Rebuild time?

[Honda.rider5871]

I've been getting small puffs of blue smoke every now and then on my 04 , until the last ride i took it out on its been getting worse. Still only smoking when i get on it , and I'm not loosing any power from what i can tell. I've never had a atv motor apart ( mine was took to a motor builder) , how hard is it to do for somebody that doesn't have much mechanical experience , besides things like changing oil and basic maintenance.

If i end up doing it i'm either going to just do rings and valve seals (and of course take it to get honed and clean up the head) , or do a 10:1 or 11:1 piston , Stage 1 or 2 hot cam , GT HD head studs (depending on comp. piston) , and want to keep the bore as close to stock as possible , as the bores not really where the powers made.

[426kidz]

buy my 426...barely broken in solid as can be.strong and fast!

[Honda.rider5871]

wasnt really looking for a complete motor unless you will let it go cheap.

[CJM]

Measuring the bore, piston and the ring clearance will dictate if you need a new bore.

Me, Id just go to an 11:1 407 and do a stage 1 cam.

Its not really hard to do the work, but if you have little to no idea Id enlist some help or have someone do it for you.

[Honda.rider5871]

I have a buddy thats done complete rebuild on many 2 stroke bikes that i'm going to get to help me , also i'm getting a clymer service manual . I called a couple mechanics and everybody's charging just as much as the dealers it seems like. One mechanic told me if he puts new rings and valve seals in it , that it will smoke for about a month afterwards and clear up, is this true?

I plan on taking it to a shop to get the cylinder walls and everything checked out , have them clean up the valves and install new seals , and clean up the cylinder however it needs to be done. Its a 04 , meaning it was probably bought in 03 so its 8 years old , probably time to refreshen the motor anyways.

Will there be any heat problems with 11:1 piston? also should i run stage 1 or 2 hot cam. Stage 2 seems to be like the best all around cam, as stage 1 is for stock motors with hardly any top end power.

[426kidz]

not lettin it go cheap lol its just as built as you can make it so figured you may be able to use it. im building a hybrid so that the only reason id sell

[CJM]

It depends on how much you bore it, Id do a 407 to start with and an 11:1 piston with a stage 1 cam if you plan on riding in the woods. Now if you go to alot of more open areas a stage 2 would be better-but it performs much better on a larger bore say a 416 or 426. Reason I suggest a 407 and not something larger is the performance is very good going from a stock setup and it also means should you have to bore it again you can bore it 2 more times before you either need to do a 440 sleeve or go back to stock.

As for an 11:1 and heat, I dont have any issues there. But I only run 93 octane or better and I jetted it right.

As for the mechanic that claims rings and valve seals and smoke-yea dont ever call him again, hes an idiot.

As for manuals, a factory service manual (you can download it on the net), the clymer is also good as well. Its not hard to do the topend at all really.

One more thing, you might want to consider heavy duty head studs. They are worth it as insurance if the heat builds up and the studs pull out. Also you want to get cometic brand MLS gaskets.

[jgar]

Does the mechanic give you a 30 day warranty...:D

[Honda.rider5871]

Im going to go ahead and tear it down in about a week with a buddies help (he doesn't get back from a hunting trip til next sunday). I've researched step by step forums on how to do a top end , it doesn't seem that difficult.

Im going to wait until i tear the motor down to see what the cylinder looks like before i decide wether to do the high comp piston, hot cams , etc. Is there a noticeable difference from stock 9:1 piston to 10:1 , and then what about 10:1 to 11:1 difference. Also i normally ride trails , but do open it up pretty often also, i don't want to get a stage 1 cam and loose all my top end power , but i don't want to get the stage 2 and loose a lot of bottom. Is there something in between these 2 ? i know sparks and everybody makes their own cams .

Also what SPAL fan does everybody use , seems like there common and very effective, I'm planning on getting one if there not too outrageously high in price.

As far as jetting , I'm running a 155 main , 3.5 turns out on a/f screw, with HMF slip on , UNI filter , lid on . Out in the coal mines of kentucky (somewhat high elevation) , Plug looks good maybe a little rich , but no bogs so nothing to worry about.

Should know in about a week what the plans are for the motor , if its not bad i may just do rings, hone, and clean up the head , until i can come up with the money to do HD studs and everything and build it right.

[CJM]

Its a WORLD of difference when you up to 11:1. Compression is power, you can have the same size piston and up from 9:1 to 12:1 and believe me its powerful (and of course HOT b/c the EX is aircooled). I like 11:1, my buddy just built his 407 11;1 and is quite happy with his stage 1 cam. As far as a stage 2 cam, larger displacement does help-but it works well with such a high compression ratio as well.

Imagine it like this: your 400ex is stock or mostly, a 450r is faster of course. The 11:1 setup usually falls between the 2 but more towards the power of a 450r. You wont beat them, but you will easily keep up with them.

Dont buy a sparks cam, its basically a stage 2 hot cam. Do a stage 2, you dont like it you can always resell and do a stage 1 or something, someone will buy the cam quickly.

Spal fans nice,t hey run about 35 bucks on ebay. You want a 4 inch puller fan 12v.

Your jetting depends on the mods, but figure somewhere between 165-175, yes tyhats a broad range, but elevation, exhaust, open airbox, fuel used all dictate jetting.

[Honda.rider5871]

Thanks for all the help CJM . I'll keep you all updated once i tear the bike down , I plan on installing Gt thunder head studs also , as they only run $60. Does any body have the link for the SPAL fan and the top end gasket kit i should be using (rubbery ones) ? I plan on going ahead and starting to order parts needed. I found apex racing on ebay that sells the cams for $70 cheaper , and have good prices on top end kits also , is that a reliable seller? Also i should be using a Wiesco piston if im doing a 11:1 right?

[Stickman400]

For the SPAL fan: http://cgi.ebay.com/ebaymotors/SPAL-4-Paddle-Blade-PULL-12V-Fan-Motorcycle-ATV-/200651769125?pt=Motorcycles_Parts_Accessories&hash=item2eb7c70525
Gasket Kit(Atleast the one I was told to buy): http://cgi.ebay.com/ebaymotors/cometic-top-end-gasket-kit-honda-trx400ex-400ex-c7825-/190518644764?pt=Motorcycles_Parts_Accessories&hash=item2c5bcbd01c
Apex*Racing is a good dealer I am told by CJM, and he knows all. I bought a Stage 2 Hotcam from them for my rebuild. I also bought a Wiseco 11:1 86mm Piston Kit for my rebuild aswell, so I'd say you're safe.

[CJM]

No problem at all.

I like wiseco pistons, they are built well and dont cost a fortune. JE is better, but if you arent a top notch racer why bother as they wont perform that much better anyways,