I think I might know why my bike won't idle

[tundrawolf]

SO I have literally gone over every port passage and reason, tried jetting, setting float level different, sealing intake, timing, valve adjustment, and nothing can keep my bike from either screaming revving too high or idling so low it dies after a few seconds.

Take a look at these pictures:

Pilot jet hole:



Pilot jet:



There is no way the flanged end of the pilot jet in my hand would seal against that hole in that carburetor. I must have the wrong jet! But I bought it directly from Honda for my year ATC.

My thought was, is fuel getting too far into the carburetor and causing the engine to race because it is entering the combustion chamber?

[bcredneck]

thats probley it

[swifty]

i had one that had a bent idle screw it would either not idle or if i turned it up a hair would rev to the moon

[tundrawolf]

I checked the idle screw, and it seems just fine. It is a new one from the rebuild kit I put in a while back. I hooked up a tube to the pilot jet tube, plugged the rear facing passage, and put the mixture adjustment screw in. I put pressure in the tube while blocking the port directly on top of the pilot jet tube inside the carb, and it held the pressure when the mixture screw was all the way in. As the screw was backed out by me, it slowly released more and more pressure which means the adjustment screw is working the way it should.

Does anyone have a picture of the flange on the end of their pilot jet? Is it humongous to accommodate the large pilot jet tube?

[Thorpe]

I had gotten a carb rebuild kit that had the wrong jet in it... # on the jet was correct, but the hole was WAY bigger than it was suppose to be...

[tundrawolf]

I had the same thing happen, but the jets that are in it right now are directly from Honda...

[tri again]

is that a crack i see in the carb casting up near the top of the picture?

Are you sure your main jet needle is being held down securely by the 'w' clip
under where the throttle cable goes into the main slide?

I've had a few flip sideways and allow the main needle to float up and down wherever it felt like
it.

Adjust everything perfectly, and it would change by itself.
either creep to full rev
or low vacuum would allow it to drop to super low idle and die.

(separate topic)
Some carbs, might be the 85+ years, has an almost invisible emulsion tube in a jet hole
that you can't see and is not real obvious when you pull the jet out..

[Dirtcrasher]

It's where the castings mate.....

You may have an EBAY carb and I warn everyone that they use different jets.

[tundrawolf]

I put a carburetor off of a CT110 on. I transfered the jets, the oring, and the float.

Starting with the needle in the middle position, it idled roughly, but it idled. Power was down. Bog was bad but manageable. When ti died during idle it was very sudden. Idle speed would temporarily hang when I gassed it.

Needle in +1 richer from middle, it didn't idle at all, wouldn't start unless I kept off the gas. No power, bog was terrible. Idle hung longer than the medium position.

Needle in +1 leaner from middle idles pretty good, starts first pull and idles well, fairly good power, bog only when cold, lacking a little on the top end.

The last carb ran REALLY well, but would not idle. I think I will stay with this combination for now, because it is a PITA to keep going through the things I have gone through. At least it idles.

Do the Ebay carbs have the same markings that the stock ones do? Because they are marked them same.

[TurboTacoma]

That looks like a casting line. Ok... Yes the cheap ebay carbs are all over the place with there jetting. I got my shindy jet kit and jets from jetsrus.com and have had great results. A few tips that I hope help you out. One if turn in the mixture screw all the way closed and it still runs... Idles... But crappy. Your slow jet is too big. Go to the next size down. Had this problem on 2 ebay carbs. Next check you idle screw that raises the slide to increase idle speed. With it running... Touch it and move it if you can. Mine would move and idle speed would jump 100rpm or so. Shimmed the spring between the carb and screw with a small washier. It put more preload on the screw and threads. I also put the shindy idle screw in place of the ebay carbs cheap screw and even more stable at holdong the idle. Now another thing to check... Is were your needle goes into the carb. My brass needle guide that is helded in by the main jet tube was moving around. I had to remove 2mm off the main jet tube casting on the carb itself. This allowed the main jet tube to tighten against the needle guide.

[TurboTacoma]

It could be marked like the stock carbs and still be off! Again the reason why I got a jet/needle kit when I got the larger carb. Everything was wrong. Slow jet/needle/main jet!

[tundrawolf]

I went to change to the leanest position just now and found out I have that backwards, the more I lean it out the worse it bogs, the richer it goes the better it runs! However the top end is completely gone. Areas where I could make it in 4th I now have to shift to 3rd and sometimes 2nd.

[tundrawolf]

It seems that if I keep it at 3/4 throttle it has plenty of top end power, but when I give it full throttle it just wants to slowly bog down. Any ideas on how I can fix this?