250-500cc Running Rich... Question

[Doch80]

So I just got my 1992 WXE 250 about 2 weeks ago. Took it out last weekend for a shakedown run and I think I'm running rich. Not incredibly easy to start cold or warm and won't idle for more than a minute or two after warm-up/running without throttle input. Idle seems really slow and can't be adjusted with the idle screw. Took the plug out and it shows to be running rich. After a plug change I tinkered with a air screw and it seemed to help with idle a bit. Righty righty and it seemed to increase a bit.

Question is where to start. Need to check for air leaks I guess but do I break open the carb (Mikumi) to see what jets I've got and get some smaller ones and go through re-jetting or should I start on something smaller?

If I need to re-jet I'll research the process more to determine the appropriate steps to adjust things but if I don't need to go that far yet I'd prefer to start with the low hanging fruit first.

Thanks for the help!

Chad

 

[2premo]

if you turned the air screw to the right and your idle increased it is a lean issue
airscrew allows air in, if the idle mixture screw is at the front of the carb it controls the fuel flow, if at the back it controls the air flow
so you essentially reduced the air which technically leans it by turning right and closing the air flow
probably wise to remove the carb at this point and not guess, see what jetting is in it now
there is a jetting section here on Cafe Husky, know this,, the 92 jetting is not the same as other years, so stay with 92 jetting
I had a 92 and agree with your intro in "pictures", mine was a runner too, but jetting was different from my 93

 

[Doch80]

Thanks for the response. To make sure my heads wrapped around it correctly... the idle adjustment screw is in the middle of the carb and the air screw is in the rear under the air intake. I was thinking it was too rich b/c the idle screw had no affect. I thought I needed to turn the air screw to the left (loosen or back out) the air screw to increase the air to reduce the richness or lean it out more to be able to adjust idle... Am I thinking about that correctly? You had mentioned that turning the air screw to the right reduces the airflow, or leans it out. I thought too much air is a lean condition and too much fuel is a rich condition. In my head I thought by reducing air I’m making a rich(er) condition. Have I got it backwards? It smokes a lot and sounds like it may be backfiring. I pulled the plug, who knows when it was last changed so not a good picture maybe, and put a new one in. See below.

But you’re right, need to pull the carb. Question is what to do with it after it’s pulled go smaller or larger or just see what I’ve got and put it back together? I thought I’m too rich and need to go smaller but after your post, I’m too lean and may need to go bigger?

I’ll continue to read and gather information... and determine what I actually have. Thanks for the help!

 

[Doch80]

Picture for reference

 

[2premo]

if you turn the idle mixture screw clockwise and the idle improves your pilot is either partially plugged or too small, or you have an air leak
turning the screw clockwise reduces the airflow to the pilot circuit and changes it to a richer mixture in that circuit
your black plug might have to do with an old plug not firing clean or a needle being too small or lifted too high and causing a rich mixture off idle as you roll it on
since most of tight trail riding is in that circuit there's a possibility it is not correct
on the smoke there is one actually two more issues, first is it the right plug and is your ignition giving good spark
if your ignition is original it should be a Motoplat, time might have taken a toll on that
pull the mag cover, my 92 had a PVL very nice, but no lighting circuit, mostly a day rider so it was fine
since you bought it used pull the carb and see how dirty it is inside, get the needle number the needle jet number, the main jet number and note or have epic of your needle clip position
we can start there

 

[Doch80]

Thanks for the info. I'll get the carb pulled in the next few days and gather info.

I'll figure what where the mag cover is and how to pull it to see what I'm working. Is there an upgraded ignition for the age of this bike? Are they pretty standard for 2 strokes? I'll post what plug was in there and what I put in there... thought I got the correct one but can't vouch for the old one.

Thanks for being patient. I'm a Jeep guy (95')... a post-carb jeep, so carbs are pretty hoodoo voodoo to me.

 

[Doch80]

So, took things a part tonight...

Spark Plug (came with bike) - NGK B8EGV
Spark Plug (New-installed) - NGK (3981) BR9EIX

Ignition - PVL w/ Dmon module

Carb - Clean inside, PO said he had previously cleaned it and looks to be true

Needle: 64 or 1-64
Needle Clip Setting: Middle or 3 of 5
Main Jet:360
Needle Jet (Pilot Jet?): 40 or 140

 

[2premo]

 

[Doch80]

 

[Picklito]

Do you have a screen type spark arrestor? If so, pull it out and clean it.

 

[Doch80]

So it looks like, after looking at the Mikumi schematics, that I have a newer version pilot jet in an older version TMX. I have a N224.103 pilot when I should have a VM22/210. Don't know how that happened. but the question now is, do I go back to the correct jet of the same size or stick with the same type jet and go smaller. It runs with the new style jet but would it be better with the correct style?

 

[Doch80]

Do you have a screen type spark arrestor? If so, pull it out and clean it.

No, I don't but would like one. I just have the muffler with the open outlet riveted in.

 

[Dirtdame]

No, I don't but would like one. I just have the muffler with the open outlet riveted in.

Don't ever run a screen type spark arrestor on your 2 stroke. They get plugged up too quickly and are difficult to clean and maintain. You can always get a FMF universal spark arrestor and get it to fit. The reverse turbine design will flow and work much better than a screen, and never get plugged.

 

[Saabman82]

Hey not sure if youve sorted this out yet, but i ran into a similar issue while sorting out the carb on a 1994 wxc i rescued a few months ago. It also had the n224.103 jet in it. I put what i believe is the correct jet type Vm28/486 in it. The difference between the two is the vm28/486 tip is a smaller diameter and allows the jet to fit into the carb and seat completely. Its hard to tell that the n225.103 jets dont actually fit untill the tip breaks off...ask me how i know!
Anyway i also got new reeds which made all the difference in the world. The old reeds still sealed tight in the cage but i got new ones anyway and that fixed 90% of my issues and it actually idles now. (Boyesen #615) Still fine tuning it now (tough and probably useless this time of year ...below freezing temps).
How are you making out with your carb?

 

[Doch80]

Hey not sure if youve sorted this out yet, but i ran into a similar issue while sorting out the carb on a 1994 wxc i rescued a few months ago. It also had the n224.103 jet in it. I put what i believe is the correct jet type Vm28/486 in it. The difference between the two is the vm28/486 tip is a smaller diameter and allows the jet to fit into the carb and seat completely. Its hard to tell that the n225.103 jets dont actually fit untill the tip breaks off...ask me how i know!
Anyway i also got new reeds which made all the difference in the world. The old reeds still sealed tight in the cage but i got new ones anyway and that fixed 90% of my issues and it actually idles now. (Boyesen #615) Still fine tuning it now (tough and probably useless this time of year ...below freezing temps).
How are you making out with your carb?

The short of it, changed reeds and adjusted floats. Need to fine tune the jets but at least it'll start fairly easily, and can be adjusted.

The long... I figured out what the stock jets were and put those in. Very hard to start cold or warm. Changed the reeds and it didn't really help. Adjusted the floats and that helped a lot but was still running really rich so I put the jets that came with the bike back in which are smaller. It'll idle now and I can adjust the air screw and idle screw and affect it. Before nothing changed when adjusting those.

I needed to find a baseline but that was hard to do when the bike was really hard to start, wouldn't idle well, etc... I'll look into the needle. My mid range isn't the best so the needle probably needs some adjustment.