Back again with another stupid jetting question

I had EG do a 265 kit on my YZ 250. Had the head cut for race fuel and got the mid/top porting option. Totally rebuilt the engine with a fresh crank, bearings and seals. He gave me some settings to start out with and I had to change them up a little bit. I started out at a 48 pilot and experienced a blubber off throttle. The only way I could get rid of it was to turn the A/S out to about 3 turns. I dropped it down to a 45 and found the best throttle response but I could not get the bike to idle. Went down to a 42 and experience a slight surge. So I installed the 45 pilot and rode with it to see if it would get any better once the bike was run hard. The new motor is VERY sensitive to A/S adjustments too! When I started riding it was about 75 deg and sunny and the bike responded the best to 2 turns out on the A/S. Later in the night the temp dropped to about 60 and I had to turn the A/S back to about one turn out to get the same off idle response.

I cannot even pull the clutch in without the bike stalling instantly if the throttle is not held open even while riding.

The other issue I have is if I shut the bike down or stall it while on the throttle the bike will start back up first kick, but if I pull the clutch and the bike stalls it is extremely hard to get going again I almost wore a hole in my boot last night I kicked the thing so much. When the bike is cold it starts and idles perfectly. I turn the choke off after about 3-5 secs and let the bike warm up it will idle for about 30 secs before dying. Then once warm, it will not even idle for a full second. Its just a PITA for track riding while trying to put my goggles on.

I will post up a vid (which there is not much riding involved but you can see my issue very well and I apologize for the length of the vid). You can hear that every time I pull the clutch the bike tries to die which makes brake tapping impossible. It doesnt bother me much through the corners but in the air Im deathly afraid of stalling the bike. I literally had to bump start the bike everytime I tried to roll across the side of the track.

Here is another one, you can see how long it takes me to get the bike going after stalling with the clutch, I had to sit there through an entire session so the bike would cool down. Then the bike stalling immediately after pulling in the clutch after it started.

Does anyone have any suggestions of something I may be over looking or why the bike would be so sensitive to the A/S? I would like to have the bike idle for at least 10 secs so I can adjust the throttle or if I would need to stop for a sec to readjust something. It just does not make sense to me. I do not know what I should be looking for. Do I really have to scrifice throttle response in order for the bike to idle?

Made for a shitty day at the track!

Edited by BDubb106

Does it idle with the 42 or 48 pilot?

No... it is a little better with the 42, it does not die immediately when I pull in the clutch without fuel but it will not idle at all when in neutral. Off idle throttle response suffers though. Also has the surging issue.

Where is your jetting set at now? It might be your needle position. Are you running the JD kit or a stock needle?

JD red needle, 3rd clip position. I doubt its the needle. Everything was just replaced including the valve and seal.

Its pretty rich but I've always ran my needle and main a little rich, and EG also recommended that I did with the mods that were done in combination with the pipe I am running.

Edited by BDubb106

Arne brought up something that I forgot to mention via email...

The idle screw does nothing either once the bike is warm. When the bike is cold, the idle screw works fine.

Don't know if that helps, but I thought it was worth mentioning!

Sounds pretty rich too, how about a small test and change the needle to second? Quick run should tell you if its better. IMO all circuits are connected and inter-related. So raising the needle you can go higher on the main.

Edited by arnego2

I'll give it a shot, but I've tested the 2nd clip position before and it gives me a hesitation right before the PV opens. With the 265 kit and mods done, I doubt it will be any better since every circuit needed to be richened up a step or 2 based on throttle response. The main is already pretty rich at a 178. Was at a 175 prior, and it made me a little nervous so I bumped it up and the top end seems stronger and revs much further than before. I may even try a 180 and 182 to see what happens.

I love this image :)

effects3.gif

it shows the interrelation of carb circuits nicely.

I have that same image on my computer. Along with a few other jetting charts.

Have you tried going down on the pilot to get a proper idle then adjusting the needle straight diameter to fix the response down low?

Maybe warm up the bike completely then swap to a 40 pilot and see if it idles correctly. If it does you may want to try a different needle with a richer straight diameter. I think the JD blue does this?

Or just buy a lectron and be done =]

Have you tried going down on the pilot to get a proper idle then adjusting the needle straight diameter to fix the response down low?

Maybe warm up the bike completely then swap to a 40 pilot and see if it idles correctly. If it does you may want to try a different needle with a richer straight diameter. I think the JD blue does this?

Or just buy a lectron and be done =]

I've only went as low as the 42, once I found out that the 42 was surging I immediately swapped it back to the 45

If I had the money I would love one of those carbs... but its not there right now. Ill try going lean and see if I can correct it with the blue needle. Your correct about the blue needle as well.

I was told a red needle for stock motors and a blue needles for bigbores or port jobs.

ill give it a shot and see what happens

Pilot seems real lean to me....I'm in Michigan with a stock bike. It runs perfect at 1.0 turns out on the air screw and 52 pilot.

A big bore with high compression makes me think it needs more fuel, not less.

Pilot seems real lean to me....I'm in Michigan with a stock bike. It runs perfect at 1.0 turns out on the air screw and 52 pilot.

A big bore with high compression makes me think it needs more fuel, not less.

The only reason I am running the 45 is for off idle throttle response. It was the best with the 45. The 48 was rich, so I know going any higher will be too rich.

How are yours reeds ?

Brand spankin new. The whole motor was rebuild. Including the intake

Pilot seems real lean to me....I'm in Michigan with a stock bike. It runs perfect at 1.0 turns out on the air screw and 52 pilot.

A big bore with high compression makes me think it needs more fuel, not less.

45 gives best response on my bike too. I don't go to a 48 pilot till it's <50F. Not stock pipe/porting/etc though

No go on the 42 and blue needle in position 2, 3, or 4. No idle but throttle response remained great and no surge with this needle. Gonna try the 40 tomorrow.

Create an account or sign in to comment

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

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now