FJ1200 base gasket leaking

[FJscott]

I agree Noel. The negative pressure inside the airbox is an definite advantage for scavenging crankcase pressure.

That's the reason pro stock drag bikes have (several) vacuum pumps.

I looked at my UniPods to see if there were a way I could pipe in the crankcase vent hose but there was no room that I could see on the Uni's rubber mounting base.

After a long hot ride, stopping at a signal and smelling the blow by coming off the crankcase vent is annoying

What if you made a vacuum manifold coming off of all the nipples on the intakes? The ports we hook up the sync gages. Parker/ rancor company makes vacuum breakers I believe as small as 3/8in. Our crankcase filter we install would attach to the top of the vacuum breaker. Huh...second thought, probably a bad idea to equalize vacuum on intake side of carb. Should be on filter side of carb

Scott

[simi_ed]

Yup, need to be on the filter side of the throttle butterfly.  Downwind=manifold vacuum, NG.  I remember looking for a place to install a hose barbed fitting and there was no room.  Maybe on the next-gen of Uni-pods ...

I guess nobody got/liked the Hunt for Red October reference, huh?

[FJscott]

I got it, being ex bubblehead...couldn't find the "like" button

S

[JMR]

 Did you use any type of sealant on that gasket (Hylomar etc).? I have seen Cometic fiber base gaskets "push out" when gasket sealer is applied or if they become saturated with oil..
It looks like the oring lifted as well in that pic....that's odd and interesting. Fiber gaskets suck in general IMO....MLS, Viton coated steel, foam/steel core or orings are what I prefer. Copper seals well against everything but oil.
I wouldn't bother with cylinder head retorquing either.

[andyb]

The interesting way to create an artifical vacuum is to use the exhaust, not the intake.  A venturi tube in the collector at the appropriate angle with a fancy high-temp, high-speed PCV valve can be used to evacuate the crankcase pressure very effectively.

I've never seen an actual pump type setup on a drag motorcycle.  Occasionally on cars, though.  Seems that the weight is excessive on a motorbike.

[JMR]

Years ago pro stock were using vacuum units and than started stacking them. They were then regualted to one unit, Gast still sells them though I don't know how they are used with the Vtwins (if they are used). I don't the exhaust units actually pulled much vacuum as there was always reversion etc.

[andyb]

That's why you ran the flapper valve, to stop the reversion.

[Bozo]

Interesting replies, I agree the vacuum from the intake would help, but I still believe there is a problem with the gasket material. It turns into mush, remember I had no sealant it was an OEM gasket, std cams, Wiseco 1200, slightly higher compression etc. 28K kms since rebuild compressions even from 160 to 170psi.

The couple of riders from the KZowners forum had the same problem as I did with my Z1-R. I do know it was a quality gasket but my log doesn't state what type (45K kms)

[aussiefj]

I've had the same problem with fumes at a standstill when the motor is hot, currently trying this set up, only been running it a month or so, gets rid of the fumes and doesn't seem to have any adverse effect on carburration, but  I read some posts that say it's better to vent to air than recycle through the carbs, so I'm not sure about carbon build up etc. long term, and then again some say the oil helps lubricate the valve stems. Does anyone know truth in all this?
Anyway I used a Chammy container, don't know if that's what you call it elsewhere, the larger tube comes from the crankcase breather and each carb should more or less get an equal dose, you can see the condensation in the tubes. I made them all push fits so there is nothing to come loose and end up in the intakes. Not sure if some sort of filter would be a good idea inside the container, but so far the is no build up of oil residue etc. in the bottom of the container. The alloy checker-plate has nothing to do with it, that's just where I keep my tool kit.

Cheers, John

[Pat Conlon]

Thanks John, that's a nice setup.....yea, I'd love to do something like that with my UniPod foam filters, but no way I'm going back to a paper filter. I have not had good results from K&N oiled paper filters, except in my Miata.
No room for nipples on the rubber base material on the Uni's so that leaves the foam filter material itself.
Some threaded hose nipples with washers might work on the foam, but I doubt it, the hose stress on the foam material will probably cause a failure.
Inside the UniPods there is a stainless spring that holds the shape of the intake chamber, preventing the foam from collapsing from vacuum.... Perhaps there is a way that spring can be used to support the vent hose?
I'm working on it.....

Re: Lubrication...I suspect the oil vapor coming off the crankcase won't be any lubrication benefits since it would the thoroughly diluted with the fuel/air mixture from the carbs.

Cheers Pat

[aussiefj]

Hi Pat, I'll probably tidy it up a bit once I'm happy it works ok it looks a bit cheap and nasty at the moment but it was just bits and pieces I had lying around. I did try it first with the foam uni pods, by making a hole through the back between the two outlets but there is a piece of foam between the two springs that gets in the way and I managed to tear a hole in the outer foam cover mucking around with it but there is a possibility there, I may play around with it a bit more, just need to attach a right angle fitting in there between the outlets run two hoses into a Y piece and onto the crankcase breather, it would be a lot neater set up and hidden under the pods.

Cheers, John

[racerrad8]

I am going to let my inner voice of reason speak here...

I believe that is a bad idea.

On the factory air box the breather hose is venting out of the direct suction of the carb throats. The air box connection is under the carbs so the oil & water contaminants can drop & drain before being sucked into the engine.


The slides are not very happy when they get anything on them as they then start sticking. The water vapors you see in the hose will also be in the throat of the carb and cause corrosion of the raw aluminum carb bodies and oil vapor will allow crud to build up and cause slide problems over time.

And finally, the amount of suction you have at the pod air filter is so much greater that you no longer have a crankcase vent, but a PCV system. Sure, the air box is considered a PCV system as well but it is using the totality of the vacuum from the carbs at a 180* and greater distance from the vacuum source.

Randy - RPM

[Bozo]

Did you use any type of sealant on that gasket (Hylomar etc).? I have seen Cometic fiber base gaskets "push out" when gasket sealer is applied or if they become saturated with oil..
It looks like the oring lifted as well in that pic....that's odd and interesting. Fiber gaskets suck in general IMO....MLS, Viton coated steel, foam/steel core or orings are what I prefer. Copper seals well against everything but oil.
I wouldn't bother with cylinder head retorquing either.

Sorry haven't replied earlier, I'm still on a job away from home. As I stated the gasket was installed dry, the O'ring was brittle? it also was put on with a silicon lubricant (Randy stated that the O'ring is not necessary). My motor ran very hot when I had the Megacycle cams especially in the Oz summer in peak hour traffic (vapour came out of the oil breather when stopped at lights) so I guess that cooked the O'rings as for the gasket???. Now I have XJR1300 base (steel) gasket and the standard steel FJ gasket, both lightly coated with "Copper coat" just to be sure.

[aussiefj]

I am going to let my inner voice of reason speak here...

I believe that is a bad idea.



Randy - RPM

Thanks Randy, maybe time for a bit of a re-think then, how about some sort of filter between the tube from the crankcase breather and the the tubes to the carbs? and a drain to get rid of condensation.

Cheers, John.

[Pat Conlon]

Actually I was thinking along the lines of a sealed catch can (not vented) This would allow the oil to condensate and collect before routing thru the carbs. Fill the can with scrub able stainless steel to help separate the oil out of the blow by vapor. Have a drain at the bottom of the can where you can periodically drain off the accumulated oil.

We use this set up in turbo Miata's all the time. It works well. Not exactly CARB approved 'thou...

I'm mean, jeeze, we got all this room now that the airbox is removed. We can come up with something.

I'm tired of a stinky bike at stop lights.