Engine oil leak

[skipper]

Got a dilemma. Engine oil leak, appears in valley under middle gear case. It's not gear oil, I run moly oil (black as coal) this is clear engine oil. Can't be rear trans seal (I have spare) as that would over fill middle gear, right???? That seal goes in from the inside after splitting crankcase, don't really want to do that!!!! Thought it may be gasket, but after removing middle gear, no passage to crankcase. Gear case bolts go into blind holes. No sign of oil on outside of crankcase, it just appears under the middle gear case. I'm really stumped. Gonna leave middle gear off in hopes one of you guys has an answer.

[brcree]

oil ....

Skip....I had some leaks as well that i couldn't find where they were coming from. You can get a dye from an auto parts store. Put some into your eng. and run it awhile. You will need a special black light flashlight...I got mine on ebay for 3 bucks. Use this light in a dark place and trace the yellowish looking oil to its source. It will also work in the fuel as well.

[BA80]

Got a dilemma. Engine oil leak, appears in valley under middle gear case. It's not gear oil, I run moly oil (black as coal) this is clear engine oil. Can't be rear trans seal (I have spare) as that would over fill middle gear, right???? That seal goes in from the inside after splitting crankcase, don't really want to do that!!!! Thought it may be gasket, but after removing middle gear, no passage to crankcase. Gear case bolts go into blind holes. No sign of oil on outside of crankcase, it just appears under the middle gear case. I'm really stumped. Gonna leave middle gear off in hopes one of you guys has an answer.

If it's UNDER the middle gear it almost has to be coming from where the middle drive connects the the transmission through the case. There is a passage and a gasket between the MG and the case to seal engine oil in the crank case.

[skipper]

Actually, no Greg. That's what I thought was happening but that gasket only seals in gear oil (there's a reservoir in the lower crankcase for gear oil and the drain plug), no passage to engine oil, except the oil seal. A few years ago I replaced the rear MD seal and re-used the gasket with some sealer. Thought "great, Dummy, you got caught taking a short cut", doesn't appear to be the case. Really got me bugged!

[CaptonZap]

Starter gasket?
CZ

[BA80]

I actually had to go look but yes, your correct skipper. There is a seal in there. I stand corrected.

CZ might be onto something though, it could be the O ring seal on the end of the starter or the seal inside the starter itself and could be leaking from the starter motor.

The only other possibility there is where the 2 halves of the case meet.

[bikerphil]

If the oil is on top of the middle drive, it is probably the O-ring on the starter. Had this happen on both my bikes, just removed the starter and on one I RTV'd the O-ring and under it, for the other bike I had a replacement.

[skipper]

Thanks guys, I wondered about a leak around the starter. Possible it could have run under and pooled under the MD. I forgot to mention that it doesn't leak around town (2 to 3 thou rpm), only at interstate speeds and heavy engine load (75-80 mph, 4000 to 4200 rpm). I'll put the MD back on with a new gasket and look some more.

[BA80]

Another thought, the crankcase vent is right behind the MD. Is it properly vented?

[skipper]

Ahh, good thought Greg. I have pods on the carbs and a small filter on the vent hose. I'll clean the filter tomorrow (shouldn't need cleaned, was clean when I put it on,,,,bout ten years ago)