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Knock Light

DeBo

Pro
Joined
Mar 30, 2019
Messages
195
Age
41
Location
NH
Country
USA
Snowmobile
Sidewinder
So I have about 300 miles on my Hurricane tune. Have the 225/240/270.

First few tries on the 225 and 240 went well. 270 had the knock at the beginning. I assumed fuel quality. I run 91 octane.

Starting yesterday I had knock on 240 and today 225. Same 91 octane. I'm lost. Must have a boost leak somewhere?

Thought this would have gone smoother. Any help appreciated
 

It can be a lot of things...

Track too loose, clutch rattle, any rattle on the chassis, poor fuel quality, boost leaks, RPM too low, fuel starvation. and I'm sure a few more things I'm missing.
 
Thanks Knapp. Wow now I'm overwhelmed lol.

I'll check the track. How much sag is needed? Have 144 picks. Why the track?

I'm assuming I'm losing power when it goes off?

Clutch Rattle? What am I looking for?

I dont think it's fuel now but did fill up at a different place today to try.

I've seen 114 on the speedo two weekends ago and now 112. Conditions are the same
 
You should be able to see what the boost pressure is at for the 270? I would add a good Octane boost to the fuel, just to see if its the fuel. Then, I would first start by tightening clamps. Whatever you do, don't stay in it long when the light comes on, just in case the fuel is bad. Run the track to spec as to what the manual says, even a tick tighter. I believe it is 2" from the bottom of the slider @20lbs. Use a fish scale.
 
SOME have had knock from certain stud patterns and or the track. Causing false knock.. Not super common but possible.
IMO I would start with boost leaks.. Do you have a boost leak tester? Also a lot/including Hurricane found the leaks around the throttle bodies boots on top and bottom to be cause.
Stock fuel pump is suspect on the bigger tunes.. ESPECIALLY under 1/4 tank of gas..
Maybe a quick can of octane boost to eliminate fuel?
 
I dont have a tester. Where can you buy one?

Heading out with the kids and snoscoots now. Will pull in garage later. Want to figure this out.

I'll check those clamps. Any pics of them would be greatly appreciated.

I'll check the local dealer for octane boost as well.

Plug and play would be nice lol
 
I dont have a tester. Where can you buy one?

Heading out with the kids and snoscoots now. Will pull in garage later. Want to figure this out.

I'll check those clamps. Any pics of them would be greatly appreciated.

I'll check the local dealer for octane boost as well.

Plug and play would be nice lol
Most make their own testers. Run a can of octane boost through and see. Klotz, Torco, Lucas, etc.
Then look for leaks/tighten clamps. Careful not to over tighten clamps.
If you can see your boost levels take note where they are on each tune..
Good luck. Don't let it eat you up, its probably a boost leak OR bad gas. Very fixable
 
Well put some klutz in. Cleared all knock lights up.

Bad news: pulled 114 two weekends ago and now pulling 103. Racing going on at the lake in northern NH this weekend.

I just lost to an old mach z 1000, (2) f7, and two arctic cat 800s. Couldn't catch them in a quarter mile. Something is wrong
 
Well put some klutz in. Cleared all knock lights up.

Bad news: pulled 114 two weekends ago and now pulling 103. Racing going on at the lake in northern NH this weekend.

I just lost to an old mach z 1000, (2) f7, and two arctic cat 800s. Couldn't catch them in a quarter mile. Something is wrong
Well for sure something is wrong.. That's a pretty big drop. Are you still running the ROV? Many possibilities. How's the clutching look? Like the belt and the sheaves on both clutches? You temp check them after hard pulls?
Going to have to list a lot more info then what you gave..
 
Sorry rov?

I'm going to look in a minute. I'm not happy.

Sled is
 
What's ROV?

Belt is fine. 1200 miles on it looks good. Do dust debris. Don't like how it sits below the sheave but it's been that way since day one
 
Sorry maybe secondary. Sits below top. Used to it being at least a 1/16 above but again been this way since the beginning
 
Yea never did anything with that. Only upgraded blow off valve
 
Okay so your running Hurricane buddle? What year is the sled? what's the clutching? studded, track? . 137" ?. Going to have to list tons of details to get any feedback. Not being rude but understand coming on and saying you got beat in a race and loosing speed is not going to get you much. Make sense? Reason I mention ROV is because on the newer sleds the ROV/air routing allows oily moisture to dump into airbox and then it drips down onto clutches..
 


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