Hi, what can cause the belt to slip in bottom of the clutch, only when I start... I can see a black mark caused by belt slippage at the bottom of the clutch.

Do I need to change my spring tension, weight, Helix and/or spring in secondary to correct that?

I went to change my gearing, I was using 25-40, now I'm using 25-39, for more top speed. That work great, better milleage, better speed... But I just want to correct the clutch slippage and maybe in same time, give me some bottom end.

Thanks for advice...

ok,

there is two possible problems:

belt slip on take off (which i'll explain later ) or the belt is too high in the secondary as the machine sits idle( which i'll explain later)

first,

the engagement phase:the primary will slip a trimendous amount until it engages the belt.

the transition phase: the flyweights have overcome the primary spring tension and clutching begins along the low ratio line but your clutch has not reached full rpm.

the clutching phase: the flyweights have overcome the belt tension from the driven clutch and are generating force to your specified goal rpm and are shifting at your specified rpm.from here on in your rpm should be as straight as a grizzly bears dick,through to top end. if your gearing is too low, you'll expereince over run which means that your primary will over rev and you'll be off of your power curve, your at full speed and not climbing but the rpms are.


now the secondary:

with the sled on a stand,adjust the belt height in the secondary until the track just creeps. this is the primary position for the primary shift curve.what this accomplishes, is that you start your clutch off in a higher gear ratio than possible with the stock set up. instead of a 3:1, you are now 3.1:1.bigger gear better take off. or did i go the wrong way boys?
but you get my drift. actually,it shoud be a 2.9:1

just a thought

uncle neil

Thanks, nice explanation of the problem, but what I want to know, is how to resolve this problem ?

look at the top of your secondary and if you see where it has been shined up by slipping then that will cause it to leave rubber in the primary,if you dont have your belt running as tight as possible with your belt deflection when you go to take off it will engage the primary,if the secondary is not taking up all the slackit will spin on the secondary until the belt starts moving up in the primary,now when all the slack is taken up it will grab in the secondary and start moving the machine,the rubber gets left behind because you are actually starting in a higher gear and is burning the belt,so try and set your belt deflection as tight as possible without creeping and try that

Thanks a lot guys, I'll try it this afternoon, I'll came back to tell you if that work.

Thanks again

Assuming you belt is correct and you HAVE to use that tall gearing (even though it I'd say it's part of the problem) you could tighten the secondary up. Also don't ride slow, do break the track free every time on take off and don't pin it until you feel the secondary "break" open. Sounds dumb I know, but that's what it'll take with that tall gearing.

Hi all, I tightened my belt, put a harder clutch spring, drop Weight from 71 to 70, and it's awsome !!!!

No more belt slippage and the clutch temp is cold when I touch it after a ride.

Now it's snappier than before even with a taller gear ratio... Great setup...

Thanks everyone, it's what I needed to complete my setup...

Hi all, I tightened my belt, put a harder clutch spring, drop Weight from 71 to 70, and it's awsome !!!!

No more belt slippage and the clutch temp is cold when I touch it after a ride.

Now it's snappier than before even with a taller gear ratio... Great setup...

Thanks everyone, it's what I needed to complete my setup...
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How could it possibaly "snappier" with that gear ratio? 1.56
Get it geared down to a 2.00 or more then you will have something to say about being snappy.
What are you engauging at? If its anymore than 4500 + that 1.56 ratio + if you weigh over 200# that is why you are frying the clutches.

It engage at about 4200 and I just weight 135

It engage at about 4200 and I just weight 135
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If only I weighed 135#
Those 2 figures are great but I would still gear down to a high 70's low 80's ratio.
A weaker primary spg. and more flyweight will also give you more belt squeeze.

If only I weighed 135#
Those 2 figures are great but I would still gear down to a high 70's low 80's ratio.
A weaker primary spg. and more flyweight will also give you more belt squeeze.
[/b]

How it work ? high 70 low 80??? How to calculate it ? And, I added more flyweight, better with 71g... But I have to reinstall stock gearing 25-40 because my chain is too long and I got broken adjustement bolt... I have a 74p and a 76p, 76 too long, 74 too short ??? Maybe my 76 is to old... I'll try to remove a tooth of my 76, maybe it will be ok ? Here it's now time to test, lake are great for that in the end of the season, we have more than one month of snowmobiling to do!!!

Hi, what can cause the belt to slip in bottom of the clutch, only when I start... I can see a black mark caused by belt slippage at the bottom of the clutch.

Do I need to change my spring tension, weight, Helix and/or spring in secondary to correct that?

I went to change my gearing, I was using 25-40, now I'm using 25-39, for more top speed. That work great, better milleage, better speed... But I just want to correct the clutch slippage and maybe in same time, give me some bottom end.

Thanks for advice...
[/b]

Hello:
1]Is the black mark you mention on both sheaves or just mostly noticable on one sheave?
If on both sheaves, is there one side that has higher or more black than the other sheave?

2] Has this been revealed since you've changed to a new or other belt?
A test....With your sled off the ground, the engine running, does your track turn like this?
http://www.dootalk.com/forums/index.php?showtopic=48975
...Read comments, then click on the video.

nuther video
http://www.dootalk.net/gallery/albums/album1643/MVI_0957.avi

Hope you can answer questions..
Thank you

Joey