Topic: Snowbound's 77 CB750F2

[Snowbound]

so here is another build for you guys to follow.
I'm new to the forum, and really, I am new to building a project bike.
I fell in love with Cafe bikes and decided after a year and a half of looking for the right bike, to finally take the plunge and buy a CB750F super sport. I ended up stumbling upon this bike literally 15 minutes down the road from me.
It was in a barn, collecting dust for the last 5 years, apparently ridden up until 2008. it was not running when it was picked up, brakes seized, no oil, some hand made side covers...but the engine cranked over and it felt like it had decent compression.
I got it for less than half the asking price at $600. so I was excited and brought it home and immediately tore into it a bit...
Filled it with new gas. replaced the blown fuses and the thing started first kick. So I have a good runner as she sits.
I plan on turning this thing into a cafe style build, and will attempt to tear this down, clean (carbs and everything else), and reassemble (with various modifications). not much to show off now. but I hope to update this through out the winter this year.

It came with some highway bars, leather saddle bags, and a sissy bar/rack that will not be going back on...

Cheers,
Snowbound

[SOHC4 Cafe Racer Fan]

Bring it on, Snowbound.  Looking forward to your build.  I'm sure you will have some great knowledge to pass on to the rest of us on wiring.

That's a hell of a sissy bar and side cover!  Great steal ($600) for a running bike.

[Snowbound]

not too sure about "great knowledge" but I might have some good resources!
ordered some gaskets and a master cylinder rebuild kit off ebay today. the thing leaks oil from the mission cover like mad. pics to follow when I get parts.

[lwahples]

Nice looking bike for the price.Traded a chainsaw for a 78F,but yours is much cleaner.Nice that it runs.

[Snowbound]

Anyone have this problem before? couple of cracked/broken bolt holes on the mission cover/gear selector cover?
I'm looking for some suggestions on possible fixes. I was getting a slow leak before I took the cover off. I am still getting a slow leak with a new gasket on. The threads still grab which is good because they are a little bit further down into the case.
And just for fun here are some pics of where a mouse found some building material...

[iron_worker]

A similar thing happened to one of my bolt holes. It was my lower timing cover bolt hole. I had a machine shop TIG it up and re-drill & tap it. By the look of yours, you don't have much else for choice either. You could try some sort of epoxy but I really don't have faith in fixes like that.

Not sure if you can braze aluminium but that would be a good fix as well IMO.

IW

[Snowbound]

I thought welding and drill and tap would be the way to go.
I don't trust the epoxy either, at least not for a very long time... I'd rather do it right the first time!
thanks IW

[madmtnmotors]

"Fixing" the broken sections does not appear to be necessary on the two bolt holes shown. It looks like the affected holes are where the locating dowels belong and the threaded portion of the case is unaffected. Where the case is chipped away to the inside (1st pict) would permit oil to weep out around the head of the bolt which could likely be remedied with a copper crush washer under the head of the bolt (thinking of the fork oil drain bolt sealing washer here).

[Snowbound]

madmtnmotors you are right the affected holes are exactly where the locating dowels belong. I'm not sure exactly what you are thinking in terms of the copper crush washer. are you saying you would put it on the outside of the cover? It really seems like my leak point is coming from the second picture which is the bolt hole closest to the alternator/stator. I only have a very slow drip at this point, but I will lose all of the oil in the bike over a few days. I was considering wrapping the bolt with a wrap of teflon tape to see if it would help.

[madmtnmotors]

I'm not sure exactly what you are thinking in terms of the copper crush washer. are you saying you would put it on the outside of the cover? It really seems like my leak point is coming from the second picture which is the bolt hole closest to the alternator/stator. I only have a very slow drip at this point, but I will lose all of the oil in the bike over a few days. I was considering wrapping the bolt with a wrap of teflon tape to see if it would help.

Yes, the crush washer would go under the head of the bolt, on the outside of the cover, because there is no longer any gasket surface between the oil (inside the engine) and the bolt in the first picture. I would expect oil to migrate out under the head of the bolt at this location. As for the second picture, there is still a gasket surface between the bolt and the oil (again, oil on the inside), which makes me wonder if the oil is leaking at the top bolt (1st picture) and migrating down to drip off of the second bolt (2nd picture)?

Anyways, Teflon tape will not help regardless of which bolt is leaking. The oil is not being pushed past the threads since these bolt holes are not "bottomless". The oil could be from one of several places:

>Through the bolt hole in the outer cover. This would be oil pushing past the bolt, through the bolt bore in the outer cover. This is not a threaded hole (threads are in the case) which is why Teflon tape would not help with this condition.

>Some other irregularity in either the outer cover or engine case mating surface creating an oil leak at the gasket itself. Clean everything (before you take it back apart) and use some spray powder between short runs of the engine to try to pinpoint the exact location of the leak.

>The adjacent alternator cover could be leaking, and the oil migrates down to drip off the bottom bolt in the transmission cover.

The copper crush washer is merely an alternative to restoring the little bit of gasket surface that would normally isolate the bolt from the engine oil (again, first picture).

What about the cover itself? Is any of the mating surface of the cover damaged in any way similar to the damage to the engine case mating surface?

[Snowbound]

the cover is in good condition with no irregularities. I'm pretty sure that the PO replaced it at some point.
thanks again for the info!