400 ex starting problems

[markvette]

we just picked up a 400ex from a friend of ours on a trial basis. we plan on racing it a couple of times and then decide if we want to purchsae it or not. it has a curtis sparks built 440 cc motor with all the good parts. this quad will not start when it is cold. i dont mean the temp is cold outside. if it has sit for over 30 minutes it will not start. we have to pull start it. after it is warmed up it will start up no problem. i have heard that the white brothers high rev cdi will cause this problem and this quad has one. the coil was replaced back last august and one off from a blaster was put on it but i dont think that is the problem. like i said this is a curtis sparks 440 cc motor with 12.5 to 1 compression. what plug should i run and what octane gas. the friend we got it from said he ran only 108 octane. can we run lower octane or add octane booster to premium pump gas and if so what type and brand of booster can we use. thanks. right now the starting problem is the first thing we need to get fixed so all help would be appreciated.

Mark

[nojoke4stroke]

well im not sure what it is but i know what its not.the rev box only has trouble when the air temp is cold,and even then it has to be below freezing for it to even be a problem.anything above 12:1 compression must run race gas,octane boost in pump gas will not work,93 octane with octane boost will give you around 96 octane.i know this because i had some tech questions about my quad and talked to allen knowles of ct racing and this topic was covered in our conversation.good luck

[lil400exman]

get a oem coil and a oem black box and u wont have trouble at all man i could start my ex with a good battery in -5 condiotions........................:)

[lil400exman]

and do a jetting for cold weather and that will help and i am at 1,600 posts! i can die happy!:D

Get rid of the POS WB CDI box...that's your problem for sure...outside temp doesn't mean squat... your battery must be at a full charge at all times to work correctly with the WB CDI box..

[Leo]

ditto to what Rico said..

especially with a hi-comp piston and such if the battery isn't 110% it won't crank the motor over fast enough for the CDI to fire the coil..

oh, you might want to ditch that coil and go for the real deal.. 400EX parts are cheap.

Leo

i dont think the cdi is the problem. my batery was about half dead after sitting for a houta month, and cranked over my quad fine, but yea get the 400ex coil, i wouldnt go cheap on a high performance quad, and if you can ditch that piston, reliability is out the drain with that, get a JE 11:1

[nojoke4stroke]

Well air temp. does mean squat when its cold enough to thicken your oil making it harder to turn over the engine which combined with the cold draining your battery 10 times faster is when the CDI will effect your starting.But you being in long beach eliminates cold weather.But it being pull start might point to the CDI which i doubt,if you know some1 with a stock CDI switch to it so you can eliminate that as a possibility.Second check your jetting.You'll probly end up going with 3 and thats replacing the blaster coil with an OEM.Check the first 2 cuz theyre free and simple then spend the money on a new coil.