Help. Rhino carb settings not even close
 

Rhino 250: So I picked up a Mikuni clone, and re-jetted to the recommendations of 30 / 115. Also installed a new air filter, the round foam kind. PCV tube is not connected to the air intake just zip tied off to the side. I am at sea level and idle / performance are not even close! >:( Wont' idle unless choked, even warm. idles around 1800 - 2100 on the first notch. Immediately stalls when I release the choke. Made sure that when I installed the throttle cable, I held it when installing so the cable did not get twisted or kinked, it moves freely up and down no issues. No gaps between carb and TB. Also adjusted the needle to the forth notch from the top.......

And on anther note I can’t seem to get the choke lever set correctly. There was a spring on the old carb that seemed to ensure the choke returned to open when the lever was opened back up, that spring doesn’t seem to work / fit on the new carb choke lever, so for testing the carb, I manually adjusted the lever on the carb and not from the handle bars. How have you guys dealt with this in the past. Don’t think the two are related. Any help would be greatly appreciated.

Check for a vacuum leak, get some carb cleaner and spray all around the intake and carb while its running. If there is a leak the idle will jump when the carb cleaner hits the leak.

Dragon, thank you. I’ll give it a try in the morning. I paid special attention when bolting the carb on to try and avoid a leak, but maybe it’s something I can’t visually see.

Try turning the idle screw in a little if you have one

Retested this morning. No air leaks, idle screw dosent seem to help either. Moved the needle retainer to the middle setting, 3 down from the top. When cold will only idle full choke, when warm stalls on full choke and no throttle response, boggs on half choke and will not run open RPM shoot to 2700. 115 pilot, 30 main. Im lost at this point.

Catch me up, Justin. How many hours do you have on this machine? Did it run ok before the carb swap?


Also, where do you have the pilot mixture screw set to? What do you mean by PVC tube (please show us)? Assuming the stock carb was a Keihin clone, the spring should swap over to the Mikuni; that's how I've done it. Please show us how it fits on the stock carb and then any difference with the Mikuni. If I pick up a quad/bike with no spring, I'll just use the stock lever on the Mikuni and forget about the cable.

Weldangrind, About 5 hours on the Rhino. Running very lean with the stock carb. Checked the plug about an hour ago and its now too rich, very sooty plug and very strong exhaust smell. Idle screw backed out 2 1/2, same with air mixture screw. I changed the pilot jet to 22.5 and the main to 110. Still the same.... The PCV hose is coming from the crankcase, and since the new air filter does not have a nipple to connect it too, it’s just sitting off to the side. I came up with a solution for the choke and that part is now working fine. The spring I mentioned was for the choke, not the slide, which seems to be operating smoothly. Is it possible that the 22.5 and 110 are still too rich at sea level, 40 degrees F.? As soon as I take off the choke, I’m still revving to 2800…… Seems to all go back to the pilot jet?




This is the carb I am using. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


It was shipped with a 100 main and 40 pilot.

It sounds like the slide isn't seated right. Might be 180 degrees out. Pull it out spin it, and re-seat it. The air mixture screw should be 1-2 turns out. 1 1/2 turns is best to start with.


My bet is it's something to do with your throttle cable or slide not seated right. I actually had to remove 1/4 inch of shielding off of my cable to get the throttle right. Without that it wasn't slack enough to let the throttle relax.

What Darth mentions has happened to most of us that switched carbs on these atvs. The top of the carb where the cable goes in is smaller than the original carb. This causes the cable to not seat down far enough pulling the slide up. Some have taken the cable end off to seat the end into the cap, others (myself) have used the original carb top cap that threads on. Also, as Darth mentions, the slide can be put in backwards. Take off the air cleaner and check in the throat. The slide should be all the way down or very close to it with no throttling.

Seriously, it came with a 40 slow jet? I've never seen that in a Mikuni clone.


I believe the idle screw to be in too far. The screw mates with the ramped portion of the base of the slide, causing the slide to lift as you tighten the screw (replicating what happens when you turn the throttle). Back it out completely and then turn it in a bit, just to lift the slide a little. Once you get it to run properly, you can set the idle speed to whatever you wish. BTW, that's an excellent way to confirm that the slide is in properly; the ramp on the slide must line up with the idle screw.


I'm with Darth on the pilot mixture screw; I'd start with 1.5 turns out from gently seated. I'm also at sea level, and I've never been successful with less than 27.5 slow and 110 main. Once you improve the breathing, it needs even more.


I was also talking about the choke spring. It should swap from the Keihin to the Mikuni without any fuss. Glad to hear you found a solution, whatever that is.

Winner winner, chicken dinner! And that’s why this forum is amazing! Went back to the 115 / 30 forth notch down, used the old slide cap, which by the way, was secured by red thread locker from the factory, WTH!



It was the darn idle screw! Had to back it out completely so the slide completely seated, then backed it out until I saw it start to rise just a little. She fired right up and is running smooth and strong now. No more lean / overheating condition.



And yes the Mikuni clone was sent with a 40 pilot. Got me.


As far as the choke spring goes, the choke lever on the new carb is different from the stock one, so I have no idea how that goes back into place, I fiddled with it for a while to no avail. I rigged a tiny bungee to the lever to create resistance to return the choke to open when the handlebar lever is opened back up. If anyone has a pic or diagram of how that spring is to be seated correctly I would greatly appreciate it, as my rig job is kinda hokey. Thank you guys for the help! Greatly appreciated.

Glad to hear you got it working.



For the choke I just switched the parts over from the stock carb.


This is how the stock carb is setup for the choke cable......
https://fms8011.triple8.net/images/P...titled_484.jpg

Darth, Thank you for the picture. I can see where the spring hook clips to the choke screw hole. I will mess with it again tonight, however the black lever is a different mold on the back and is slightly longer to actuate the choke, so I am not sure it will work. I will let you know what happens.. If I can get it to work, I will take pics and post to hopefully help someone else... Thanks again.

No problem.... I'm a bit hazy about how I changed it over.. just remembered it was pretty easy.. just a matter of swapping the parts out.

I got rid of the cable on mine. It's pretty easy to just reach down and switch the choke on and off. I figured that doing this eliminated something that could go bad.