89 YZ250 no start cold

[UnatralyAspirat]

I picked up a YZ 250 at the end of last season and the the power valve blew up and smoked the cylinder/piston. I put a 'completely rebuild' engine i bought from a guy on eBay. It obviously was rebuild and it has good compression. It will not start cold without ether. Once its warm its 1-2 kicks, it runs awesome and idles decent. I am wondering if the choke is working. put the engine in just as snow was falling so i havnt messed with it yet. just thought i'd see if anyone has any experience. FMF Gold pipe, stock reeds, not sure on jets.

Thanks,
Chris

[Aus_Rider_22]

What number is on the sparkplug?

I was thinking maybe heat-range is way off???

I am probably way off!

[Yardpro393]

if the correct plug is in it then it is a carb issue. choke circut or air screw

[ossagp]

The enrichening circuit and the pilot jet are the likely culprits. Being two of the smallest passages in the carburetor they are prone to clogging. You may want to look under the jetting specs that companies like FMF have posted to see if it would be worth it right off to just buy a different pilot jet. They can be hard to clean because the passages are so small and they are easy to "burr" up even with welding tip cleaners.

It could be that your low speed screw is set too lean as well,,start it 1.5 turns out from just lightly seated in.

The fact that it runs good once started and starts again tell me that it is something really minor.

The starting drill for any of my two strokes goes like this for cold. Throttle all the way off (just be ready to roll it on in some cases). Enrichenor (some call it a choke) in full rich,,kick hard,,,and roll it on slightly when it hits.

Hot, you do just the opposite,,,full throttle no enrichenor. On really cold days my cr500 likes having the air screw turned into .5 turns out. It starts easily there and I reset before I ride away. (Kicking it ten to 20 times at 1.5 turns out just isnt worth it.)

[mtk]

Originally Posted by ossagp

The enrichening circuit and the pilot jet are the likely culprits. Being two of the smallest passages in the carburetor they are prone to clogging. You may want to look under the jetting specs that companies like FMF have posted to see if it would be worth it right off to just buy a different pilot jet. They can be hard to clean because the passages are so small and they are easy to "burr" up even with welding tip cleaners.

I've found that soaking them for a few hours in carb cleaner gets them good as new. I put them in a small 5ml glass vial, fill it with carb cleaner, and then cap it and leave it. By the following day, the jet is good as new. I've done it with jets that were totally plugged and they came out perfect.

[UnatralyAspirat]

I've got the carb parts soaking now. I did notice that the plug is incorrect, but only minimally. Its a B8ES instead of the B8EG that it should have, the only difference is the diameter and material of the center electrode (S is the standard 2.5mm and G is the fine wire type). I cant imagine that that would cause a no start but obvioisly I will get a few of the correct one to rule it out. I will also order a new choke plunger too, this one has been tampered with.

Thanks for the tips,
Chris

[Satch0922]

check the reeds...if any of the petals are not sealing flush against the reed block that could be your problem.

[ossagp]

I wouldnt worry a great deal about the reeds if it is starting warm ok. Dont worry about the eg vs es either. I dont use anything but the ES in any of my rigs and I run 20-1 with good plug life, and mine start good or I fix them.

I think once your jet is out of the cleaner you will be good to go, and a buggered up enrichenor should always be replaced,,usually however the bad ones let fuel pass and affect the warm running adversely.

What kind of carburetor cleaner do you use MTK? I still have a setup from "GUNK" that works, but the scent is enough to make me shy away from it, and the spray types that I tried didnt get dried in fuel out well at all.

[Satch0922]

Originally Posted by ossagp

I wouldnt worry a great deal about the reeds if it is starting warm ok. .

Question.....if the bike won't start cold......how do you ever get it warm to see if it starts warm????

[ossagp]

Satch,
You would have to read the original question at the beginning of the thread to know how his poster is getting his started.

Get back if you are still wondering how all this can happen ;-)

[Satch0922]

lmao.....ether.....there is the problem LOL

[ossagp]

Ether the problem?? Engines start that way in this country all the time. Outboards,,,snowmachines, atv's you name it.

[mtk]

Originally Posted by ossagp

What kind of carburetor cleaner do you use MTK? I still have a setup from "GUNK" that works, but the scent is enough to make me shy away from it, and the spray types that I tried didnt get dried in fuel out well at all.

Just your normal, run of the mill carb cleaner spray, shot into a 5ml vial. I think it was Gumout brand, but I can't be sure without checking. I put the jet in the vial, fill it with carb cleaner from an aerosol can, and in a few hours it is good as new.

With a dirty jet, the stuff bubbles like Alka-Seltzer until the jet is clean. I thought it was pretty amazing the first time I did it, to be honest.

[ossagp]

I will try that brand,,you know the "gunk" i am talking about i bet. Smells like that creosote sheep dip.

[Satch0922]

Originally Posted by ossagp

Ether the problem?? Engines start that way in this country all the time. Outboards,,,snowmachines, atv's you name it.

Ok..what's your point? I am just stating the obvious. I have never HAD to use ether to start a motorcycle or anything else for that matter......ever! Why would you? If it won't start FIX THE PROBLEM!

[ossagp]

I give up.

[Satch0922]

lmao!! Come on man I didn't wear you down that quick!

it's all good!

[ossagp]

LOL,, the things you miss out on by living in the warmth!!

[Satch0922]

good point!

[UnatralyAspirat]

well i put the carb back together with the old choke plunger (still waiting on the new one). It started and ran for a few seconds then quit like it ran out of fuel then wouldnt re fire. I'm waiting on the choke, in the mean time i will check the reeds. compression is good, so if it still doesnt start i will investigate an air leak somewhere between the carb and the cylinder, cant be much else to keep it from starting... has spark and compression.

Thanks again,
Chris