Pretty sure I have a bad crank seal...

[75RD350rider]

Did you replace the o-ring on the water pipe?

[speedfrk]

I did... new oem Yamaha part. I'm about to pull the clutch cover off and let the rest of the goo drain out. I wonder if the o-ring got pinched. I've seen that happen before.

[75RD350rider]

I have had it happen to me as well. A friend of mine told me to fill the cooling system and kick the bike over with the plugs out and cap off to burp the air out with no oil in the transmission. Wait 24 hours and check the coolant level. If still full good. Remove the drain plug and if no antifreeze comes out it is good. That coolant pipe design is awful.

[speedfrk]

No problem with the o-ring I can see. Looks perfect- it was new and was no pinched. I had coated it with a little red grease before assembly. I'll use some Hylomar this time and make sure it is sealed! I'll also replace the pump shaft seal.

On the crank seal issue... I pulled the clutch and drive gear and the seal looks perfect. The gear shows the normal shiny rings on the shoulder but there is no ridge that your fingernail can even catch on. The key and slot is very sloppy. the left side of the slot is almost .003in and the slot in the crank end is .0025. Don't know if that is sloppy enough to suck that much oil through or not. Anyone with experience, please share...

[Evans Ward]

You’re not too far from Ed Toomey in S.C. Might be time to have an expert repair it?

[silverstrom]

Once the primary drive gear (pinion gear) and the smaller gear are installed and the conical washer correctly installed and the nut properly torqued there should be no leaks. If you get any of that wrong you could end up with a leak. It's pretty easy to get it correct, so it seems unlikely that would be a problem area for you. A proper leak-down test for pressure and vacuum would quickly show any problem areas.

Right now it does look like a water pump sealing issue. That would be good news and it's a simple fix.

[speedfrk]

I pulled the oil pump off while I was waiting for the new water pump seal and a lot of 2 stroke oil came out. I had rebuilt the pump with all new seals but was wondering if the worm drive part of the pump should have oil in it? Any wisdom on this?