250-500cc 2012 WR300 Starting issues driving me nuts, can anyone help?

Hi Guys,

I have just picked up a near new(200kms) WR300, the bike is in mint condition and when i can get it to start its awesome. Unfortunately its very temperamental, yesterday it was starting within 2-3 kicks, today it was more like 10-20 kicks. Surely the the Mikuni cant be that sensitive can it? I pulled the carb out and it has a 420 main jet and a 32.5 pilot, airscrew was 1.75 turns out, don't really know what the needle position is. I am in Adelaide SA so i am at sea level.

It kicks back hard, my right foot is feeling the painful result of extreme kickback. When it does start it seems its when i'm putting in only a moderate kick and it hits TDC half way through my kick.

Anyone else experiencing this? Is there a fix?

I am seriously worried about stalling it in the middle of nowhere and not being able to restart the bike, in fact it stopped at the traffic lights tonight and i had to roll to the side of the road and give it around 8-9 kicks.

Since you say you drive it on the road, I assume you have lights. Do you have a switch for the headlight? They don't like to start with the headlight on. Mine has always started in one kick even if it sat for a couple weeks, but the last couple times I rode it, it took several kicks. Now it has no spark and I haven't had the time to figure it out.

I have been reading that the the Keihin Airstryker is the way to go, i am more than happy to buy one but want to be sure its the right thing to do. I am looking at buying one straight from JD already jetted.

It will kick back if you don't kick hard enough. You really have to give the 300 a good strong kick.

Definitely put a switch on the lights so you can turn them off when starting.

When I had the Mikuni on my 300 it was always just a little rich and would kick back like you describe. I would hold the throttle open just a tiny bit to start it. Keeping my index finger locked on the front brake lever helped keep the throttle from opening too much while kicking. That seemed to make starting easier. I only did this when the engine was warm. It would start fine with the choke when cold. It now has a Lectron.

You may want to try one more size down (30) on the pilot jet to get rid of the kickback.

Yes if too rich it will take LOTS of kicking. The float is too high from the factory. Your pilot and main seem good. Verify needle and float and wear mx boots when starting

My Mikuni also liked just a touch of throttle when starting hot.

Go back to your technique. You say when you kick halfway through it's hitting TDC? Push it to just past TDC prior to starting your kick. Get in good position, up on top the tank and give it a strong kick all the way through from the top. If all the resistance half way through the kick, you're not giving the engine enough momentum to carry through the compression part of the stroke, which is where it's going to be starting.

Kick backs -- be sure you're wearing boots. I broke the plastic shank on a pair of hiking boots when I got a kick back once testing it in the garage. Foot was swollen for a week.

It's been a while since I messed with the Mikuni, but I think your jetting should be pretty close where you have it.

09 here. Just ordered Lectron..for the heck of it.

With mukini now, it starts just fine. 1-2 hot, 5-7 cold. Definitely can't start it in gear though. I am 160 and I do have to put lot of power in the kick. I can't start it with left foot on the ground, I need to be on the pegs when kicking. I can start it in hicking boots, but I will feel it the day after.

My jetting is as follows


Main 430
Pilot 45
Slide 4
Clip 2 from top
Needle:6BFY43-74 2nd from TOp

Thanks for the advice guys, I will give it a go again today. Also I am running motul 800 at 32:1. Is it a little rich? Could this be part of the problem?

32:1 is fine and won't contribute to problem. That's same ratio husky recommends for first four hour break in.

Goodness. Somethings way off with carburation I would think. My 09 with lights, gps , grip heaters always on always kicks over within 3 kicks. Cold or warm with the keihin. Just bought the lectron and now three kicks cold one kick warm Everytime.

Ok, I'm seriously considering a lectron or keihin, which one to go for and why? Price differences and where to get them from?

I cold started my Mikuni equipped 300 today one kick. JD jet kit and float adjusted. Firecrotch's bike doesn't have the Ducati digital ignition which requires lights off to make fire reliably. I don't have lights on mine tho.

Ill have a bit of a play with the mikuni float levels today and see if I can find a happy medium.

I had the same issues when I first got my 2014 300 Mikuni equipped. I got the JD Jet kit and it's much better. About a month ago I finally adjusted my float level as it was pouring gas out
whenever I had it on the kickstand with the gas on. Now it's perfect. Colds starts with choke on it starts first kick every time. Hot starts out on the trail is one or two kicks.
On a side note, after reading all the jetting and carb threads and seeing how many people bought the Keihin carb I was set to do the same. I called JD Jetting and talked to one of the guys there
and told him what bike I had and told him I was interested in getting the Keihin carb and he said why? I paused for a sec and felt kinda stupid because the only reason I could come up with was because
that's what everyone else is doing. Long story short we chatted for a bit and I told him the conditions I normally ride in and he gave me some recommended settings: Red needle two from top,410 Main, 32.5 Pilot, Air screw 1 3/4
That's what I'm running now and it runs perfect. He could've just sold me the Keihin and made some money but instead gave me some good advice. I thought that was pretty cool.

I think there,s a chance you might have the JD jet kit in it,because 32.5 pilot and 420 main is what they recommend to start with,so might want to pull the needle out and see if it has a colour on it.I have a 12 300 with the JD kit,I'm in Brisbane and when cold sometimes it takes a bit of kicking to fire up,but when warm 1 to2 kicks max.As stated earlier you need to use the right method eg just over tdc and don't be a girl when kicking it.

Yep, just need to work out how to adjust float levels now haha. I'm a tuning novice.