'72 Wombat (94) Stopped on me twice

[taber hodaka]

It looks like the head gasket may have been leaking some, on the front right side by the head bolt. I would suggest to not jet by performance but by being close or the just under the too rich side. If you have not mastered tuning try to work with someone that has. Some of the manuals cover it very well.
My $.02 cents worth And it could be that you are a the master of tuning.----- Clarence

[TheBevman]

Jetting isn't my strong suit, but I did follow the manual. I was running a 160 main jet and recently moved to a lower elevation (from 3200ft to 1500ft) and haven't gotten many miles on this bike yet but started fouling plugs, of course I now know why but then I tried jetting down to correct it. Following the manual I went down in incrimentally (160, 155, 150 & 145), proformance was about the same but I was getting uncomfortable that there wasn't a change so went looking for my problem elsewhere, but I put the 160 main back in. Then I pulled the spark arrestor, as Roger recommended earlier in the thread and she did not like that at all. So, the leaking seals had me running in circles.

I agree that the head gasket was leaking but there weren't any bubbles then I pressurized the engine, guess it was leaking at temp.

I honestly thought the seals were fine because they passed the pressure test. Odd that everyone recommends a pressure test but no one says much about testing the seals against vacuum. It took some time for me to some info on it too.

The welding is as rough as it looks, and the fin is a bit misaligned, but it's on there.

[Bullfrog]

I haven't mentioned the vacuum test as often as I should . . . but you are quite correct, sealing well to prevent air from going IN to the engine is as important as the OUT direction which the pressure test reveals. Lots of folks don't ever do a pressure test . . . which is tooooo bad. And among those who do, a majority seem to forget (or don't have the vacuum gauge) to do a vacuum test. Luckily, in the vast majority of cases, a vacuum leak failure will also be a pressure leak failure. Um, but not in this case . . . which is why vacuum testing IS a good idea.

Seems like there are several issues that you are qetting squared away . . . life will get better.
Ed

[MTRob]

Hello Bev
When I rebuilt my 125 94A Wombat engine, I ordered all the parts needed for the engine rebuilding the engine was the last thing I did after I had rebuilt (restored) all the body completely done with brand new wiring hooked up to everything even the turn signals, head light everything. Then I started with the engine ordered oversize .20 piston and rings from Paul then took the my cylinder with piston and had it bored then powercoated the cylinder black. Took the engine completly apart ordered a carb kit from Paul and spent a day cleaning every single part even used air to blow out any crap. I forgot to mention I did order a 125 workshop Manual. great help Bev if you don't have one Paul does order one. Back to carb I polished the sh-t out of it cleaned the sh-t out of it I only wanted to do it once. New the allitude so put in right jet, check float level put it back together and set it a side. Pulled the clutch modification chart off of Strickly Hodaka website and redid the clutch. Ordered new clutchs from paul then did the mod. Clutch works alot better. After replaceing everything else the engine needed. I installed it in the frame. Put it all togeather air cleaner, turned on the key for wiring checking to make sure the battery worked everthing lights ect. Put gas in the engine turned on the petcocks watched the fuel flow through to the carb. Turned on the choke, turned on the key checked to make sure netural light was on and I was in netural.

Now the momment of truth Bev had same problem you have being having, But Fixed it

More of the story to come

MTRob

[TheBevman]

Ed and Rob, thanks. I'm a glass is half full kinda guy and this is part of having old bikes. Besides you eventually run out of problems to fix. My ol' 66 Triumph took me a few months to get straightened out after her rebuild. I've actually come to enjoy the problems that arise out of old bike ownership, usually it's an opportunity to learn something new (unfortunately, that can get expensive) or see how not to do things. I'm on a fair number of bike forums and have learned much from others and their mistakes. Perhaps, someone will learn something from mine, here.

Oh and Rob, I'm a believer in manuals. When I was in the Marine Corps i used to troubleshoot the armament system of the AV-8B Harrier, if nothing else my experiences taught me that someone in the same position has probably made mistakes before and wrote the correct way to avoid them. No manual usually = no work for me. Good luck with your 94A, I'm rooting for you!

[dcooke007]

Bevman,

Based on the pictures of your piston, I have to wonder if the piston to bore clearance is to small. Cast iron cylinders with stock Hodaka brand pistons require more clearance than you would think. Hodaka mdl 94 / 94a piston to bore clearance specs out at .004 inch. Even with a new piston don't assume the new piston will be the same diameter as the your damaged one. They were not all made to "exactly" the same size.

Danny

[Bill2001]

Good followup on this story! And good info on needing to also do a vacuum test, as well as a pressure test. One gauge I could use with my newly made pressure tester is an old fuel pressure-manifold vacuum gauge, so now I know which one I'll use.

And this is a good cautionary tale about assuming an engine was rebuilt, or that it was done correctly. The engine in my bike was allegedly done by a "Famous Builder", but it wasn't. So I'm getting ready to go through the engine myself.

[MTRob]

Bev
Now to finish this story, now ready to kick it over, this sucker better run, one kick nothing, second kick fired right up. The idling was off so had to adjust
the carb abit was stilll running pretty good it was smoking more than it should so i new it was running rich. Adjusted the air fuel mixture. But after two years I had to ride it.
Took it out of the garage turned the throttle put in gear and away I went almost as happy as my first born kid. Up the hill down the road gears working perfect.Then all of a suddened it died. Sitting there only about1/4 mile to push home, Sat there trying to fiqure out what happened. Waited 5 min kicked it, it started and I headed home Quickly, nobody wantes to push a bike at are age. What the hell is going on I pulled the cover checked timing all good, great spark, pressure tested all good. now what. It was still smoking more then it should. Took for another ride ran great slow and fast throttle
then it died again. I had a new spark plug with me so I changed it. Kick it over started righ up. Went home next day pulled the plug cleaned it and went for another ride same thing ran great then died. I was going through plugs like beers in my garage. Sleeped on it driving me crazy. Then I thought oil fuel mix might be to high on oil .I mixed it 32/1 when I put the gas in. Drained the gas out put in 29/1 and I have never had a problem since.
To much oil in the mixture was fouling my plugs and stopping me. Since I run 29/1 balray I have never had a problem.

Oil and gas mixture has alot on how an engine runs also I use non ethanol 91 oct
MTRob.

[matt glascock]

I'm not following accurately. Gas-to-oil at 29/1 would be richer yet in the oil department if you were running 32/1 before. I had a similar problem that responded well to a THOROUGH cleaning of the pilot circuit beyond a squirt of Gumout carb cleaner. Fine copper wire through the passages revealed persistent varnish. A followup blast with the carb cleaner and I was in business. If you are getting better performance with a richer oil mixture, that's not a bad thing although you might need to adjust your jetting to allow more fuel to the engine. Oil lubes and burns off but its the gasoline that produces the power during combustion.

[Bullfrog]

I've got to suspect heat build up in an ignition component or loose wire or . . . Just up and dying (without a seizure) doesn't seem to be fuel/carb/jetting related.

Also gotta go back and check for the tank vent working (the little hole in the rubber washer/seal for the fuel cap must be open). Also, plugged exhaust/plugged silencer/spark arrestor.

It just doesn't seem to be acting like a carbureation/fuel mix problem.
Ed

[matt glascock]

Have you been able to do any jetting runs? I'm having a hard time getting my head around the problem being solved by running a higher oil concentration unless the additional oil, by providing more lubrication, is solving a heat related problem such as an air leak or condenser/coil issue by allowing the motor to run cooler through a reduction in overall internal friction or otherwise. At that mix, you're actually running (slightly) less fuel through the motor. That would possibly (slightly) improve a too-rich jetting issue in either the pilot circuit or main jet. How much compression is the cylinder/piston generating? Is there a major difference in compression cold versus warmed up? I have applied the Captain's suggestion of decoking the pipe when I have had issues like you describe with great improvement. Ditto on clearing the exhaust outlet of excess carbon deposits. Interesting conundrum. I'm looking forward to learning how this problem gets resolved. We're all here to learn.

[MTRob]

Sorry got the oil to gas mixed up I put in less oil and more gas, to cut down on the oil. quit fouling plugs ever since I have had no problem at all
MTRob

[matt glascock]

That makes more sense. Thanks for the clarification. I'd still recommend making some jetting runs as a cheap and effective way to assess the overall operation of your motor now that you have it dialed in. Plus, if you are like me and do your jetting runs on the street in front of your house, your neighbors will love you

[MTRob]

Matt
Changed jets so many times I could do it in my sleep and setting the ignition, the 170 works the best at our allitude 3800 ft. Lucky for me have no neighbors that don't care I live up in the Montana mountains buy old man Clarence Taber.
MTRob

[mac]

MTRob, you did a really nice job on the 94a,very nice looking bike!

[matt glascock]

Been there. I really like the ease of changing the main jet on the Wombat. It really gets tedious having to pull the float bowl to get to the main jet. That's one beautiful Wombat you have there. Have fun, and great job!!

[TheBevman]

Help... my thread has been hijacked... Err, not really, but wanted to ask for some help.

Well, Wombat (94) 0.20 pistons seem to be quite rare so I'm going up to a 0.30, I've already source the piston through Paul and need some help.

Can anyone recommend a good shop or individual that could bore (94)Wombat cylinder in the NorCal, Pacific North West area? I'm in Redding, CA and willing to bet there's a dozen nearby, just hoping to get someone reputable. I called a local shop that says they can do cylinders but the guy seemed to busy to answer my questions and started fast talking and telling me all that he's done. He wants me to "just come and drop it off" so I'm steering clear of that nonsense, as parts are expensive and BS is cheap. I'd also need the pin bore sized as well.

Appreciate any help. Thanks

Bev

[viclioce]

If you don't know who to use locally you can always mail it to Rich and have him do the work! Here's his website! Victor

http://richstaylordporting.com/index.html

[Bill2001]

Good followup on this story! And good info on needing to also do a vacuum test, as well as a pressure test. One gauge I could use with my newly made pressure tester is an old fuel pressure-manifold vacuum gauge, so now I know which one I'll use.

Found the old gauge, cleaned it up and checked it out. In perfect shape for 40 yrs old. Reads to 10psi press and 26" Vac, so the midpoints of those scales should be ideal.
Question: when testing under vacuum, how do we tell where the leak is if we see the needle falling? Apply thin solvent to the joints and watch it disappear? Apply a thick oil and watch the needle-drop slow down? Or just use go/no-go and consider it a secondary test?

Yeah. Details. That's Bill.

[Bullfrog]

In my own experience, it seems that vacuum leaks in an engine with NO pressure leaks - the vacuum leak is always a failed inner lip on one of the crankshaft seals. Since trying to find the exact location of a vacuum leak is difficult - I've decided to work with the following procedure:
1) find the location of any pressure leaks using soapy water spray (case seam, die casting porosity, seal, leak through lower stud threads up the "tunnel" to the cylinder head washers & nuts, base gasket, head gasket, etc)
2) I generally don't even do a vacuum leak test when I've already found a pressure leak. I just go to "jail" and start the engine rebuild.
3) If pressure test is good (less than 1 psi pressure loss in 1 minute, starting at 6psi), then do a vacuum test. Sorry, I've forgotten the "numbers" on a vacuum test. Target is no change for 1 minute - but some very minor (SLOW!) leakage can be tolerated. (Again, sorry - I've forgotten the numbers.) If vacuum test is a "fail", crank seals are probably the "fail" location. Go to "jail" and start the engine rebuild. I have to admit, I would probably change out the magneto side seal and repeat the pressure and vacuum tests before starting the rebuild. Of course, if I do that, Murphy's Law dictates that the failure will be in the clutch side seal.
Ed

[Bill2001]

Good starting guidelines. And I'm repurposing an old gauge that I've had "since I was a kid".

[TheBevman]

Ed's, comments confirms the info I found on vacuum tests, 5-7 in Hg, with less than 1in Hg drop in a min. I used a harbor freight vacuum brake bleeder to perform the test. My leaks were audible and thus easy to identify, both main seals were out. I used gear oil to check, 90w I had lying around, and the gauge held for a few fleeting seconds before dropping again. My motor was out by then so it was a bit easier to get the oil on the seals.

Here's where I found a bit of info.
http://www.dansmc.com/vacuum_tester_instructions.pdf

Hope it helps.

Bev

[TheBevman]

Just received my cylinder back today and proceeded to measure the ring gap, I figured I'd need to file the rings a bit, I thought they'd be tighter on tolerance. To my surprise the gap is .010 and I've yet to take a file to them. Bore is .030 over and manual states that it should be .004 to .012, giving me .002 until they're out of tolerance. I got the rings and piston from Paul, they're nos Hodaka, and I know he knows his stuff. The piston to bore clearance is .004.

Do I have anything to be concerned about with the ring gap already at .010?

[hodakamax]

Your end gap is within tolerance and it appears all is well. These are set-up tolerances and will grow as the engine breaks in. In our race engines of the past, the fresh bore was ran to what we considered to be break-in. Ring end gap was then measured again. For maximum performance the minimum tolerance was desired. Next oversize rings were used and filed to the desired minimum tolerance. This was checked after each racing event and the ring was replaced if necessary.

This was probably overkill and in your case I'd just use it. You could check your compression now and down the line and if necessary replace the ring with the next oversize but for now enjoy the ride!

Max

[TheBevman]

Thanks for the info Max. I was thinking the ring gap was a bit wide to begin with, depending on how things go I may just try what you mentioned. Compression feels pretty stout now, I'll have to check it when I find my comp gauge.

Well, continuing this saga, she's all back together now and ready to break in... and I need some direction. I did some searching here, on the forum, but came up with little on the subject other than run quality non-ethanol mix a 28:1, jet rich and only ride her carefully after a few heat cycles, making sure she's dead cold between each.

Truth be told, I'm probably making more out of it than I should be but I'm a bit concerned I'm gonna screw something up. Can anyone provide some sage advice to this 2 stroke rookie?