22 mm Mikuni float height

[swcaudill]

I recently installed a 22mm Mikuni on my Ace 100 Trials bike. I've tried at 7/8" and 1.0" but bike is very hard to start and seems to run out of fuel at higher rpm's. Any suggestions?
Sterling

[Joe Ormonde]

Is the carb new or used ? First things first: pull the fuel line off the carburetor and check for fuel flow. If it`s OK, tear down the carburetor and give it a good cleaning. Be sure to remove the fuel inlet nipple with the Needle and Seat assembly removed and blow it out in both directions with Carb Spray Cleaner. There can be a flake of something under the Nipple that lets the fuel flow then moves and plugs it off. That passage quite often is overlooked in the cleaning process. A Fuel Filter is a must have. I spray the carburetor passages out so that anything that does come out is caught on a white paper towel. I want to see what if anything washed out. I`ve seen bugs and hair on the paper towel that washed out of the inlet passage. Joe.

[Bullfrog]

It is a standard design feature of the round slide Mikunis to set the float level with the float arms parallel to the float bowl gasket surface. (no measurement needed)

The reported symptoms seem to me to relate to the possibility of a plugged pilot jet (partially plugged) or jetting. Try this. Check your pilot air screw setting to identify how many turns "open" it is. (i.e. how many turns does it take to turn it all the way in?) Write down what you find. Then re-set the pilot air screw to that setting and start the engine. After warm up, turn the pilot air screw "in" one-half turn. Did the idle speed increase? If so, your pilot jet is probably lean.

With the proper pilot jet, you should find best (highest) idle speed at 1.5 turns out on the pilot air screw. (NOTE: It would be good to go to the Official Hodaka Workshop Manual and follow the procedures for pilot air screw tuning.)

As for running out of fuel at higher RPM - again, check for flotsam in the fuel. Plugged petcock fuel screens, other.
Ed

[thrownchain]

Running out of fuel at top end also is a classic sign of too small a main jet. Check all jet sizes against the manual.

[swcaudill]

I should have mentioned these items. Mikuni carb is a 22mm and is new, it came with a 30 pilot and 100 main jet. The slide is a 2.0. I modified the Ace manifold to accept the larger flange. The carb I replaced was a stock 20mm Mikuni. It ran well but was hard to start. I thought the problem would be solved and the idle would be easier to adjust.
The tank is plastic with two outlets and flows really well. I've had the carb apart several times and sprayed it with carb cleaner, blew out the passages and removed the jets and float needle assy.
Back to the barn.
Sterling

[olddogs]

You don't mention why you changed the carb. Was it for performance or tuning issues you couldn't resolve? A bigger carb flowing more fuel and air, more exhaust gasses need to escape. You mention back to the barn, you may want to check that the mice haven't started any homebuilding projects in your pipe. Something easy to check by just backing off the nut on the pipe to cylinder joint. Sometimes its the little things.

[Joe Ormonde]

We can pretty well eliminate the fuel system. So , let`s get to the Ignition System. Spark plug first. Just because it`s new doesn`t make it good. The Cap. The Factory Cap Part#933002 is TROUBLE! One thing that I did that caused my Super Rat to have your problem was this: Anti Seize. I put too much and it caused the Spark Plug not to ground itself. You would think that not possible. Paint too! Paint can also cause a poor ground situation. Combine a painted Head with too much Anti- Seize and you get what I had: A PERFECT Ignition System with a Spark Plug that couldn`t be grounded. Joe.

[ossa95d]

Years ago I had a Hodaka that ran great, but then developed a problem. Sometimes would start hard, it would run out of fuel and starve and then it would load up. Sometimes it would start first kick, but when it quit I would have to push start it, and then it would suddenly jump to life. I cleaned the carburetor, pulled all the vent hoses and blew out the passages... but here was the problem, like an idiot I put the vent hoses back on without checking them for clear passage of air. It was simply a plugged vent hose... DOH!!!

[Al Harpster]

Ive used the "stock" Mikuni 22 jetted just as the member indicates he has.

I thought it was a good carb.

I suspect the problems reported are not carb problems.

My guess follows Joe's. I'd have a hard look at ignition using the Hodaka Workshop Manual as a reference.

Since you've had 2 carbs not "do what you want" I'd look elsewhere for problems.

Great work modifying the Ace intake.

I sure would like to know how you did it.

Lots of guys hunting for the few remaining VM 20's might use your work to skip the hunting & go with all new VM22.

Not sure a pressure test is in order here, but I'd be inclined to make plans to execute one. Eliminate as many possible problems as you can.

A new VM 22 isn't a likely source for your problem. Just my two cents worth.

[swcaudill]

Problem solved, stator plate screws loose. Also I forgot to mention the Ace 100 has a Mega Fire ignition. I installed it years ago. Bullfrog (Ed) and I had a conversation about that device years ago. Search in archive for the post.
Thanks to everyone who posted.
There are two types of the Mega Fire module. I don't remember but the one I am using has only one terminal connection, the other has two.
Sterling

[Joe Ormonde]

One question we all missed is: Has the Engine been Reed Valved ? Reed petals are far too often overlooked when troubleshooting an Engine problem. They only last so long. They loose their tension, arch, twist and Burn up. They can also glue themselves down. That happened to me when my Super Rat sat for 2 weeks. I was Mixing Castrol R in the gas at the time at a ratio of 20:1. Strange things happen! Joe.