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Discussion Starter #1
Last week when passing a car, I downshifted into 4th gear and when I hit 60mph the rev limiter seemed to kick in and I shifted to 5th gear and completed the pass. I duplicated this several times and even tried in 3rd where it started to miss at 45mph, shifted to 4th and increased speed to 60mph where it once again began would miss until I either slowed or shift into 5th gear.

The issue is very consistant and I do not know for shure if it is the rev limiter or something else. Other than this the bike runs great.

Any suggestions?

Thanks
 

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Super Moderator "Loose Nut"
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I would check the plugs. When plugs age the gap gets wider making it difficult to achieve a good fire under load. Keep us informed.
 

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Well, you should hit the fuel cutoff at 71mph in 3rd and 89mph in 4th gear. Hitting the rev limiter would be at 81mph in 3rd gear and 101mph in 4th gear.

Something else is going on, could be the sensor is not sensing rpm right and cutting it earily. I personally would go for the sparkplugs first, might just be iginition is delayed from a faulty/carboned plug.
 

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check your airfilter too - if its not white like paper replace it.

It would not necessarily act like a rev limiter, but a dirty air filter is like only being able to open your throttle half way - the air cannot get thru it.

I waited till mine looked like an old grey tee shirt before I replaced it, and then HOLY !&^@% the bike came alive with the new air filter - esp at the peak HP points (55mph in 4th and 70mph in 5th on my 650).
 

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Discussion Starter #5
The problem is definitely rpm related, there is no miss before I hit a certain rpm. I will check the plugs and filter this morning, but I am not sure where to go from there.

Thanks,
 

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Discussion Starter #6
Checked plugs and TPS and both checked good. Screws are tight on the carb boots so there should not be any vacuum leak there.
 

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Last week when passing a car, I downshifted into 4th gear and when I hit 60mph the rev limiter seemed to kick in and I shifted to 5th gear and completed the pass. I duplicated this several times and even tried in 3rd where it started to miss at 45mph, shifted to 4th and increased speed to 60mph where it once again began would miss until I either slowed or shift into 5th gear.

The issue is very consistant and I do not know for shure if it is the rev limiter or something else. Other than this the bike runs great.

Any suggestions?

Thanks
if the engine is running on rich side it can't reach maximum rpm but it will stutter like it has my 650 would stutter at 80mph in 5th after leaning it just a little it hits 90 no problem and still didn't hit the limiter to get an engine to hit the limiter it really needs to be in perfect tune it can be a little lean and get there but you risk damage but too rich and it just won't get there
 

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Discussion Starter #8 (Edited)
Thanks Pauli466, I am thinking my original idea of the rev limiter causing the problem is wrong, what made me think that is the was it runs fine until I hit 60mph while in 4th and all of a sudden it starts missing and will not go any faster.

Maybe it is running rich, I inspected the plugs and they are fine color wise.

I will install some new plugs and reset the PMS screws this weekend and let you guys know what the outcome is.
 

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The PMS set positions in the tables for exhaust and intake mods, are the recommended starting points to set them to, after you have modified the engine, or disassembled the carbs to clean them.

You still need to adjust them further after you set them to the recommended number of turns, based on how the bike is running.

There are two methods for doing the fine tuning - look it up, that might be what the problem is.
 

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I just don't think it's a PMS issue. A needle position or main jet maybe if it was the carb at all. Maybe something got into the carb and partially clogged it?
It should be running rough at idle if the PMS was misadjusted.

 

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Its also possible you got some bad gas, with more ethanol than its suppose to have, or with some water in it.

Running some Seafoam thru the engine can only help - and its easier than tearing into your carbs.
 

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Discussion Starter #12 (Edited)
Then it seems to point to a problem with the main jet.

I think that if I had bad gas it would miss at all speeds

Maybe the main jet in one of the carbs is plugged and it is starving for fuel when I hit 60.
 

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Discussion Starter #13
What is this part and is it supposed to allow air flow in both directions, I searched on a carburetor schematic and did not find it.
 

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it will usually come down to the mains even a half size makes a big difference when nearing the redline, pilot screws won't affect WOT by much, i mean it does but it's hard notice it
 

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Then it seems to point to a problem with the main jet.

I think that if I had bad gas it would miss at all speeds

Maybe the main jet in one of the carbs is plugged and it is starving for fuel when I hit 60.
seafoam can clear out a partly clogged jet

every year in the spring there are many posts - bikes dont run well after being stored for the winter - 4 ounces of seafoam in a full tank of gas is usually all it takes to clear out the goop, unless a jet is completely plugged and there is zero gas flowing thru it.
 

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Discussion Starter #17
Thanks for the input everyone, I guess I will clean the carbs tomorrow.
 

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Discussion Starter #18
Opened up the carbs and found one of the main jets had come loose and was laying in the bottom of the bowl.
 
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