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looking for opionons on my build

1415 Views 7 Replies 6 Participants Last post by  Helmut
i got a 400 ex that im in the process of building. i have decided to go with the 426 bore kit. i do alot of hill climbing and looking for the perfect setup. which cam stage would do me best 1 2 or 3? and what would i expect from each? of course im going to get a full pipe and a fan for the oil cooler. which would be better on the carb. jet the stock or go with a 450r?. im confussed on the compression choices i have seen and dont seem to know which is best. i would like to run pump gas like 03 octane but with my build dont know if thats possible. would a bigger cdi box be needed or help?would like the bike to run cooler as when we do ride its hard and long in the mountains and some mud. im also replaceing the timeing chain with the better one cant name it off the top of my head but i know what it is. is there anything else that would improve my proformance that im missing like port and polishing my head? valves? again im open to all suggestions and would like to compare them with other threads i read. i want a good reliable bike withe the power in all ranges with it of course being reliable in the trails. also im been searching for a free downloadable manual for my bike but have had no luck. any suggestions would be greatly appreachated thanks
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also im been searching for a free downloadable manual for my bike but have had no luck.
You can find the repair manual for the 400EX at
Click on the link I posted earlier and scroll down to the bottom. There is a usefull cdi trick/info.
That is some good info. I went ahead and copied it and posted here.


Many aftermarket CDI boxes sold for the 400EX are actually stock Honda XR250R boxes. The unmodified XR250 box will give you about 800 more rpm on top and a faster ignition curve. You can purchase this directly from your local Honda dealer and save money.

Order: CDI for Honda XR 250 1992-2004 Part #30410-KCE-671
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