Maybe TNC will see this. He's running a 36 on a 300 kitted KLX250. He's in Texas, so not sure how much the climate/elevation will differ.

I take it the 30 degrees you refer to is 30 degrees C. It always helps if you put your general location in your signature, that way people have a clue when you refer to things that might be affected by where you are located.

 

OP, I have the same carb on an '06 KLX250 that has a factory KLX300 cylinder and piston. The exhaust is a full Muzzy headpipe and muffler. I run a Twin Air air filter with the stock airbox lid opened up more than OEM. My home elevation in Abilene, TX is 1700'. For my bike and conditions the pumper performs smoothly and cleanly. I assume you've printed off the Mikuni instructions for this carb. They are fairly short but cover all the bases. You can generally find them under Mikuni HS40...bigger carb but same overview of the tuning elements. Here are my specs.

Main jet...127.5
Pilot jet...17.5
Needle jet...P4
Air jet...0.9-------most people don't change the 1.0 OEM air jet, but mine wasn't crisp off idle until I changed it
Needle...9EBY1-50
Needle Clip...middle, 3rd from top
Idle Screw...2.5 turns out
Float Level...20mm
Pumper spray nozzle...as per manual, directly at needle, and with the timing of the pumper as per manual, 1/8 to 3/4

The suprising thing to me is how altitude tolerant this carb has been. I no longer change the main jet or anything when I go to the mountains out west. Yes, the engine burbles a little as I crest mountain passes at 10K and higher, but honestly you find yourself at that those extremes for such a short duration.

 

There ya go! Kind of like Superman swooping in to save the day! TNC ;you de man!

I copied it to my desk top for when I install the 300 cylinder, carb, and header/tail pipe.

 

Superman? C'mon, dude!...you know I hate tights...LOL!

Honestly, I give a lot of credit to some of the old hands who dove off into this carb years ago with their big bore kits. Not all of their results were the same as mine, but it sure saved me from having to start from scratch and reinvent the wheel...LOL!

 

Hey everyone, just wanted to do an update, as I feel like I sorta started a thread then ditched it without a resolution.

I ended up caving in and buying the mikuni kit, they sent me a size 15 pilot (what I was gonna buy anyway), a 125, 130 and 132.5 main for tuning, a 9EBY1-50 needle, and a p-2 needle jet.

After putting the 15 pilot in, all my starting issues have gone away. the bike starts first kick no matter how long I've been riding it, with the exception of if I've just come off and the bike have been on its side. then it's just a matter of kicking it over for around a minute before it fires right back up.

I tuned the mixture screw on the bottom of the carb, with it stalling at .5 turns out and 2 giving me an average of 1.25 turns out, which seemed a little low, but it works so I'm happy.

I put the 130 main in and havn't touched it since, although the bike seemed to break the rear wheel loose much easier (could have been placebo, gonna focus on that later).

the main problem i have now is midrange. with the new needle and needle jet, I couldn't get it to rev smoothly throughout the range, trying all the spots on the clip before giving up and going back to the old needle/jet combo. I found that the new needle/jet worked best with the clip 1 from the bottom, but even then at around 1/3 throttle it would misfire like crazy. With the old jet/needle though, it runs extremely rich, to the point where black soot appears on the rear fender. I haven't checked the plug, but I'm pretty sure I already know what it will look like.

I've thought about it, and after reading up a lot more on jetting, I think the new needle should work well with either a p-6 or a p-4 needle jet. I'm probably gonna order a p-6 tomorrow and try that when it gets here.

The idle seems to "hang" at 3k rpm, before dropping back down to 2.2k (what I've tried to set it to) after around 10 seconds of idling. this could be due to a dodgy o-ring I put on the air screw last time I took it out, and the original one flew off into the garden, landing who knows where. I'm planning to order a legit one with the p-6, so that I can combine the postage.

After pointing the fuel squirt directly towards the needle, the engine seems to bog slightly when going from no throttle to any throttle. It doesn't happen if I keep the throttle on slightly then rev back up though.

It's coming to that time when I need to buy new sprockets, and I'm thinking of going from a 14 and 48 to a 14 and 51, for a 5.9% increase in torque. whats everyone else running? And whats the top speed? With the current sprockets I can get up to around 136km/h.

Where TNC lives in texas has almost identical weather to where I live, so hopefully if the p-6 doesn't work out, the p-4 will.

Sorry about the lenghy post, I've just had a lot of "progress" with finding the right jets, and wanted to keep everyone updated/ask more questions. Thanks in advance.

 

"After pointing the fuel squirt directly towards the needle, the engine seems to bog slightly when going from no throttle to any throttle. It doesn't happen if I keep the throttle on slightly then rev back up though."

Time to adjust the accelerator pump. There are two very small allen screws to adjust. One adjusts when then a/p starts shooting gas and the other how long it shoots gas. I've got mine set to start shooting when the slide starts to lift and then adjusted the duration for best throttle response.

Ride on
Brewster

 

Turtle,

Did the stock throttle cable work with the nu tm36 carb you installed?

 

The stock throttle cable works with the 36.

 

Yeah, stock cable worked, removed the push cable though.