smoke from crank case vent?

Hi,
I have an XJ750 powered Trike, it’s been in storage for a few years now because of a smoking problem,


A brief history:
• Bought donor bike as good runner with refurbished engine.
• Dismantled and started Trike project, built frame.
• 6 year wait while we moved house, raised son started new business etc.
• Completed first build of Trike. Noticed smoking oil from breather vent
• Life interrupts again, back in storage for 3 years.
• Fresh fuel , and a BIG oil cooler fitted fires up no problem but still smoking from crank case vent

As you can see in the picture the exhaust isn’t quite standard, so my question, can that exhaust cause a back pressure problem? Is it likely to be worn rings?( it smells of oil not exhaust). Is this normal for XJ750 and not noticed before because it had a pipe that went into the old air box? (Has K&Ns now) Or can anyone suggest an alternative cause for the smoke?

 

Mine used to let a little smole out after I shut it down I noticed. Then I found this form and just ran it into the airbox (there was even a nipple to hook it to there, duh) and it runs alot better now. The fumes oare supposed to be vented back into the engine to be burned with the fuel mixture.
The previous owner ran a long hose up under the seat and out the back for some stupid reason and I always wondered why?

 

Blue smoke or more like a steam ? It's supposed to "steam" out the vent , which normally you would never see because it is plummed into the airbox . Built up condensation in your crankcase burning off when everything gets hot , sorta like dew turning into fog when the sun burns it off

 

I wouldn't think the exhaust would be a problem. It looks short and loud enough. :lol:

I would suggest a compression test. One dry and one wet.

I'm guessing that after the rebuild it may not have many miles on it and may not have bedded in yet. Also the sitting around for so many years the rings may be stuck allowing some bypass pressure.

Compression test will indicate if that is the case.

 

Hi Nosebolt,

I've got exactly the same on my XJ650 Trike, it is the blow by gasses, and as previously mentioned you wouldn't normally see them because it goes into the airbox, at the moment I've stuck a 13mm KN style air filter on it and still get the gasses coming out. If you're an environmentalist, this may cause you a problem as they are supposed to be burnt. I'm looking at modifying one of my air filter pots to take a hose from there and back into no2 carb.

Hope this helps.

Lea

 

na it was the exhaust, all those bends are causing to much back pressure forcing exhaust gases past the rings, tried it with just down pipes and it stopped. Runs loud but sweet.

Decision time now, what to do with a very expensive one off hand made pipe that don’t work? Will have to see what I can salvage and maybe rework it with less bends.