Decompressor

[dustin_j]

I was wondering if someone could explain the decompressor to me. I just got a used 400 and was wondering what the decompressor does and how often it should be on (you can definately hear when it is on). Thanks

[REDRIDDER]

The decompressor is mechanical device located on the end of your cam witch will allow the engine at start up to slightly open the right exhaust valve to lower copression therefore easier starting can occur and once the engine is started the decompressor disengauges.Basicaly just lowers the copression and makes it easier on the starter and battery.

[dustin_j]

So the decompressor should only be on when starting the quad? Will it kick on while you are riding it and make noise? Thanks

[REDRIDDER]

The decompressor should only work when staring the engine.If its stuck you will notice a little power loss are you sure your not hearing the valves rattle have you checked them in a while?do you have any aftermarket parts?

[dustin_j]

I just got it and the engine is stock, but I don't know when the valves were checked last. I will try to check the valves soon; I also need to get a service manual. The "ticking" noise I'm hearing gets louder as I rev the engine. It has a T4 silencer and a UNI air filter, but stock jets. I don't know if this has anything to do with it. I plan to rejet it (if I can figure out what jets it needs) and check valve clearance. Anything else I should look at? Will I ruin anything running it as it is, because the previous owner thought it was the decompressor making noise so he has run it as is for awhile. Thanks

[REDRIDDER]

IM willing to bet its just your valves need adjusting and if you get a manual buy a clymer.

[hondaman440ex]

Yeah it is probley the valves, I have a K&N air filter and a t-4 when the motor was stock and I ran a 155 MJ and the needle at the second clip from the top @ 1000 ft. Hope that helps with the jetting.

[dustin_j]

I will have to try that jet setting, are the MJ and needle all I should need to adjust?. Could you tell me what the valve clearances are since I don't have the manual yet? Thanks

[JBDIV]

Here ya go: Excellent directions and has great pictures to get you through...

Good Luck!

http://www.atvriders.com/articles/valveadjustment400ex.html

[JBDIV]

It truncated the link on that reply... the last part should be

/valveadjustment400ex.html

[dustin_j]

Thanks for the help guys