Crankcase Leak test on 94 SPX? Tips and/or How to?

[randomguy]

As some of you know, I've got my 657 crankcase together and my top end on. I've done a squish test and need to change the base gasket to get my squish in spec. So I've got a few days down time and figured I should be checking for crankcase leaks.

I'll be borrowing a pressurization system from a buddy, but I'm wondering how everyone does this?

1. RV on or off?
1a. If it's off, how do you seal the intake holes?
1b. I've left my intake manifold and my carb together as a big sub-assembly. If everything should be ON, do I need to plug ALL the holes? I'm pretty inexperienced when it comes to carbs.....
2. What do you guys use to seal up the exhaust system?
3. Through which hole do you apply pressure?

I've got access to a water jet through work, so I guess I could make some little plates and bolt the gaskets on to the jugs' exhaust ports. I can use the spark plugs and the temp sensor to close up the top side, but I'm a little lost on what I should do about the intake side.

Suggestions? Doesn't really look like there's anything in the manual and I searched around here for a "leaks for dummies" type post and didn't find much. Thanks a bunch!

 

[Dr Honda]

There is 3 block off plates. One for each carb, and one for the manifold. (Remove the carbs, and the tuned pipe) Then... you cap off the 2 oil injection nipples, and they pulse hose. Then... you pressurize though one of the spark plug holes.

If you remove the manifold, and block off each of the ports... you need to use a "Y" to pressurize both spark plug holes.


Your engine should hold 10 psi for 5 to 10 minutes.

 

[randomguy]

Ok - So I got the carbs off the intake manifold. I'll make the block-off plates tomorrow at work. I've got to get some of the larger oil line tube and I'll plug those with a bolt or something and a hose clamp.

But I'm a little stumped about how I'm going to interface with the spark plug holes. A buddy of mine says he's got a pressure test system that I can borrow for the fuel system, but I'm assuming that it doesn't have some kind of special fittings to mate with the plug holes. Seems like the the threads are M14x1.25, which is an extra fine pitch. What do you guys do to be able to apply pressure there? Are there store bought fittings for this, with a male M14x1.25 and a barb or something on the back end for tubing?

Thanks!

 

[randomguy]

I got all my parts together and made up my leak test rig. I didn't want to have to get my gaskets wet with soapy water, so I bought some gasket paper from AutoZone to make some temp ones up. They were out of every kind but one so I got it. Put everything together and my block off plates on top of the oil pump leak like sieves at 10psi.

Then I noticed on the gasket material that it says "for water and coolant". Is it normal to leak air like this? The gasket material is pretty tough..... Should I go somewhere else and try to score some thinner stuff? What type and thickness do I want? I intend to leave them in for the intake side permanently. Will the exhaust ones leak air and/or is it a problem if I soap the edges of the gasket while sniffing for leaks?

Thanks!

 

[Dr Honda]

What did you make your plates out of? 10 PSI puts a lot of force on the plates. They could be bulging, and letting the gaskets leak.

 

[randomguy]

I wondered about that... I used aluminum. So I looked up some block off plates online and they looked like anodized alum. 10 PSI on a 1.5" diameter circle is almost 18 lbs of force. I wouldn't *think* that would be enough force to create enough deflection, but I can't do the math on it since a two bolt flange isn't a uniform cross section. I guess I'll shoot another set today out of steel and see what happens.....

Do you think the gasket stuff I got should work though? It's pretty thick and it cuts like crap with scissors. Looking on AutoZone's site, I think it's Fel-Pro 3075, which is described as "Fel-Pro/10 x 26 x 3/64 in. rubber and cellulose gasket material sheet".

 

[Dr Honda]

if you do them out of either aluminum or steel... I would make them out of 1/4 plate. (Even thin steel flexes)

 

[randomguy]

Yeah the first set I made was 1/4" aluminum..... And I used a torque wrench to tighten the bolts.

I'm going to look for some 1/4" steel. If I can't find any scraps, I'll use 1/2" alum. I think there's enough stud sticking out to still get the nuts on with a 1/2" plate.....

 

[randomguy]

Ok, so I made some plates from 1/2" alum and I have just enough stud for the nuts to grab. At a coworker's suggestion, I soaked the intake gaskets I made in a little oil before assembling. I assembled and applied a little pressure and soaped. There still was a tiny little bit of leaking, but it was next to nothing.

Then the front crank seal blew out of the case. I'm pretty much beside myself at this point. I didn't get pressure above 12psi or so. I can get the seal worked back in there, but now it blows at about 6psi.

What do I do now (other than head out for beer)? Very frustrated......
***** edit *****
Just realized something. I don't have the FW housing or the coil on. Seems to me that the coil would hold that seal in there. Should I install the coil (or a dummy plate) and retest? Should I consider that seal blown and worthless or will it still be cool once it's assembled?