Bad miss under 3000rpm's

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Duffdad

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My 2007 FZ1 with Dyno PC, Dyno ECU, Ivan's everything. Cylinder 1 is missing. We (Yamaha dealer) by-passed all the aftermarket stuff, replaced the plugs, switched and tested the coils, replaced the injector, blew pressurized air through the manifold and still there's a miss under 3000rpm's. Remember all the aftermarket parts were removed and stock electronics were plugged in. The mechanic wants to do a "pressure down" test on that cylinder. There is only 2500 miles on this bike. He can't seem to figure out what's causing this cylinder to miss. He put a thermo-gun to it and it's running cooler then the other 3..After 3000rpm's the bike runs strong. Any ideas?

Duffdad
 
I'm wondering if it isn't a few valves way out of spec on that cylinder. If theyre very tight already, you'd be losing a lot of compression. That would definitely cause a misfire.
 
I think the pressure down test will show if that's the case. This bike was running great until last Thursday. It had not been run for about three weeks, then the missing started. Thanks for the reply...Waldo
 
He said they swapped coils. On top of the fact coils usually don't work part time. It's almost always all or none. I would stick a scope in there and see if you see any issues. Could be valves but could be it was too lean and burned an edge off a piston.
 
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The coils will cause this issue. I'm not saying that it could be something else. The coils are a somewhat common problem. Mine tested fine. I went as far as cleaning every electrical connection greasing everything you could and taping the coils. Worked for about a week and the miss came back. Replaced all of the coils haven't had a problem since.


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Sebastian F7 said:
On top of the fact coils usually don't work part time. It's almost always all or none.
Click to expand...


Coils often fail slowly and start with an intermittent miss often at lower rpm. Many will test within spec but are actually the problem.

You can find a lot of threads about failed Gen II coils and misfires on the other FZ1 forum.
 
hey mate i had a similar issue with my 08 fz1 c1 missing. my yammy dealer couldnt sort the problem. took it to dyno put a new set of plugs in and runs fine now, after reradin everything i could find on forum i belived the coils were at fault?? but new plugs sorted it will be able to tell if the coil is failing if it occurs again because a faulty coil will chew your plugs. hope u get baack on the road! without the bs nnnnnnnnnnnnnnnnnn rooom.
 
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