Primary getting hot

[greencat900]

I have an 04 900 efi. Last year sled ran perfect. During off season I changed tracks from a 151 x 2 to a 153 x 2.5 I have been out twice this year and it seems like something is wrong in the clutching area. The first ride a burned up a belt and when I finally smelled I checked the clutches and the primary was super hot. This happened when I was in 2-3 ft of powder.

I put on a new belt but it was only for the trail ride home. It seemed fine on the trail.

Second ride out it seemed like the belt was slipping whenever i got into the powder. The primary did get a little warmer than usual but I was checking it often to prevent losing another belt.

The sled has 1150 miles and motor is stock except I will be putting on an rkt 14.8/1 head. I plan on taking the primary apart to check for wear on the weights. I am thinking I should replace the spring but don't know if I should go with the same one. I mainly ride 8,500 - 10,500 ft.

Any suggestions would be appreciated as I am new to the whole clutching thing. Any ideas on why my primary is getting hot when in the deep stuff?

 

[Idcatman1]

Your clutch gets hot because the engine is having to work harder plowing around in powder than it does running down the trail. The track with taller paddles also puts more load on the belt, so more slippage there too. Slippage causes heat which adds to the stress on the belt and will cause it to come apart eventually. Most stock 900 clutching setups I have seen have a fairly high engagement which also creates more slippage and heat playing in the powder. Most people on here would probably think my clutching ideas are stupid but I have good luck with a soft spring for a low engagement and lighter weights to get the peak rpm back up.

Just my $.02 worth

 

[diggerdown]

Might sound dumb, but you did change drivers when you changed the track didn't you? I don't even know if it would be usable, but if it would turn you would sure be overloading your drive system!

 

[Idcatman1]

Great point, I didn't even think of that. The stock 151 track is 2.52" pitch, the 153 is 3". I would think you'd be lucky to get it out of the garage with the wrong drivers before things bind up.

 

[greencat900]

I did change drivers to go to the new track. I am running stock 3.0" pitch extroverts from an 05 king. The stock were 2.52" pitch. I believe stock are 10 tooth and the kings are 9 tooth but that is just going off memory.

diggerdown - what are you refering to when you say you don't know if it would be usable?

Idcatman1 what spring and weights do you recommend as a starting point?

Should I be looking at changing the gearing also?

 

[diggerdown]

I was referring to the difference in driver pitch and the effects it would have had if you had not changed them out. You could have enough extra pull in the powder that you will need to put a torque rod on the engine. I did this to my king and it was a noticeable improvement in keeping the clutches lined up. I had a bolt break on the torque rod mount one day while riding and I knew something was not right in the way the sled was performing. I made on out of a old heim joint and steering rod.
19/41 gearing, 65gr. weights with a spring around 118/285 and a R/Win the driven with a 49* helix would be a good place to start.
Idacatman1 probably has better ideas, but these are mine.

 

[Idcatman1]

diggerdown is right about the torque link, makes a big difference in keeping the clutches lined up right and decreasing belt slip. I have also made one with a heim joint and a piece of small angle iron. You want it to pull the clutch side of the front motor mount snug so that the engine can't pull toward the driven clutch under load. There are several aftermarket companies that make them also if you don't have the tools to make one. I am running 18 to 40 gearing, a lot of guys go even lower, 18 to 43 or 44. The weights and cam sound about right. I am running a big bore so the I need heavier weights. I also run a spring that is softer and believe that if you get the jetting right, which isn't an issue with your EFI, that you don't need the lower gearing.