Jump to content

1986 YZ250 anyone with knowledge on it??

Recommended Posts

I'm looking for some help with my 86 yz250.

I picked this bike up for 500, runs decent and is in fairly good shape. 

It has a carb for what I'm assuming is a 90s bike..

Has anyone experienced that?

I have an issue now where it won't idle, and will only cold start with starter fluid.

Once it's been fired up, it starts up every kick after.

 

Share this post


Link to post
Share on other sites

I ordered a new Piston, cables, etc.

Two weeks and I'll be back home to work on it, cold compression was 93psi, haven't tried hot.

Used to idle when I picked it up but still had the initial start problem.

Haven't tried after cleaning carb and readjusting needle. 

IMG_20170728_154825548_HDR.jpg

IMG_20170805_182434258.jpg

IMG_20170805_172524054.jpg

IMG_20170805_182446253.jpg

IMG_20170805_200150829.jpg

Share this post


Link to post
Share on other sites

they ran those carbys on the 89 up yz250

piston has a bit of blow-by ( burn marks ) - not too much carbon build up on the piston

might not want to start because of low compression

how does the intake boot look ? no cracks or perished

 

  • Like 1

Share this post


Link to post
Share on other sites

2 strokes are 70% or so all the same, fire away. I'll know or I won't and will not mislead in any way.

Share this post


Link to post
Share on other sites

Looks to me like a 88 model year, not a 86 maybe helpful when ordering parts and gathering information

  • Like 2

Share this post


Link to post
Share on other sites

Definitely 88 - 86 & 87 still had drum rear

Gold shock canister on 88 - silver on 89

Holes in the frame near the brake pedal on 88 - none on the 89

  • Like 1

Share this post


Link to post
Share on other sites

Sorry guys, have been on the oil rig, just got back in town.

Ordered a bunch of stuff before I left, including a new Piston so tomorrow will install all the new stuff and let y'all know how it does. 

I'm sure it's going to be lack of compression, but also readjusted the carb and cleaned it.

Looks like when the original owner had it, he put the needle attached to the slide/throttle cable in wrong. The plastic piece and little spring we're in wrong, etc etc. Throttle seems to work shit tons better but we will see when running. 

Thanks for the help, will post later. 

  • Like 1

Share this post


Link to post
Share on other sites

Ok so got it all put back together, new Piston, clutch cable, etc etc.

Bike won't start up, even with starting fluid. 

Backfires like every fifth kick or so out the exhaust. 

Will check timing tomorrow, plug was wet. 

Share this post


Link to post
Share on other sites

Ok, so after doing compression test, found that there was no compression. The previous owner had not upgraded the bike, but found that the stock piston of 68mm was too small, and the bike has been bored out to 69mm.

Should've checked beforehand, but was lazy with it and just assumed.

Put old piston back in and fires right up Everytime.

Running a 50:1 mix, thinking of lowering the oil ratio to reduce some splooge in exhaust...

Also, I'm running a b8es ngk plug, does anyone recommended upping it to like a b9? Or just go with the irridium?

Runs great, only issue left is getting new Piston the right size, which can be ordered, and the idling. Still doesn't idle but for a couple seconds if that. But could also be jetting due to the setting where it is to have a touchy throttle response. Have tuned to lift up and take off/snap at any gear with the throttle.

Share this post


Link to post
Share on other sites
On 8/15/2017 at 6:56 PM, S.O.A.N.Z said:

Definitely 88 - 86 & 87 still had drum rear

Gold shock canister on 88 - silver on 89

Holes in the frame near the brake pedal on 88 - none on the 89

So I just saw your reply for some reason, you think it's an 88??

Share this post


Link to post
Share on other sites

Old-school 2-stroke thinking was to set the idle so that the bike would only run for a few seconds unassisted. If you want your bike to idle longer, just up the idle speed until it does. Idle adjustment is usually a screw that sets the slide height.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×