Clutch Spring Cap Screw Modification

kent_in_kc

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Recently I disassembled and removed my clutch basket to replace the infamous defective starter gear.

When it came time to remove the six Phillips-head cap screws holding the pressure plate and discs together, I noticed that they were very tight. It took a lot of beef to get them loose. When I reassembled the clutch, I twisted one of the six screws off! Grr.

So I took the basket apart, removed it, welded a rod to the end of the broken screw and (luckily) was able to remove it. Making a note to get another screw, I resumed reassembly of the basket only to have a second screw snap off when tightened!

I may be dumb but I ain't stupid... or something. So I disassembled everything and examined the remainder of the screws. They were all stretched and thin in the center, unable to withstand any tightening at all. Apparently a PO had run them in with an air wrench.

That's when I posted the problem on XS650.com's forum an got a suggestion from 5Twins. He suggested the mod that I used to successfully get my bike working again. Not only did this save me a few days waiting on new cap screws, I believe it is superior to the original design.

Here's why: the stock cap screw threads in almost all the way before bottoming out against the shoulder. What happens then is, as the mechanic tightens it and normal torque stretch occurs, only the tiny segment right at the innermost end of the threads next to the shoulder stretches. All of the torque is absorbed there. Thus, the cap screw snaps.

With 5Twins' mod, all of the cap screw length that passes through the spacer absorbs the torque and stretches evenly.

Here is a pic of both the stock cap screw (on the left) and the modification. Notice the thin, stretched section of the stock cap screw:
100_1672.jpg

Since the stock screw is stretched, it is a bit longer than our new cap screw. To do the mod, cut off the threaded part of the stock screw:
100_1674.jpg

Next, lock the stock cap screw in your drill press vise and drill down through it with a 15/64" bit.
100_1676.jpg

Here is the resulting spacer and the new 6mmx40mm socket head cap screw.
100_1673.jpg

One final note. When tightening your new cap screws, use a bit of blue thread locker and torque them to 7 ft. lbs.
 

gggGary

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Looks like a great solution. There are clutch removals in my future.
FWIW I recently did two and broke no bolts but several of the phillips slots were pretty ugly. I was not looking for stretch, I will check the one that is just sitting with the bolts hand tightened. The Hex head seems like a major plus to this mod as well. I assume there is still plenty of clearance to the cover with the clutch in?
 

Earz

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Excellent tech article. Definately needs to be in the tech section.

Posted via Mobile
 

5twins

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Well actually, I didn't come up with the idea, just passed it along. A poster called Cootersandwich on another list came up with it about a year ago. Great mod and also saves you like $25.
 

XSLeo

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I did that on a set of screws I had. The Phillips head was stripped out on most of them. I took a 1/4 inch drill bit and drilled a hole through my drill press vice right where the jaws come together. This hole holds the screws straight to the drill press head. I didnt cut the threaded part off first, I just drilled through and the threaded part falls of, saves a step.
I counter sunk the heads of the screws a bit. Looks a bit better that way.
 

XSLeo

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I finally used my modified clutch screws, I shouldn't have counter sunk the Allens into the screw, I put the clutch together and had some problems with it at first. Seemed to be locked up. After a few miles it started acting ok.
I did my first oil change after about 100 miles, the new 750 engine. Found way to much aluminum fillings in the engine.
WTF, I said. Thought about it for awhile and decided it must have something to do with the clutch screws.
Pulled it all apart and the Allen bolts went through the hub just far enough to hit the basket. They cut a groove maybe 1/2 mm deep in the basket.
I put all the modified bolts into the hub and ground off what stuck out flush with the back of the hub. I then pulled the bolts and dressed them off on the grinder to bevel the cut edges so they would thread in the hub with out any problems.
So I might suggest any doing this mod to the bolts assemble the modded bolts into the hub and check for bolts that protrude out of the hub. Fix this first.
Other than that minor set back they work much better then a Phillips head screw.
 

jimdi

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It may be me just gettting older but.... My 81 Special (16K) - when I go for long rides it seems the clutch gets harder to pull in. I have a new cable that is well lubed.
When cable is properly adjusted - I don't seem to have trouble finding neutral - could it be the Clutch Push Screw Assembly is getting worn?
 

72XS2

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I've just done this mod on my clutch, works definitely better than phillips heads. I don't know if it's better, but this way, the sleeves are made of steel instead of aluminium like the ones you can find in kits.
 
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Classic

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Just buggered up mine. Looks like I'll be investing more than I wanted into my shift shaft replacement. :mad:
 

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angus67

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im doin this the next time im in there. makes a whole lotta sense. you can actually torque it correctly with the allen heads (7lbs?)
 

XSLeo

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Classic, did you try a hand impact wrench to loosen those screws? Drive the bit into the screw then put the hand impact on the bit then push in and turn the impact in the direction you want it to turn then hit with the hammer. They should pop right loose.
If that wont work, a small cold chisel held at the right angle and hit with a hammer can get them loose.
Once they are out modding them for an Allen head bolt is easy.
 
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