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Discussion Starter #1
After 19 hours track hours on my T140 long rod racing motorcycle I decided the motor needed refreshing (plus I have new pistons and beehive valve springs ready). Upon disassembly of the gearbox I noted both layshaft bronze thrust washers locating pins had worn flush with the casings (both leaft and right) and it appears the thrust washers were spinning.
One thrust washer measures 0.0865 inches thick and the other measures 0.0920 inches thick. All gears and hardware were in place including the circlip near the right side drivng dog.
Of course there are two questions:
1. What caused this? Too tight or too loose layshaft clearances?
2. How does one replace the locating peg (57-0912). Is this a hardened piece that would be impossible to drill? Should I just drill a new set of holes?

The gearbox shifted fine but the last race session I did miss third gear once. It didn’t seem too bad and I fail to understand how the missed shift could have caused the damage.
I could not find any excessive wear on the shifting dog, layshaft or layshaft high gear. The measured distance from the outer face of the layshaft high gear to the outer face of the driving dog (57-4661) is 4.917 inches. I am not sure if this is excessive or undersize.
I am interested in some thoughts from the experts of this forum on my two questions.
Thank you.
Team FASTLIKEJUDY
 

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Sorry, not an expert. The issue does seem strange to me. But what I'd like to know is, what is a 'long rod' T140 engine? A T120 engine with 750 top end? Or a T140 engine with 650 rods somehow made to work, and if so, hwo and for what reason? Not being antagonistic, just genuinely curious!
 

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Discussion Starter #3
A long rod T140 is a 10-bolt 750 with a special cylinder to run 650 length carillo connecting rods. Increases torque.

Team FASTLIKEJUDY
 

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Hi - I am no expert either but another question is where is the pin metal ? - cant see how the thrust washers could wear them away as they are softer than the pins - could they have been pushed into the ali castings ? but if so how ? - sorry no help just more questions ! cant see a problem with drilling for new pins in a different place - but that does not solve your problem - what has caused it ( thanks for the explanation on a long rod motor - new to me too )
 

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Is that roller bearing tucked in flush? the picture looks like it is.From the bit i know,that roller bearing needs to stand out proud,and,just a bit lower than the thrust bearing.Other than that,i have no idea how it would cut that stud off .
 

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Discussion Starter #7
Rambo, Yes the needle bearing is flush, that is not correct. I am going to check the needle bearing tonight to see if it is loose.

The needle bearing on the left side the proud but the locating pin is also ground down.

Do you suppose that if the right side needle bearing moved, and the thrust washer started to swing about, that would cause excessive side movement?

I am sure the mystery will be solved, it will just cost money. This is really one of life's easy problems.

Thank you for your response

Team FASTLIKEJUDY
 

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If the thrust washer was not located by the bearing shoulders,it could oscillate around and would probably chew itself up.Hard to see how it would break that hard pin though.Who knows what went on in that box.Its a bit of guess work.Best way to secure the bearing could be some loctite bearing lock.Not really a great idea when it comes to replacing it again but i would use it if a bearing was able to move.
 

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The pins aren't hard. I've drilled and tapped one with a small tap,and used a small screw (about 2 mm or 2.5 mm diameter) to pull it out.

It's usually a result of bad assembly, if the pin is flush with the case. If the washer didn't sit on the pin properly, the washer pushes the pin into the case when everything is tightened up.

The pin is 1/8" diameter. I just used a piece of 8 gauge welding electrode to replace it (had to polish the diameter a couple of thou smaller, to make it fit).

Hopefully both needle rollers are still tight. I wouldn't count on Loctite, if they aren't.
 

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By coincidence, I met someone this afternoon who has a T140 in bits, which had done exactly the same to its layshaft thrust washer locating pins. Looked like both had sheared off, but maybe, as Pete suggests, bad assembly caused them to be pushed too far in? It isn't an issue I've ever come across before.

Why would Loctite not be likely to do the trick on less than tight needle rollers Pete? I would have thought it would be ideal, as long as the enlarged housing is still round.
 

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Discussion Starter #11
Needle Bearing is not Loose

I checked the right side needle bearing last night and it is not loose. I hate to admit it but I believe the mechanic installed the needle bearing incorrectly flush and not proud of the inner cover to center the thrust washer.

Unfortunately I need to look at the mechanic when I shave in the morning.

Anyhow, I decided to grind the existing locating pins completely flush and install new pins. I just don't understand if I did not install the right needle bearing correctly how that would cause both locating pins to rub down.

Thanks everyone for your assistance, below is a picture of me at Daytona last October.

Team FASTLIKEJUDY
 

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Very nice looking bike - looks like a standard conical rea hub? If so, glad to see your brake cam lever goes on fine upside down, as I was thinking about doing that. What final drive gearing do you use? I'm interested because I imagine that, racing on circuits with long straights, 21T gearbox and 47T rear would be way too low? Am I right, and if I am, how do you get around this?

PS: An afterthought on the mis-assembly explanation, where the thrust washers aren;t located onto the pins and push them into the casings when everything is bolted up: Ion reflection this seems improbable, because (a) it would take a noticeably greater than normal effort to tighten the fasteners and (b) even if this was done, there would surely be obvious witness marks on the thrust washers? Whereas, if the bearing is flush instead of proud, there'd be a lot of scope for movement radial to the shaft axis and in use, I suppose that tendency to move can only be resisted by the little pin for so long?
 

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Discussion Starter #13
John A,
Grearing with my conical rear hub is improved with the Hayward belt drive. The Hayward belt drive has a ratio of 29 crankshaft and 54 clutch compared to a stock chain drive with a 29 sprocket and 58 clutch. The Hayward belt drive provides about 7.5% taller gearing. My typical gearing is 21/50 for most tracks in the US. I go (down?) to 21/47 only for Daytona and 21/49 for Road America.

I have not done any further work on the gearbox (I work as a mechanical engineer). THis weekend I intend to make some detailed measurements.

Thank you for your response.

Team FASTLIKEJUDY
 
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