I am getting a Bill Blue Mikuni TM33/34 pumper from another forum member. What are the recommended jetting for my situation?

Here are the stats:

Sea level - about 600 ft.
Stock 250cc
FMF Powerbomb header
HMF Muffler w/ quiet core
Smog removed
KDX snorkel

For reference, the jetting listed on my signature for the stock carb works flawlessly for my current setup.

Thank you in advance.

 

i have the carb you are getting and a megabomb and a q4, i kept the jetting the same and it works great much snappier but i could go down on the pilot a little to keep it from bogging the very little it does under load

 

What do you mean the same? You mean the way Bill Blue set it up for you? Do you know what the jettings are?

 

same as they were for the old carb i belive its a 130 main and 40 pilot but i'm tossing the idea of a 38 pilot becaue of a slight over fueling at low throttle opening and a quick shot of throttle but its hardly a stutter just not as jumpy as i like and think it could be better with the smaller jet, i did the carb and now don't think i big bore it the bike is now perfect for me but i'm 6'2'' and 160 so i don't neen big power to get around

 

Thanks, so the stock Keihin and the TM33/34 jet sizes are compatible? I have a 125 main now so I should stick close to that with the Mikuni? Bill Blue ships the carb with P-8 needle jet, 127.5 main jet, 0.7 main air jet, 37.5 pilot jet.

The seller told me he installed the Q-0 Needle jet, 142.5 main jet, 0.8 main air jet, and 42.5 pilot jet; but he also has a 292 cc head (KLX300) and lives at 5300 feet elevation. He also installed the short pumper rod.

So when I receive the carb, should I resort back to the original Bill Blue setting? The set up the seller has right now is too much for my 250 at sea level?

Thank you.

 

yeah get it set back up for around sealevel and work from that setting it for 5300 and being at 600 will be way off, and not to mention the diffrent mod's he has and it was a bit difrent than the cvk but it goes right in

 

I emailed Mr. Blue and he replied and helped me out even though I bought the carb used; what a guy.

He said for sea level, I should have 140 main and 40 pilot. Since the original owner put in 142.5 and 42.5, maybe I will leave it in for the first trial run, I may even remove the lid to lean it out a little. What do you think?

 

i think it will be a bit rich just did a 38 pilot and it now responds so fast its almost like a crf250x for snap so much better than stock

 

Interesting....I have the 40 pilot now, do you think that contributes to the lack of snappiness? I never thought of it as the 40 pilot seems to work perfectly for me. The bike starts up instantly hot or cold and idles perfectly.

 

So an update....

Based on what Bill Blue suggested and the fact that the original owner had the carb set up for 5300 feet and 292cc head, I figured his set-up would be very close, if not a tad rich. So I removed my airbox lid and kept all the original owner's setup. Lucky for me, the bike ran perfectly right off the bat from idle to redline at all throttle openings all while returning 59 mpg (which included a lot of full throttle runs to redline so the mileage should improve). The only glitch is that the idle sometimes goes up from 1300 to about 2000 rpm which may be the pilot is a little big. I also have the fuel mixture screw at 2 turns out. Once I figure out how to access it (I miss my kouba screw), I will try 1.5 turns out. Any suggestions?

This is the current setup:

142.5 main jet, 0.8 main air jet, Q-0 needle jet, 42.5 pilot jet, short pumper rod, and fuel screw 2 turns out.

Anyway other than the fluctuating idle, the bike runs like a raped ape, feels very snappy and no longer has that fluffy throttle response.