[pdoherty]

Hi All,

Been looking around and it seems like there is a wealth of info and helpful members here. Couldn't find anything specifically addressing my problem, so here goes.

Was having carb problems a year ago. Pulled the carb and cleaned it. I think I didn't miss any ports. Have a Honda service manual. Was hard to start and fouled the plug regularly. Ran ok afterward, but not 100% right.

Switched to a hotter plug and ordered a rebuild kit for the carb.

Now my attention is back on this project. Mentioned the previous to let you know I may have underlying problems on this very old machine.

A typical round of "lets get the 4wheeler going" after it has sat around for awhile is to clean the mice out of the air intakes and then pull and clean the plug several times until it runs. Added screens to the fender openings and also to the inside of the air filter box inlets - hardware cloth. Hopefully that will keep the critters out.

Last time it did something new. Fired up, and proceeded to rev as high as it could. That was without any throttle input and the throttle was not stuck open. This is extremely hard on this old engine and very unsafe. First time it did it was after a stall out in the field. The next time was a few days later in the barn on the intitial startup.

Pulled the carb this morning to do another cleaning and to install the parts from the rebuild kit. Throttle plate and piston seem to work smoothly. Haven't started the rebuild yet - just holding it in my hand. The throttle cable action is also smooth (disconnected from carb).

The choke plunger thingy doesn't have any obvious damage and moves with the handle bar slide lever. Understand that a choke is a temporary enriching circuit. Don't understand the plastic plunger and spring arrangement on the cable.

I may be getting a small air leak from the intake boot (not as pliable as new) and couldn't find any cracks in the air intake plastic runner. Saw that several people had idle problems and an air leak was suggested as the culprit. Could an air leak make it redline?

Black sooty plug means that it is running too rich (when it is running). Haven't figured out which circuit is the culprit yet. Hoping the rebuild will take care of the problem. My notes say that the pilot (idle) jet was set at 1 - 1/2 turns. The pilot jet was completely plugged the last time I took it apart.

Any ideas on what to look for that could be causing the runnaway rpms at what should be idle?

Thanks,
Patrick

 

[Hghgrad]

Air leak could easily cause a high rev. Hows the o ring on the intake boot?

 

[pdoherty]

By "o" ring, do you mean the rubber boot between the intake tube and the carb? Mine is rubber with clamp rings and funnel shaped screens in it. The rubber is stiff and may not be making a tight seal.

 

[TRX2fiveO]

that part is held on by two 8mm bolts there is an O-ring behind it. I would check the throttle cable at the crimped ends top and bottomsometimes the plastice separates from the metal coil inside and will cause the throttle to stick, my 250X did it right where it makes the bend into the carb

 

[pdoherty]

Moose,
Do you mean the fitting on the engine head that connects to the output side of the carburator? It is a metal fitting screwed to the head with 2 bolts and then transitions to a rubber boot with bands then the carb. Is there an "o" ring under it?

A leak in this area would allow air directly into the engine and reduce air through the carb resulting in a "rich" condition???

Have the carb apart.
Main needle has the clip all the way to the top groove. (most lean right?)
The old middle jet that the manual calls the "Slow Jet" has a huge hole compared to the one in the carb kit.

There are two tiny orifices right in line with the butterfly (when closed) that may be plugged. Couldn't get any carb cleaner to show up there when cleaning and blowing out the obvious passageways.

Are they part of the pilot circuit? A third orifice under the pilot screw is clear.

There is an additional jet that the manual doesn't address. It is in the collumn closer to the pilot side of the carb and has a rubber plug in the top. Down on the side is a short brass jet. Any idea what it does?

Patrick

 

[pdoherty]

Took the fitting off of the head and found the "o" ring. It was old and flattened. Still had a little stretch and there were no stains indicating a leak. Matched it to a G35 from my metric assorment. Does it need a special heat rating, or can a generic "o" ring be used?

Poked a fine wire into the two orifices I was unsure of. Both are clear. They connect to the common chanel that goes to the pilot.

Both the old and new "slow jets" are marked "35", but the new one is way smaller than the old one. Don't know which is right, but since I'm dealing with a "rich" problem I installed the new one. In the hope that the old one was oversized, I set the main needle clip to the recommended 3rd groove as specified in the manual.

The carb is back together, but still on the bench. Ended up with an extra "o" ring and a rubber seal. The "o" ring is really tiny and the seal is cupped on one side. No idea if they are needed in this carb or not. Couldn't find anyplace to put them. Have had other carb kits that had extra parts so the kit could work for a number of different carbs. Not familiar enough with this carb to know.

Patrick

 

[pdoherty]

Success!

Pilot set to 1 turn out,
Main needle clip set to 3rd groove (middle).

Started with no choke and no throttle - but just barely.

Had set the idle screw just touching with the butterfly fully closed on the bench.

After it started, I turned the idle screw in about a turn. Smooth idle. This machine has never idled this low since I got it. Good throttle response. Revs right up and right back down again. Sounds way better. Sounds right.

Let it idle for about 5 minutes. Shut it off. Then restarted no problem. Hopefully plug fouling is a thing of the past.

Will button it up tomorrow and take it for a test ride.

The #35 Slow Jet must have been the problem. The hole in the old one is huge compared to the pin hole in the new one. Must have been dumping way to much fuel into the system making it hard to start and idle high (not the runaway idle - don't know what was causing that).

Went ahead and re-assembled the intake boot with a new "o" ring. Don't know if the old one was leaking or if the new one can stand the heat. We'll see.

Patrick

 

[shadetree]

Took the fitting off of the head and found the "o" ring. It was old and flattened. Still had a little stretch and there were no stains indicating a leak. Matched it to a G35 from my metric assorment. Does it need a special heat rating, or can a generic "o" ring be used?

Poked a fine wire into the two orifices I was unsure of. Both are clear. They connect to the common chanel that goes to the pilot.

Both the old and new "slow jets" are marked "35", but the new one is way smaller than the old one. Don't know which is right, but since I'm dealing with a "rich" problem I installed the new one. In the hope that the old one was oversized, I set the main needle clip to the recommended 3rd groove as specified in the manual.

The carb is back together, but still on the bench. Ended up with an extra "o" ring and a rubber seal. The "o" ring is really tiny and the seal is cupped on one side. No idea if they are needed in this carb or not. Couldn't find anyplace to put them. Have had other carb kits that had extra parts so the kit could work for a number of different carbs. Not familiar enough with this carb to know.

Patrick

that tiny o-ring goes in the pilot air/fuel mixture adjustment hole..o-ring..washer..then spring..then your needle..then there is also a o-ring that goes in the lower groove of that needle ( air/fuel mixture ) needle...make sure you didn't leave the old tiny o-ring inside that needle hole ( air/fuel mixture ). sometimes they are so small..you can never see them.

 

[pdoherty]

Thanks Shadetree!

Its the right size to fit in there. Do you see a problem with leaving it like it is (old one probably still in, new one on the bench)? If it is missing, then could explain the 1 turn out working instead of 1 - 1/2 out. Awkward to check without pulling the carb again.

Could the cupped seal go between the spring and the carb on the idle adjustment screw? Don't know how to describe it. Rubber washer with a lip on one side.

Patrick