Lubricating a honda trans without pressure

[albertaphil]

Well, after 3 years hiatus, it's time to finish Hondarini, which is a 1980 CB400 into which I have shoved a Ruggerini MD151, which I found on Kijiji for $200. Booya!

Anywho, I'm using the Honda 6spd transmission which I cut off the original engine. Of course, the transmission used to be lubricated by engine oil under pressure from the oil pump. Sans oil pump, the simplest option seems to be filling the gearcase up until the oil just tickles the gears, at which point it will also be touching the main bearings. Great, right?

Well, I'm also using the original wet clutch, which I'll be chain driving in a sealed chaincase. The problem is that there is no way to completely seal the clutch side of the transmission case, and hence the chaincase from the transmission. I've attached a picture showing all the holes between the gearcase and the clutch case. I've plugged the gaping holes between the two sides, but oil will certainly seep through the main bearing and shifter rod way down at the bottom. And I doubt that I'll want to have my clutch running half way up in oil all the time, making foam and heat.

So, I need some way to have the oil level in the chaincase about 4 inches lower than in the gearcase. At present, all I can come up with, short of installing an electric pump between the two, is to make a small hole between the two sides at the bottom of the case, and then running a hose from my airbox or air intake pipe down to the transmission, thus creating a low pressure area in my transmission and allowing atmospheric pressure in the chaincase to push oil through the little hole I made back up into the transmission side. You know, start the bike, let it warm up, and only have to ride for a couple of minutes until the oil is all back where it is supposed to be.

I'm planning on running some kind of light engine oil, rather than gear oil.

What are the odds that my scheme will work? Obviously, it the amount of vacuum present in my airbox or intake pipe will determine any sucking of the oil from the chaincase into the transmission, and i would also need to ensure that the chaincase is at atmospheric pressure via a hole to the outside world that I'll have to keep dust and crud out of.

I'm extremely open minded when it comes to other ideas that are easier, cheaper, and more effective:-) Thanks in advance.

[XLerate]

Interesting. Sorry, I don't have an answer to your questions.

Do you have more pics and the details of cutting down this CB400 Honda engine into a trans only? Can't see much in the pictures posted and focus doesn't allow any detail when zoomed larger. Some more info on the trans might help with some answers to your questions.

[albertaphil]

Hi there, I have a thread from way back here: https://www.dieselbikeforum.com/view ... =31&t=1225

In its original configuration, the oil level was several inches below the level of the gears in the transmission, and was pressure fed to the bearings and gears. I hope the photos give you what you need. Thanks.

[tappy]

Hmmm, not convinced. I think it'd be hard to ever know what you'd actually got / what was going on in there. If the engine over-heated or the oil produced too much vapour could you get a runaway engine also? Particularly when the clutch starts thrashing harder with a hot engine?

Why not just install a small electric pump (or gear driven pump) to pump the oil through the original oil jets instead? Exactly as Honda intended, and all oil thrashing problems gone...

[XLerate]

Hmmm, not convinced. I think it'd be hard to ever know what you'd actually got / what was going on in there. If the engine over-heated or the oil produced too much vapour could you get a runaway engine also? Particularly when the clutch starts thrashing harder with a hot engine?

Why not just install a small electric pump (or gear driven pump) to pump the oil through the original oil jets instead? Exactly as Honda intended, and all oil thrashing problems gone...

If the two are separated I don't think the trans oil could cause an engine runaway. Regardless, the simplest solution is often the best and as suggested an auxiliary oil pump or connecting to engine's oil pump if it has one sounds best.