Bogs at 6800 RPM

[Rickb1b]

Ok I probably should have mentioned this earlier but the machine is running really rich. Anyone know how to test the Det sensor.

 

[IceCap]

Your TPS may still be the problem. When mine went it some times worked, then it went all screwy, then it worked again.

Your TPS may check fine at an idle, but it may have a flat spot at the 6800 rpm.

 

[Rickb1b]

OK I have now determined I have two problems going on.

First, with the hoses from the exhaust valves unblocked the machine runs up to 6800 RPM and will not go any farther. This is the problem I originally wrote about. When I block the hoses I can get it to run up to 8000 RPM. So it is now clear, the solenoid is either sticking or broke. I'll fix this first.

Second, with the hoses blocked the machine will run up to 8000 RPM but has a midrange studder or bog. This is the problem I was thinking may be TPS related.

Once I get the solenoid fixed I'll report back. Who knows the two may be related.

 

[Rickb1b]

OK guys I've been fighting this for about a year now without any luck.

Here's a quick recap:

new pistons/jugs
SLP Pipe, intake, flash
SLP clutch weights/springs

This thing always had a hesitation/bog at around 6.5-7.5K RPM. After the new pistons the bog occurred right at 6,800 RPM. I then plugged the vacuum hoses and the 6,800 RPM bog went away but I still have the hesitation at 6.5-7.5K.

It acted like it was something to do with the throttle, because if I "feathered" the throttle the hesitation would clear and the RPM would come back, then drop off again. Thus, I replaced the TPS and the harness. I built the tool to set the TPS and set it correctly (I assume I did it right because it idles and runs fine, even reverse).

So as I'm troubleshooting this in the garage, I noticed a correlation. Every time the hesitation occurred the exhaust valves were closing. Made me wonder if the valves were closing because of the hesitation or if the valves closing were the cause. If it is the later, could it be the springs are too stiff for the corresponding pressures at the high RPMs.

I don't even know where to start on these springs. I have a 05 800, so I put the springs from it in the 900 to see what would happen; no change. Unfortunately I don't really know what springs are currently in the 900. They are kind of worn and dirty but near as I can tell they are purple.

I would like some opinions on whether I'm chasing a wrong path with the exhaust springs. Also, can someone give me a baseline to start with and I can adjust from there. Is there a "standard" guys are using with the SLP setup? Most of my riding is done at sea level to 3,000 ft.

Thanks.

 

[sno_mo_racer]

Just a thought. If you just put the slp pipe on at the same time I wonder if they might have used the wrong flash for the ECU? Or when installing it maybe one of the injectors weren't put in properly on the engine?

 

[BIGGDAWG]

have you plugged your exhaust valves? removed the lines from the solenoid and then plugged the ports on the valves?

also check your exhaust bellows you may have a pin hole in them. you may want to try this mod that a lot of us have done http://www.snowestonline.com/forum/showthread.php?t=228545

the stock spring is purple one way to test it also is to run with out a spring completely i have heard of a few guys doing that especially if it has slp porting.

 

[Rickb1b]

Yes the exhaust valve lines were completely plugged. Also the bellows were replaced with new ones. Although there was nothing wrong with the old ones, I was just grasping for ideas.

Making a run without the exhaust springs sounds interesting. Anyone know of a down side to trying this.

For my education, should the exhaust valves stay open when at WOT? Mine open and then close at WOT.

 

[BIGGDAWG]

the valves should stay open anytime over 6000 rpm if they are closing that more than likely is your problem and the valve modification will help that.

 

[Boozer]

Rick it sounds like we are having the same problem and I also ride at your elevation most of the time.
If you get something nailed down let me know, I've been fighting this thing since last year also.
Good luck keep me posted