1988 250 WR jetting?

[ajcmbrown]

Hi all, time to ask for information from the collective knowledge here.
Can anyone tell me what main jet they are running in a 1987 or 1988 250 WR?
My bike runs great at low to mid revs but seems to "four stroke" wile trying to rev out.
Jon Hicks (jonhicks) had this issue also and ended up going down from a 460 (std main jet size!) to a 320 before it would run cleanly if I recall correctly! Mine also has the std 460 main jet.
Can anyone else tell me which main they are running on a std carb?
Tony.

 

[86 400 XC]

Yes mine was doing it too, it has the 370 main which was ok for my 400 but not so much for the 250.
I am at 3500'

 

[justintendo]

hmmm, mine runs great on book spec jetting...only husky that will! i am running a straight core silencer, no arrestor tho..mild port cleanup.

bike has 215 psi compression, after who knows how many hours on the stock piston. i pulled the engine out of fear of breaking the piston from age. awaiting a "freshen" when i get tired of the 430 mill currently in it. i miss the stroker 250!

 

[ajcmbrown]

Yes mine was doing it too, it has the 370 main which was ok for my 400 but not so much for the 250.
I am at 3500'

Similar altitude, I'm at 2800 feet. So your 250 is running a 370? Hmmm I only have a 350 here I may try, but probably buy a range of jets and have a tinker.
Tony.

 

[86 400 XC]

Have to change mine soon, its going down to a 350 next and see.



That funny building is where the Flames play. (hockey) Saddle dome

 

[justintendo]

i guess you guys are at about 2k higher elevation..i wonder if thats whats going on

 

[ajcmbrown]

i guess you guys are at about 2k higher elevation..i wonder if thats whats going on

I'd bet on it! The problem is, if I jet for my altitude, then go down to the coast, I run the risk of seizure, so I'll have to find a compromise.

 

[2premo]

I'd bet on it! The problem is, if I jet for my altitude, then go down to the coast, I run the risk of seizure, so I'll have to find a compromise.

it's called Lectron or APT Smart Carb
don't forget to compensate for temp on your jetting numbers

 

[2premo]

does anyone have altitude settings for 87 250?

 

[86 400 XC]

Any luck with the jetting changes?
My 88 with the 400 is doing it too, i went way down on the main jet with no luck.
Going to pull some timing out next. I can avoid the rattle if i hit the throttle hard.
Any light throttle in midrange its bad.

 

[justintendo]

Any luck with the jetting changes?
My 88 with the 400 is doing it too, i went way down on the main jet with no luck.
Going to pull some timing out next. I can avoid the rattle if i hit the throttle hard.
Any light throttle in midrange its bad.

really? i have never heard rattle from any of my swedes..i do run a bit retarded timing but thats odd..

 

[86 400 XC]

Maybe its the gas or the carb. i use non ethanol Shell 91.
but
The lectron on the 430 is sweet as pie
I made a tweak on the timing, after work tomorrow i will beat on it a bit wing it out on the streets and see.

 

[justintendo]

i had always used premium pump 93 or 94..but in order to get rid of ethanol i also started using real 91 gas. i was concerned about 91 not being enough so the past 2 years have been mixing my fuel 50/50...91 pure/110 vp leaded to get my octane close to 100. the jetting seems much more consistent. the 91 octane "not being enough" is just speculation by me...but 110 is readily available by me and has excellent shelf life so i made the switch.

 

[2premo]

Maybe its the gas or the carb. i use non ethanol Shell 91.
but
The lectron on the 430 is sweet as pie
I made a tweak on the timing, after work tomorrow i will beat on it a bit wing it out on the streets and see.

all things being equal, a Lectron is not equal
the Mikuni in the 400, I assume Mikuni,,, has a needle jet, pull it out and look at it, if it gums up it affects jetting

 

[suprize]

if your rattling on light throttle, sounds like your needle is lean. drop the clip one and see how it goes.. changing the main and nothing happening says needle or air leak!! my 400 has a bigger main than std and could go 1 more size i rekon. but the needle is 1 off what was std and its sweet.

 

[suprize]

i see the 250 in 86 had a 420 main as std

 

[ajcmbrown]

Any luck with the jetting changes?
My 88 with the 400 is doing it too, i went way down on the main jet with no luck.
Going to pull some timing out next. I can avoid the rattle if i hit the throttle hard.
Any light throttle in midrange its bad.

Not yet, I ran it at the last Vinduro of the year on 23-24 September, now I can play with it and test it on my farm.
I also have several size main jets ordered, just waiting for their arrival.
My Huskies don't rattle, sounds lean or air leak as surprize mentioned, maybe ignition timing?
Tony.

 

[86 400 XC]

Plug is very black still. I still had the issue with timing change and swapped out the SEM and put a motoplat back on for the bush and to be safe. Put all the timing to it like the other was set. I raised the clip to the top. Its damn near perfect, 95% good lol.
I can go through the gears on light throttle and the bike goes great.
1 more rejet maybe, but i need some smaller 1s now.

 

[suprize]

be carefull with the plug color as crappy fuels make them burn black a fair bit anyway. always best to jet the main up till it blubbers then come back till its clean

 

[justintendo]

if the needle clip is at the top to run best, you need to install next size smaller needle jet. this will return the clip to the middle position