1975 Yamaha RD350(LC) Preservation-mod Hellride

irk miller

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Much thanks.

It’s been a blast to ride, except I spun something in the transmission. Any guesses before I pull the motor? Still does everything it’s supposed to, but with lots of noise.

 

irk miller

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May have isolated the issue to the main axle that holds the clutch basket, without pulling the motor. Still diagnosing, but I can spin that shaft with my hand and get the sound pretty quick and easy. Possible bearing, I would think.




 
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teazer

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Good news is that it's not hard to fix. bad news is that the motor has to come out and be stripped. It does sound like the double row bearing has collapsed or the inner cage is split, but it has to come apart to change it and to see what's wrong.
 

irk miller

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Good news is that it's not hard to fix. bad news is that the motor has to come out and be stripped. It does sound like the double row bearing has collapsed or the inner cage is split, but it has to come apart to change it and to see what's wrong.
I added a video since you replied. No doubt I am pulling it apart. Does a change when shifting isolate even further? Just curious before I drop it.
 

irk miller

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I hope it’s really this simple, but two gears were dry as a bone. Not sure if various models or years have different dipsticks to make me read my levels wrong, if I’m stupid or if I lost oil somewhere. Nor can I think of any reason this happens besides low oil. The gears just lay in a pool of oil. Can’t think of why this was just two gears.

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irk miller

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Slathered it in oil and everything got quiet. Not the end of the world pulling the motor. I get to check over everything. A better clutch is on the way. After chatting with another fella on Facebook who LC'd his engine, I am going to relocate the coolant pump to under the reed boxes. I can always go back to an oil pump now, if I want.
 

pidjones

Over 1,000 Posts
Proper, measured quantity of gear oil in my RD400c indicates WAY over-fill on the dipstick. I'm staying with measured quantity, but if it were the other way around, would use the dipstick. I would expect clutch problems before gear damage if they were installed with a good slosh of oil on them.
 

teazer

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With the dipstick, don't screw it in to check oil level, just rest it on the case. It's hard to tell from the picture and video but some of the dogs look to be worn. Run it through the gears with the cases open and see if you can better determine the source of the noise. If a shift fork is bent, it might be pushing too hard against one or two gears. If the shift forks are OK, you may still have to shim the gears to get the right amount of clearance between each gear. In other words, if it tries to "over ingage" a gear it will make noise. There should always be a small amount of free play.

I had an RD400 years ago that was slightly low on trans oil and it made a similar noise but nowhere near as bad as that. And as PID says a little too much oil is a safer place that too little.
 

john83

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Such a cool bike Irk. Man, you drop and split an engine quick! I would still be standing around cursing about it


Sent from my iPhone using DO THE TON
 

irk miller

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Haha. Thanks, John. 2 plugs disconnect electrical and it’s out in 10 min or less. Another 30 to take it apart. They’re so easy.

In the meantime, I have a few parts on order, particularly clutch. Until then, more tuning which also means the running gear. Did a fluid swap in the forks and pulled one rotor. It was never a question that this bike had way more brake than necessary. It was way too much brake, especially at 7lbs per side.
 

irk miller

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Back with updated beauty shots and to report. The Economy clutch, which is FZR friction discs, new OEM metal discs, and heavier springs makes a world of difference. I thought there was a chance I was losing power in the clutch. It’s scary good now. The transmission is oiled and quiet. I averted disaster there.

Put back together with 1.85 on timing, and holds 6psi in the leakdown.

Temps can reach 165° during a succession of traffic lights, but cruises below 150°. I’m really happy about this.

The CB650 forks are decent, but I want to see what I can do to make them better.

It’s incredible what deleting 7lbs of unsprung mass does. I’m hoping to weight in somewhere near 300lbs, though I have no idea. Regardless, 7lbs is a chunk.

The bike feels all around better now. Power delivery is pretty crisp. If I lay it on, it want's to shudder the back wheel. Not sure if this is something I can tune out with the rear suspension, or if it's just the nature of power to weight. Regardless, grip is good and it's getting off like a rocket.

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pidjones

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I suspect the Georgia mosquito population will not be happy! Will it be doing similar near Birmingham in October?
 

irk miller

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I suspect the Georgia mosquito population will not be happy! Will it be doing similar near Birmingham in October?
Definitely Mid Ohio. Still to be determined for Barber, but most likely I bring it there.
 

teazer

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Looks great. Shudder you say. That's unusual. I wonder if the clutch hub cush rubbers are shot and allow it to cycle back and forth. Are there rubbers in the rear wheel as well? If so they may need to be changed out. It might also be a drive chain snatch effect as the power is fed in. Try it with a few more revs as you launch to see if it clears up.
 

Rider52

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Barber is hosting a modified Metric show this year. Part of the VJMC collective but modified bikes will be shown separately.
 

irk miller

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Looks great. Shudder you say. That's unusual. I wonder if the clutch hub cush rubbers are shot and allow it to cycle back and forth. Are there rubbers in the rear wheel as well? If so they may need to be changed out. It might also be a drive chain snatch effect as the power is fed in. Try it with a few more revs as you launch to see if it clears up.
It feels like wheel hop when drag racing. Can't hurt to swap for fresh rubber, regardless.
 

irk miller

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Working out the kinks on suspension. The jackhammer/stutter/wheel hop thing was just that- wheel hop. Softened the suspension a bit and it eats the pavement much better. Maybe I was feeling a hard tail effect? Who knows, but it's much better now. I was way too stiff on the front end, as well.
 

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