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2002 Honda 400EX Problem


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I just recently bought a 400ex 440 bore, wisco pistons, and a hotcam in it. Quad runs great, however, it's hard to get started. It has the stock starter on it, brand new battery, and we have eliminated that the starter cylinoid is bad. It will however crank over with a battery charger that is on 12v Start Engine selection. Why is it doing this? It roll starts no problem. Do you need a hotter starter with the 440 bore? Need help asap. Thanks.

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Since it's modified, it may take more cranking power to get it started. That is my guess since you said you put a new battery in it and it's difficult to turn over.

It does however turn over when hooked up to a 12V source.

Even though it is a new battery, it could be defective and not taking a full charge. You may want to have it tested at the place where you bought it.

I believe that atv takes a battery #YTX9-BS which is a Yuasa number if I'm not mistaken.

If it tests good, you could try finding the same group size battery but with more CCA. (Cold Cranking Amps)

Have a look at these Honda batteries, notice the CCA: Honda ATV batteries

You may also want to doublecheck your charging system..as a second possibility..

"The Honda TRX400EX uses a full wave permanent magnet type of charging system. To test the charging system the battery must be fully charged. To accurately check the charging system and its components you will need a digital multimeter. A set of alligator clips for the meter leads will make some jobs much easier.

To test the charging system as a whole, leave the multimeter set to VDC, touch the red meter lead to the positive post of the battery and the black meter lead to the negative post. Start the engine with the meter leads still connected to the battery posts. Rev the engine up to approximately 4,000 rpm and compare your reading with specification.

(Specification for battery charging voltage with the engine at 4,000 rpm is 13 to 15.5 VDC)

If battery charging voltage does not reach 13 VDC, the charging system is not working and the components must be checked.

If the battery charging voltage goes over 15.5 VDC, the regulator is defective and the regulator/rectifier must be replaced."

Edited by ATVmechanic
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  • 11 months later...
I just recently bought a 400ex 440 bore, wisco pistons, and a hotcam in it. Quad runs great, however, it's hard to get started. It has the stock starter on it, brand new battery, and we have eliminated that the starter cylinoid is bad. It will however crank over with a battery charger that is on 12v Start Engine selection. Why is it doing this? It roll starts no problem. Do you need a hotter starter with the 440 bore? Need help asap. Thanks.

because you increased the compression on it but when you put in the hotcam you had to take out the compression release out so the hot cam could work properly to gain p0erformance that is something youll have to deal with mine does it also more in colder weather in warmer weather youn wont notice it.

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  • 4 weeks later...

Opie, did you notice that this thread is a year old? This poster has not logged on since last February. I am curious however about the fact that you have to remove the compression release with the Hotcam on the 400EX. My friend put a stage 1 Hotcam in his 450R, and it worked with the compression release. I wonder why they would not make the EX cams compatable with the compression release?

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