View Full Version : 400EX COLD STARTING ISSUES

01-04-2002, 01:58 PM
I have the jet kit in my ex and it is still won't hardly start. My buddy has a bone stock brand new ex and it won't start. Exact same problem( gas fouls the plug). Once we burn it off and clean it up it starts right up. If the stock jet gas fouls the plug how can putting a larger jet in help? Plus the choke set-up on an ex's carb is at full chocke it gives 50% gas and 50% air. It should not matter what size jet you use. I have tried to start mine every way imagineable(by the book, no choke, etc..) I spoke with a local atv acc. shop owner today and he said that the valve adjustment is where the problem stems from. He said to change it to the high(loose) end of the range of honda's guidelines. Does anyone know what this is? He also said that this problem was not in all 400ex's. I disagreed. Everyone I know or read about on here has this problem. He also said that a properly adjusted motor should fire up in the cold no matter what size jet is in it. I figure I would try the vavles b/c nothing else has worked. Any comments or suggestions would be great. CJ

01-04-2002, 02:06 PM
all i know is that i have a K&N, the dynojet needle down one notch, a 155 main jet, and a supertrapp IDS2 silencer with 9 or 12 disks and it starts immediatly in below freezing temp. I put the choke on just to start it, then back it right down to half choke, then 5 seconds later no choke. It runs awsome. This is with out the 440 piston or the lectron carb. I have yet to have the time to put them in.:(

01-04-2002, 03:32 PM
get a 42 pilot jet it will fire right up.. Here in canada it is like -10 c( below 20 f) and it will fire right up 2nd time on the starter botton but thats in a insolated shed i got to test it out in the snow!!!@!

Winged Warrior
01-04-2002, 08:29 PM
the larger pilot jet made a big dif for me too.no more fouling!!!!but keep a new plug just in case.

01-04-2002, 08:37 PM
I went to a DPR7EA-9 plug which honda does use in some of their utility quads, and I have had no more troubles, still cold blooded thing to get warmed up but does start and no more foul outs.

01-05-2002, 03:55 AM
Try what Bro and Warrior posted. It helped with mine.

01-05-2002, 10:48 AM
Then the mofo will start right up!

01-06-2002, 01:31 PM
I turned out my pilot screw out 1/2-1 turn out from stock, and it helped it idle better once I got it fired up. still started hard. recently, I raised the needle in the carb, and it is much better. Before when I started it, I had to give it gas with the choke, or else it would sputter. Now, with the raised needle(one notch from stock) I only need choke to get it fired up. It helped out a lot more than I thought It would. I also have a 155mj, supertrappIDS2 pipe, and 6 1" holes in the airbox lid. runs clean, crisp, and strong. starts well, and no bogs, sputters, or backfires. good setup for 200ft-700ft elevation( most of the trails I ride on are in this range)I may try a 160mj now to see if there is a difference. I just need the foot of snow to melt and harden, because I can't get 5 feet unless it is a snowmobile track. Most guys want lots of snow. Let me tell you, any more than 6 inches and the quad works the whole time, and is not much fun. However, with a couple inches of power snow, it is a blast! Went off topic a bit, but try either a 42 pilot, or screwing out the pilot scerw out 1/2 turn, and raise the needle. worked good with mine.