Smokey YZ250

[Cutlass372]

Hey everyone, I just rebuilt the top end on my 87 YZ250 and the bike seemed extra smokey. I didnt mess with anything with the carb just put it back together and ran the carb settings that were there. The bike has been bored 2mm over (I think?) if that matters... Any way i can get it to smoke less? I think im going to mix some more gas tomorrow cause the gas that I am using is rather old.

 

[CRazy250]

give it a nicotine patch, i hear it helps quit smoking. no seriously what are your oil ratios, re tune your carb reguardless, check the jetting and see how far from stock it is, does it have performance reeds or pipe?

 

[Cutlass372]

Haha good one. Yes it had a FMF Fatty and I think FMF reeds (I didnt put them in). I am assuming the oil ratio is 32:1 cause it is written on the cover of the manual I have (by the previous owner). How do I check that stuff? I never really had 2 mess with any of the carbs on my bikes...

 

[just_a_rider]

Where does every one keep digging up these old bikes? I wan't my 85 KX125 back :(
At 32:1 ratio you would mix 4oz of oil to 1 gal of gas
20oz of oil to 5 gal of gas

 

[Cutlass372]

Yes I dont think I should have a problem mixing the gas. I didnt mix the gas thats in the tank now so I dont know what was done. Also I got the bike from a place I used to work and got it for free :)

 

[just_a_rider]

Free is a word I like :) Have you ran the new top end in good? A good 30 min casual ride should do it, don't rip it just ride. If you think your jetted rich take you carb off, remove the bowl and there on the bottom of the carb you will find 2 jets the center being your main and the one off to the side will be your slow jet. Their will be numbers on the jets, mine are 158 main and a 45 slow, going smaller with the numbers will lean the system but go in one size diferent increments at a time. Changing your needle jet will also change the system, choosing a diferent clip setting on your needle, move the clip twords the top and it will lean it. Best bet is to do a jet search on here, their are many links.

 

[76GMC1500]

How long have you run the bike for after rebuilding? I used a lot of oil on my piston during assembly. The bike filled the whole neighborhood with thick smoke, it took it a long time to clear out (over 5 minutes). The neighbors were very unhappy, good thing it wasn't my neighborhood. Anyways, run it hard and clear it out and it will probably stop smoking.

 

[Cutlass372]

I JUST rebuilt it. I finished it up tonight at about.. 8:30 and didnt have time to putt around and break it in (lots of ice on the ground). I started the bike in the garage and It filled it with smoke, running it for a few minutes. On the rings I put some oil but not an excessive amount. I figure I will break it in and see how it goes from there.

 

[76GMC1500]

You're fine, clear it out and it will stop smoking. If you rev any 2-stroke under no load, it will start to smoke a lot. You've got to run it at more than half throttle to really clear it out and you can't do that without a load.

A word of warning, now that you've started it in the garage and ran it for a minute and shut it down, it may be very difficult to start tomorrow. I had to pour a little gas down the spark plug hole and then run it up and down a hill about 18 times before it started to run. Then, it still didn't run great till it cleared out.

 

[CRazy250]

clear out? when i put boysen reeds in my bike they said it will cause bike to run rich, get a manual if you dont have one and see what the stock jetting is and go a bit leaner from that, never compensate jetting for problems.

 

[Cutlass372]

Started the bike up and took it for alittle ride. The smoke seemed to stop yet the bike seems to be sputtering or bucking sorta. Like it is cutting out? The bike felt strong yet im not sure if its all there. What would cause something like that to happen?

 

[76GMC1500]

Did you baby it around or did you run it hard? It will continue to sputter and buck until you CLEAR IT OUT! You've got to kick your 2-stroke around a bit and show it who is boss. If the buck is during deceleration, you need to lean out the idle a little with the choke knob. I like my bikes to idle only for a few seconds, this keeps them from bucking while entering turns.

 

[Cutlass372]

I did make 1 high speed run down my road into like.. 3rd. I noticed the bucking while making slow turns with light throttle and when accelerating slowly throught the gears.