Belt issues

[poor farmer/logger]

Hey everyone been having a little more then usual trouble with belts on my nytro this winter. Used to get 2,000 Kms on a belt without much trouble. Now on this last one I'm down to 1100 Kms. Went through two this winter. Other one had about 1600 Kms on it. (Had been installed the previous winter)

When the first one went this winter I went through and did some checking. I set the clutch offset to about 15.8mm. I also put new Ramps in on the secondary and a new spring. Bushings were good yet.

When I took the belt off yesterday I noticed the fixed sheave on the primary was hotter then the rest. It's also always the inside of the belt that the cords start to separate on. I've never actually had a belt blow up but the cords always start to come out.

Conditions have been heavy going the last month now as we've had a lot of powder snow. Most of my riding is off trail. Sled is completely stock except for the 1.75" backcountry track. I know I should drop down a couple teeth on the gears but haven't done that yet. I'm sure that would help some with belt life.

Any advice on what to look for and check is appreciated.



Thanks.

 

[SaskAttack]

Lots of Km's on sled, is c to c still good?

 

[74Nitro]

Hey everyone been having a little more then usual trouble with belts on my nytro this winter. Used to get 2,000 Kms on a belt without much trouble. Now on this last one I'm down to 1100 Kms. Went through two this winter. Other one had about 1600 Kms on it. (Had been installed the previous winter)

When the first one went this winter I went through and did some checking. I set the clutch offset to about 15.8mm. I also put new Ramps in on the secondary and a new spring. Bushings were good yet.

When I took the belt off yesterday I noticed the fixed sheave on the primary was hotter then the rest. It's also always the inside of the belt that the cords start to separate on. I've never actually had a belt blow up but the cords always start to come out.

Conditions have been heavy going the last month now as we've had a lot of powder snow. Most of my riding is off trail. Sled is completely stock except for the 1.75" backcountry track. I know I should drop down a couple teeth on the gears but haven't done that yet. I'm sure that would help some with belt life.

Any advice on what to look for and check is appreciated.



Thanks.

Put a straight edge up against both surfaces of the primary sheave, make sure they are not worn.

 

[poor farmer/logger]

There is 9600 Kms on it now. Haven't checked c to c yet. I'll have to do a little digging and see if I can find the spec. I don't think it shows it in the service manual. If it does I haven't seen it yet anyways.

There is a slight groove near the bottom of the primary on the fixed sheave where the belt sits at idle. Last belt was set up with proper deflection as I had just gone through the secondary.

Thanks

 

[SaskAttack]

If I am reading sm correctly, page 9-10 it has offset at 13.5 to16.5 and sheave distance at 267-270. My thinking is that over time something has changed with your clutches, maybe twist on frame or engine settled back. Good call on grooved sheaves as 8DN is known to be a hard belt, especially if one cruises at set speeds a lot.

 

[74Nitro]

There is 9600 Kms on it now. Haven't checked c to c yet. I'll have to do a little digging and see if I can find the spec. I don't think it shows it in the service manual. If it does I haven't seen it yet anyways.

There is a slight groove near the bottom of the primary on the fixed sheave where the belt sits at idle. Last belt was set up with proper deflection as I had just gone through the secondary.

Thanks

Don't worry about the little groove at bottom. I've had a few very bad belt eaters come through my shop over the years. When they start eating belts fast, it's because the sheaves on the primary are worn about half way up, usually 2-4mm.

 

[poor farmer/logger]

Thanks everyone I did a crude measurement and tried to establish a good centre to centre measurement. I measured outside diameters of the stub shaft and secondary shaft then measured outside to outside distance and subtracted half of each diameter. It came out to 266.8mm. That was before I read these comments so no cheating was envolved lol. Primary spring length is 91mm.

There's no flat spots on the rollers or on the weights. Bushing has very minimal play on it on the cap. I put a straight edge on both side of the primary and aside from the groove at the bottom they're still relatively true.

My subframe is tweaked a little. You can see the centre hole on the bottom is not flat any more. I caught a barbed wire fence that was laying on the ground on the one side this winter and I think that's what bent it. Wasn't going very fast thankfully but I could feel it pull the left side fairly hard.

Thanks for the help.

 

[poor farmer/logger]

Well I put the clutches back together and did a extra cleaning of them on the sled. Used a scotchbrite pad and hot soapy water followed by another scotchbrite pad with just hot water. Never done it this way and was pretty impressed at how clean they can out. Had always used brake clean and paper towel before but I'm a believer now lol. Might help them grab a little better. Going to check alignment again after everything's torqued back in and the new belt is on.

 

[herndonp]

Hot soapy water and scotchbrite and a good rinse with warm water is the way to go. Don't use break clean or any other chemical as the aluminum absorbs those chemicals. Some guys run them thru the dishwasher. I just take them both apart and submerge them in the soapy water and scrub away and blow them dry with compressed air before reassembly. Scrub new belts with soapy water or simple green and scotchbrite to get belt release agent from manufacturing off them and let dry overnight. I typically get 1500-2000 miles out of a belt and clean everything annually!!

Pete

 

[poor farmer/logger]

I've used brake cleaner for years but the scotchbrite and warm soapy water gives a far superior result. Easy to do too. Just run the engine for a bit with the belt off. I ran over it again going up and down with a clean pad and worked my way around the clutch. I cheated a little on the secondary. I took my half inch Milwaukee drill and put a 1/2" socket adapter in the chuck. Put a socket on and spun the jackshaft. Took a little bit of effort to hold the drill but it sure was quicker and easier then trying to run around it and turning it by hand.

 

[Hooray!]

Blowing through belts sounds like more than clean clutch plates... Did you go through the service manual clutch maintenance and alignment section? I noticed the height the belt should sit it also only a few mm from in spec to out, worn out or not even if looks good, this surprised me. Suggest running though it step by step and then at least you have a baseline to troubleshoot from... The cleaning suggestion is good too. I like the drill idea!

 

[poor farmer/logger]

I went through the centre to centre measurement and reset belt deflection again when I put the new belt on. Last belt was siting just below the secondary. Think the book says .5 mm below to 1.5 mm above. Siting st about .5 mm above right now with the new belt on. I didn't check the offset again after resetting the belt deflection but before it was at 15.8mm. Took out the 1mm shims so that likely brought it back down some more on the offset numbers. Heading out for a bigger ride tomorrow so hopefully all goes well. Shooting for around 150 miles. Haven't had a chance to break the new belt in yet so I'll just take it easy for the first half a hour or so.

Drill worked good as it didn't loosen the bolt off at all. Made it a little easier anyway.

 

[Hooray!]

Let me check the manual again, did you put the straight edge along the primary and confirm in line with secondary so no twist being put on belt across the "pulleys"? I can't believe you are tearing through belts in 100 miles without a major misalignment vertically or horizontally or worn plates. If you put a straight edge on plates, do you see a wear indentation? I have a slight one low down which is common where the belt sits at idle but otherwise mine is good and flat. I have been far from easy on my belt, hard on and off throttle and have over 1200 miles on mine this season with no visible signs of wear even on the edges. Do you have pics? Would be good to figure out as we all could be exposed to the same thing at some point.

I do like your drill idea... : ) good luck tomorrow.

 

[Hooray!]

Just went back through the service manual, pic attached is what I was thinking. Surprised it can be off by as much as they suggest. I assume you have read each page and adjustment 10x already... Baffling. What rpm does your clutch engage at and what is your top mph?

 

[poor farmer/logger]

3-3400 rpm, it's hard to get a exact number while you're watching everything. Kind of miss the needle style tach in a way. Seems easier to watch. Less fidgety anyways. I've been through the manual fairly thoroughly, only othrt thing possible left is a error in measurements. Checked everything multiple times but with a flimsy straight edge it is a little difficult to get the exact same measurements from front to back of the secondary. I'll get through this winter ok with it anyways. Probably wont put on more then another 3-400 kms. With some luck I'll have something different to ride next winter anyways. I've had my nytro now for 6 seasons and I wouldn't mind to have something different again. I know this is a bit sacrilegious but winters been around long enough it can start to melt any time now lol.