Lots of testing and believe we have the offset nailed down

[Thunder Products]

With all the tuned Sidewinders (belt blowers) coming into the shop, we needed to do some intensive testing as these "belt blowers" need to be a thing of the past. Using a precision ground bar and depth mic, I started to really get down to the nitty-gritty on this issue.

Belt blower #1 (2020 SW LTX studded track)
3 belts in 115miles. Nothing but heat from belt and clutches. Offset was 61.2mm with 1 shim. 300 TD tuned with Daltons.
After machining 3.5mm off of the back of the secondary, with 1mm shim and the circlip, the offset now was 58.7mm.
After numerous back to back runs, basically riding the sled like an a$$hole (owners own words), the belt showed a little "chipping" on the top cogs, one side only. But, no blown belts and this was 150-200 miles.
Took out the shim and butted up against the circlip, the dimension is 57.7mm and no issues. The owner is happy and has well over 500 miles on his belt as of last week.

Belt blower #2 (2017 SW RTX non-studded track)
3 blown belts on 1 ride, puppied the sled back to the trailer with an old Yamaha 8DN. Offset was 60.9mm. Precision EFI 280 tune and Thunder Products Clutching. Got a call saying he's dropping of the sled at my shop and wanted it just like Belt blower #1.
Machined 3mm off his secondary, offset is now 57.8mm and after a good weekend, no more belt issues.

Belt Blower #3 (2017 SW BTX with 153" 2.5 track)
Usually not a belt blower, but could blow a belt on command when full throttle. Offset was 59.9mm...no shim and against circlip.
TD tuned, with all the tunes including race tunes.
Machined 3mm off of the secondary and with a thin shim, the dimension is 57.8mm with 1 shim. No issues so far.

Belt blower #4 (2019 SW tuned with RCMP?)
Blew belts on command. Clutches always hot and not happy with clutching setup. Installed Thunder Products Clutching Big-V setup and did some offset checking, he is now "catwalking" his sled down fields he could never do before.

3 more sleds in the works at the shop.... 2 of them with Hurricane bundles running 300 horse and 1 Precision EFI 280 that were set between 57.5-58.0mm. Will be updating this thread when we have more info.

P.S. there are so many more out there that we have told to run this offset and know of a few that have been able to hold it wide open for long periods of time without blowing belts.

Post here is it is working for you

 

[TPAY243]

Thunder Products are all of these machines running your recommended clutching and did you guys check any off the stub shafts for movement. Great post keep up the good work.

 

[Thunder Products]

Thunder Products are all of these machines running your recommended clutching and did you guys check any off the stub shafts for movement. Great post keep up the good work.

No, these SW's are a mix of tunes and clutching.

Belt blower #1 as mentioned has Dalton's

Belt blower #3 has had different clutching, but now Thunder Products Clutching

2 of the Belt blowers currently being worked on have Stingray's mod kit and STM's

Will post results soon as they are getting miles put on this week and weekend

 

[justinator]

My offset with yamaha primary was right there at 57.7mm all of last winter running xs825 belt and logged 2300 miles on max spool16 with zero belt issues. That was everything from casual trail riding, off trail riding and extended wide open throttle runs. I am now running the tapp clutch and wasnt sure if offset should be the same but after speaking with them at powderlites they said the clutch was assembled to use the exact offset that we were using with yamaha primary with success.....so that is where I shall leave it. I blew an 8JP on eco trail with 300 miles and it had almost no abuse on it before getting the offset reduced.

 

[JerryBones]

I'm having some issues with hot secondary and belt temps, too hot to hold onto for any period of time. I have never blown a belt, 3800 miles on stock 8jp and offset was at 61 ish. This year i went to the hurricane 240 ss tune, with bov and map sensor, put in QAY-70's and a new XS825 belt, updated Dalton B/O wrapped at 6-2. I finally got to test this set up last weekend and did some WO pulls to check on RPM's. I'm running these weights with just the 1/8" set screw and still only seeing it touch 8800 and then it holds at 8600. Primary clutch i can hold all day long, but the secondary and belt are too hot to keep my hand on for any amount of time. I was expecting to have to load up these weights to keep it off the rev limiter, but looks like i'll have to run them empty to get the RPM i need to be at. is the B/O too much spring for the 240 tune? or do i need to wrap it tighter to 6-3 to prevent it from slipping? I had to remove the washer and the circlip behind the secondary to get offset to 57.88, and now i'm using an OSP belt adjuster to keep deflection in check. With my stock setup i never had hot clutches even with the offset out by that much. Stock primary spring is not broken, does have some paint wore off on the sides of the coils perhaps its binding slightly?

 

[fatchance]

JerryBones.......
Definitely slipping in the secondary. Any marking?
The XS825 belt runs hotter IMO.
B/O spring is not too much spring for the H240SS tune. I had to go to heavy Cat springs to keep the heat down
What do those weights weigh now? Not familiar with the Dalton weights
3800 miles on an 8JP is pretty darn good. why change the offset? If it works stick with it and change as needed

 

[STAIN]

I WOULD WRAP THAT SPRING TO 6-3 AND TRY AGAIN

 

[JerryBones]

JerryBones.......
Definitely slipping in the secondary. Any marking?
The XS825 belt runs hotter IMO.
B/O spring is not too much spring for the H240SS tune. I had to go to heavy Cat springs to keep the heat down
What do those weights weigh now? Not familiar with the Dalton weights
3800 miles on an 8JP is pretty darn good. why change the offset? If it works stick with it and change as needed

no markings, i did take it a part and clean everything last night but nothing worth noting. The QAY 70's are 70g empty so i would imagine i'm around 71. I just expected to be able to pull more weight than this based off the info i read on here. I was told when i tuned it that the offset had to be between 57-59 so that's why i changed it. I guess I just didn't want to risk blowing a belt and causing excessive damage so i figured it was better to be proactive about it. Don't get me wrong the sled works great I am just concerned about the heat in the secondary, If it's slipping should I wrap it tighter? 6-3? Are the issues even related? would the belt slipping in the secondary cost me some RPM or am i looking at 2 different issues.

 

[JerryBones]

I WOULD WRAP THAT SPRING TO 6-3 AND TRY AGAIN

that's what i'll do then. Thanks Stain!

 

[fatchance]

Don't fixate on a weight because everybody's set up is a little different. Take Stains advice and wrap it tighter and see where you are at. If it's not slipping in the primary at that point and it's still hot in the secondary, you might want to adjust offset.

 

[2004yamahaviper]

Jerrybones I am running xs 825 with stock muffler hurricane ss tunes as well. 225/240/270. Bov, 3 bar. Dalton qay 70s. I tried the dalton black/orange at 6/1 and 6/2 I think it is to much for that belt at 240. I had way to much belt heat and found it worked better and cooler with less spring. With the qay 70s empty it was only pulling 8700ish on the 240. I would try with your stock spring. I'm running a yamaha white at 3-3 my rpm is up a smidge and my clutches are way cooler even on the 270 tune. 2000 km on this set up now no blown belts.

 

[JerryBones]

Jerrybones I am running xs 825 with stock muffler hurricane ss tunes as well. 225/240/270. Bov, 3 bar. Dalton qay 70s. I tried the dalton black/orange at 6/1 and 6/2 I think it is to much for that belt at 240. I had way to much belt heat and found it worked better and cooler with less spring. With the qay 70s empty it was only pulling 8700ish on the 240. I would try with your stock spring. I'm running a yamaha white at 3-3 my rpm is up a smidge and my clutches are way cooler even on the 270 tune. 2000 km on this set up now no blown belts.

2004yamahaviper thanks man, sounds like you had the identical set up as me with the same results. I'm assuming you are running with the stock 35 helix as well? I'll give the stock spring a try at 3-3 as well and compare. I appreciate this info, I really wanted to up it to the 270 but not until i can resolve the secondary heat issues.

 

[fatchance]

2004yamahaviper thanks man, sounds like you had the identical set up as me with the same results. I'm assuming you are running with the stock 35 helix as well? I'll give the stock spring a try at 3-3 as well and compare. I appreciate this info, I really wanted to up it to the 270 but not until i can resolve the secondary heat issues.

JB just make 1 small adjustment at a time so you don't get lost. And remember there are many more variables from sled to sled....track, studs, exhaust, helix, springs, driver weight and the list goes on.

 

[SidewinderConvert]

I am another one of the ones with a former belt blower. At 59mm offset I could blow a belt in 1/2 mile every time. After setting to ~57.8mm offset the sled did 3 back to back 1 mile pulls at the end of the weekend without blowing the belt (Clutches were definitely hot at the end of that though).

In order to get the offset right I had to pull the stub shaft and press it back into position then run the secondary without shims or cir-clip right against the bearing. I will be sending my secondary in to be machined this off season so I don't need to re-do the stub shaft if I do blow another belt.

Huge thanks to Mr. Sled for his help on the stub shaft!

 

[MrSled]

I am another one of the ones with a former belt blower. At 59mm offset I could blow a belt in 1/2 mile every time. After setting to ~57.8mm offset the sled did 3 back to back 1 mile pulls at the end of the weekend without blowing the belt (Clutches were definitely hot at the end of that though).

In order to get the offset right I had to pull the stub shaft and press it back into position then run the secondary without shims or cir-clip right against the bearing. I will be sending my secondary in to be machined this off season so I don't need to re-do the stub shaft if I do blow another belt.

Huge thanks to Mr. Sled for his help on the stub shaft!

Glad I had an open spot in the shop to get your sled back together and it all worked out that you could actually enjoy your winder for the weekend!!