[Jcg78]

Hello. I am trying to help a family member with their quad.
Bit of a novice at this so I’ll try to explain the best I can.

The initial issue was it wouldn’t start because it appeared that no fuel was getting to the motor/spark plug. After googling and reading threads here I did the following:
thoroughly cleaned the carburetor.
installed a carburetor rebuild kit.
installed new fuel line with an in-line fuel filter.
installed a new spark plug, as the old one was jet black and a little worn looking.
Filled it up with fresh gas.
Inspected inside the fuel tank and petcock-both were surprisingly clean.
Everything else seems clean/proper (air filter, no oil leaks etc.)

After doing all that, it starts up right away now, but it immediately goes to a very high idle. Too high to safely put it into gear. But, if I slide the choke halfway on, the RPMs drop dramatically, to just a little above stalling out. It’s drives good now, but the choke has to be halfway on to put it into gear. I can slide the choke off and drive it but probably not a good idea.

So back to the shop.. I have taken apart the carb several times now.. giving it another heavy cleaning, double checking and triple checking everything so that I’m not missing anything. I’ve checked the throttle cable, it’s fine, not binding, a slight bit of slack. The choke/plunger cable is clean, o’rings in decent shape. Adjusting the pilot screw does absolutely nothing. I’ve checked for vacuum leaks. I’ve even started swapping the old jets, needle back into the carb. Nothing seems to make a difference.
I haven’t done a compression test yet... and I have not adjusted the valves, because given my lack of experience, I don’t think that’s something I should be touching.

Basically as it is now, it has a super high idle, the new spark plug has already turned black (after 1 hour of use) and there’s a tiny bit of smoke coming out the exhaust (can’t tell what color). I assume it’s running rich now? But I have no idea how to fix this, since I’ve pretty much covered everything I can find.

This is my last hope before it goes to a proper mechanic shop.
Any suggestions are greatly appreciated.

 

[shadetree]

ummmmmmm..maybe use the black knob on the right bottom side of carb to turn the idle down ??..lol.

 

[fishfiles]

.. could it be as simple as lowering the idle with the idle adjustment knob on the bottom of the carb ------maybe the reason the idle went up after a carb rebuild might be cause someone idled it up before because the low speed jet was clogged and it wouldn't idle and die , now that it ain't clogged no more , it is idled high

 

[shadetree]

.. could it be as simple as lowering the idle with the idle adjustment knob on the bottom of the carb ------maybe the reason the idle went up after a carb rebuild might be cause someone idled it up before because the low speed jet was clogged and it wouldn't idle and die , now that it ain't clogged no more , it is idled high

lol..that was my response ^^^^^ !!..lol. scary thought huh ?..lol.

 

[Jcg78]

I wish it was that easy. I’ve already covered that several times over... Rear tires screech when putting into gear without choke half on.

 

[fishfiles]

.. could it be as simple as lowering the idle with the idle adjustment knob on the bottom of the carb ------maybe the reason the idle went up after a carb rebuild might be cause someone idled it up before because the low speed jet was clogged and it wouldn't idle and die , now that it ain't clogged no more , it is idled high

lol..that was my response ^^^^^ !!..lol. scary thought huh ?..lol.

I seen you bet me too it , I started typing and went to get a drink

 

[Goober]

I wish it was that easy. I’ve already covered that several times over... Rear tires screech when putting into gear without choke half on.

The only thing i can think of:

Are you sure the carb linkage is synchronized with the throttle cable? Sounds like it’s too tight to start.
When you install the carb, the idle screw should not be in contact with the throttle linkage. Take the slack out of the cable first—it has to be snug without opening the throttle piston—then begin running in the idle screw. Does this sound like it might address your condition?

 

[Jcg78]

I’ll go over all of what you said again. Hopefully this evening. It’s totally possible for sure. Thanks.

 

[Jcg78]

Just went over everything mentioned above (again). Same result. I even unscrewed the idle screw all the way and took off the throttle cable from the linkage, throttle piston as low as it can go. Zero affect. Grr.

 

[fishfiles]

What about the piston which slides in from the top of the carb, I have been in the 250 carb many times but it has been a while , some pistons(slide valves) have a cut out on one side , can't remember if the 250 is like that or not , if it does have a cut out then it can only go one way and be right , if you turn it around it will run fast

you wouldn't happen to be in Louisiana ??? I bet I could dig up 10 or more 86-87 250 carbs

I think I would take the idle adjustment screw all the way out the carb and use my finger or even pliers to be sure that the arm is going all the way and not sticking at a point

 

[retro]

Check & readjust the throttle valve synchronization. Also make sure all of the small o-rings are installed where they belong. See the attachments.

Are you using the service manual for guidance? Using a Shindy (china kits don't work) carb kit? You can find a copy of the service manual here if you need one:
https://drive.google.com/drive/folders/1GcqS65GYd3yFmEAGsI7LP-eZp2jMRVJU?usp=sharing

 

[Jcg78]

Fishfiles- you’re right there is a cut out, but it’s in the carb itself, not on the slide. The slide comes to a rest on the cutout and leaves maybe a 1/4” gap.
There appears to be no sticking, the slide moves nicely. Everything appears proper and smooth.

Retro- it appears to be perfectly synchronized. But, I did end up with 2 o’rings that didn’t get used. They were in a little bag with the jet needle.. I checked the service manual, videos, diagrams and I still have no idea where these two remaining o’rings are suppose to go. One o’ring is your standard little o’ring, and the other is thicker (higher walled) than the other. Maybe for the choke cable?
The brand of the carb rebuild kit is “All Balls Racing”.

Thanks for the help. Appreciated.

 

[Goober]

Okay i have used an All Balls before with no problem—now that carb needs to be clean enough to drink whiskey out of it right? Just to rule that out sometimes you have to disassemble them more than once to be sure.

A weak fuel stream with air in the line can cause high idle too. How you test for that well, drain the fuel tank and peer down into it with a strong flashlight. Look for debris around the petcock screen and cracks in the fuel line—mostly near the connections
I don’t know how this one is setup. But don’t give up it’s running

 

[Jcg78]

I was thinking that too.. pull it out again, and give it another heavy cleaning with more attention on the jet ‘chambers’ etc. I don’t think I did the best job there. Tomorrow’s project. Thanks for the help.

 

[retro]

Try putting all of the OEM jets and hard brass parts back in it while its apart. China jets can be anything but correct. Shindy is the only kit maker that I have ever seen get them right.

 

[Jcg78]

I got it running pretty much perfect now.
I didn’t really do anything different... Just re-cleaned the carb, but took my sweet time with it. Almost 2 hours. Hah. Triple checked every single thing, installed it back in, and bingo.. so I haven’t a clue what I did wrong the first few times. I can only assume some dirt or junk finally came loose that I missed, like in one of the jet chambers or something(?). But I’m a novice so there’s that too..
Thanks to everyone that helped.
Appreciated.