The Hodaka Club Forum

Does anybody put anything on their head gaskets?

I thought base and head gaskets were supposed to go on dry but when I put the engine together after replacing them, it leaked oil (or premix) from the front and rear on the head while running. I've got some permatex copper spray gasket I was gonna use. Is it leaking because it was dry or because the mating surfaces might be warped?

I don't know if it makes a difference but I've got a 1972 wombat 94 with an 0.080 over piston/cylinder, 28mm Mikuni, Uni filter, expansion chamber sealed with RTV, with new base, head, and intake gaskets (that all went on dry)

I recommend applying plain old axle grease to the base gasket, then wiping it all off prior to installation. The grease application may(or may not) aid sealing (I think it does a bit), but I know it is a great aid when it comes time to remove the base gasket the next time the top end comes off for work.

I install head gaskets dry and CLEAN - all surfaces must be clean.

Your head gasket leak could have come from any one or more of the following items:
- grunge
- warped/damaged head
- warped/damaged cylinder surface
- damaged head gasket
- improper/un-equal head nut torque (Workshop Manual recommends 170 in-lbs. for the 125cc engines, modern day recommendation is 250 in-lbs - 300 for a high zoot racer 125cc) I like to tighten down all the head nuts in 50 or 75 in-lb. increments to keep from distorting the head.
- and here is a strange one . . . check that ALL your head nuts are tapped deeply enough to allow them to tighten down on the head properly. (I've bumped into a situation where one head nut was not tapped deeply enough. That nut would "jam" on the end of the cylinder stud and 170 in-lb torque could be reached BEFORE the head nut/washer came down on the head. This resulted in 3 properly tight head nuts and one "floater". Not good. Allowed head leaks to develop repeatedly.)

Ed

I had my 94 Wombat bored by Danny Messmore and while on the phone I told him about my 95 Combat Wombat engine that was also freshly bored and that the compression was low, he said a light coat of silver spray paint may help due to it's metal content. I have not tried it. I did not have the problem with the 94 Wombat engine.

I have used silver paint for years building hot rod engines that used steel head gaskets and on some hodakas as well , but it wont fix a warped head it will aid in filling small machining grooves though , but if everything is perfect no sealer is needed. Best take a flat piece of glass with a sheet of sand paper on it and scrub the head accross it evenly till all low spots are gone.

Rich

Thanks for all the advice

I tapped all the bolts prior to putting it together and cleaned all the studs. They should have all gone on freely. When I torqued it, I did it in 5 ft/lb increments (about 60 in/lb), 3 times around making it about 180 in/lbs. I was using a bar torque wrench so I don't know how accurate it was.

I just got some glass the other day just for this. I'm gonna do a couple passes with 220 and see if there are any high/low spots. That will at least let me know if it is the head at all. If it's still leaking after I run it then my guess is it's the cylinder.

It sounds like you did everything in a craftsmanlike manner, so "non-flat" sealing surfaces are the prime suspects at this point.

The bar type torque wrench has a lot going for it. It is dead simple, there are no detents to wear or moving parts which can get gritty -- only a simple "beam" and a pointer and scale to show how much the "beam" has flexed. Accuracy (actually, repeatability) of torque depends primarily on the use of craftsmanlike repeatability of procedures when tightening the head nuts . . . and I am confident your procedures are sound.

Note: You can be quite comfortable bumping your head nut torque specification to 250 in-lb on the 125cc engine. This advice is coming indirectly from Harry Taylor through an ex-PABATCO Service Dept. guy - (me, who has backed HT's recommendation down by 50 in-lb for general use engines) - to you.

Ed

If your using " flat glass", be sure it is at least a quarter inch thick. Anything less is extruded rather than poured..................D

Also look at the ends of the bolts. Ive seen some with casting blobs on the end that will make them bolt bottom out. I trim my bolts by a few mm . Also check your bolt washers are standard thickness, a thin washer (or No washer)could also allow the bolt to bottom out.

Good thought Kev. In addition, it occurred to me that simply running a tap in and out of the head nuts to clean the threads may not really establish whether or not the threads go to the proper depth in each nut. A specific check of the threading depth is recommended when otherwise un-explained head gasket/base gasket leaks appear.

Ed

I got a 1/4" piece 12"x12"

Ok, I will go with 200 in/lb this time. I'm pretty sure the bolts are free of any "blobs". I cleaned the outside of them up on the bench grinder and would have noticed something like that. I actually got new washers before I bolted it up so I should be good on that too.

Is there any way to check the bolt depth without taking the jug off? I would like to avoid this if possible just because I have everything hooked up already (exhaust sealed, intake, carburetor, air filter, etc.)

Easy just sit the head on and with a washer in place measure down to the shoulder in the jug. Now compare with the bolt depth. I'm sure that will be ok. Just one other thing , the case studs have different length threads at either end. If one of these has been reversed over the years it could cause a problem but you could tell because the bolt washer might still spin when the bolt is torqued up .
I had an after market head that would not seal ,dispute all efforts and measurements . The fix for this was to turn down the head surface a few thou, except for the flame ring (liner). This enabled the head to bite into the gasket better. Always seals now.
Kev

Ok I will try that thirdstone.

I cleaned up the mating surface earlier today. All around the inner edge was low. The worst was in front and in back right on the inner edge. This is where it was leaking. I started with 220grit using wd40 to lubricate and did it in a figure 8 pattern that I remember seeing in a different manual. I had to keep doing it over and over until I couldn't see anymore low spots. Then did it a couple times with 320 because it seemed like there were too many (light) scratches left. It looks pretty good now. My guess, just from looking at where the irregularities were, is that the person before might have over tightened the bolts. That's why the high spots were on the outside and around the bolt holes from the aluminum pulling in with all the torque. Also when I took the bolts off for the first time they were really on there and much harder to break loose than this time that I took them off with the right torque. Does this make sense to anyone?

We'll see if this works.

If we didn't have a new head gasket we baked an old one in the oven for a while. Also we could spray Al paint on the head gasket. I always hand lap my heads on glass with wet or dry. I oscillate the head back and forth in a quarter circle rotating the head now and then. I use an inch pound torque wrench when inch pounds is specified and always use a quality adjustable break away torque wrench. Clarence

I noticed the same issue this weekend. Not sure what happened. I'm positive it wasn't leaking before. After searching, I finally used Permatex Motoseal 1 sealant. The website doesn't indicate usage on head gaskets but it does on the packaging. It's still holding after 30+ miles of medium to heavy riding, trying to break it open again.

Roger