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Rev limiter? Trouble at 9500+

Nerobro

Nerobro

Forum Mentor
During a time where I was having issues with sticking floats, we reset my float height. I'm going to put that out there first.

SO, when I open my throttle all the way, in a seccond or two, the bike looses power. it keeps running, but only barely. If I close the throttle a little, the bike will pick up again.

This problem gets worse at higher RPM's. in fact, even just slowly raising the rpms I have difficutly getting the engine to exceed 10,000rpm. (this is a GS650 engine and carbs, so I should be able to blow past 10,500 without even blinking)

This is what I think is happening. In an effort to gain more closure force on the float valves we set the carbs to the high side of float height. So that the fuel level is fairly low in the float bowls. I think that the float valves can't open far enough to keep the fuel level high enough in the carbs when the engine is really spinning fast, or the throttle is wide open.

When riding the bike, it feels like there's a 9500 rpm rev limiter. in top gear, it will only pull to 9500 rpm with the throttle partially closed. If I open the throttle all the way the bike will loose speed.

I do have the larger dynojet jets in place. This did help the situation somewhat.
 
clogged fuel petcock? Try using the PRI when you test you bike next time :)

I just figure i had this problem yesterday.
 
I have pleanty of fuel flow, and this is not the same symptoms as the petcock dieing. This is almost instantious. Petcock issues always seemed to take 5-15 secconds of WOT to maifest themselves.
 
I dont know about the fuel thing but i think you may have gone way past the point of making power at 10000 rpms, i have a 650 also and i have changed gears long before 10000. 8O just my thoughts
 
Ran into the same problem on my Kat. Reset the floats for a higher bowl fuel level. When I put in a jet kit I would suck the bowls empty exactly the same way, It acted like it was out of gas as soon as I hit 7k.
 
Re: Rev limiter? Trouble at 9500+

Nerobro said:
If I close the throttle a little, the bike will pick up again.
Click to expand...
I do believe that is a sure symptom of lean fuel mixture. Reset the floats for higher fuel level.
 
check the voltage at the coils with the engine running.
a voltage drop off at the coils will make for a weak spark, exagerated by high loads and RPM.
 
stop trying to garage tune it, set every thing to factory specs and or dyno jet specs, then synce the carbs with a merc stix and while you are at it try doing some tests with those crappy emgo filters off your bike and see if it behaves any better, i was haveing similar issues on the 550 when run those pods, they didn't flow enough air at 6k +

that should get you pretty close to what every thing needs to be. also are the carbs spot less? every little hole poked with a fine wire, all float needles either replaced or the screens cleaned how about pulling the needle seats and checking the needles and seats for sticking and or sealing

-ryan
 
As stated above, set the floats correctly and test. If it still has a problem, let us know.
 
first timer said:
that should get you pretty close to what every thing needs to be. also are the carbs spot less? every little hole poked with a fine wire, all float needles either replaced or the screens cleaned how about pulling the needle seats and checking the needles and seats for sticking and or sealing

-ryan
Click to expand...

Except for the mercury synch test everything else has been done... ask him I *made* him check the float height cuz at first he was going to eyeball it. As for cleaning... everything has been gone over. jets soaked, cleaned and what not....
 
Ryan, the Emgo's are not at fault. I've got almost 12,000 miles on mine...
 
bah the emgo suck, what does it hurt to try and take them off and see how it runs that way, adam you are also running vm carbs which have a smaller mouth on them, greg is running cv's which have a bigger mouth and they are more sensative to air pressure and vacume. so please greg get everything set, take a run with the filters on then take a run with the filters off and see if it changes.

-ryan
 
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