Help, clutch adjustment screws breaking.

[Roy Harris]

I bought a new Hortsman steel nytro 3 disk clutch for road race, KT-100 sit-up, A-2 pipe, gearing 5 to 1, stall speed 10,000 rpm. After the first race one of the spring adjuster screws had broken. I had it repaired at the shop I normally use. After the second race 2 spring adjustment screws were broken. Any ideas what might cause these to break?

Roy Harris

[John Valerio]

Roy,
It could be that the spring height may be off. When you got the clutch back from the shop did they set it up for you? Assuming they did.....make sure that all the springs are the same hieght. This can be done by taking a dial caliper and measuring the distance between the bottom of the aluminum washer to the surface of the aluminum weight plate. they need to be very very close to one another. Another important thing to remember the clutch may be bottoming out ie: to much air gap or springs below the minimum tolarences/ recommended hieght.

hope this helps
John Valerio

If not call Horstman Direct.....they are awsome with technical advice!

[Roy Harris]

Thanks for the reply John.

I thought the problem might be with the air gap or spring height as you mentioned but wasn't sure. The shop set all the springs to the same height but the stall was at 8600 so I had to adjust them at the track. I don't know if the shop checked the air gap. Maybe I should get the tools I need and learn how to work on it myself.

[John Valerio]

Roy,
go to horstmanclutches.com
go to tech section and click the steel nitro link.
there you will find all the info on the clutch. its not rocket science by any means. The horstman clutches are bullet proof when they are set up properly. If you dont already have one get a decent dial caliper and a good feeler guage. Run the green steel nitro oil......
best of luck

John Valerio

[Patrick Hubbell]

quote:

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Originally posted by Roy Harris:
I bought a new Hortsman steel nytro 3 disk clutch for road race, KT-100 sit-up, A-2 pipe, gearing 5 to 1, stall speed 10,000 rpm. After the first race one of the spring adjuster screws had broken. I had it repaired at the shop I normally use. After the second race 2 spring adjustment screws were broken. Any ideas what might cause these to break?

Roy Harris

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Roy, why are you stalling your clutch at 10,000 RPM? Is that where your motor makes it's peak torque. I have found that stalling the clutch 200 rpm before peak torque works best.

[Mike Walpole]

Most of the sprint guys running that clutch and pipe are setting the clutch @ 10.5K. Peak torque is ~@ 9.8 - 10.2K range.

[Roy Harris]

Patrick,
I haven't had my engine dyno'd with the pipe on it so I don't know for sure where the peak torque is however I was given a range of 10,000 to 10,400 to use as a stall speed so I went on the conservative side. I have only road raced at PIR so far and there it is flat out all the way around the track except one corner so the stall is mainly used at the start. I have run well all year except for the springs breaking.

Thanks for all the help.

Roy

[Joe Klenotich]

Proper airgap, no warpage, fresh oil every session, RPM set right on--they still break; does a nice job in the inside of the cover.
Also finished the SBRP national in Y Lite; looked at the driver and half the driver teeth were gone, but hey we used it 3 times
welcome to Horstman.

[pat slattery]

Joe I had the same thing hapen to me in Yamaha heavy in the feature at Manufactures cup race at SBRP. Were you using a 10 tooth driver? I have had 3 10th drivers break on me this year alone. I have had no trouble when I run the 11 tooth.

Pat slattery

[Jimmy Moore]

Roy,

Road racing with a 5:1 ratio most often requires an axle clutch. If your engine clutch slips at all out on the track it will burn up pretty quick under those conditions. That being said, the bolts should screw into the pressure plate with a little resistance. These bolts have to be replaced quite often because they take a beating. You should use the 10gram weights and the lighter springs, this will make life easier for the bolts. What exactly is happening? Are the bolts stripping out, do the heads break off? You are using the special Horstman adjuster bolts aren't you?

[Roy Harris]

Jimmy,

The bolts are breaking, not stripping. The first race it was new so the bolts were stock. I can only assume the shop replaced it with a hortsman bolt, it is a reputable shop. The second race two broke so logic dictates at least one of those were still stock. I know some drivers use axle clutches but since I sprint also, I try to keep change over to a minimum. The shop I go through has told me that some of the sprinters have had problems with the bolts breaking on the HDC-4 clutches. I don't know if they are the same or not.

thanks for the help,

Roy

[Joe Klenotich]

Pat--sheared exactly in half--didn't notice until about two weeks later when I was taking it all apart for some R & R; think a big issue is the spacer needed for 10T; always very thin.