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Author: Subject: MK Indy Fireblade Misfire
LBMEFM

posted on 9/4/20 at 01:29 PM Reply With Quote
MK Indy Fireblade Misfire

MK Indy Fireblade Misfire

I have a MK Indy fitted with a 1995 Honda Fireblade engine which has developed a misfire. I removed the carbs thoroughly cleaned them and replaced them. Checked the wiring on the coils and HT leads all seem to be OK. If I remove the leads one at a time the No 1 cylinder has no effect ,therefore, I thought is was the plugs moved this to No4, misfire still is on No1 cylinder. If I manually open No1 carb's butterfly it revs nicely so there is fuel from the carb. The No1 lead has a really good spark and, I ,haven't got a compression tester that fits the small plug holes, but if I put my hand in turn over the plugs holes when plugs are removed their seems to be similar compression. To conclude, there is fuel going in, there is a very good spark and their is compression. It's driving me crazy, any ideas welcome please.

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CosKev3

posted on 9/4/20 at 04:01 PM Reply With Quote
Might be some compression, but perhaps not enough?

How does it compare to a non misfiring cylinder?

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rusty nuts

posted on 9/4/20 at 04:24 PM Reply With Quote
Valve clearances?
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watsonpj

posted on 9/4/20 at 07:11 PM Reply With Quote
so does the exhaust got hot at all? What do the plugs look like?
when you stripped the carbs did you check that the diaphrams didn't have any pin holes or rips one of mine had a small hole and it causes issues.
Have you tried swapping the two coil packs?

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LBMEFM

posted on 10/4/20 at 02:48 PM Reply With Quote
Thank you for your answers, I have done everything you suggest. Replaced both coil packs, checked valves, all have clearance and non are stuck. Replaced the diaphragms, when the butterfly opens you can see the slider rising. Its mad, there is fuel and air going into the cylinder, its being compressed and the plug is firing so why wont in run on four cylinders.

Would the pulse generator have any effect on a misfire?

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rusty nuts

posted on 10/4/20 at 03:51 PM Reply With Quote
Air leak? Test by spraying around the suspect carb/ manifold with something like WD40 with the engine idling . If leak is found engine revs will increase. Also double check the carbs are balanced
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number-1

posted on 10/4/20 at 07:06 PM Reply With Quote
I tried this recently with WD40 and it had no effect. There were a few leaks but the revs didnt go up.

Id listen more for a squeal or hiss as an indication for an air leak.

[Edited on 10/4/20 by number-1]

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ReMan

posted on 11/4/20 at 01:04 AM Reply With Quote
So is it misfiring on no1 , whilst running or not firing at all?





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LBMEFM

posted on 11/4/20 at 08:43 AM Reply With Quote
Not firing at all, just don't get it , it is so frustrating. As before there is compression, a spark, fuel and air the valves are working correctly but still it will not run on No1, I never been so baffled by an engine in my life.
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LBMEFM

posted on 11/4/20 at 09:00 AM Reply With Quote
just a thought, what sort of PSI/KG figure would you expect to see on a compression gauge
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ReMan

posted on 11/4/20 at 10:42 AM Reply With Quote
quote:
Originally posted by LBMEFM
Not firing at all, just don't get it , it is so frustrating. As before there is compression, a spark, fuel and air the valves are working correctly but still it will not run on No1, I never been so baffled by an engine in my life.

You definitely changed the plug ,lead and cap on no1?
If yes
Have you tried easystart on no 1 whilst its running?
Youd be unlucky if it compression (holed piston) or valves as youve mentioned.
Tbh if it was one Leaky valve it would probably still work! Theyre normally very robust!





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LBMEFM

posted on 11/4/20 at 02:48 PM Reply With Quote
It does drink coolant, however the is no sign of oil in the coolant or oil contamination, how about a warped head causing the misfire
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LBMEFM

posted on 11/4/20 at 02:56 PM Reply With Quote
Hi ReMan, just tried easy start in the No1 intake, makes no difference, however, put an old plug I found in and it seems better, I know they are sensitive to plugs, unable get out and buy some currently due to this damn virus but as soon as I do I will buy a new set of plugs and give it a fast thrash down the road and see what happens. Thanks for your suggestions.
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ReMan

posted on 11/4/20 at 07:24 PM Reply With Quote
Head gaskets possible,again rare, unless abused/overheated .
Odd where your coolant is going though so perhaps too big a coincidence to ignore.
But. If it was escaping into a cylinder, Id expect it to pressurise your cooling and blowing it out somewhere visible?

Re plugs. Yes they can be sensitive, mainly to flooding
However, its rare they really die.
I,d try cleaning with a wire brush and heating no1 plug over a gas flame it often enough to revive them
Also try starting it I the dark, you may find you can see a ht lead or cap breakdown

Hth





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