TKI Belt Drive

[Chadly]

Anyone have many miles on one of these? I already have broke one on my turbo after about 20 miles. I don't think the instructions are clear (or I am just a simpleton). Tom has tried to be helpful but I just don't get what the tension should be at because I did what the instructions say and when I sent him a video of the tension he says it is too tight. I figured what I had on the turbo was too loose because twice before it broke it definitely skipped the cogs. About half hour after it skipping on the cogs the second time, I was stopped on a sidehill for a few minutes and then went to take off like normal and bam the belt snapped. I have zero confidence now in the belt drive on my NA 850 and negative confidence on the belt drive on my turbo 850. And anyone who talks about changing these belts in the field is crazy. It is quite task to change a belt especially with the MPI turbo kit on because you have to remove the exhaust to even get to it... Anyhow I was just looking for some pictures or even a YouTube video for reference of what the correct tension looks like on a warmed up belt. One more broken belt and these things are going in the garbage and chain drives are going back on my sleds

 

[BIG JOHN]

300+ miles on mine from last year with turbo
1/2" deflection max (1/4" in 1/4" out)
no issues

 

[treeboy]

Ok I got the c3 belt drive on one of my older big bore sleds with well over 20,000 miles on the belt drive. I’ve only broke two belts on it and those were the gates belts and it was my fault from hard landings under power. Now I’m running the mitsuboshi with now problems, also they are better for heat too, and no blue dust.
The right belt tension is the trick with the belt drive, sounds like your too tight still.

 

[winter brew]

Yep, when it seems too loose, that's when the tension is correct. I have installed many and a few in our group with the bigbores and at least a couple turbo's. Have not seen a failure. They typically do need a couple adjustments as the belt wears in (100-200 miles??), then tension seems to stabilize.

 

[boondocker97]

Not a ski-doo, but know of several on cats (including mine) without any issues. When a new belt goes on I have to re-tension it between 10-20 miles as it gets much loser in those first few miles. Then again at 50-100 miles. It doesn't change after that. I run 3/8" deflection (cold) from the back flat part of the belt at rest to pushing it in with my finger with light pressure. When everything is warmed up the belt is just tight. Not fiddle-string by any means but it's not loose anymore. This is using the Gates belts Tom supplies.

If you're sure the cogs skipped, I wonder if you started on the loose side with your tension when the belt was new, then it got too loose when it did it's initial early mile stretching and skipped?

 

[Chadly]

Well that is why I am confused that if it was too tight how and why did it skip? It definitely wasn't the track ratcheting. It was a sound I have never heard before and it sounded like that belt slipping on the cogs. So does the belt stretch out after more miles or does it continue to shrink with more heat and miles?

 

[Chadly]

Yep, when it seems too loose, that's when the tension is correct. I have installed many and a few in our group with the bigbores and at least a couple turbo's. Have not seen a failure. They typically do need a couple adjustments as the belt wears in (100-200 miles??), then tension seems to stabilize.

I guess we need to go riding Paul so you can set the tension on my belt drives and you can test out my MPI turbo 850

 

[Wheel House Motorsports]

The only ones I have ever seen break were always too tight. They do seem a little loose when they are sitting cold but like others said, thats right where you want it.

 

[boondocker97]

Well that is why I am confused that if it was too tight how and why did it skip? It definitely wasn't the track ratcheting. It was a sound I have never heard before and it sounded like that belt slipping on the cogs. So does the belt stretch out after more miles or does it continue to shrink with more heat and miles?

The belt only stretches/loses its blue break-in coating (both make the belt looser) in the first 100 miles or so on a Cat. G6 belt is really long so might take longer/more revolutions to fully break in. The belt doesn't actually shrink with heat per say. The large aluminum lower pulley expands slightly with an increase in temperature. Not a lot, but ever so slightly. On the Cats the big change comes from the magnesium chain case back plate expanding with heat from the cooler and under hood heat buildup. With the little bit of research I did magnesium has a much larger heat expansion coefficient than aluminum. Like 17 times greater. Some quick math using 18" center to center distance between top and bottom shafts showed that theoretically the belt length between cold and hot conditions was almost 1/16". Doesn't seem like much but that translates into a huge change in tension. Pretty sure this is a lot of the reason some Cats have problems with auto tensioners in their chain cases. One extra click when it's cold spells bad news when it warms up. So if the summits are using a magnesium chain case it's going to be the same deal.

 

[Summit74]

Running the Mitsuboshi belt and MVM drive. I haven’t measured it, but I bet I can push the belt almost an inch. No breakage. Not running a turbo though either.

 

[die hard poo]

I just installed a TKI kit on my sled, only put a few miles down the road on it. I have heard that running them too tight can break the belts. So Id say if TKI says its too loose, maybe try running it a bit more loose than you had before? I set it to the ~1/4" deflection when cold. We shall see.

 

[SeanMSullivan84]

I've got 1200 miles on my xm running an 8lb boost turbo. Still on the original belt. The deflection when cold is 3/8 with a very soft push of the finger. I've had great luck with toms kit.

On a side note though... How is your mpi 850 running?? I can't seem to find much info about actually users running them and their reviews. I really want to turbo my 850.


Sent from my iPhone using Tapatalk

 

[winter brew]

I guess we need to go riding Paul so you can set the tension on my belt drives and you can test out my MPI turbo 850

Soon! And yes, would like to take a spin on your sled.
Maybe track ratchet was what your heard??? Too much power.

 

[PaulAnd]

Yep^^


Sent from my iPhone using Tapatalk

 

[nuttyn01]

TKI Belt drive

I ran the belt drive on my 15 and 16 XM's with aerocharger and my G4 last year with MPI turbo....no issues. I would guess you were hearing track ratchet. I had to go band saw tight to keep it from ratcheting on the G4.