Pretty sure I have a bad crank seal...

[silverstrom]

Typically a right crank seal failure results in gear box oil being sucked into the crank well which produces lots of visible smoke and if the bike continues to be ridden it eventually fouls the right side spark plug. I've never seen a right side crank seal failure result in the right side pipe getting so hot it peels the paint. Consuming the gearbox oil wouldn't create the very lean condition needed to seriously overheat the pipe. I suppose that if the bike was ridden long enough for most the gearbox oil to be consumed then perhaps at that point it would be sucking air and run lean and hot, but that seems unlikely. I think it's more likely the catalytic converter that comes into play here. They run crazy hot as it is, and then you add the gearbox oil and things really heat up.

[speedfrk]

Hopefully, with all new seals, case sealer, gaskets, etc the problem will be solved. Plugs looked fine but it really hadn't been ridden very far- maybe 10-15 miles. Cases cleaned up nicely but there was a lot of carbon around the seal and lots of oil in the case...

[silverstrom]

It might be worth looking into how to clean oil from the pollution control system. It would suck to rebuild the engine and then have issues with serious overheating again.

[speedfrk]

It made a ton of smoke for a while then just stopped- I assume when the oil level got below the crank seal. Then started getting hot, I assume, from sucking air. I'll pull the baffle from the pipe and look at the cat. You can see it easily from the end. I'll pull the pipe from the air injection and make sure it isn't oily in there, too. What I really need is a set of stock Canadian pipes so it looks stock but without the worries of the cats.

[speedfrk]

Engine is back in... I could see a definite difference on the inner lip of the rt seal compared to the new seal. I'm adjusting the oil pump and my manual pics are so grainy that I can tell what mark I'm supposed to line up the pointer with. Bottom pic is with the throttle closed and top is open. Can someone educate me?

[speedfrk]

Just an update... took it out for a ride after bleeding the oil lines and it runs perfect with all the new seals and gaskets. Also rebuilt the oil pump since it was apart and I didn't really want to worry about it. Used the digital thermometer on the pipes to make sure both cylinders were synced good. Got the cdi back from Hugo in Montreal and it is actually on a different 84 but it is fixed and runs great as well. Things are looking up in RZ world!

[speedfrk]

Well, I spoke too soon. I went for a longer ride and and came back and checked the oil level in the gearbox and it was down below the dipstick. Rt side exhaust was also quite a bit hotter than the left. So, apparently it is still sucking oil through the rt crank seal. But it was not excessively smokey from what I could see in the mirror- compared to the first time. These were all OEM parts, from a Yamaha dealer, so no ebay stuff. Pretty disappointing and I'm at a loss for what to do next...

[silverstrom]

Did you lubricate the inner seal lips? If you don't the crank will run dry in the crank seals and quickly wear them to the point of leaking.

[speedfrk]

I lubed everything with 2 stroke oil as I was assembling it. I did not use any kind of grease on the seals, though. I think the manual says to use 2 stroke oil...
Can it be sucking oil in around the key on the shaft?

[silverstrom]

There isn't much that can go wrong that would lower the gearbox oil level. It has to be either the crank seal has failed or you are losing oil around the outside of the spacer or inside the spacer and the primary pinion gear. That spacer should be well oiled on assembly to protect the crank seal on initial starting. That spacer will wear over time and it's common to find a groove worn into the steel. The typical solution is to swap the spacer end over end and get a smooth surface again. I just assembled a bottom end for someone on Thursday (Aug 17th) and had to turn that pinion gear spacer around due to wear. You also need to have the pinion gear properly torqued. If it isn't the seal will leak. If you do a leak-down test with the pinion gear not tightened and torqued you quickly discover it won't hold any air pressure.

You didn't put the right crank seal in backwards did you? The early repair manuals and parts lists showed the seal backwards. The 4 raised areas of the seal and supposed to face the crank bearing. This shows the INCORRECT installation https://www.cmsnl.com/yamaha-rz350-1985 ... /A-07.html

Many have installed the crank seal backwards due to the manual and parts list errors. In most cases there are no problems, but anything not correct has the possibility of leaking.

Poor sealing between the crank well and gearbox would cause problems. Are you sure you aren't losing gearbox oil from the gearbox vent located are the very back of the upper case half.

Did you use genuine Yamaha crank seals?

I used owner supplied crank seals several years ago and advised that I would not recommend cheaper Yambits crank seals but the owner insisted so he could save a little money. During the initial build it held 5 PSI for almost an hour. 100 km later the engine failed a leak-down test. It would get to 3.5 PSI and drop to zero. That's what cheap Yambits crank seals will get you. Sometimes saving money is expensive.

When I was building the bottom end Thursday I discussed all of these things with this owner.

[speedfrk]

All new parts from Yamaha, no reproduction stuff. What spacer are you referring to? The one inside the clutch basket? If you have a part no on a diagram that would be great. I pulled up both the crank diagram and clutch and I'm not sure what you're referring to. But, this is a 4k mile motor that showed no wear on anything and even the seal I took out looked perfect and was still very soft. I did make sure to put it in correctly! I've rebuilt several of these motors and this is the first one I've had a problem with but I'm by no means an expert on them. There is no oil coming out of anywhere, completely dry engine but when I took it apart, I did notice that the breather tube was completely clogged shut with chain lube and dirt. But, that's fixed.

[silverstrom]

Don't mind me with the spacer. It was 0230 and I was prescription cannabis medicated. The spacer, of course, is on the gearbox output shaft and if leaking you will lose gearbox oil. Not sure how my brain combined the two locations, but what I should have said was to make sure there are no grooves worn into the pinion gear as it passes through the crank seal.

There aren't a lot of ways to lose gearbox oil and it looks like you've done everything perfectly. Did you pre-soak your clutch friction plates before installation? Just thinking that if you didn't that would definitely lower the oil level.

Ultimately, I think the only way to know for sure that the crank seal is good is to pressure and vacuum test the motor. Test the right seal from the right cylinder and if your right crank seal is gone you'll find out quickly.

Before that, I'd refill the gearbox to the correct level with the dipstick sitting on top of the threads and go for another ride. If you do lose gearbox oil this time, you most definitely have a problem somewhere.

[JonW]

You should always pressure/vac test every new build imho, that should tell you if you have a leak.

[silverstrom]

You should always pressure/vac test every new build imho, that should tell you if you have a leak.

Definitely. It's far easier to do it on the workbench than in the frame.

[speedfrk]

Well, the plot thickens, or thins like this oil. Pulled it in the shop and drained the oil so I could take off the clutch cover and this is what drained out. I assume the water pump seal is bad? I had just checked it when I rebuilt the oil pump and it was actually tight on the shaft when I spun it. No burrs of ridges on the shaft at all. Would that affect the apparent oil use that had me question the crank seal? This bike is driving me nuts...