What Mod's to do to make this yz400f a one kick starter?

New valves might be necessary, but porting and cams will be a complete waste of money if the carb's no good. Convert it to an FCR-MX from an '05 up, and solve most of your problems.

For hot starting, the decomp cam allows you to just focus on starting the bike without worrying about getting TDC etc. This makes hot starting a lot easier. Also it makes kicking over easier.

It doesn't necessarily improve the actual hot start itself

Ok thhanks guys.

I've finaly got the carb dialed in. It started tonight on the second kick. Rode it for about 20 min and shut it off. It restarted the first kick. I pourpously stalled it and hit the decompression lever kicked it 5 time then the 1st kick it fired rite up. When im starting it hot or cold I have quit using the compression lever all together. I can kick through it with no problems.

That's what's working for me rite now.

Edited by slyfox83c
Ok thhanks guys.

I've finaly got the carb dialed in. It started tonight on the second kick. Rode it for about 20 min and shut it off. It restarted the first kick. I pourpously stalled it and hit the decompression lever kicked it 5 time then the 1st kick it fired rite up. When im starting it hot or cold I have quit using the compression lever all together. I can kick through it with no problems.

That's what's working for me rite now.

Out of curiosity, what jets did you end up with? Did you just replace the pilot and increase the idle a little?

Had to do the exact same technique on my buddies 08 cr250f, I could kick it all day without twisting the throttle and it wouldn't fire.

If you prime the throttle 3 times then start to kick, it will fire up.

i went from a 175 main needle jet to a 170. im running a 200 main air jet a 100 pilot air jet. a 65 idol jet and i forget the other one. ive got it wrote down at the house. im at work rite now. the biggest problem with mine was there was some junk in the idol passages. between the main body and the lower body where the bowl bolts on. i had to clean it extensively then ran thin wire through the passages and blow the out. i called James Dean jetting amd told them what problems i was fighting and they sent me thier kit. they also sent me a new pilot needle and spring kit for it. that made it a lot easier to adjust the fuel mixture. i never could find a short enough carb screwdriver to adjust it on the bike with it running. this one extends past the bowl and has a T handle for easy adjustment. i backed it out 1 1/4 turns off the seat and that is where mine runs the best. if you get that kit and needle read the instructions because you have to file a little bit of the hole out on your bowl for the threads on the needle to fit through. its no big deal. it took me about 10 min to make the modification and put it in. it was worth every penny. $110 for the kit and needle set.

hope this helps you. it has made a world of difference on mine.

Edited by slyfox83c

if your still having problems check the o ring in between your gate valve. this is tge main that moves up and down when you twist the throttle. it is a 2 piece unit and will go in either way. make sure the hole is on the bottom and it is on the engine side of your carb. if that o ring starts getting wore or flat it can start causing problem. If the rollers on the side of it are wore it will cause problems as well. the bad news is these are still OEM parts from yamaha. you have to order them separately.

ive been a mechanic for years, i race and build UMP Modifieds and ive never seen a carb as tempormental as these are. i cant count how many 4 barrels i have tweeked and rebuilt over the years. these things are somthing else.

Good luck and i hope this helps.

Chad

i went from a 175 pilot jet to a 170. im running a 200 main air jet a 100 pilot air jet. a 65 idol jet and i forget the other one.

The 170 is a Main Jet, not a pilot. The pilot jet is the "slow jet" in the manual, and controls the IDLE circuit (idol is something you worship). The #65 jet is much more likely to be the Starter jet, used by the cold start circuit. They do make series 22 pilot jets as big as 65, but Yamaha never listed any bigger than a #52 for the 400, and I'd be really surprised if you had a 50 in it. #45 is the original size.

According to my Manual the way my carb is set up. I have a 45 pilot jet 65 starter jet 170 needle jet with the blue needle on the 3rd setting from the top (check your elevation when setting this one, i live just north of Cincinnati OH). Pilot air jet 100, main air jet is a 200.

These numbers are what are stamped on the jets.

Sorry for the error gray racer. I was at work and trying to post using my cell and going on memory. But these are the actual jets and sizes according to my carb and the break down in my manual.

Now im ready to ride.... :smirk:

According to my Manual the way my carb is set up. I have ...170 needle jet with
MAIN jet.

The "blue" needle is JD, not OEM.

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