thinking rebuild this winter.

[GAZ-V-21]

Lately my 400 puffs a little blue smoke on decel it dont do it at all while on the gas and when i checked the oil after about 15 hrs of riding its still pretty close to full my first question is am i safe still riding until this winter when i might rebuild? My next question is when i do rebuild what all should i get im wanting to stay around 1000 dollars tops. I was thinking weisco piston but dont know which one to get and will new piston fit right in or do i need to have it bore? What kind of shop do i go to if i need it bored? Next thing i want is hotcam should i get stage 1 or 2? Also was gonna get cam chain or timing chain whatever it is. What else would you guys recomend i would like to get a little power gain if possible. Honestly i wish i could make it another summer before a rebuild so really would like opinions on if a rebuild this year is necassary.

[TheAwesomehonda]

Do a compression test. That should tell you the condition of the top end.

[GAZ-V-21]

How do i do that test and what should the results be if my 400 is still good for a while?

[CJM]

Need a compression tester, remove the plug and hook up the tester. Then turn the fuel off and hold the throttle open and crank for about 4-6 seconds.

It will read how much air pressure the cylinder builds. leave it connected and watch for anything to leak out for a few mins.

Then repeat the test another 2-3 times. Pressure should be at approx 100-120 psi. If its anything less than that you need a rebuild.

[GAZ-V-21]

Cool i work at a car dealership will the testers they use on cars work on my 400?

[Stickman400]

There are a lot of different types of ends for different engines. You're just gunna have to try each one until it fits. Or maybe someone else on here knows what size and thread pitch it is.

[hondaREX]

Plug thread is 12mm-1.25. Most automotive kits dont have that adapter, it is a small engine or motorcycle kit. But some bigger kits will include it, like a Snap On or Craftsman kit. Or you can use a cone-type tester but that isnt as reliable and takes 2 people to use.

[Pittsburgh400ex]

You can rebuild it and easily be well under 1k. I woukd get wiseco piston for sure, always had good luck with them, i detroyed a JE 416 in 5 hours. Some swear by je though. Stage 1 cam is gonna hit hard on bottom. 2 will be mostly mid but will affect the entire range. If your cylinder isnt scored no need to bore it, your rings are probably just starting to go. I did cam chain, 416 kit, sparks full exhaust snd stage 2 cam for about 900 altogether and that included boring it.

[GAZ-V-21]

So lets say i wanna go to a 406 what all do i need to do do i just need a puston sleeve and piston or do i need to have the cylinder bored

[chronicsmoke]

You just bore the cylinder, I'd bring it to a 416 if you're boring it out already but that's just me.

Buy the piston and bring it to a machinest and have him bore the cylinder to match the piston size.

[GAZ-V-21]

Which wiseco piston do i need

[chronicsmoke]

Originally posted by GAZ-V-21
Which wiseco piston do i need

87mm

[GAZ-V-21]

Im wanting it to last a few years also should i go with stage 1 or 2 hotcam i ride trails dont need much top end

[chronicsmoke]

I'd use a st.2 cam with an 11:1 piston, I didn't find I lost any bottom but it pulls harder on top for sure.

[Pittsburgh400ex]

Or you can stay stock bore and up the comp. Thats the first upgrade i did and its noticeable and reliable, went to 416 only cause i was bored with it. Had stock piston high comp since it was literally 2 months old in 1999.

[GAZ-V-21]

I think i might go 416 im gonna order parts little at a time for winter rebuild get piston first stage 2 hotcam next new cam chain what else will i need? just wanna put a list together of everything im needing so i can price and start ordering. Do i need bigger oil tank? If theres a way id like to do something to make engine run cooler.

[chronicsmoke]

You don't need a bigger oil tank or SPAL fan, just be carful and take your time while jetting. If you are jetted correctly you wont have any overheating issues.

order your piston, cam, cam chain, and gaskets. Your valves should be fine, mine were still fine after they were lapped in 2011 after 6 years with a 426 and many hours of abuse.

[Pittsburgh400ex]

Yea i wouldnt worry about heat unless you go over 12:1 and a 440 or bigger. Even then you'd probably be fine with stock setup. Wont need hardened rockers or new valve springs, replace the cam chain and guide, its a problem area. I only run 93 pump in mine if i have to. It will knock a little on top end winding out on 87. Normally i mix turbo blue and 93...probably dont need to just a habit i got into a long time ago.

[HondaRacing83]

if my cylinders fine i noticed im startin to smoke a little to ill probably do a stock bore 11:1 wiseco with a hotcam.

[GAZ-V-21]

Will going to 416 with wiseco piston and a stage 2 hotcam make a very noticable difference in power?

[CJM]

Compressions power, not bore size. Dont do a 416, should it blow or wear out then you gotta do a 426-should that wear out your back to stock or a 440 kit.

Do a 407, 11:1 compression and stage 2 hotcam. I have a 426, friend has a 407 with same mods as me and honestly I aint that much faster.

[GAZ-V-21]

Will the 407 be noticeably different than stock?

[CJM]

Originally posted by CJM
Compressions power, not bore size.

[HondaRacing83]

So are you saying a stock bore with 11:1 comp and hotcam be similar to my buddies 440 with hotcam same compression?

[CJM]

Originally posted by HondaRacing83
So are you saying a stock bore with 11:1 comp and hotcam be similar to my buddies 440 with hotcam same compression?

Not necessarily.

Get your reading glasses out, its a long, long post about why higher compression is better than a bigger bore and how you could actually run higher than 11:1 on an EX
http://www.exriders.com/vbb/showthread.php?s=&threadid=487458&highlight=high+compression

Higher compression yields more power-less space for the fuel to ignite due to the domed design of the piston thus better burn.


FWIW I cant beat a 450 in an out and out drag. But stock for stock they aint that much faster than me. What they have is more power of course and get to speed quicker than I can-but still my setup aint no slouch.

[b0rn c0nfused]

Originally posted by GAZ-V-21
Will going to 416 with wiseco piston and a stage 2 hotcam make a very noticable difference in power?
Yes I just did this setup and I love the power! Not to start anything but if it wears out your don't really need to go to a 426. You can buy a new sleeve correct?

[CJM]

Originally posted by b0rn c0nfused
Yes I just did this setup and I love the power! Not to start anything but if it wears out your don't really need to go to a 426. You can buy a new sleeve correct?

Yea but then you gotta bore it to the size you got already or go back to stock.

Sleeves easy to put in, heat the jug up and it flops out.

[chronicsmoke]

Originally posted by CJM

Sleeves easy to put in, heat the jug up and it flops out.

Agreed which is why he might as well go to a 416.. How long will it be until he has to rebuild again? 3-4 years probably, then he can get 3-4 years out of a 426.. If there isn't a big difference, might as well go with a bigger one.. Just an opinion there aren't any wrong answers ;)

[HondaRacing83]

Ill have 8 years or more out of my stock bore when i rebuild it :o

[chronicsmoke]

Originally posted by HondaRacing83
Ill have 8 years or more out of my stock bore when i rebuild it :o

Exactly.. So 16 more years on that cyl. with that math.. That's if he goes straight too a 416 :p

I was being conservative sayin 3-4 years lol. I'm going on 6 with the 426

[HondaRacing83]

i was thinking of going 402,407,416,426 to be really conservative but then realized i wont have my 400ex that long... lol so if my cylinders fine ill do stock bore if its scored ill go straight to 407 or 416.

[GAZ-V-21]

If i can get 2 or 3 years out of 416 i will be happy

[HondaRacing83]

youll have that EASY if its built properly. i might do a p&p to

[GAZ-V-21]

I know its probably different everywhere but what should i expect to pay for port and polish?

[quadmanw]

P&P is very expensive because it is very hard work I hear. But I think you should pay around $300 or something

[GAZ-V-21]

If it makes it run even better i might get it done

[GAZ-V-21]

Need more power
https://www.youtube.com/watch?v=hfPHPpHszDk&feature=youtube_gdata_player

[quadmanw]

Put an 11:1 piston and P&P the motor with a 416 and you won't be able to keep it on the ground lol

[GAZ-V-21]

Now thats what i wanna hear

[quadmanw]

I just did it to mine over the winter and I am very pleased. I love everything about the bike. It rips a lot more than i thought it would. I'm a huge believer in the P&P after I was talked into doing it. I haven't even cammed my bike yet

[GAZ-V-21]

Originally posted by quadmanw
I just did it to mine over the winter and I am very pleased. I love everything about the bike. It rips a lot more than i thought it would. I'm a huge believer in the P&P after I was talked into doing it. I haven't even cammed my bike yet SWEEEET I cant wait now

[quadmanw]

Let me know how it goes man

[GAZ-V-21]

i think while i have it apart this winter ill have the frame powder coated or painted and get new plastics when getting new plastics can i just get front and rear fenders or do i need to get everything? I want black where can i get them at reasonable price?

[chronicsmoke]

what's your suspension setup? I know it's nice to have a nice looking quad, but suspension is where it's at.

I'd spend my money there first :)
(tearing it down is still a good idea, replace every bearing and bushing, shocks over fenders imo)

[GAZ-V-21]

True should i go with 450 r shocks?

[chronicsmoke]

I'm trying not to give you a biased opinion, but.. I have had 450r shocks on a Z400 and a 400ex and they perform alright once you play with the settings.. I also have YFZ shocks on my Raptor and they helped quite a bit but seem to bottom easier (could be due to the extra weight of the raptor, I'm not sure)

From my experience they are both pretty good cheap upgrades.. Personally, I'd rather the 450r fronts, but I am slightly biased as I've had rebuilds built and I know how they perform.. I'm sure the YFZ shocks can made to be as good though.

The real guy to ask is Nick @ Jet Susp. He has answered quite a few of my questions over the years and is always more than happy to help.

[HondaRacing83]

stock for stock on stock a arms yfz or kfx shocks will give you the smoothest ride. back the preload off 450r shocks and itll give you a pretty smooth ride but most effective on extended a arms.