Anyone tried the Powerbloc 80 primary clutch?

[Redbeard]

On my Viper I run PB80 with Tp orange set at 3-2 and like it. Did you notice some heat on the secondary?

I didn't notice any excessive heat on the secondary.

I like the performance feel of the orange spring, but I ended up switching back to the stock pink spring for my backpack trip.

 

[sledjunk]

I have PB-80's on all three of my Vectors and they work very well. They are easily tunable by adding or removing weights in the pucks used to activate the clutch.

Only one caveat, though. The stock bolt to hold the primary in place is 12.5mm x 1.25. It is definitely an odd size. However, CV-Tech ships a 1/2 x 20 bolt with the clutch. After many emails back and forth, they finally shipped modified Yamaha bolts to me.

1/2 -20 converts mathematically to 12.5 x 1.27.

Pitch of 1.25 converts to 20.32 TPI.

The stock bolt needs to have the shoulder near the head machined flush with the shaft of the bolt. I would not trust the SAE bolt as the difference in thread pitch will throw off the torque when mounting the clutch. This is probably the one bolt that can be disastrous if the torque is not right and the clutch comes loose.

I can provide a PB-80 manual in pdf format, if anyone is interested.

 

[Redbeard]

I have PB-80's on all three of my Vectors and they work very well. They are easily tunable by adding or removing weights in the pucks used to activate the clutch.

Only one caveat, though. The stock bolt to hold the primary in place is 12.5mm x 1.25. It is definitely an odd size. However, CV-Tech ships a 1/2 x 20 bolt with the clutch. After many emails back and forth, they finally shipped modified Yamaha bolts to me.

1/2 -20 converts mathematically to 12.5 x 1.27.

Pitch of 1.25 converts to 20.32 TPI.

The stock bolt needs to have the shoulder near the head machined flush with the shaft of the bolt. I would not trust the SAE bolt as the difference in thread pitch will throw off the torque when mounting the clutch. This is probably the one bolt that can be disastrous if the torque is not right and the clutch comes loose.

I can provide a PB-80 manual in pdf format, if anyone is interested.

I have PB 80's on both my Apex and Vector. They work well and I'd buy them again! The gentleman that that I dealt with could not have been more helpful and I'll recommend him to anyone that asks!

The stock Yamaha bolt, however, is not a 12.5 x 1.25mm. The unthreaded portion of the bolt mic's @ 12.7mm, which is equivalent to 1/2" SAE. This is the correct area to measure bolt diameter. The threaded area will always measure slightly smaller in diameter from the thread cutting or rolling process.

Also, a 1.25mm thread gauge does not match the stock bolt thread pitch. Look closely under magnification...close, but not quite (read first link below). If you take an SAE 1/2-20 thread die and screw it onto a stock Yamaha clutch bolt, you'll notice it fits perfectly with no slop or binding.

Don't be afraid to use the SAE 1/2-20, grade 8 bolt shipped with the PB 80. They thread into the crank, by hand, just fine and have worked great on my sleds for thousands of miles. I've had both clutches apart and back together several times, all using the supplied 1/2-20 bolt. There's nothing wrong with having the shoulder machined-off the stock bolt either, but there will be less thread contact into the crank at assembly, as the PB 80 is slightly taller than stock. That's the reason CV Tech sends a longer-than-stock bolt. However, it sounds like machined stock bolts have been a non-issue for all your sleds.


Clutch bolt thread and pitch:
https://ty4stroke.com/threads/clutch-bolt-thread-and-pitch.149537/

Power Bloc 80 clutch:
https://ty4stroke.com/threads/cv-tech-pb-80-primary-clutch-apex-vector.149604/

 

[sledjunk]

Sorry to disagree. Here is a picture of both bolts. You can see that the threads do not mesh.
The 1/2 -20 bolt will thread into the crank by hand for a few threads only. The thread pitch is CLOSE but not exact. The Yamaha bolt will thread in much further by hand because it is the correct pitch.

This is a photo of a known 1/2 - 20 bolt matched with the bolt supplied by CV-Tech.

 

[Redbeard]

Sorry to disagree. Here is a picture of both bolts. You can see that the threads do not mesh.
The 1/2 -20 bolt will thread into the crank by hand for a few threads only. The thread pitch is CLOSE but not exact. The Yamaha bolt will thread in much further by hand because it is the correct pitch.

View attachment 138435


This is a photo of a known 1/2 - 20 bolt matched with the bolt supplied by CV-Tech.

View attachment 138436

You're posting incorrect information that might prevent someone from buying a PB80.

I know the supplied PB 80 bolt works. No issues.

 

[Dr. FeeLGooD]

So, if I have a set of Ulmer weights (50y) for my Yamaha Nytro clutch, what does one need to set the equivalent into one of these? My factory clutch needs all new parts and the sheaves are not as smooth as they once were. Maybe this is the way for me to go. I know very little about clutching and my current set up worked very good for 11000 miles or so.

 

[sledjunk]

Not sure how to comment on the Ulmer weights. However, the clutch comes with 12 weights for each of the three pucks. (more are available for a few bucks) My clutches came with 9 installed in each puck so you can easily add or remove them to tune to your liking.