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Cam journal and cam FUBAR

chuck hahn

chuck hahn

Forum LongTimer
Past Site Supporter
Well if I didnt have chitty luck I would be bored to death...HA HA

73 TX750 has spun the left side cam end and journal. But the flip side of all my bad luck is that an Ebay seller has a new NOS cam and left side cam holder......so nearly 300.00 later the parts are ordered up.

Project1000C055.jpg

Project1000C053.jpg
 
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If you do a little research you will find that, that particular problem was one of the many that was the demise of the TX. As I recall I think it was Kenny Roberts who was racing for Yamaha at the time, found that out first hand.If I remember correctly for Daytona races in 74 he toasted like 3-4 engines between practice and the main race
My mistake he rode the TZ750, but here is a good read
http://whitelinepsychos.blogspot.com/2013/04/yamaha-1974-tx-750-non-hand-grenade.html
 
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I am very aware Harry...they had problems due to the counter balancers frothing the oil and the scavanger pump loosing prime because of it. There was just over 9,000 on the clock when i got it and I have put on around 1,300...so it wasnt an unexpected find. In short..I knew it was gonna happen sooner or later..and I am just glad I got new OEM parts found.

One thing I think will help is to drill a small hole thru the top of the cam journals ( they are solid and you put each holder on over the cam ends like a sock) so that oil can be more readily drawn to the cam / journal surfaces. Cant ruin or hurt the journals with a small hole.
 
There looks to be enough meat around the bearing that boring the housing out and inserting either a needle roller or a ball bearing should be possible.

That would solve the oiling problems in that area anyway...

If you stick with the stock setup, Honda twins have an oil hole on the top of the cam bearings with a large countersink area to catch and direct the oil.
 
This is exactly what I was think Greg with the drill a hole idea. Its the easiest fix I can think of , and yes theres about 1/2 inch of metal surrounding the cam ends so I dont think it would effect anything structural.

Like i said, everything was well oiled when I took it apart so I know the top end IS getting oil to it. Just need to be sure these ends get well lubed all the time.
 
The original parts are recoverable too. Machine the cam end to a nice fresh surface - usually less than .020in to come off. Then bore the bearing to maybe 3/16in oversize and press in a bronze bush. Finish machine to around .002 - .003in clearance, add the oil hole and jobs done...

i've recovered a number of Honda CB350 cam bearing caps in this way so i know it works.
 
Well I dont have the machinery to do all that Greg. If you do, how much would that run me..send the old stuff and have it refurbished.
 
Given where i am, postage would be the dearest part....

find yourself an old guy with a good home workshop, and cosy up to him.

Oklahoma....There should be a lot of dirt car race engine shops there surely ? They're set up for this sort of work and may be interested in a small cash job....
 
Greg... I got the new NOS cam ordered yesterday off Ebay and he wanted 215.00 and i didnt even blink. And the new left side cam block was another 65.00. And seeing that I may never find them again due to the scarcity factors coming to play, Shipping them to you would be a wise investment.

I could even get another used right side off ebay and have you do that side and send me back a set ready to go with the rollers for the ( kets pray not ) next time.
 
Oil delivery line fixed

Oil delivery line fixed

Broke down and got a 10MM Helicoil kit and a new banjo bolt and just got the repair done...Cost way way more than the dang thing should have but its done now. Bolt, crush washers, and the kit came to $55 and change.

Got a course threaded banjo bolt and matching kit because thats all Oriellys had. Base gasket should be here Thursday or Friday so I will be stuffing the engine back in this weekend hopefully.
 
Well today I got the new oil rings installed and new valve stem seals too. Re used the compression rings as they only had 1300 miles on them. Hopefully all the issues regarding cams and the oil smoking are addressed. Just waiting on the cam chain master link to get here so I can put the cover on and get the bike reassembled.

Hopefully she will be smoke free again.
 
Chuck, is there any way to add a top end oiler to the engine?
 
What do you mean?? Its fed thru a feeder tube that runs up the back of the engine. Then the oil goes thru passages that are running thru the cam blocks. these passages in turn feed the hollow centers of the rocker arms..then its pumped out onto the cam lobes. Its kinda a wierd routed oil delivery system if you ask me.

One set of passages is supposed to feed the cam journal ends also. I have blown the passages with lots of carb spray and air and am very confident theres great oil flow now.

Thats why the idea of drilling a feeder hole thru the block itself was added.
 
I'd think you could safely leave it off. yamaha were a tad paranoid about breaking cam chains on the early efforts and that is mainly a guard to prevent damage...

thanks for the link to the parts fisch - I'd still reckon bronze bushing the cam bearing blocks is feasible. Price up postage to NZ...
 
Chuck, could you just cut the center section of that guard and peel them up to form wings that might direct the slinging oil towards the cam ends?
Sort of out with a downward angle? :-k
 
GregT, machining for a needle bearing sounds like a good idea if you can drill it for an oil passage then deburring the hole so it doesn't bugger up the rollers.

Chuck, 'can' you update to the later style balancer, or have you already if it's possible?

What oil did you finally go with when you first re-built the motor?
 
I didnt mess with the cams the last time Dale as they didnt show any signs of wear. The oil was Honda 50/50 synthetic blend HP4. This is what Randy suggested as you may recall from the earlier project.

I wasnt aware of any upgraded balancers from all that I have been able to find and read regarding the oil issue. An article in Motorcycle Classics ( I think it was ) detailed the issue of the oil being whipped to a froth and the fix back then was the added 2 inch "spacer" that made the sump deeper and thus required more oil in the tank as well.

Randy said the Honda oil had anti foaming agents and would be a great oil for the machine. In any case just because I didnt see anything in particular the last time doesnt mean these blocks and cam werent already on the way out.
 
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