Dead at 6000 RPMs

[tkent02]

I am torn between the cam chain and the igniter.

If a cam chain was that worn it would retard the cams, if anything that should be better for high RPM, should move the powerband up...
I agree there would be all kinds of noise before any issues with how it runs.

Valve springs going soft, could let the valves float, but that is a LONG way below the redline RPM. I think it would take years for this problem to progress as far as not running correctly down at 6,000 RPM.

Never seen springs cause this, have ridden some GSes with a ton of miles and years on them. Could be possible I guess. Especially if the engine has gotten really hot, enough to weaken the springs more than most?
In cars, valves floating has a distinct feel to it, kind of a fluttering sort of thing, like every power stroke its at a different throttle position.

So exactly what happens at 6,000?
Is it just like hitting a rev limiter at 6,000?
Does it start misfiring?
Switch off like a kill switch?
Just get less powerful as if you closed the throttle?
Does it happen at partial throttle as well as wide open?
Is it the same in any gear?
Up or down hill?
If you hold it in this RPM of the problem, then do a plug chop, what do you see?

Is the fuel flow adequate?

[Guest]

Ed,

All the timing marks line up & there are 20 pins between the marks, it's not a tooth off.

Dan

the test i was referring to calls for a measurement between those 20 pins (can do it on 10 pins as well) and tells you if the camchain is stretched beyond acceptable or not

[Guest]

If a cam chain was that worn it would retard the cams, if anything that should be better for high RPM, should move the powerband up...
I agree there would be all kinds of noise before any issues with how it runs.

Valve springs going soft, could let the valves float, but that is a LONG way below the redline RPM. I think it would take years for this problem to progress as far as not running correctly down at 6,000 RPM.

Never seen springs cause this, have ridden some GSes with a ton of miles and years on them. Could be possible I guess. Especially if the engine has gotten really hot, enough to weaken the springs more than most?
In cars, valves floating has a distinct feel to it, kind of a fluttering sort of thing, like every power stroke its at a different throttle position.

So exactly what happens at 6,000?
Is it just like hitting a rev limiter at 6,000?
Does it start misfiring?
Switch off like a kill switch?
Just get less powerful as if you closed the throttle?
Does it happen at partial throttle as well as wide open?
Is it the same in any gear?
Up or down hill?
If you hold it in this RPM of the problem, then do a plug chop, what do you see?

Is the fuel flow adequate?

Not fuel related. Did the dance.
It is almost like a rev limiter. Just doesn't want to climb over 6-7. Fine till that point even at wot. Reminds me of a governor I had on a moped when I was a kid.
If a bad cam chain would move the powerband up I'm leaning towards a bad igniter but the chain was worn. LOTS of back and forth play.

[Guest]

i imagine you would have thought of this but just in case ...

automatic cam chain tensioners can get stuck and cause a loose camchain, it pays to have the tensioner checked, cleaned, lubricated

[Guest]

i imagine you would have thought of this but just in case ...

automatic cam chain tensioners can get stuck and cause a loose camchain, it pays to have the tensioner checked, cleaned, lubricated

I pulled it off and checked it out. It's OK.

[Guest]

I pulled it off and checked it out. It's OK.

i thought as much, chef, but you never know when you have a problem it's sometimes easy to overlook something simple
good luck troubleshooting [-o<, i'm watching the thread with interest

[salty_monk]

Today it was doing the same thing but not at 6,000rpm, much earlier in the rev range & pretty much at all throttle positions.
Better in high gear than low gear....

Dan

[49er]

Not fuel related. Did the dance.
It is almost like a rev limiter. Just doesn't want to climb over 6-7. Fine till that point even at wot. Reminds me of a governor I had on a moped when I was a kid.
If a bad cam chain would move the powerband up I'm leaning towards a bad igniter but the chain was worn. LOTS of back and forth play.

It won't be the stretched cam chain or weak valve springs causing these symptoms. Stock springs last forever with stock cam lifts. I'm still running the original springs in my 850.
When the motor peaks out at 7000rpm, does it miss or completely die. If it dies, try backing off the throttle until it runs normally and then snap the throttle open again and see if it pulls cleanly up to the same rpm. If it does, you can rule out fuel starvation. If not, you need to recheck the fuel supply, to and through the carbs.
If it's acting like a governor, there won't be much missing, just a sudden power drop, and refusal to rev higher.

[Guest]

Today it was doing the same thing but not at 6,000rpm, much earlier in the rev range & pretty much at all throttle positions.
Better in high gear than low gear....

Dan

I bet at this point with a weak spark your plugs are fouled.

[salty_monk]

Could be.... I just thought about the test we did on the coils... No volts at either connection pointd with the ignition on to either coil terminal...

Anyone know if that's normal or should there be a permanent live 12v to them with the ignition on?

Cheers,

Dan

[Guest]

Switched out his old carbs with my old 34s. Switched out the jets. Still the same issue. Even cut his new fuel line shorter so no hills to climb.
If you let off the throttle till it runs good and hit it hard it does climb to that same rpm.
He does have the original petcock but he said it flows good.

[salty_monk]

hehe we tested it when you left it switched on prime remember no way it can be drinking at that rate!

[Guest]

Could be.... I just thought about the test we did on the coils... No volts at either connection pointd with the ignition on to either coil terminal...

Anyone know if that's normal or should there be a permanent live 12v to them with the ignition on?

Cheers,

Dan

kill switch "on", there should be permanent live at the coils (there is on mine anyway)

[Guest]

Stock springs last forever with stock cam lifts. I'm still running the original springs in my 850.

hi 49er

not sure how long "forever" is, but mine were shot at less than 90k kms
i would think the wear would also depend on how hard you push them

however, in this case it doesnt seem to be the issue
cheers

[salty_monk]

uh... kill may well have been off, it was late by that time. I can double check that easy enough though.

I have Dyna Suppression wires fitted to dyna greens, stock igniter & NGK B8ES plugs from Z1.

Maybe it is the igniter...

Dan