Another rookie question and possible mistake.

[Dunn111987]

So I thought I had things sealed up and in good shape on my ace 100 engine. But there's premix coming out from around the base gasket now. I got one end sealed up and now the other is leaking. Is it possible I may have put the base gasket on backwards? I feel dumb now. Sorry I keep bugging you guys with my rookie questions. Lol

[taber hodaka]

It is possible, but not likely as it corresponds to the shape of the cylinder and crankcase. Are you sure the fuel is not coming from the exhaust? --------Clarence

[Dunn111987]

Almost positive it's coming from the base of the cylinder. I was turning the flywheel back and forth and I can hear it seeping out. And see it getting wet.

[Bullfrog]

If you got the base gasket on the wrong way, there should be some significant bits of gasket sticking out and quite visible. Since the gasket is symmetrical side-to-side, it doesn't matter which side is up IF the front of the gasket is indeed toward the front of the engine. But if the front of the gasket is facing to the rear, the "bump outs" for the transfer passages are going to be in the wrong place.

The engine has to be air-tight . . . so seeing and hearing leakage means the top end has to come back off to figure out what is wrong.
Ed
PS: This is how you gain experience. We've all been there. And the group will try to help in any way it can. Hang in there, it'll come together.

[thrownchain]

Are the cylinder head nuts properly tightened to spec?

[viclioce]

That would be my first guess as well. Did you use a reliable torque wrench to tighten the head bolts? 125 inch pounds or 10.4 ft lbs. Victor

[thrownchain]

I'd shoot for the 200 in/lb range.

[taber hodaka]

The ace 100B torque is 105 inch pounds. Be careful here, you already have had cylinder bolt failure. 105 will get the job done unless there is something wrong. Also what diameter are the studs? I do not have the spec torque for the 100B+. I would not use foot pounds on smaller bolts. ----------Clarence

[thrownchain]

Make sure the studs are the correct length, you want to make sure you have enuff threads to get the head tight before you run out of thread. If the studs aren't threaded far enuff into the case they will be too tall at the top side.

[Dunn111987]

I tighten the nuts to about 8 foot pounds. I don't have an inch pound torque wrench. I went off the 100b specs in the manual. Is it possible maybe that's not tight enough to seal right? Have to check the stud diameter. And the torque wrench is brand new. Thank you to everyone for being helpful with suggestions and advice. Makes me feel better about learning this stuff. I have a great desire to become good at working on these older 2 stroke machines.

[Dunn111987]

Maybe it's possible I didn't get them tight enough into the cases! I was trying to be careful and not damage anything. So I didn't go too tight with them.

[Bullfrog]

Since it is important, I'll repeat the comment that the proper head nut torque for the 100-B engine is 105 in-lbs (8.75 ft-lbs). So just shy of 9 ft-lbs on your "ft-lb" torque wrench should be good . . . and since straight up 9 ft-lbs equals 108 in-lbs, using 9 would be fine and might help assure accuracy/repeatability when torqueing all 4 head nuts down.

I'm not sure where Victor came up with 125 in-lbs - that is not the correct specification for the head nut torque on any Hodaka engine. So Victor, you might want to double check that . . . and don't use that spec on the Road Toads you are working on. The correct specification for Road Toad cylinder head nut torque is 170 in-lbs (14.2 ft-lbs).

Thrownchain is probably onto the problem - the nuts are probably "bottoming out" at the inner end of the threads on the studs BEFORE coming up tight on the cylinder. If that is the case, you have at least one nut which is torqued to 8 ft-lbs onto the stud, AND the stud is torqued into the case at 8 ft-lbs also (all of which is OK) EXCEPT it is all as though the cylinder wasn't even there (cuz the nut hasn't clamped down on the cylinder head/cylinder stack yet - so it is sort of "floating" between the cases and the head nuts). It would be good to "chase" the theads in all four head nuts just to be SURE there is no problem there. (I've personally bumped into head nuts on a 125 engine which did not have threads tapped deep enough.)

Here's what I would recommend - short threads on the studs go into the cases. Use Blue Loc-tite and torque 'em to 8.75 (or 9.0) ft-lbs. Grease your new base gasket before installation and make sure the front is to the front (transfer passage "bump outs" will match the gasket). Install cylinder, head gasket and head. Install head nuts and torque to 8.75 (or 9.0) ft-lbs (NO locking compound here). You should be good to go.
Ed

[viclioce]

Someone else told me 125 inch pounds for the Ace. If it's wrong, I wasn't aware. That's what I've been going by. I think 170 is what I have been using for the Toads! Thx! Victor

[ossa95d]

Ed can you please clear something up for us. You mentioned putting the short threaded end of the studs into the cases. If the long threaded ends of the studs are bottoming out in the cases before using up all the threads, this would definitely give you more threads to work with on the top of the studs, effectively shortening the studs. Some of us recommended orienting the long threaded end of the studs into the cases to give more strength to the threaded connection into the aluminum. I think I have oriented the studs this way but maybe I am using thicker washers. Now I am thinking that my memory may be wrong. Since you would know better than anyone, here is the question... "Which orientation is correct, long threads up or long threads down?" Thanks

[Dunn111987]

Uh oh. I put the longer end into the cases. Maybe I made a mistake there!

[ossa95d]

That's what I was thinking Dunn. If the studs bottomed out before using all the threads on the long end that could make the stud too long to fully clamp the head and cylinder in place. Might be an easy fix.

[Dunn111987]

I will give that a try later on today! Sure hope that will fix it.

[Bullfrog]

Ivan, you may be just the guy to double check me on cylinder stud orientation. I based my comment on stud orientation on a fuzzy memory AND the actual situation with 125cc (Model 94 and later - includes late model, primary kick 100's). Since the only ACE type engine I have on the place is a toaster tank Dirt Squirt and it is in running condition, I'm not going to pull the top end to check stud orientation. However . . .

. . . it is certain the 8mm cylinder studs are intended to go in the cases with the short threads down . . . and I can document that with photos as soon as I learn how to post photos directly. (working on that in the background - or maybe the photo will show up when I post this)

The threads on the bottom (short thread end) of the 8mm studs have "flat faces" at the "peaks" of the threads rather than the normal "sharpish" thread "peaks" found at the top end (long thread end). This provides for an "interference" fit into the cases so the studs won't tend to back out when the cylinder head nuts are removed. Ivan, would you grab a magnifier and compare the "short thread" end (bottom end) to the "long thread" end (top end) on an ACE type cylinder stud and report your findings? I'm semi-confident you will find the same thread differences. And if you do, it will confirm that the "short thread" end is indeed the bottom end of the cylinder stud on the ACE engines also.
Ed

[Bullfrog]

OK, trying again to attach the photo.

[img]CylStudsLrg0326Cweb.jpg[/img]

Ed

[Dunn111987]

Ok so I turned the studs back around. Base gasket leak goes away, but the head won't tighten on that one corner now. It's like the longer threads were able to reach further down and tighten up. Would it be possible to find a stud with longer threads on each end? Or do I have to try and fix the hole? Was hoping to ride this fall, but I don't have a whole lot of extra time and money to tear the motor apart and possibly replace the case half. Is it possible to maybe add more threads to the short end of the new stud? Just things running through my mind. Lol.

[Dunn111987]

I know this probly sounds crazy, but would it be possible to add more threads to a new stud? Just trying to think of ideas for a temporary fix for now.

[taber hodaka]

What part of the country are you in?? If you are in Montana I have got you covered.-------------Clarence

[Dunn111987]

I'm in Washington state! Lol

[Bullfrog]

If you have reasonable confidence that the stud is threaded into the case far enough to "hold" under the tension which 9 ft-lbs of torque will produce, sure you can thread the stud farther - and I wouldn't even call that a temporary fix. That would be a good and workman-like fix.

However, you should examine the head nuts too. Make sure there are NO buggered up threads inside the nuts - running a tap through to be sure would be a good idea.

Ed

[Dunn111987]

Right back to square one. Base gasket puking now. And the stud won't hold the torque. I just had to walk away. Lol.