Top end throttle bog/ distortion on a '02 RMK 800?

[Summitstef]

Took the sled out today for its inaugural run with the new top end today. Noticed a little bog on the top end of the throttle but it seemed to clear itself up. After stopping for lunch for about 20 minutes, I noticed the same bog in the top end however, it didn't clear itself up? Its not so much of a bog, more like its not crisp sounding but distorted??
The sled is a 2002 Polaris RMK 800 151", stock pistons, BPR9ES plus (which are a nice milk chocolate brown), Holtzman ATACC, SLP Y Pipe, Pipe, can and larger intake, Stock clutching. Any help would be appreciated. Thanks!

 

[sled_guy]

What revs and what altitude you riding at.

I'm betting you aren't loading it hard enough. With an SLP pipe on it you should be pulling 4 grams or so more in the primary even with the stock secondary.

Could also be too rich although the 800 BB can handle a crazy amount of fuel on the top end without bogging. Maybe the ATACC is richening it too much? I've never tuned one so I don't know.

sled_guy

 

[Andreas83]

What revs and what altitude you riding at.

I'm betting you aren't loading it hard enough. With an SLP pipe on it you should be pulling 4 grams or so more in the primary even with the stock secondary.

Could also be too rich although the 800 BB can handle a crazy amount of fuel on the top end without bogging. Maybe the ATACC is richening it too much? I've never tuned one so I don't know.

sled_guy

You need heavier weights if you are running the stock ones, when I installed a SLP single on my sled it was over reving like crazy. Added a set of MTX 68 grams with a 3gram rivet in the end, works good for my elevation (1000 - 4500 feet.)

 

[theultrarider]

What elevation? And what main jets? Need more info. Sounds lime way fat on the the jets, and not enough weight.

 

[Summitstef]

Elevation was 4000', temperature was around 20 degrees f, and the bog starts at about 6500 to 7500 RPM. Sled is clutched for 4500 to 8000'. Running 390 main jets. Sled ran like a top from the morning till lunch. Stopped for 20 min. and then the issues started...

 

[theultrarider]

6500 rpm is where the powervalves should be opening. Shoulds like you ripped a bellows since it was running well and then changed like it did. Pull the Black plastic cap off of each valve. They should be totally clean on the cap side of the bellows. If one of them is all black and full of oil you just found your issue. Then go ahead and pull them both the rest of the way out and clean them up good while you are that far into it.

 

[whoisthatguy]

My ATACC was toast after 2 seasons. The MFR warned me that they will do that. Or you just may not have calibrated the ATACC correctly, since on a 2nd hand sled, you probably have no idea what base elevation that the blue tube was supposed to be unplugged and replugged in. I think of a bog as having not enough oxygen or too much gas. If you disconnected the blue tube at a higher elevation that you have been doing (assuming you did that), then you may be getting less gas all up and down the rpm range which could eliminate the bog if the ATACC is still functional. You might also change back to stock jetting and seal up the hole in the top of the carb, and see if that makes a difference. The single SLP pipe was also pretty much plug and go for me, except for removing all the hood aluminum heat shield, foam and plastic that was within 6 inches of the pipe. The SLP pipe has no integral heat shield so it sheds a lot of heat and melts things under your hood. Like the belly pan for instance, so be sure and leave heat protection tape on that. The needles also need to be in the #2 position, but that is mid range rpm stuff.

 

[sled_guy]

Check the bellows as ultrarider suggests.

sled_guy

 

[Summitstef]

6500 rpm is where the powervalves should be opening. Shoulds like you ripped a bellows since it was running well and then changed like it did. Pull the Black plastic cap off of each valve. They should be totally clean on the cap side of the bellows. If one of them is all black and full of oil you just found your issue. Then go ahead and pull them both the rest of the way out and clean them up good while you are that far into it.

That's exactly what the issue was! Thanks for the insight ultra rider! Pulled both covers off and sure as sh!t, it was the Mag side that had a small rip in the bellows. Went to the local dealer and replaced the both of the bellows. The thing hauls @$$ and then some now! Thanks again for all the helpful info guys!

 

[theultrarider]

Glad that I could help and that it was a simple fix!