FJ1200 base gasket leaking

[Bozo]

I had an incident last week where my base gasket started to leak after 28K kms after the last rebuild. I found that the gasket started to "disappear", basically in places it disintegrated and in other areas it was brittle (OEM gasket was used). The head was re-tensioned after 1000kms.

I had a similar incident with my Z1R where the base gasket fell to pieces, I'll take a guess here but it appears that the newer gaskets don't have asbestos and basically can't handle the heat too well.

After a quick email to Randy, I found out he uses the steel XJR1200/1300 for the same reason - (Again what would we do without Randy's Knowledge)   

Maybe its just me but I couldn't find similar topics so I posted mine to make people aware of this problem.

[racerrad8]

John,

I think I saw an order come through for you but I don't recall a base gasket. Did you find one local?

Randy - RPM

[turbocamino]

wow...thats nasty...has to be some cheap azz material !

[Bozo]

wow...thats nasty...has to be some cheap azz material !

No this was a genuine Yamaha gasket, Randy apparently has seen this before so its not uncommon.

[racerrad8]

wow...thats nasty...has to be some cheap azz material !

The same stuff you had on your clutch cover...

Randy - RPM

[ribbert]

I had an incident last week where my base gasket started to leak after 28K kms after the last rebuild. I found that the gasket started to "disappear", basically in places it disintegrated and in other areas it was brittle (OEM gasket was used). The head was re-tensioned after 1000kms.

Maybe its just me but I couldn't find similar topics so I posted mine to make people aware of this problem.

I have my original engine in bits for the same reason, not sure what the mileage was but probably a bit more than that. It was a Wiseco supplied gasket (came with the 1219 kit) and literally blew out in a couple of spots while on a trip, enough to get oil all over my left boot which made for some terrible gear changes.

Noel

[Pat Conlon]

What blows this base gasket out?
Crankcase pressure? If so, then can you take any steps to relieve the pressure? Additional venting, etc?

[FJ_Hooligan]

Pat,
The pressure results from having to move air under the piston.  The piston is moving fast and that air has to go somewhere.  If it doesn't move fast enough to the cylinder(s) moving in the opposite direction then pressure will build.  Manufacturers have tried to relieve this by boring holes in the side of the cylinders (near the bottom where the rings never get) to aid the airflow between cylinders, but there's only so much they can do.  The rest is physics. 

[Pat Conlon]

Thanks Hooligan, I vaguely recall a modification where additional holes were drilled for this purpose (air balance) but my memory is co-mingled between the Miata's BP1.8 and our FJ engines.

Is there anyway this can be done on the FJ?

[racerrad8]

That gasket failed for no other reason than substandard gasket material combined with expansion & contraction of the case & barrel.

This was a problem addressed by Yamaha a long time ago when they went to the current steel coated base gasket.

Crankcase pressure, not in a normal operating FJ, unless the rings are worn out. If crankcase pressure was an issue, Yamaha would have done somethin different.

Randy - RPM

[oldktmdude]

I have my original engine in bits for the same reason, not sure what the mileage was but probably a bit more than that. It was a Wiseco supplied gasket (came with the 1219 kit) and literally blew out in a couple of spots while on a trip, enough to get oil all over my left boot which made for some terrible gear changes.

Noel

Noel, how many kms did you do before this problem occurred? I have the 1219 kit in my '85 and have done approx 30,000kms, so hopefully I don't encounter the same situation.  Pete.

[ribbert]

Pat,
The pressure results from having to move air under the piston.  The piston is moving fast and that air has to go somewhere.  If it doesn't move fast enough to the cylinder(s) moving in the opposite direction then pressure will build.  Manufacturers have tried to relieve this by boring holes in the side of the cylinders (near the bottom where the rings never get) to aid the airflow between cylinders, but there's only so much they can do.  The rest is physics.  

I don't understand this at all.

The cylinder protrudes well beyond the casing into the crankcase, the base gasket is not subjected directly to this pressure, only general crankcase pressure.
The cylinder already has a hole to relieve the pressure from the descending piston, a 3" hole directly under it. How can the pressure build when there is nothing to restrict it.
The bottom of the cylinder is open to the crankcase with no restriction, the pressure has plenty of places to go and the FJ is a short stroke engine anyway.
If you've got a 3" hole directly under the piston I can't see how small holes around the base of the cylinder are going to achieve much in terms of expelling air from one cylinder and drawing it into another, unless you're talking extreme performance engines where every 000001% helps.
I wasn't aware manufacturers considered this a problem on production engines.
Then again, possibly I'm just out of the loop with what's going on.

Noel

[ribbert]

I have my original engine in bits for the same reason, not sure what the mileage was but probably a bit more than that. It was a Wiseco supplied gasket (came with the 1219 kit) and literally blew out in a couple of spots while on a trip, enough to get oil all over my left boot which made for some terrible gear changes.

Noel

Noel, how many kms did you do before this problem occurred? I have the 1219 kit in my '85 and have done approx 30,000kms, so hopefully I don't encounter the same situation.  Pete.

I don't know Pete, I don't keep records of anything for the bike, but it was probably about 50 or 60,000 km's.

Interestingly, it failed 600km's into a ride literally the day after I removed the crankcase vent into the air box and replaced it with a small filter. Not saying this caused it but I do suspect it brought it on.
In my opinion, replacing the original configuration, which sucks air from the crankcase, with a filter that creates a restriction (not much though) is going to raise crankcase pressure.
Not that this is any reason not to fit unipods, the gaskets were dodgy anyway, but the previously dry, and never touched motor currently in my bike, has become increasingly weepy around the base gasket too.
Engines since the 30's have always had some sort of assisted venting. Many will remember the old "draught tubes" and mesh filled oil filler caps on cars. The length and angle of the tube was by design to catch the airflow under the car and suck the fumes out.

Randy would know better than me, but I'm not overly confident in Wiseco's ongoing commitment to supplying low volume items, I'd get a set of rings and a head gasket (not very expensive) and stick them on the shelf in case you need them one day, and if you don't, and they become unavailable, you can double or treble your money.

Noel

[Pat Conlon]

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

[FJmonkey]

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

Just pretend that the smell is positive ions.... Ride on my friends....