JD 300 has got me stumped...running poorly

grasscutter97 · Post by **grasscutter97** » Sat Dec 03, 2005 2:22 pm

Ok, here's where I'm at (completely stumped). 295 2AX kohler in a JD300. Complete new top to bottom engine (new crank, seals, pistons, ...nothing spared). Rebuilt stock duster clutch.

Engine starts from cold in 2-3 pulls. Idles beautifully all day. Put sled on track stand and operates and goes through all its shifts smoothly. Pulls up to a little shy of 70mph (on the stand).

Take it for a drive, in about 3-4 inches of snow, and immediately starts bogging down. In order to get it up to a max of about 25-30mph, I have to squeeze the throttle very slowly and eventually she will get going. But even when shes is going, seems to be struggling. I have the cowls off that cover the carb and have fiddled with the high and low adjust as she's running and nothing changes.

Next, I would lift up the back end and get it reving up high then jump on! Even then, seems like no power.

Went back to shop, checked fuel lines, filter, compression (at 125psi both sides), checked muffler obstruction. All ok. Even checked all bogie wheels to make sure there was no excess drag in the track area.

ICCF left me specs on putting a mikuni on, and I found some parts that got me pretty close to the carb specs for the 340 kohler. Could not get sled to idle or start very well, so went back to the stock walbro.

I am at a loss. What else do I check? Obviously it is an 'under load issue', as sled performs flawlessly on the stand. I even did 5 different tests on the stand...rigged throttle to stay open at 20, 30, 40, 50, 60 mph, and then at WOT. Held each position for 3 minutes. No problems. Checked duster clutch engagement more times than I can count, all seems ok.

I would very much appreciate the help! If there are any JD gurus that are close by, I would even be willing to bring the sled up to you some afternoon, (within a 100 or so miles of Omaha, NE), if they thought we could figure this problem out together. Just a thought! Thanks.

400brian · Post by **400brian** » Sat Dec 03, 2005 4:58 pm

You didn't mention the pickup tube in the tank, have you looked at that?

When running, are you seeing fuel and bubbles moving in the return line?

Has the carb been rebuilt? It sure sounds like fuel delivery.

With 2 strokes the frustrating part is not getting them running, but getting them to run right

Good luck

JDFanPa · Post by **JDFanPa** » Sat Dec 03, 2005 6:37 pm

When you ride it a bit are the plugs getting wet or are they a white color like a lean condition. When you had put seals in and you removed the stator did you but it back in the same spot. When I first got my 300 it ran crappy like your desribing all because the previous owner pulled the stator plate to change points and it was out of time. In addition how are the points and the point gap misadjusted or very worn points will actually effect the timing aswell.

grasscutter97 · Post by **grasscutter97** » Sun Dec 04, 2005 12:43 am

Update. I installed clear fuel lines on both inlet and return fuel lines. Fuel seems to be moving smoothly. I pulled out the 2 lines going into the tank and installed a new screen/check valve on the pickup tube.

This sled I have spent way too much money on. Its been in the family since new, so I have a bit of nostalgia in getting it restored. I originally sent entire engine, carb, muffler, clutch to Image enterprises and told them to do it. They did the work (including the new points, timing, and rebuilt the carb). Then they bench ran it. Which now I am seeing I can get it to run fine with track in the air, so I guess a bench test really didn't show me anything.

I will run it Sunday afternoon around the yard and then check the plugs for color and wetness. Thanks for the tips so far!

---I am a bit leary to get into the electrical as I have zero success any other time I start messing with timing, points, etc.

grasscutter97 · Post by **grasscutter97** » Mon Dec 05, 2005 12:24 am

Update:12-04-05.

Took it for a ride and after about 5 minutes checked the plugs. They are dry. THe color does seem to be very light, almost white. That would indicate a lean condition, which indicates a lack of fuel under load.

When I sent the engine to Image I asked Bob to have the mechanic give me their notes on exactly everything they did, or found wrong with it when doing the bench test. I looked back in their notes and one entry shows an odd carb problem. Quoting: "found one passage in carb to be completely blocked with hardened fuel residue. Had to drill out passage to open it up." The next entry is: "engine now starts, idles, and reaches peak rpm."

Here's what I think. The sled had been sitting 20+ years. Likely there are a few other passages in the carb that are completely blocked. I have had the carb soaking in carb cleaner numerous times, I have blown it out with cleaner and air. Obviously there is still something blocked somewhere. Also, from what I read, you are not supposed to drill out any carb passages, as that changes the fuel flow!!

Does anyone have a WDB-31 (or 34, its not completely clear), that I could borrow (that is off a running sled), to test run this JD300?? I think that may just fix the problem.

JDFanPa · Post by **JDFanPa** » Mon Dec 05, 2005 12:45 am

I ended up putting a tillitson HD on my 300 because I had a rich condition that I couldnt get right. I loaned it to a co worker who is bad about returning things to try and get a sled of his running. If I can get it back from him your welcome to try it it ran fine at high rpm but ideled rich. Its not perfect but atleast it would seem to be getting plenty of fuel.

400brian · Post by **400brian** » Mon Dec 05, 2005 3:08 am

Did you see the post a while back when we discussed a fuel starvation problem that was discovered to be a bent ( misadjusted ) metering lever in the Walbro carb.
This does the same thing as a float in a float bowl carb. If you are looking at the carb, don't forget to check this.

speedy295 · Post by **speedy295** » Mon Dec 05, 2005 5:21 pm

I say get the mikuni back on it and get it jetted, so it will run. If the carb is in good shape there is not reason that it woun't run. From the sound of it , it sound like it is very lean I would try a 230 or 240 main jet and go from there.