Driven clutch mounting bolt broke

[Rusty-Gunn]

Hi. The 4" bolt that holds the Comet 780 driven clutch to the T20 output shaft broke, leaving a broken stud inside it. This happened about 4-5 years ago. I was able to extract it easy enough. I bought a new "square-type" extractor and the proper drill bit for this bolt.
To think we just traded out the missing/worn down cam slider buttons! Dang, here we go again. The engine and T20 needs to come out again (Max IV). Not happy about this.
I intend to order a new driven on Monday. This one has been giving us fits lately. Dumping slider buttons like it hated them. Sctatches on one cam as a result. Vibrations we can hear. I'm unsure if I'm preloading it properly for a green spring. Dang. And it was new last year spring time! It hates me.The wife is not happy.
Any advise to help in this situation is greatly appreciated.

[tbone9]

I feel your pain. I went the cheap rout and replaced all the buttons again and sanded the helix smooth. We will see how long this lasts. As for your mounting bolt I’ve never had that happen however you mentioned earlier that you had the driven off a few times maybe the bolt got fatigued from reusing it. The longer the bolt the more fatigue. If I lose another button I’m going to a different style clutch with rollers. I preloaded the green spring 1/3 rd of a turn and it works good.

[Rusty-Gunn]

Thank you for responding. I did buy a new bolt (obviously). I wasn't aware fatigue could be a factor. Whats funny, is I did intend to trade that bolt out with a new one but I bought the wrong threading, and reused that old bolt again . I bought the proper threaded bolt this time.
I preloaded this one either 2 or three cams, depending on how you consider the first cam. At relaxed state the first cam was barely an inch away or so. Then I moved it past the next two.
It held for one ride, until that bolt broke

[dirtdobber]

Are you perhaps over tightening the bolt and weakening it?

[Rusty-Gunn]

Over tightening? Probably. I made it tight, such that I didn't want it coming off. It had rattled off twice, but that was because the clutch lost a slider button and had a bit of vibration both times.
I also used red lock tite, but the nolt broke. I'll be sure it isn't over tightened this time. I sure don't need more clutch problems. Thank you.

[Rusty-Gunn]

I bought a new driven clutch and have it installed on the T20, using a new bolt. This time I I tightened it good, but not over-tightened. I also used red lock-tite.
We'll go from here and see what happens.

[tbone9]

What clutch did you go with?

[Rusty-Gunn]

OEM-type, from MFG Supply. This is the third one we bought over the years.

[Rusty-Gunn]

I forgot to mention that when the clutch bolt broke off the clutch slid to the left, into the tub wall, and cut a crescent-shaped slit into the tub! About half way through. Dang. Going to need some plastic welding to fill in that groove.
To prevent this from happening again, I installed a 3/8" thick UHMW sheet, about 5x13 inch (?) size to the frame, inbetween the clutch and tub. Now, the clutch will rub against this UHMW sheet and not the tub.

[Rusty-Gunn]

On a ride two days ago the secondary center bolt rattled loose again! A friend helped me tighten it back, with him turning the wrench, and me holding the clutch from rotating. This got us home from a ten mile tide out of town.
The UHMW sheet I installed between the secondary and tub worked excellently! I am very glad I put it there. The secondary rubbed against it, not the tub.

[dirtdobber]

Wow. So you bought a new clutch and a new bolt last month and installed them using red loctite on the bolt and it still came loose? I have to ask - is the input shaft on your T20 bent, or is there excessive play in the needle bearing? I'm looking for a source of vibration that is causing the bolt to loosen. OR....what type of washer are you using on the center bolt? If you are using a thin, lightweight washer maybe it is getting deformed in the tightening process and keeping things from truly tightening. Also, when I use loctite, I make sure the threads are clean and dry by hitting them with some carb cleaner or ether - or anything else that will remove oil and grease residue.

Just throwing ideas out there.

[tbone9]

That’s crazy. Check the key and key way. Maybe it’s got some slop in it as well as the other suggestions.

[Rusty-Gunn]

I didn't clean out the shaft hole threads. Maybe it's dirty?
I'm confident the input shaft is fine, new needle bearings installed as well.
The machine sounded and felt very good on the trip until we got to our destination, at which time the bolt rattled loose.
I'll see about cleaning it out before I install the bolt back, and will use a new lock washer ( iy has that thick washer it came with). Lots of lock tite as well.

[tbone9]

Rusty, is the new bolt a little longer than the original one and maybe bottoming out and not tightening on the clutch? Just a thought.

[Rusty-Gunn]

I don't think so. It tightens up tight. Late last night we removed the bolt, coated it with a lot of blue locktite and put it back on, tightly. I used another lock washer, as well.
I didn't have red locktite, so I used the blue. And I didn't have anything suitable for cleaning out the threads. I am wondering if a brass brush for cleaning rifles might work? Interesting idea, might work.
We're going on an over-night trip this weekend. I'll post if any thing goes wrong.