Need a little trouble shooting help!

[YZ/250]

I have a 91 yz 250 that I picked up a few weeks ago. It was a cheap bike and I kinda wanted to ride again. The top end was rebuilt before I got it. The bike fouls plugs after 15min of riding unless Im riding full bore beside the tracks. :)
I've rebuilt the carb and replaced the reeds ( they were shot) and changed the air filter. I was thinking of maybe going down in jet size.? I was wondering if the crank seals are going.( I pulled the crank case oil after riding and didn't detect any gas in the oil) The plugs are oily and wet when I pull them out. It originally was getting way to much fuel. The local dealer told me that "if it were the crank seals the bike wouldn't run at all". I've tried backing out the air fuel mixture screw to lean it up....no luck there. I really cleaned up the carb and checked the floats when I rebuilt the carb. I was wondering what you guys thought. I really don't want to take it to the shop and pay $$$$ per hour when I can do it myself. I've know cars, BUT these two stokes have me puzzled.

 

[whenfoxforks-ruled]

If you have good compresion, then check your ignition timing first,

 

[IndyMX]

I'd say it's probably running a bit rich.

Probably not a timing issue at all.

 

[whenfoxforks-ruled]

Read the thread titled Plug reading 101,I did twice.http://dirtrider.net/forums3/showthread.php?t=92818&page=1&pp=20

 

[zroadrider]

I had the same problem with my 94 wr250 with it ideling too rich, heavy smoke, bogging, air/fuel screw ineffective and hard to start. I replaced the pilot jet and adjusted the fuel float with no effect. I then blew out all the air passages with carb cleaner and it runs sooooo much better.

 

[YZ/250]

Zroadrider, thats sounds just like my yz. I know all my air passages are clear on my carb though. Wish it where that quick for me! :) I know it can be something small at times.

 

[oldguy]

I had a 91 YZ 250 once upon a time and found that it started first kick after sitting a couple days but after running maybe 20 minutes hard and then shutting down a nd sitting for a few minutes would not start until I replaced the plug. The plug was always wet after sitting. It turned out that altho the float level was set right and the bike was jetted pretty close it would still flood out sometimes when riding slow. The float was so soaked that it wouldn't float and aftter running it the fuel would keep flowing and eventually overfill beyond the jets and on first couple kicks flood the plug with raw gas. Make sure your float is floating up and that the needle is seating properly to shut off fuel flow when it should

 

[maddmack]

the old guy seems to have it

 

[jdon88]

YZ/250 - Did you happen to buy the bike from a guy in Sayre, PA? I checked out a '91 YZ250 there about a month ago. I didn't buy it because the shock was leaking oil and the crank bearings had a lot of play in them. If it is the same bike maybe the crank seals are gone as you mentioned earlier.

 

[YZ/250]

Thats to funny!! Where are you located? To answer your question about the 91.... yes, I did buy from a guy in Sayre. Im just glad he took my offer( it was a lot lower than what he was asking). The shock was seaping a little oil but after riding it and giving it a good bath it hasnt seemed to leak. Im sure the shock will have to be replaced soon. I have toyed with the idea of down sizing the jets. Trial and error I suppose.

 

[jdon88]

Wow, that is funny....I'm not from that area, about 3.5 hours away in Pottstown, PA. I saw the bike for sale online auction site and noticed it was near my friends place in Orwell where we go hunting. So while I was up there for hunting I stopped by and checked the bike out. It seemed to run good for the short ride I took, had plenty of power. I think the guys name was John, the price was right but looked like it was going to need some work in the future so I didn't buy it. Good luck with it.

 

[YZ/250]

Small world ehh? Orwell is just a stones through away from my place!

 

[NO HAND]

I suggest you follow the advices from Old Guy and then read on how to jet. This knowledge becomes very helpful with any 2-stroke. Go from the low speed on up. Btw, shocks can be rebuilt for much cheaper than a new one. you can even do it yourself.