250r diesiling (run on)

[resto250r]

I have an 83 250 r atc I rebuilt the top end but had to go back in because the botom end was sheddin aluminum (still havn't figured out why). Anyways I bought another motor went threw the botom end replaced the crank bearings and all the seals then reinstalled the previous top end I had rebuilt. Seems to run great but my problem is after about 20 mins or so of riding it wants to diesil when I shut it off and stays running. I assume it's overheating but I never had an overheating problem when it was on the previous bottom end. I am runnin what I belive is a stock carb (27mm keihn) with a 55 main (which I think may be a little fat because I'm fouling plugs) but if it was fat I would think this would help my heating problem. I live i phoenix , az so maybe I just need to wait till winter. This is my first two stroke and it is a learning process for me so any info would be great. I do now the basics of 2 strokes (I am a auto tech) but just not alot of experiance. Thanks guys!!!

[3Razors]

I once had an 82 that did the exact same thing. The problem I had was a blown base gasket. If your trike continues to run (dieseling) even after you shut the ignition off then you definately have and air/fuel problem. A very very lean 2 stroke will diesel once it gets hot enough. Check all the gasket by spraying soapy water around them and check for bubbles, the only way to check crankcase seals is with a leak down tester which maybe a shop could help you out with. Your stock jetting should be a 30mm Keihin 130 main 50 slow 1.5 turns out on air screw, needle clip 3rd notch from top. Only run at least 91 octane to avoid detonation. Is your bike all stock? By the way what part of Phoenix are located? I'm in Chandler myself.

[350xsx]

my 350X does that sometimes, but only real quick like less than a second i thought the switch might have just been a lil messed up tho

[resto250r]

I think mine is mostly stock with mild port job, DG exhast. Carb is I think a 27mm @ least the number begins w/ PE 27. It has the stock reeds but I'm gonna put a set of boyseen reeds. Right now I'm @ 55 thats after leaning it down. not sure on my slow jet I'll double check that though. With these mods what do you think I should be @, and wether a keihn is better or worse than a Mikuni?
Great advice on the diesiling I could probably sneek a leak detector from work and check 4 any crankcase leaks. I tried just sprayin brake clean around gaskets listening 4 any idle change.

[resto250r]

oh yeah I'm in GLendale by the way

[resto250r]

I was off it has a 152 main, 52 slow

[Tri-Z Pilot]

sounds like you are way lean, either too much air, or too little fuel. Check for intake leaks, and improper jetting. If your bike diesels after you shut it off, wick the throttle, the cool incoming fuel charge should the stop the dieseling process.

[3Razors]

With your air box are you running a UNI or K and N? With the lid on or off, also what fuel mixture are running at? On 2 strokes every tiny little thing affects the jetting. We are lucky being in AZ because we are very close to sea level. The 81-82 carbs are labeled PE 23A, the 83-84 are labeled PE 30A. When choosing jets be very careful to only get the genuine Mikuni or Keihin Jets as the aftermarket ones to not have as close of tolerances and can cause a nightmare of jetting troubles. Personaly I don't like any of the stock carbs that came with the air cooled 250r's, they are way to small to provide the fuel that this thirsty beast needs. We switch to a 38mm flatslide Mikuni or Keihin on our bikes and it makes a huge power difference! Either one are good quality. The Keihin is a little more user friendly. With you jetting right now I put the needle clip on 4th from top, drop in like a 180 main jet just for test purposes to see if it clears up the diesel problem. If that doesn't do it then you got to have some sort of engine sealing trouble.

[resto250r]

I'm runnin an open uni filter, PE 27. Now that u bring it up I had been runnin yamalube @ 24:1, but this last run (when it stared diesiling) I had tried runnin castrol full synthetic closer to 32:1. Maybe I should just look 4 a 38mm and try it what should I start my jets @ with it? I hope I'm not askin 2 many questions but this is the first 2 stroke I've ever messed with.

[resto250r]

I pressure tested my crankcase and top end and found no leaks it holds 6psi for probably @ least 20-30 min and drops slowly after.

[3Razors]

If you want to go to a new and bigger carb go with a Keihin 38mm PWK. Set you jetting at 175 main, 55 slow, DEF needle. You will have to take off you intake manifold and put it in a oven to heat it up quite a bit, once hot and soft, stretch it on carb and let it sit overnight. You will have to run a clamp on uni filter behind the carb as it will not fit the stock air box. Don't use K&N because they let way to much Arizona fine dust in the motor. Your PE 27 sounds like a mystery to me maybe a previous owner put an odd ball carb or something?

[resto250r]

hey thanks alot I'm lookin 4 carb on ebay now!

[resto250r]

anyone have a carb?

[resto250r]

Sorry guys I **edited** this one off! I was just out in the garage lookin @ this carb and the numbers on it aren't pe27, it's pe37. According to my book this carb is off a 85 and is a 34mm carb. What should my jetting be with this carb, my book says stock is 142 main and 52 slow. I'm @ 152 main and 52 slow, w/ an open uni, DG pipe, and .020 over w/ mild port. And I just put a set of fiber reeds. Thanks in advance!

[TimSr]

I highly doubt you have a carb problem so severe as to cause dieseling. A quick plug check will make it obvious. Dieseling is caused by a plug so hot that it ignites fuel without spark. I cant say that its impossible, but on a single cylinder 2 stroke, your piston will usually suffer meltdown before it reaches that point. Check your plug. If it looks normal or rich, start looking at your kill switch contacts or its ground connection. Pull the coil input wire, and see if it dies without firing.

[resto250r]

Whats weird about the whole thing is that the plug is actually wet and oily like it's rich, my compression is @150+ and climbs steady each kick. It seems to run great till the plug starts to foul. Can a rich condition cause dieseling? If it was an ignition problem why does it only do it when it'e hot. I"ll try pullin the coil wire if it acts up when I get a carb back on it, but @ this point I either need 2 build this carb or get a bigger one. One more thing my main reasonin 4 wanting to build or replace this carb is because this one seeps gas and makes a mess of everything. Thanks

[resto250r]

bump any ideas?