Missfire/ Spitback at Specific Revs

golightly · Mar 14, 2018

Mille SV engine, all mods done and had a dyno setup done on the PC3, ridden about six times since then was perfect after the dyno and a lot better (managed 124.9 BHP at the wheel)

Rode it the other day and its got an hesitation/ misfire around 3750 RPM, fine before and clears about 4000 RPM. Also it occasionally sounds like its spitting back through the throttle bodies. I have changed nothing since the dyno, checked plug leads and re-plugged a whole bunch of connectors, stumped

Any ideas chaps?

Hessler · Jun 16, 2018

run some cleaner through the fuel system.
probably kicked up some muck in your fuel tank with the extra power.
Not sure what is recommended but used to be redX,
someone on here should know or maybe just search posts

golightly · Jun 16, 2018

Tried that mate, still confined to that range, pulls fine above, not had the CO done since the Dyno so that's on the cards next month, maybe that will help but the boys at Aprilia Performance will be looking at it for the first time since I built it so I'm hoping their expertise will pay dividends

Hertsrsvr · Jun 17, 2018

Have you had valve clearances checked lately ?
Spark plug might be failing...is another. These bikes don't smooth out until above 5k rpm, so it might be something temporary like bad fuel or dirt somewhere. Chack all electrical connections it could be corrosion some where ?

golightly · Jun 17, 2018

Plugs are good, not checked clearances for a while though but as it happened from one ride to the next I doubt that.

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Missfire/ Spitback at Specific Revs

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