Minkuni Carb Help!
 

Hey guys. I'm installing a minkuni carb and I need some help. I am having some trouble keeping the atv idling at half choke. It idles when I close my choke but when I put it in the middle it does not iddle at all. What should I do? I tried playing with the idle screw but no luck. What should I do to make it idle at half throttle.

Try adjusting the air / fuel screw. If necessary, you can gently turn the screw in all the way and then back it out 1.5 turns as a starting point. With the engine warmed up and idling with the choke off, adjust the screw until you can rapidly open the throttle with little or no bog.

Thanks, Weldandgrind. I'll try that.

Not wanting to sound ignorant here.. but does it matter if it does not idle with choke open?

Sometimes mine won't run unless I open it, other times it seems to want it more to the closed end to run properly. I assumed this was due to air temp and air quality, engine temp etc.

When it runs with choke closed and you move the throttle does it bog out or rev like it should?

When I run I close the choke it does not go fast and it bogs. It goes probably half the speed of half throttle. It literally does not idle at half throttle. If I brake and let go of the throttle, I will have to start it up again.

Hmmm.... the atv also misfires but I do not really care abt that. Anyways, it's still not idling, should I change the jet to 4 or should I leave it at 3.

What do you mean by change the jet to 4?

I mean changing the jetting to 4.

That still doesn't compute. Dumb it down for me.

Re: Minkuni Carb Help!
 

I'm cornfused, You want the bike to run good at half choke?
You run it with the choke on? And idle at half throttle confused me more?

Are You saying You want it to run with the choke off? If it won't run with out the choke on it is running lean open up the mixture screw. But I am not sure that's the right answer because I am not sure of the question.

Sorry, for the confusion. The bike does not idle when the choke is on. It will idle when the choke is off but when it is on it does not idle.If I turn the mixture screw should I turn right or left for it to become more rich. Sorry, I'm just not good at expaning.

Let's start with some philosophy. If it idles without the choke, what is the problem? Four stroke engines (and two strokes for that matter) have no need for the choke once warmed up. Your quad likely doesn't need the choke at this time of year. Once the weather begins to cool, your quad will require the choke, in which case you might find that it works properly.

On to the mixture screw: it only controls the air / fuel mixture while you're idling. As soon as you open the throttle, the jet that is below the throttle slider controls the mixture. Don't worry about which way leans out the mixture, but rather focus on how it runs.

Again, adjust the screw so that the engine doesn't bog when you open the throttle quickly. Does that make sense?

You mean that it only idles with the choke ON, right?(i.e. choke plate closed).

This seems to be a problem that is common to virtually all of these carbs/Chinese ATVs.

Take the carb apart and cleasn it out (yes, even if it's brand new).

While apart, check the float action. Sounds like that is your main problem- float shutting the gas off too soon.

Recalibrate the carb before putting it back on.

Check tightness of carb to manifold bolts, and manifold to engine bolts (they are almost always loose, and cause the mixture to be lean, no matter what you do to the carb).

Youir problem is definitely one of these tghings...and more likely, a combination of two or more.

See this thread for more details:
http://www.chinariders.net/modules.p...ewtopic&t=8204

Sorry, yea, it only idles with the choke on. All the screws are tight. I will try to clean it out. Also how do you "recalibrate" your carb. Sorry, for all my stupidity.

Not stupidity at all, Just not well put in the original message....Simple gets results.

Yes I think some clarification is needed as to the problem.

If it bogs with choke closed, does it run with it half open, or still bog? Mine is set normally in the middle position, I just leave it that way. Occasionally it seems to run rough and I need to reposition the choke.

Can you not drive this thing at wide open throttle at all no matter where the choke is?

Also, I'd ask what kind of gas you're using and how old it is? The book says these things want 90+ octane. I have 87 in mine and if it sits in there for two long it runs like crap.

I think it is imporant to note you have replaced your original carb with a mikuni unit as it seems that was lost a little throughout the thread.

It does not bod with the choke closed. If the choke is on it misfires and does not go to it's full potential speed. I usually set it at middle position but the problem is that it misfires or backfires. I don't know the difference between them but it either misfires or backfires. A person with a little more knowledge could explain me the difference. Yes, this is a minkuni carb. Also another problem is that the choke cable is a little to small.

I just opened the spark plug out and it was all black. Does that mean the atv is running rich.

Yes. Black plug would be rich.

Allen

If it were rich would you turn the screw in or out.

I believe in to lean it. Are you sure the choke is operating correctly?

Also what size jet is in the carb? Maybe it is too large.

Allen

The choke is operating correctly. I do not know the size of the jet but it is the stock one that came with the minkuni carb. Also what jet are you talking about, I thought there were 2 or 3 different types of jets.

Clarify for me what size engine(cc) and what size carb(mm).

If you are installing a performance carb on a stock engine it may be jetted for performance filters and pipes etc. The easiest solution is to change the main jet to a smaller size.

Allen

This is for a 110cc atv. The size of the carb is a 19mm. Why does it matter about the engine size.

It said on the website this is for a 50cc to a 110cc.

Okay. That carb is appropriately sized. It may actually be a bit small for a 110.

A 50cc engine is going to require less fuel than a 110cc engine. So the same carb may work, but you would need say a size 86 main jet for the 50 and a 98 for the 110. Those are just examples, I don't know what size you really need. Someone else may know. (Forchetto)

Another thing may be the float setting. It may not be set right.

Allen

Is your carb like this one?

http://dratv.stores.yahoo.net/19waca.html

It looks like for your ATV you should have about a #75 main jet and a #38 idle/slow jet.

I have a parts 19mm carb that I think it from a 70cc engine. Will open it up and take a look to see what it has.

Allen

I'll open my carb up to see what size it is. Before I even get into anything I will try to play around with the mixture screws.

Try the mixture screw at about 1.5 turns out and adjust from there. Not sure if you will be able to adjust it enough though.

Allen

Take the choke cable off and let the choke open all the way, You said it was too short right.

Yea, I already removed the cable.

Check out this video.

Excellent job showing all the parts and explaining things.

http://www.youtube.com/watch?v=BakwC3VoEGo

Thanks katoranger. The video was very good and informative. I will clean my carb out.

While you got it apart take a look at the little numbers stamped on the jets. That will let us know if maybe you are overjetted.

Allen

Yea, will do katoranger. Thanks for ya help. 8)

Wondering if you got this baby running hot yet?

No, not yet. Were goin on vacation soon so I didn't bother. Anyways, I got my butane torch.

UPDATE: The problem is fixed I turned the mixture screw 3/4 turns to the right to make it more lean.

Glad to hear you have it sorted so you can enjoy the speed!

Ehhhh... nope. Looks like another problem. :evil: When I ride my atv and go to 1/2 throttle it starts to bog after awhile. Then I let go of the throttle and the atv shuts off by itself. Don't know what the problem is. Maybe I should clean the carb or something.

what position is the choke when this is happening?