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Discussion Starter · #1 ·
Hello fellow bevel head owners. my name is Jim and I live in the finger lake area of N.Y.S. I need help. I believe my 75 GT has upper rod knock. Does this motor have upper rod bushings?? can they be pressed out without splitting the case. If not, who can rebuild the crank? Thank you for any help.
 

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Hi Jim,

I'd be very surprised if your engine noise is upper rod knock. What makes you suspect it? The usual culprit is the big ends knocking, although piston slap can be heard on high mileage engines. How many miles has your's got on it?

Yes the upper con-rod bearings are plain bushings and they can be pressed out, but the problem is that they need reaming to size, which is a job for someone with a honing machine, but honestly, they never wear, the gudgeon pin wears a lot more.

One thing to check - are both the exhaust rings tight in the heads? as the pipe rattling can cause a knock; other than that it looks like it's time to remove heads and barrels and check for play.
 

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Discussion Starter · #3 ·
both exhaust rings are tight. Sad to say this motor was run low on oil.(not my doing) The motor sounds good under load, but when you let off the throttle one can hear a distinct knock. because the rear upper pin gets its lube from splash I thought that this may be the problem. this bike has around 20 thousand miles. Duccout, Thank you for your help!
 

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I don't want to sound doom-laden, but the knock may be big ends. It is probably a good idea to pull off the heads and barrels and see how the rods feel.
 

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Discussion Starter · #5 ·
I know and want to get this bike to a doctor. I do not know of any bevel experienced shops/dealers in the northeast part of the US. I don't mind spending money to rebuild this motor. I want an A-1 job. I have read that it took a factory Ducati mechanic 8 hours to assemble one motor using new parts. I'm hoping that someone on this site can hook me up with an experienced bevel motor rebuilder somewhere in the northeast US.
 

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Hi Duccout, thought i would jump in here as i have just pulled the barrel from my vertical cylinder to check the big end as i had a noise coming from the bottom somewhere, could be the play in the bevel bearing support but thought i would check the bottom end while i had it apart and will be waiting for shims now. I have a little play in the big end, bugger all but there is sideways movement too. Just how much play is too much?
 

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Hi Shark64,

I'll tell you a tale: Many years ago, when my 750 Sport had about 50000 miles on it, the engine began to get noisier and because of the reputation of bevels to lunch their big-ends, I though I'd better check it out. After removing the barrels I pushed and pulled the rods this way and that and there was definitely some play in the rear big-end bearing. So the engine came apart and the crank went off for a new big-end assembly. When I got the crank back along with the old assembly there was just as much play in the new big-end and my old one was still perfect.

I'm not a professional Ducati mechanic, but if the bike were mine I would leave well alone unless the play is really noticeable. What I know now is that there is play in big-end bearings and according to Brook Henry and Godden Engineering in the UK, one of the reasons for Ducati's big-end problems was not enough play in the bearings. Possibly, it may be an idea to squirt clean oil through the big-end and then check for play.

I read an article in Cycle World about a 750SS that had been raced and had covered 90000 miles and when the big-end was stripped for inspection was still ok and went back in the engine. I think that you may be on the right track with the lower bearing supports for the bevels - I've found that the circlips wear in the grooves allowing the bevels to rattle about; it is a good idea to replace the circlips and try to get a slightly thicker shim under the circlip to take out any play in the bearings.

Let us know how you get on.
 
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