Ace 100 Fuel Mixture/Cooling

[Bullfrog]

A few important items have not been discussed.
- Compression. It sounds like this engine is completely stock, so excessive compression should not be a problem. But the only way to know for sure is to do a compression check. Hold the throttle wide open and kick till the gauge reading stops climbing. 160psi is the maximum allowed for premium, non-ethanol pump gas. Excessive compression is a rather direct route to detonation and perforated or seized pistons.
- Air leaks. A two-stroke engine MUST be air-tight. Leaks at seals, gaskets, case joint or ANYWHERE will allow extra air into the engine and cause a lean condition.
- Fuel grade and quality. If possible, use only non-ethanol, premium grade pump gas. Bouncing around between ethanol-blends and "straight" gas as your fuel source will cause jetting changes in much the same way that changing pre-mix ratio does. A steady diet of non-ethanol, high octane gasoline is best.
Ed

[dscinta]

I watched a video on the Compression leak down test for an ACE 100 a few years ago. I would be willing to do it but it seemed excessive to build the tools in order to test. You have to build seals for the exhaust and the intake, plug hole and install a valve and a pressure gauge (few other steps I can not remember off hand). If I was a mechanic and I was gonna be testing other motors in the future that made sense but for a 1 time check at it seemed excessive at the time. We used to spray carb cleaner and listen for rpm changes but you cant do that everywhere.

As for the Gas: I run Non-Ethanol from WaWa that is 89 octane. I could drive 30 min to a marina and get REC90 what we all use in our boats on the water. I always felt the WaWa 89 ethanol free was close enough. I think you are saying just be consistent. That I will be

I will double check the compression as soon as I get the front tire back on and can give it a good kick. Thanks for the tips. Never know what you will find until you test....

[Bullfrog]

If you have other two-stroke bikes on which you maintenance & repair, they ALL must have airtight engines too . . . so a crankcase pressure testing rig is a HIGHLY recommended equipment set.

Lots of folks have gotten away with bolting things together and running 'em for decades, but the emphasis ought to be on the "gotten away with" part. A piece of flotsam which accidently gets bolted in at the intake gasket could cause a catastrophic leak (ditto elsewhere). An inadvertently folded over or nicked crank seal lip might only be noticed when it suddenly gets quiet and the rear tire starts sliding. A crankcase pressure test should be on a final checklist prior to placing an engine back in service after a repair.

Ed

[Bill2001]

One of the first special tools I made for my Hodaka was a pressure test rig. I do a pressure test yearly during the "Spring tuneup".

[dscinta]

RESULTS:
Starts better, More pep, More bottom and top end power.

I used the less sophisticated/less specialty tools/less accurate method of checking and setting the timing. Using the case marks and a buzz box I found it was firing significantly early. Set the timing and I no longer have the cold hard starts and bogging that I initially reported. I also re-cleaned the carb (4th time) and my father suggested I lightly oil (10wt) the needle valve seat as carb cleaner dries the metal to the bone. It appears no matter how clean I would get it, it would intermittently stick. Of course the vibration of riding would free it up so this was an underlying problem. My Father believes the jetting is correct as the bike is running/starting/idling perfectly at 1 1/2 turns out on the fuel/air screw and has all its power through the full rpm range. Float set properly and no more needle sticking. Seems to be running a little warm to me... he says that we are at sea level with an outdoor temps of 85* - 105* and thick sugar sand. Lots of wheel spin and low speed riding the motor is gonna be hot. It is air cooled after all. I was probably over-revving as I have only ridden bikes with "power bands." Official 1 hour test ride this week hopefully. I will keep you all posted.

Gents, I would like to thanking everyone that commented. I am still rounding up supplies to build the leak down tester but I am feeling pretty confident that it is not. Final questions. Anyone know what the external Head Temp should be. I can just ride it for 20 min and shoot it with my Laser Thermometer. Should be close enough? What would be an obviously hot head temp?

[taber hodaka]

I just looked at your piston picture, It looks like your head gasket is leaking. The black carbon stain on the head gasket. -------------Clarence

[dscinta]

That was my old motor but i was sooooo upset I never even looked into it. I just pulled the motor and chucked it in a cubby in my garage. It hasn't moved since. If it was a head gasket another proven point that I should build that leakdown test asap.

[matt glascock]

Maybe a bit of blow-by around a couple of the studs too, Clarence.

[dscinta]

I was 12 yrs when I bought the bike from my older best friend. Used my mowing money. Rode it like I stole it for 5 years. It only knew full throttle. Parked it when I moved out at 17 old. It actually popped 6 years after that when I was just testing how bad I had left it. 18 years of ownership I spent a bunch of time and money replacing all the missing and broken parts from all the abuse I gave it. Bought the Ace 100 motor and a fuji motor with 0 miles a year later. Never made time to finished the bike and parked it again for 5 years. Now interested in casual trail riding and scouting out secret bass lakes.

[dscinta]

Final Results: Failure!
Timing set and checked: Fixed hard cold start
Carb thoroughly cleaned 3x: checked the float
Pressure leak down test: Passed at 7lbs for 3 min and 5 lbs for 10 min.
New Fuel: ethanol free 89 octane with 32/1 yamalube


Took the bike out for a legit test drive. Running well, full revs, started 1 kick, choose a trail I could keep the bike moving as to the initial concern of overheating. Ran about 12 min at 1/4 throttle in 4th gear checking continuously that I was not full throttle beating the bike up. Bike was running perfectly. Got to a slight incline area and it started bogging down. Lost 90% of my power in 1 min. Would not start well but I let it cool and it did start 2x. Rode a few seconds but pushed it back to camp.

Testing after failure: changed spark plug, good looking spark, cleaned and checked float level. Not running out of gas in the bowl. Compression 120 to 140 lbs. Timing did not move. Same exact position when it was running perfect.

Totally frustrated and about to throw in the towel. Still no power. My father said 1 ring could have collapsed so you can pass a compression test until you put it under a load. Not sure. Thoughts?

[olddogs]

Once you have tried everything, try everything else. Have you looked at the pipe? Tried running it without the baffle? These little motors can do some strange things when the exhaust gasses start to build up. Overheating, not starting even with good spark, and loss of power can be clues.

[taber hodaka]

Just me But I think you are jetted lean?? The engine can run really well right up until it bogs or sticks. -------------------Clarence

[taber hodaka]

Just me But I think you are jetted lean?? The engine can run really well right up until it bogs or sticks. -------------------Clarence

[Bullfrog]

This report describes symptoms of engine operation going to pot as the engine warms up . . . classic condenser failure symptom. (Though checking the pipe for plugging is high on the diagnostics list!)

Don't give up. Thousands of little Hodies hum right along . . . yours can too.
Ed
PS: Can we see a photo of the plug you ran on the recent outing? A SHARP photo from a little bit away is wayeeeee more useful than a really blurry photo from right up close.

[dscinta]

I will get the pic of the plug up soon. I feel there has to be a failure in here somewhere. It ran perfectly for 12 min!

Maybe something inside the muffler housing broke free. The "baffle"that is at the very end of the muffler held on by one screw was trashed 20 years ago when a younger me decided it sounded cooler without it. Not sure if thats what your talking about. I could simply test ride it without a muffler for 2 min. I dont think that would hurt it. It has an instant power loss now. If I start it up let it warm up 1 min and ride down my driveway I barely have to power to make it back up the driveway.

[JackM]

While on the subject of crankcase pressure testing, could anyone post a photo of your pressure testing set-up and the process you use to go about this? If not a photo, then what all you need for a home-made tester. Thanks

[hodakamax]

Hey Jack, just below on the Day One post I built a contraption that kinda worked. Page 19. Check it out.

Maxie

[dscinta]

As for the compression Leak Down Tester I grossly underestimated how hard it would be to keep 10 lbs of pressure not in the bike but in the tester. I tried to start with what I had laying around. Not worth saving a couple bucks. Here are the list of failure items for me and my leak down tester:
*1/8 Aquarium hose. Very moody in temperature changes and does not seal around barbs well.
*Rigid ice maker line with Compression fittings worked well in some spots but was not soft enough for the barbs.
*Plastic T barbs. I started with some aquarium grade. It was crap. Though I was upgrading to automotive vacuum fittings. Also Crap because of cheap plastic molding. Spend a few bucks on metal ones from Home Depot.

What worked for me:
*#4 rubber cork from Lowes perfectly fit the intake hole. Drilled a hole in the middle and used 2 washers and the existing nuts. That never leaked for me. (see pic)
*I used a blood pressure checker pump ball. Most are about 10 lb max so they are very safe.
*You can probably use the Blood pressure gauge if you just google MMHG to lbs converter. I tried that and a higher quality automotive tire checker with an adapter from Homedepot. Buy the gauge first. then size the adapter.
*Home Depot Metal Barbs and get the exact size for the hose. What worked for me and my pump ball was 3/16th so I used that on the intake hole, the T barb and the gauge adapter
*#5 or 6 rubber cork worked on the exhaust hole and I used large wood clamps and a block of wood to clamp to the base of the jug. (see pic)
*Automotive Vacuum hose. Know the size and how close it is to the barb sizes. Not exactly the same in my case so take a second on your fractions.

I never took a picture of the final product. I will try to upload tomorrow.

[JackM]

Thanks for the tips, guys. Max, I knew I had seen one somewhere on this site, but couldn't remember where.

[dscinta]

Oh my goodness! Maybe 10 yr underlying problem found. The muffler appears to have a blockage. My father kept saying there isn't much in them to block it off typically, but it certainly is restricted. Runs like a champ with no muffler. Feels restricted blowing into it. This would probably cause the overheating also.

Somebody is gonna have to stop me from cutting the back off it and seeing whats going on in there. As I stated in an earlier post I removed the baffle at the end of the muffler a long time ago. I am considering hollowing out the muffler and just replacing that baffle at the end of the muffler if I can find one. Thoughts?

[hodakamax]

Hey, it could just be a mud wasp nest. I think I'd try some performance pipes and see what happens. You might find some real extra horsepower! (Or a roto-rooter!)

Max

[dscinta]

I am trying not to over invest. Just want it right. If it was a Super Rat or Super Combat I would probably throw down for plenty of performance upgrades.

[matt glascock]

There are many threads on this forum and many more videos on youtube describing the process of cooking a pipe. A simple process and well worth the time. I use a MAPP or oxyacetylene torch for the sake of speeding the process along but many simply toss the pipe on top of a good wood fire and let it cook. Cook it until fire and smoke emission from the pipe stops. Afterwards a good shot of compressed air to dislodge and blow out all the ash, a quick sanding, a wipe down, and a squirt of manifold paint and you're back in business.

[Bullfrog]

Pipe surgery should not be necessary (and isn't particularly recommended). A good bonfire exhaust pipe cook out would be helpful. As would peering into the ends of the pipe with a flashlight. Unless you have "in house" welding capability, cutting the pipe open to clean out things which can be cleaned out other ways, putting it all back together will be semi-spendy.
Ed

[thrownchain]

Had to read that last post 3 times to realize that it said peering into not peeing.....