Smoke'n Bad.. Rings,valve Stem Seals Or Both?

[RR_MIKE]

first off i should introduce my self a bit.. i just registered last night.. my names mike, im 42(dont let the age fool ya).im from findlay,ohio.. i raced mx for 11 years(cr250's), i got into sportbikes 5 years ago. i currently own an 06 cbr600rr i do trackdays with....im also a drummer in band(HEXED)..
now onto my question.. i just picked up a 2000 400ex, supposedly with a 440 stage2 hotcam kit,and full duncan exhaust(which sounds sweet by the way)..,its kinda thrashed on but still somewhat decent shape to play around on.. but the problem is, when i first start it(it starts fine and runs real strong),but man does it look like a bug fogger lol..i mean real bad.. the compression seems to be good,but it still smokes a lil bit constantly when ya accelerate and let off the gas and get back on it(not near as bad) after it warms up, but at any startup,warm or cold, wow its a puffer lol... should i just do a complete topend,or just try to put valve stem seals in and see if thats the prob? and how hard is it to do.. im an old 2stoke guy lol.. i looked on line at an exploded view of the topend and it looks pretty complicated..i was told the guy prolly didnt jet right and it cooked the ex. valve seals? ive only got 400 bux in it, so i can dump a few bills in it if need be..and another question, how do i make sure that it does have a 440 kit.. i'd hate to buy all the stuff and have it be the wrong piston for the bore..HEEEEEEEELP lol...any input would be greatly appreciated... thanx......

[F-16Guy]

It sounds like a combination of valve seals and rings, since it smokes worse on start-up, but continues to smoke while running. It could be valve seals alone, but they would have to be leaking really badly. I'd say tear the top end down, mic the piston and bore and see what the tolerance is. If within limits, hone, re-ring, and get the head done. If it needs an overbore, you have a couple options depending on what's in there right now. I think the biggest piston I've seen advertised is an 89.5mm. At the very least, I would re-ring it, lap the valves, and throw in a set of valve seals. It would also be a good time to do a cam. If the cam has the stock decompression mechanism, it's either the stock cam, an XR400 cam (popular mod back in the day), or an HRC cam (pretty rare). If it's either of the first two, you'll see a noticeable power gain going to something like a stage 1 or 2 HotCams cam. Another thing to look at while it's apart are the head studs that are threaded into the cylinder. If they're stock, it's a good idea to send the cylinder to GT Thunder and have their heavy-duty stud kit installed. You could also have them do the bore or hone (whatever is required) while it's there so when you get it back, it's ready to install.

Edit -- I just realized you said it has a HotCams cam in it. It's still a good idea to verify since you don't know for sure. Also, if it's an older style HotCams cam that has the stock cam gear flange pressed on the cam splines, make sure that there is no looseness in the flange. If it's loose, you need to cal HotCams and see if they'll work with you on a replacement cam. If you run it loose, it will walk on the splines and possibly damage the head or break the cam chain.

[RR_MIKE]

cool cool.. much appreciated..thanx man..i dont have it torn down yet,but i know on car engines, they build up a ridge at the top of the cylinder, do these do that too? if ya just put a new piston/rings in and not remove the ridge,it'll break a ring more than likely wont it?..not sure if the cyl. is nikosil either? i guess not if you suggest a honing..just try'n to find the easiest/cheapest way to go for a fix lol..if all else fails, i'll just buy a whole new frick'n kit(sleeve,piston,etc..) lol.. arrrrgh, i have a feel'n its never gonna run again hahahahahaha...

[F-16Guy]

Yeah, they'll get a ridge depending on how many hours are on it. If you keep the same piston (assuming it's within limits and in good shape) and just re-ring it, it will probably be okay, but if you install a new piston (especially a different brand), I would have it bored and start fresh. No Nikasil on the stock 400ex cylinder, just a cast iron sleeve. This engine is about as simple as it gets. If it's just a basher, you could probably do an 89.5mm 11:1 or 12.5:1 piston ($140 with gaskets), have it bored and honed for the new piston ($80), and lap the valves and do Viton valve seals ($40?). That would be cheap and should freshen it up pretty well.

[Sanddraging28]

i see your in OH. only a couple of hours above me.unless the cylinder in looks really bad, i would just put rings on it and hone the bore. when it comes to cams, it is unlikely that it has a stock cam, or a xr-400 cam. if it does have the stock decompressor on it it may also be a white brothers cam. They were popular in the early 2000's. It will have a WB and a number hand etched in it on the end of the cam if it is a stage 2 hot cam, check the number laser etched in the lobe to find a part number. hotcams redid the stage 2 cam a couple of years ago. if you do find that it needs a new piston and sleeve i would suggest getting a sleeve that starts at 426. it will give you a chance to go to 440 if you ever need to. plus a 426 will make better power than a 440. watch out for pistons above 11 to 1 compression, anything higher and you are getting in to race fuel territory. no doubt that the valve seals might need replacing, but i think most of your smoke is cylinder related. while you are doing this much work i would suggest a new cam chain also. Get one for a CFR450r dirt bike. it is the same length as a 400ex only stouter. and its cheaper that a 400ex OEM chain. let me know if you need any more help

[F-16Guy]

I just looked around a little, and it seems that 89.5mm pistons are getting harder (and more expensive) to get. If you don't have the option of a re-ring, I would either do what Sanddraging28 suggested or find a cheap used stock bore cylinder and bore it to the next oversize. Good luck with the build!

[RR_MIKE]

thanx fellerzzz...much appreciated....i'll prolly just buy a whole new 426 11:1 kit(sleeve,piston/rings,valve stem seals and valve guides prolly wouldnt hurt either)and cam chain like ya said..it sounds like the best and esiest way.. and be done with it..and i should prolly buy a manual too huh? hahahahahaha...thanx again guys..

[RR_MIKE]

well, this is prolly the first and last picture of it alive(i told ya it was thrashed) lol.. time to get greasy and start tear'n it down... thanx again guys for the input and steering me in the right direction....hopefully all turns out well. i'll keep ya updated.. and if i have a few questions, i hope ya dont mind me ask'n..thanx again...
http://pic50.picturetrail.com/VOL489/8466074/15749227/360272613.jpg

[killer400ex]

if it is smoking on start up really bad than it is probly just your rings, if it was a constant like dark blue smoke even after startup then it is most likely your valves, but they very rarely tend to go. i am thinking that since it is a bored motor that you just need to replace your rings.

[RR_MIKE]

Originally posted by killer400ex
if it is smoking on start up really bad than it is probly just your rings, if it was a constant like dark blue smoke even after startup then it is most likely your valves, but they very rarely tend to go. i am thinking that since it is a bored motor that you just need to replace your rings. yea, it smokes like real real real bad at startup,like a massive cloud, and constantly even after start up but not as bad, but still pretty bad.. i borrowed a bore mic. and im hope'n its within specs. if not im just gonna get a whole new 426 kit(sleeve,piston,etc..).i also just found out tonight that it has bigger valves in it(so the guy says)...i only have a lil over 400 bux in this thing lol,so i can throw a few bills at it..im also gonna basically tear it completely down and grease and or replace all the bearings and bushings(steering,susp.wheel bearings,etc.)..i'll prolly throw a new chain and sprockets on it too..im hooked up with a dealership(honda east) through the sportbike club im in(toledo sportbike riders),and get my parts,lubes,and riding gear at 20% over cost, so that will helpout bigtime..woot for sponsors lol...

[zwark]

replace your valve seals, oil leaks onto the top of the piston while it's sitting and when you start it, it burns it off causing that blue smoke you see. if it's consistent, whether only in neutral when you're revving the engine or the entire time of you riding it is your piston rings.

[RR_MIKE]

other than the idiot before me "red" lock tighting and over tightning the bolts on the cover on the top (which resulted in 3 getting broke off grrrr)..and the front jug bolt was loose.. but heres the real clincher, the arrow on the piston faces forward right? well it wasnt lol.. and you can see where the valves just barely nicked and hammered the edges of the butterfly cuts on top of the piston..it had to be in backwards or he had the wrong piston lol.. but the good news is the cylinder is ok.barely any wear or scuffs/scratches and no ridge...just looks like it needs a finish honing..im more worried about the valves being bent..i dont have a spring compressor to take'm out though.. well, thats the latest lol...

[yellowhonda400]

i have a 2002 400ex and mine also smokes of start up until it warms then its fine i thought it could be the rings too but i wasnt positive. but i want to take the engine apart this winter and change everthing hoping this fixes the problem

[RR_MIKE]

well, ive give'n up on the basket case lol..gonna cost too much to get everything back dependable.. seems like for every bolt i take out, it just opens another can of worms lol.. so,im gonna part it out.. i also just went today and put cash down on a brand new, left over 07 400ex wooohoo.. got it for $4100 tax/title out the door..so hopefully the bank ok's me(they should) and i'll pick it up in the morning...i'll post up all the parts im get'n rid of later.. or if anybody needs anything other than the nerfbars,rims/tires,and exhaust..im keep'n that stuff...

[Sanddraging28]

i'll take the whole thing!!!!!! shoot me a pm with a price

[RR_MIKE]

will do man...

[RR_MIKE]

pm sent...