Apex belt issues...

[Modedmach1]

So I have a serious belt eating issue. I rode 80 miles this weekend & broke 3 belts. My setup is a folows:

Blue/Brown/Blue primary
STM weights @ 96grams (most of the weight in mid/tip)
14.5 rollers
45deg helix
Cat Green sec spring @ 90deg
20/40 gears
7 tooth drivers

162x2.6 Powerclaw track

I am running 15lbs of boost.
I never had a belt issue til I put this Cat track on it. I had a 162x2.5CE til mid last season. With the CE & same setup I went thru 2 belts in 2 yrs. Since changing the track I am going thru 1 every other or every ride.

I am at the point that I think it is the gearing. I think it is shifting out, trying to go into overdrive & breaking the belts?? Clutches are cool enough I can hold my hands on them, right after the belt broke. It isn't pulling cords & blowing them up, it is breaking them in half.

Hoping somebody on here can offer some advice. I am thinking of gearing it up to 22/40. Not sure if that is the right thing to do though.

Thanks in advance,

 

[icr]

Have you checked alignment and ctc?

 

[Modedmach1]

Yea, I bought the tools a couple weeks ago cause thats all I could think of. The CtoC is good, the alignment was off just a hair so I fixed that but, it didn't help. Like I said, it is ripping the belts in half, had 30 miles on a brand new one & it just tore it in two. The rest of the belt looked great & no slip marks in the clutches.

 

[up-high]

Check the motor mounts and the jackshaft bolts. Something is moving under load and stretching the belt.

 

[TBird]

I am at the point that I think it is the gearing. I think it is shifting out, trying to go into overdrive & breaking the belts?? Clutches are cool enough I can hold my hands on them, right after the belt broke. It isn't pulling cords & blowing them up, it is breaking them in half.

I am sharing your suspicion.
Slippage causing heat - checked.
Misaligment sure can destroy belts, but usualle pulls threads, cause heat a.s.o.

Have you looked @ speedo?


Sent from my Sanwa M12

 

[icr]

Gearing up is a simple test but Im not sure that's the problem. If all the mounts look good throw a 22 in and see what it does.

Have you done the sharpie test on the primary to see how close its getting to the edge?

 

[Modedmach1]

Its within a 1/8 of the top on the primary & right to the bottom of the secondary.

I have seen 95+ on the speedo climbing.

Thanks.

 

[up-high]

Did you change anything when you put the other tack on? I ran 3" tracks with no problem so a 2.6 isn't tearing belts. And I ran 20/40 gearing in all my turbo sleds.
You are using the 8DN belt right?

 

[icr]

Bottoming out in the secondary will do it. Deflection set properly? Are the bolts within spec?

 

[Modedmach1]

Bottoming out in the secondary will do it. Deflection set properly? Are the bolts within spec?

Yep deflection is spot on. Using a 8DN belt. I was more thinking that the Cat track isn't loading it like the 2.5CE, plus it is about 10 to 15lbs lighter.

I was leaning towards what ICR just mentioned, bottoming the belt out in the secondary.

Thanks for the replies, keep them coming.

 

[Shattered1]

Years ago I had an issue with an RX1 eating belts. I was going through one every 500 miles or so. I checked everything that I could think of and everything seemed to be in order.

Turned out that the clutch side jackshaft bearing needed to be replaced. When you would get on the power, the slop in the bearing would allow the alignment to change. Changed out the bearing and didn't have problems with eating belts anymore. I think the next belt lasted about 3000 miles or so.

 

[icr]

I agree something is moving and allowing the belt to bottom in the secondary. If ctc is correct and doesn't change under load the clutches can't shift enough for the belt to bottom out.

 

[Modedmach1]

Years ago I had an issue with an RX1 eating belts. I was going through one every 500 miles or so. I checked everything that I could think of and everything seemed to be in order.

Turned out that the clutch side jackshaft bearing needed to be replaced. When you would get on the power, the slop in the bearing would allow the alignment to change. Changed out the bearing and didn't have problems with eating belts anymore. I think the next belt lasted about 3000 miles or so.

Put a new bearing in when I changed the track, pulled the seals out of it today. Still full of grease & tight. Won't the primary shift more than the secondary?? I know people have had the secondary machined to get OD out of it.

Thanks,

 

[icr]

It looks like the over drive machining is on the primary sheave and the secondary helix.

http://www.schmidtbrosmotorsports.com/yamaha-primary-clutch-overdrive-machining/

If the primary could shift more than the secondary it would over tension the belt and snap it. That's why they shift the same amount.

 

[icr]

Maybe your secondary isn't shifting as much, you might take it apart and look for anything that could cause it to bind. Metal spur, etc.

Or try swapping secondary clutches with someone.

 

[Shattered1]

I was talking to a friend about this and he said that he had a problem with his boosted Apex eating belts and he couldn't figure out why a few years back.

He said that his bottom chaincase (axle) bearing had gone bad and it was causing binding, thus eating belts. He said that he didn't think it could be his bearings because he had changed all of the drivetrain bearings near the end of the previous season and didn't have many miles on them. But he said that he used aftermarket bearings and suspects that they were inferior and failed quickly. He said that he's paid the extra few bucks for Yamaha bearings ever since.

It may be worth it to check your axle and chaincase side jackshaft bearings if you haven't already.

 

[Givemeaboost]

I run my secondary with a 5/16 washer between the posts and the helix to spread out the secondary giving it a higher gear. You might want to try that.

Ken..........

 

[Modedmach1]

I am still working on it. I blew another belt this weekend but, it shredded it rather than broke it in half. I put a brand new EPI purple spring in, wound it 90deg, made it around 40 miles of hard, on & of throttle climbing in the trees @ +35deg, then the belt came apart. This one may have been on me, I wasn't easy on it but, I think I am gonna go to a 22/40 gearing & see what happens. Cant get any worse...

Might try that washer idea. Hadn't thought of that before.

 

[icr]

To be fair it was belt blowing snow too, I know two xm's that had the same problem.

 

[M5-]

I am still working on it. I blew another belt this weekend but, it shredded it rather than broke it in half. I put a brand new EPI purple spring in, wound it 90deg, made it around 40 miles of hard, on & of throttle climbing in the trees @ +35deg, then the belt came apart. This one may have been on me, I wasn't easy on it but, I think I am gonna go to a 22/40 gearing & see what happens. Cant get any worse...

Might try that washer idea. Hadn't thought of that before.

I never run higher than 19 40 gearing on a turbo sled. You don't need 95 mph track speed. IMO going to 22 40 will be even worse personally I think you should gear it down otherwise its like trying to start a muscle car in third gear. If the new track is eating belts you are loading the clutches and the problem will be even worse gearing it up. Every guy I know who went 174 ended up gearing at 18 40 due to the extra load the track put on the clutches in order to keep belts on the sled. Do a pull then pop your belt cover off and feel which clutch is hotter then you will know where your problem is, primary or secondary. Heat is the enemy doesn't matter where it comes from heat is heat and it kills belts fast. I wind my secondary 0 1 which if I remember is 70 degrees with a Cat green spring.

JMO take it or leave it.

M5