84 250R carb too rich at part throttle

[Wi200x]

I just installed a carb kit. The carb kit though didn't have a needle jet. The good news is that it runs better than before but it is too rich right off idle which makes the engine sputter. I'm guessing that the needle jet is wore but the needle jet holder is what looks like restricts the fuel flow, not the needle jet. I know it is rich because pulling up slightly on the choke will make the condition worse. I have replaced the needle jet in an 185s and that seemed to work out similiar problems. Another thing is that under cruise or acceleration engine runs good. Letting off the throttle lightly will make it sputter. I think the term for the sputtering is "four stroking". Any advice will be appreciated. Thanks.:wondering

[toocheaptosmoke]

My 84 was also way rich with stock jetting, I dropped to a 42 pilot and that helped a lot. I have a feeling that my jet needle and needle jet are worn, but I have another carb waiting to go on so I'm not throwing any more money at the old one. Just keep making adjustments and doing plug chops. :beer

[Wi200x]

I have the needle leaned up as much as it'll go. I found a schematic of the carb and according to the schematic I need part number 223272-001 which I called the needle jet holder but the schematic called it the needle jet. If the part has been discontinued I may try epoxying the jet and redrilling. It might work to shorten up the seat of the jet to move it higher into the needle.

We were running it at a riding area Saturday and another 84 250R came along and he said he was having trouble with his running rich also. An atv mechanic told him that it's the nature of the beast. I dropped the main jet from 130 to 128 when I got home and that made the topend ok but didn't do a thing for light throttle sputtering.

[Wi200x]

I pulled the carb apart again and inspected the needle jet (holder in this ap) and it looked ok but I know it's hard to know without a proper gauge. I installed a 40 pilot jet vs the 50 and I knew it would be lean at idle but thought I'd experiment. I had to use a choke to start it but ran ok after it got warmed up and adjusted the air screw in slightly. It didn't make any difference on sputtering at cruising speed though. Maybe the reeds are bad?

[Wi200x]

I blew a hole in the piston! My boys and I went to a riding area Saturday for about 2 hrs and the trike ran good-no problems except for the sputtering under light throttle. I installed the 128 jet vs the stock 130 jet and that improved the top end but today I went one further and reworked the needle jet. I took a .111inch diam. drill bit and hammered the top of the needle jet smaller and reamed it out with the drill bit. I did some calculations on the needle vs the jet and I have aprox. 1/2 of the area when the needle is all the way closed vs the opening of the main jet. Put back together and it ran great on steady throttle. No more sputtering except when backing off the throttle. I ran it hard about 4 miles and my son got on it and ran it aprox. 2 miles and the engine quit wtih no compression. Pulled apart tonight and the piston is shot! What happened? I'm running only one size smaller main jet and didn't get any "lean" feel to it at all. It was hot today (aprox 93 degrees). Running a 32to1 mix of Kawasaki 2 stroke oil. Is it possible that it was too lean at part throttle? I didn't get any surge or anything except when backing off the throttle if not coming back to idle all the way. I did notice Saturday that at idle it would start to get a surge condition after running it awhile. I called Sudco today and they said they couldn't get me a new needle jet as the PE30 carb is oem only. I wonder what machines besides the 250R ran this carb?

[toocheaptosmoke]

dang, that sucks man. There's a good possibility there was a lean spot somewhere in your throttle range, or maybe a crank seal went out or some other air leak. Did you do any plug chops at different throttle positions? They always run best right before they blow :cry:

[Wi200x]

I was able to look at some carb websites and finally came up with a Keihin part number for their PE30 carb needle jet. Sudco had one in stock so I ordered it. I'll start over on carb calibration. I was lean on the main jet (128vs130), lean on the needle (leanest setting) and carb floan level was down plus I may have been slightly lean at part throttle with the mod I did on the old needle jet and it was a warm day. Took my cylinder down to a one man motorcycle shop and he'll bore out the cylinder for another piston and we'll try again! Also order a 132 jet and will use that for break in. In the mean time I'll recover the seat and reseal a front fork that's leaking. If the needle jet is the right one I'll post a part number. This part has got to be the most overlooked carb wear item on this trikes. Most carb kits include the jet when it's not part of the needle jet holder. Live and learn I guess!