Only will start with booster pack!

[Chris S.]

My EX for the last 2 years will onlly start when cold with a booster pack. When hot it fires right up. I have had a stock motor, a built 440 and now a 500 stroker and all three have started hard. Yesterday when riding it started missing at low rpm and then finally died a little later. Seemed like the spark plug was fouling out. Today I pulled the plug to install new one and it looked perfectly fine. I then did a spark test with new and used plug and same results. I then did a spark plug test with amy lawn mower and the spark was much bigger and bright blue with out the orange. All my ignition coil and wiring harness connections are clean and tight. Is it possiable that I have had a weak coil all this time? I never thought anything of it because I always was getting spark. I have tried new batteries over the year and always kept a trickle charger on them and have also bought a new starter last year. Is there anything else in the ignition system that I should have tested?

[bradrenea]

Do you have an aftermarket CDI? If you do, its pretty common for them not to start without a battery charger when its cold, depending on the brand of CDI. I have a WB CDI on my 400 and it does the same thing.

Don't know what to tell you about the weak spark issue though.

[Chris S.]

My CDI box, ignition control module, says Shindengen on it. Is that the stock cdi or is that after market? I bought this quad in 2002 and I believe it had 2 other owners. The box looks like the one in my clymer manual but that doesn't mean nothing.

[GPracer2500]

My stock box and my WB box BOTH say that on them.

[zeppelin]

Originally posted by GPracer2500
My stock box and my WB box BOTH say that on them.
thats because white brothers uses the cdi off of a xr250 for their aftermarket cdi's shindengen is the company that makes that stuff for honda

[GPracer2500]

Originally posted by zeppelin
thats because white brothers uses the cdi off of a xr250 for their aftermarket cdi's shindengen is the company that makes that stuff for honda

That's what I've heard.

[bradrenea]

It's been a while since I have looked at mine but it seems like it had WB stamped on it somewhere, with a stamp that was obvious it was not factory.
I would guess that you have an aftermarket CDI, or a previous owner just bought a stock XR250 CDI and put it on there. If the later was the case, it would not have any odd markings like my WB box. You should be able to check the part number on your box with the part numbers for a 400ex and an xr250 on Service Honda's website.
Like I said earlier, mine does the EXACT same thing, and I have saw several posts on here saying that the CDI is the cause. The reason is that the XR is a kickstart so the motor will be turning over faster than the 400's electric start with a cold motor.