Crankcase gasket issues

[oleraj]

Hello Thumpertalk Community!

It's been a while since i've been on this site, but its definitely good to be back. 

 

I have a question regarding the left crankcase seal. The bike is a 1971 Honda SL 175, but the problem isn't specific to an aspect of that bike. The bike has leaked oil out of the crankcase seal for a while, and at the beginning of this year when I had it all drained I put in a new crankcase seal, and put the cover back on with an impact driver. Despite the new seal, the bike continues to leak, and worse than it did before. Once the bike warms up, oil will drip/pool up and eventually drip off the crankcase bolts. What's making it difficult to do a sketchy repair with some gasket glue type of thing is that the leak is from the back of the seal. The way the left crankcase on this bike is setup is essentially there are two covers. There is the actual crankcase cover, and then another cover behind (towards the back of the bike, not under) the main cover. This cover houses the shifter, front sprocket, and clutch mechanism. I was wondering a couple of things: Why would this still be leaking despite the replaced gasket? It didn't appear to have any dings or anything along those lines that would act as a channel for a leak. Also, is there any sort of quick fix for this? I really just want this bike to stop leaking oil. 

There are pictures attached, I basically just took a couple of the entire thing, and then a bunch looking towards the front of the bike inside where the sprocket cover was. They aren't the greatest because its difficult to see in there, so I took and uploaded a bunch. The gasket is on the left side of the pictures inside the sprocket cover if that helps at all.

 

Thank you very much in advance, both my father and I have looked at this multiple times and can't seem to find an obvious problem/solution. It's my grandfathers bike from back in the day and he loves to see it taken care of and still running, so I'd like to keep it that way!

 

[joshrf450]

Did you over tighten it? This happened to me but on a different bike and i actually tightened it to much and ripped the gasket! You could always use a bit of gasket seal on the area leaking

[knudsen]

Impact driver is likely your cause. Use a small torque wrench and torque in small increments in the proper pattern.

Grease the gasket.

If that fails, use a thin thin thin coat of hi temp rtv on both sides of the gasket and the case and cover mating surfaces, let those all dry just enough to get a skin. Then assemble just finger tight, just enough that the surfaces all mate. Let it dry overnight, then torque gently to spec. Oh, clean the metal to perfection first, and wipe with acetone until nothing comes off.

[adnohguy]

I started working at a Honda Motorcycle shop in the early 70's

Back then we always used silver paint on all OEM honda gaskets.

No glue, no sealer, no grease, just cheap silver spray paint. (we called it okey chrome back then.

It was also called "Barden bumper" paint.

Back then, it was the best thing we could find that always worked.

It stopped our "oil leak" comebacks.

They way we found out about silver spray paint was we were building SL100/125's into 144cc dirt bikes.

Brand new bikes were being built on a makeshift assembly line in the shop.

We used CB 750 pistons and the left 28mm carb (with choke lever and it used a throttle cable)

We bored the sleeve out and the cases, built our own sleeve from a CB92, ported the heads, cut valve reliefs on the intake side of the piston and installed a Supertrapp XDUSOR muffler.

It seemed like We built 100's of them over a period of several years.

But early on, every single on we built came back for the cylinder base gasket leaking oil.

Every thing we tried always failed.

I don't remember who in the shop discovered the silver paint solution but it was more than likely Roger Oliver.

All customers were very happy again

And from then on, we used silver spray paint on every gasket on all bikes.

Edited May 22, 2014 by adnohguy

[knudsen]

Wow, whooda thunk paint? Assembled wet?

[firstplacephoto]

paint both sides?

[adnohguy]

Yes paint both sides and let it dry for about 10-15 minutes before installing it.

Should be dry to the touch before installing.

(But takes a couple of hours to cure)

Then you can start it after that.

[knudsen]

Thanks for yet another great tip adnoh, I'm anxious to try. Just not anxious to try now, no stubborn leaks at the moment.

BTW: did you see the xducer vid? Pretty sure I posted it here. Sadly, no bug in da box sound. I've been running it for a few weeks now. Loud.

[adnohguy]

Yes, all the XDUSOR memories were great.

Much appreciated :-)