Sled seems to be down on rpms

[ullose272]

Seems as tho my sled doesnt pull the rpms it used to earlier in season and last year. Used to pull 8350-8450 all the time but this last weekend it would only pull about 8000 consistently. Would spike up to 8300ish every once in a while but on pulls it would only settle in at about 8000. I wonder if my top end is starting to go? It seems to run ok, doesnt feel like it has the grunt it used to have. Anyone else noticing this? Mods are slp pipe, epi 68g belly buster weights, carls helix, gates carbon belt, geared down with pro qd pulleys. I have a set of 10-66s i could throw in. Ideas?

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[d8grandpa]

How many miles on your belt, this is issue with worn belt.

 

[Cinno]

Seems as tho my sled doesnt pull the rpms it used to earlier in season and last year. Used to pull 8350-8450 all the time but this last weekend it would only pull about 8000 consistently. Would spike up to 8300ish every once in a while but on pulls it would only settle in at about 8000. I wonder if my top end is starting to go? It seems to run ok, doesnt feel like it has the grunt it used to have. Anyone else noticing this? Mods are slp pipe, epi 68g belly buster weights, carls helix, gates carbon belt, geared down with pro qd pulleys. I have a set of 10-66s i could throw in. Ideas?

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I replace my primary spring seasonally (mid season)now as I have broken it two times in the last three years of riding. Never know when it going to go. A sacked out primary will have the effect your seeing.

Cinno

 

[Jaynelson]

Most likely something wearing in the clutch/belt department. OR just warmer temps and heavier snow perhaps? That'll do it every time

 

[ullose272]

How many miles on your belt, this is issue with worn belt.

150-200

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[ullose272]

Most likely something wearing in the clutch/belt department. OR just warmer temps and heavier snow perhaps? That'll do it every time

Same temps snow is light and fluffy with good base.

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[ullose272]

I replace my primary spring seasonally (mid season)now as I have broken it two times in the last three years of riding. Never know when it going to go. A sacked out primary will have the effect your seeing.

Cinno

This is a possibility. Its the spring that came with it.

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[Killer Time Racing]

This is a possibility. Its the spring that came with it.

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Run it in Non Ethanol mode and see if it goes away , mine seems to be real fat ..

I change it to Non when playing and when I want to show the 850 the Back door I put it in Eth mode and pin it till I see no more Ski-Donkey

 

[G-Force]

Run it in Non Ethanol mode and see if it goes away , mine seems to be real fat ..

I change it to Non when playing and when I want to show the 850 the Back door I put it in Eth mode and pin it till I see no more Ski-Donkey

Really? I've had a 12, 13, 15, and now 16, (what happened in 14 I wonder? lol ) and have yet to see any difference at all when swapping modes on any of them...

 

[06redrevx]

How long has it been since you cleaned/checked your exhaust valves?

 

[AdrenalineAddict]

This is pretty normal at about the 700 to 900 mile mark. Combination of slightly sacked out primary spring, slight wear where the spring sits in the cover and spider, broken in secondary spring, worn motor mounts giving you long belt syndrome, some ring wear and flaking, maybe your belt has worn .004" to .005" thinner and possibly stretched a bit. I've found that new motor mounts are worth 100 to 150 r's by pulling the motor back to it's original position. Warm +30 degree air temp is always good for about a 100 rpm drop. Check your grafoil seal at the y-pipe, they are generally real thin or have the graphite blown out of them at about 1,500 miles causing you to lose the backpressure pulse your pipe was designed for. 66's should get you back on track or freshen up all the above.

 

[ak]

Clean power valves report back I bet that's what it is, do a compression test just for the hell of it.


Had the same problem on my 600, 824 miles and power valves were starting to stick. Wouldn't pull over 8,000 rpm cleaned valves and runs great again. I run ves gold oil.

 

[ullose272]

Clean power valves report back I bet that's what it is, do a compression test just for the hell of it.


Had the same problem on my 600, 824 miles and power valves were starting to stick. Wouldn't pull over 8,000 rpm cleaned valves and runs great again. I run ves gold oil.

ill check them, I haven't cleaned them, I haven't really want to mess with them mostly because it looks like a pain with the new valves. I run redline oil if it matters. ill do a compression test and report back

 

[ullose272]

both cylinders were 120, but engine was cold didn't really want to smoke up my shop. guess ill be pulling the exhaust valves

 

[SRXSRULE]

How many miles are on it now? Eric

 

[ullose272]

900ish

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[Cinno]

Really? I've had a 12, 13, 15, and now 16, (what happened in 14 I wonder? lol ) and have yet to see any difference at all when swapping modes on any of them...

The ethmode change is subtle. If you drag race another sled side by side and change from eth to noneth you will notice about one/two sled lengths faster in non-eth mode in a 0-60 mph drag race. I've done it from standing still and rolling start and got the same results.

Cinno

 

[Killer Time Racing]

In Eth mode mine gets the Rich Burble when your off and on the throttle , in Non it's crisp and Fickable

 

[ullose272]

In Eth mode mine gets the Rich Burble when your off and on the throttle , in Non it's crisp and Fickable

What fuel you running?

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[cateye5312]

This is a possibility. Its the spring that came with it.

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There are lots of reasons for loss of rpm as mentioned in this thread but the weak spring is missed by most - even my dealer missed it because in the shop or on the bench the spring looked and worked fine. It was only under load that it wouldn't hold r's. We finally swapped springs and hey! - Presto! 500 - 600 rpm gain.

Before changing the primary spring the sled would jump out to 7,500 to 7,700 rpms and then slowly sag down to 7,000 in deep powder. Now it holds 8,100 like it should (its a 6)