
have you played with the wires from the right hand casing that are from the pulse generator or are the frayed.
Check to see if they have been rubbing and may of gone down to bare wire which could be touching the frame causing a short and making the bike back fire through the carbs.
had a similar problem with a friends Yamaha XS1100, he had undone the bolt holding the ignition ignitors and not fitted it back correctly, it cased it to run fine until you opened it up and then it would back fire through the carbs!.
Oh what fun it was to diagnose, not!
odie.
P.S
Check to make sure your H.T leads have not broken down and are shorting out on the engine, could be another cause.

[smartiedarkblue]

hiya odie,

cheers for the reply, I have known about the coil being loose for some time, this is due to the mounting point on the back mudguard having broken down and not holding the securing bolts properly,
It was a problem i ment to sort when i stripped the bike and then promptly forgot, and due to the location of the coil it is a pig to get to so i left it. however i have just finished taking the back mudguard off and aralditing the securing nuts in place and then tightening the coil up proplerly. So it is now snug and tight.

As to the history not being in full, it is. The only time the coil has been moved or anything moved was when i stripped the bike in april 09 to powder coat the frame and sub mounts. But the bike ran fine after this.

As to the wiring, It has all been thoroughly checked and re-checked there is no chaffing anywhere. My first thought was also timing be it cam chains or ignition timing. By cam chains i realise they are pretty much set in stone and don;t change but i have known a cbr600rr throw its timing out with a worn cam chain tensioner, allowed the chain to jump a tooth at high revs. So they were checked and the tensioners are well within their wear limits.

Have had the engine cover off as well everything in there is tight and present and correct no chaffing was found again.

Oh and the HT leads were replaced and caps last april with brand new items.

So once again i am stuck, any more ideas anyone?

cheers
ed

[smartiedarkblue]

Hi all,

Problem is SOLVED ;D ;D ;D ;D

I Found it in the end, it turned out to be the ignition pulse pick up coils in the right hand engine case.

Put the multi meter on them, and where as one was well within tolerance the other was out by about a mile, So it was pronounced dead and thrown in the bin. Put a new set on and the bike runs a dream.

cheers
ed

[odie]

Good news then ;D

[McF]

Apr 29, 2010 17:11:28 GMT 1 smartiedarkblue said:

Put a new set on and the bike runs a dream.

Brilliant news, I bet you're pleased