I just installed a full Yosh pipe, 150/155 jets I cut two 1 3/4 holes in the air box lid and removed the snorkel.

The mixture screws are at 1 1/2. I have a pro flow form filter all else is stock.

I am at about 1000 feet (Simi Valley Ca)

I rode it up and down my street - it seems to run good (real good) but it will only idle for a few seconds and then stall out. Turning the idle screw does not seem to help -using the choke does. Anyone have any suggestions as to why?

Also, the head pipes are glowing red - normal?

 

Step up on your pilot jets your low speed jetting is to lean try 25 or 27.5
www.glafkoracing.com

 

You should be atleast 3 (probably 3 and 3 1/2) turns out on the mixture screws. Also I would go up to atleast 160/165 on the main and lower the clip on both to the 4th. You are very lean all around, lean makes good power but you need to richen it up for reliability.

 

Turn your air/fuel screws out 3-3 1/4 turns. Unless you have a pilot adjusting screw driver you'll need to take the carbs out or at least turn them. Did you move the needle clip position? If you did your problem may very well be the jet needle holder has come loose, if you don't push it in all the way it can come loose and the thing is just bouncing around inside the top of the carb. This will allow your needle to bounce around as well. Everything runs great until you want to idle then it does as you say. This happened to me and thats why it may or may not be your problem.

 

Thanks to all..I will try the screws first - I was just following the instructions that came with my pipe. They said 1 1/2. That did not seem right because most other pipe manufacturers are at around 3 turns.

I called Yosh and they stuck by the 1 1/2.

What do the pilot jets do? It does seem lean at idle, maybe it would not hurt to step up one notch to 25.

Ps I did not change my neddle setting. Also, the jets are Mikuni -no Dyno jet parts-all stock

 

Try turning the mixture screws first, but with the air-box mods it might require stepping up on the pilots, they are standard mikuni jetski jets so are easy to get. We have had to step up on a few Raps. with these mods. to give a little more fuel on the bottom end. Make sure you to some wide open plug checks to check the color on the plugs, your jetting sounds close.
GlafkoRacing.com

 

I have problems with crap building up in the choke area...the un sealed cable allows water to roll down the housing into the carbs...pull the plunger and make sure the area is clean of corrosion. Head pipes glowing is normal for the materials bieng used, I would recomend a slightly richer a/f adjustment 1/2 turn at a time until you are pleased



braaap

 

It worked!! Turned the air/mix screws out one turn each (they are out 2.5 total) Idles and runs perfect.

I wonder if I should turn them in a little...I guess a plug test will tell.

Thanks guys!! this is great forum.

Now I need to figure out how to bleed my neighbors YZ 250 front brake--

Also: Ace hardware has a flexable screw driver set for 16 bucks, worked great getting to those screws.

 

good to hear its better, I would actually turn the micture screw more unless you have a problem, 2.5 still seems a little lean as most everyone is running at 3 turns out or greater (stock is allmost 3 turns i think). MY buddy with a full yosh pipe and proflow filter is running 165-170 mikuni mains and needles down on the 5th clip..