"cough" at 3k rpm and then dead - s4r

[DucHead]

I think the units are 10^-4 inches.   

[boosted_dc2]

I am having a very similar problem.  03 M800.  Only when its hot out, temp at about 210-220.  Spitting and sputtering at about 3.5-4.5K, when the bike is cold its as smooth as silk.

Im leaning towards valves, The bike has 10K on it, valves never even checked as far as i know i just bought it.  Im wondering what effect heat has on the valves as far as expanding and changing tolerances while we ride?  Just a thought....

[booger]

Im leaning towards valves, The bike has 10K on it, valves never even checked as far as i know i just bought it

Smart thinking - I had one tight opener and three loose closers, after shim replacement it was like a brand new bike.

I think the posters in this thread will end up having to face the music and adjust their valves. It might still be bad gasoline, and the only way to rule it out is to ride a few tanks, but if the cylinder heads aren't breathing correctly it's valve time. CO and loose wires aren't the issue. OP's bike has 25k on it! And those valve measurements don't make sense. Get them checked by somebody who knows what they're doing already.

[♣ McKraut ♣]

he knows what he's doing, i just don't know what the measurements mean.  and that valve check/adjustment was only a few thousand miles ago...  i'm still leaning towards fuel adjustments.  going to see what it's like once it's fattened up, and then see about having the valves checked again.

[el_loco]

When valves are out of spec they are out of spec always, and the motor runs poorly through the band.  At least on my bike the thing runs great except for the intermittent issue.  I'm still leaning toward wiring or TPS myself.

[devimau]

Smart thinking - I had one tight opener and three loose closers, after shim replacement it was like a brand new bike.

I think the posters in this thread will end up having to face the music and adjust their valves. It might still be bad gasoline, and the only way to rule it out is to ride a few tanks, but if the cylinder heads aren't breathing correctly it's valve time. CO and loose wires aren't the issue. OP's bike has 25k on it! And those valve measurements don't make sense. Get them checked by somebody who knows what they're doing already.

how can you be so sure? I wish I had the same crystal ball you have man, I really do.

[Howie]

how can you be so sure? I wish I had the same crystal ball you have man, I really do.

Reality is no one can be sure until the valves are checked, and, if the valves are too tight nothing else you do will work, plus you will eventually have expensive damage.

[booger]

how can you be so sure? I wish I had the same crystal ball you have man, I really do.

No crystal ball, but my own experience with the same exact trouble is the basis for my assertions. Again, OPs bike has 25k miles on it. 25k. To establish a baseline for these engines, the very first step is to ensure the valves are opening and sealing as they should. Just a fraction of a fraction off and they misbehave. I thought it was a simple fueling issue too until I wasted time trying to fuel out a valvetrain that was out of whack. I apologize for trying to save the OP some trouble.

[devimau]

you have a good reason to say that, don't apologize, but if the valves were tight you'll see the problem from 170 and above and he has no issues till 210 or so, that what's leaning me towards the tuning and also that he said he had them checked recently (eventhough those numbers make no sense) and the bike started to stall after he installed the dp flasud ecu and also that I saw another post were he was saying that the vdst wasn't working for him.

[Ahks]

valves a little over a year ago measured (to be honest i don't even know what the unit of measurement is):

Front
exhaust: 77
intake: 56

exhaust: 66
intake:  66

Rear
exhaust: 66
intake: 66

exhaust: 66
intake: 77

Shouldnt there be 2 measurements per valve? opener and closer?

[battlecry]

Maybe they are cam degrees.

[♣ McKraut ♣]

there was a space between each number

[DucHead]

That makes no sense.  Valve clearances are in fractions of either inches or millimeters.

[♣ McKraut ♣]

That makes no sense.  Valve clearances are in fractions of either inches or millimeters.

point taken.  i will contact him and ask him what the numbers mean.

to the initial question, though, would a valve clearance issue stall the engine only at 3k rpms, but run great above that?

[DucHead]

point taken.  i will contact him and ask him what the numbers mean.

to the initial question, though, would a valve clearance issue stall the engine only at 3k rpms, but run great above that?

Dunno, but I think its really worth the time to learn to do your own maintenance.  It takes a while, but IMO its worth it.