new rebuild 416 smokes on startup

[vinson581]

I just finished building my 416ex, 11:1 stage 2 hotcam, all the heavy duty valve parts, new valve seals ect. upon startup the first time it smoked alot (normal because the rings having to break the glaze) i heat cycled it 3 times, each time riding it slightly more aggressive. today i started it after sitting for 2 weeks and it smoked upon startup but not as much as the first time...(wierd), now i have heard of guys 416 big bores smoking up to 3 full tanks of gas being run through them, so im not really that worried. this is prolly my 32983459082 engine ive rebuilt, so ik its not my error in assembly. i just either got unlucky and got a bad valve seal, which is no big deal in the end, or the rings really take awhile to seat with this perticular piston. other wise the bike runs fantastic. any thoughts on this?

[CJM]

Heat cycling is worthless and does nothing FYI. Im not sure whoever came up with that idea, but it just doesnt work.

Heres what I do: Warm up engine about 15-20 mins at idle. Take off slowly at first and then load it in 2nd, 3rd and 4th. Alternating between periods of hard acceleration and deceleration.

It could just take a bit to seal, could be rich (gas). If it is truly burning oil then something isnt right. Either the pistons not sealing due to install, the rings didnt seal properly for whatever reason or the valve seals are leaking.

See here for more info: http://www.mototuneusa.com/break_in_secrets.htm

[punk rock kiel]

decell creates vacuum and the rings will seat alot quicker if you downshift alot and let it engine brake itself and then the rings seat quicker.

ive worked in a machine shop and was told from day one, start the car and drive it like your gonna drive it....if its wrong, it will break in the first heat cycle or it will be all good. crotch rockets run better cause people beat the **** outta um from day one...

[vinson581]

i shouldnt have said heat cycleing per say, however i drove it slightly more agressivly everytime i took it out, and my version of an easy break in is prolly what most people would say thats beating it, but i drive it like how i intend to..and thats hard.

[CJM]

Originally posted by vinson581
i shouldnt have said heat cycleing per say, however i drove it slightly more agressivly everytime i took it out, and my version of an easy break in is prolly what most people would say thats beating it, but i drive it like how i intend to..and thats hard.

Might just be residual oil burning off, when i assemble an engine I make sure I use some 2 stroke to lube the cylinder b/c it burns quicker and coats better for that initial start up.

I just rebuilt my buddys and it smoked a bit, after a little break in it went away.

[Honda#4]

I did heat cycling on mine and its ran top notch since then. When it comes to breaking a motor in I really don't think theres a right or wrong way it's just up to you how you wanna do it.

[killer454]

when i built my motor i took it easy on it the first 3 long rides.

you can seat your rings just by putting your atv in neutral and reving from idle to half throttle setting still.

the way your rings seat is:when you rev your engine from and idle state the piston speedsup and cyntrifical force causes the rings to expand out to the cylinder harder.

i have always seated my rings this way and have never had any problems.even when a do a full rebuild on a car/truck engine,the best way to seat the rings is drive in town in stop and go traffic this is the best for seating rings.going down the highway at 65 mph is not the best way to seat a new engine.

if you watch my video on youtube called 400ex first startup you will see me reving the engineup in neutral.that is the way i seated my rings.when you try to seat them in gear their is drag on the engine and piston speed falls down to a slower speed.i seat all my rings on bike and atvs in a neutral state i dont want a load on the new parts in gear right away,that is why i rev from idle to half throttle in neutral.

i did this for about 1.5 hours i would start the atv in neutral rev it up and down for 30-15 min shut it down let it cool,and do it again.

everybody has their own way and this is mine

[vinson581]

nevermind to the whole topic, i took it on a half hour hard ride started it this morning (cold) and it runs perfect i guess for w/e reason those rings took an extreamly long time to seat. i think it was because this piston and rings have litterly sat in a box for the past 7 years, and it might have gotten some surface rust perhaps that was unseen to the eye and untill the ring edge was "scraped" it might not have glazed the cylinder completely but none the less, i checked the bore now and it looks perfect, so everything is good to go! i sware this thing is as fast as a 450r now! not quite up there with my national motor in my yfzR but damn impressive for a 400ex

[CJM]

I figured it would work itself out :)

[vinson581]

well looks like i spoke too soon...i started it up again tonight ice cold and again smoke, but less this time, im going to ride it for a few hours hopefully this weekend and see if it takes care of it itself, and if not i will make a note to self that pro-x valve seals are garbage, and i will be installing some good quality oem ones. oh well no i know

[SHIFTx450]

What kinda piston are you using vinson?

[vinson581]

weisco 11:1 416 oversize.

[crownandmonster]

What about your bore? Do you trust the machine shop/ person that did the work? Did you mic the cylinder when you got it back to make sure it was in spec?

[vinson581]

the cylinder is fine, as the bike only will smoke a little bit upon start up, if it smoked all the time it would be a bore/ring problem, im going to go ahead and tare it down when i get some time and just throw some new valve seals in it, and as far as the machine shop goes, i mean they have been in business as long as i can even remember, so i doubt thats it, and the cylinder isnt out of round because i had zero issues before the rebuild (no smoke or anything of that sort)

[SHIFTx450]

How many rings are on that piston?

[vinson581]

normal 2 ring piston, w/2 oil rings and expander.

[vinson581]

well i figured i would update this if thread even if it were for the archives.

i went and replaced my valve seals a second time, with oem honda ones, inspected everything, and put it back togeather, well it still smoked right around the same. got fustrated tore it down again and looks like there is slight scoring on the cylinder wall...very interesting, this leads me to belive that 1. the 416 piston i had put in had sat around for a long long time, and something happend to it? or 2 (the likely problem) the machine shop didnt bore my cylinder to the proper spec. i however am traveling down south with a few bikes and needed the 400 to come with me, i decided to purchase a brand new already bored to 416 (87mm) displacement cylinder, and a je 10.8:1 piston, in well very interesting 86.99mm or so je calls it a 416 or an 87mm piston...

well looks like i got another question...

87mm cylinder
je spec sheet measures piston out to be a 86.99mm

pretty sure it would be ok because such factors as the rings with take up the clearance in the cylinder, but before i go an put this thing togeather i wanted to see what everyone thought.

[CJM]

That little itty bitty bitty isnt gonna kill ya. Id put it together if it was mine.

Id suspect that in your case with the other cyl:
1. Improper bore
2. Improper ring gap
3. Something very small got stuck in there and caused damage (the scoring).

[vinson581]

im really really really extra positive my ring gap was spot on. because i measured it about 3 times, but who knows honestly the piston that went in was about 6 years old and sat and sat, it looked perfect but who knows if the rings had gotten some imperfections from over the years (corrosion, rust, ect) also this is the first time ive used this different machine shop, grr i wish the other guy i used didnt retire.

but thanks cjm you made me feel a bit better! im prolly going to do one of two things, because the smoking really is so minimal id say on startup - 30 seconds or less till the rings seal from heat, im either going to ride it down in florida, or rebuild it with my buddy when i get down there, im bringing the new cylinder and piston as a just in case sort of thing, or if we get some time to do it.

[CJM]

I honestly dont think your gonna run into to many issues since you have a whole new topend sitting there waiting. A buddy of mine ran a topend that eventually smoked worse than a 2 stroke, he bored it and we put a 86mm piston in with no issues.

[SHIFTx450]

Dude, my JE 2 ring race piston doesn't have a 3rd ring like a traditional setup, I forget which actual specific ring is nor present, but they all smoke on startup until they got hot, expand, and seat. It's normal from my experience.

[vinson581]

its a 3 ring piston, and ive never seen a motor do that unless something isnt right, ive built some pretty aggressive engines that havent ever done that, but when i say smoke i mean like a good amount of smoke pouring out then less then a minute later on warmup the smoke ceases, keep the engine hot and let it sit for 45 mins start it back up and no smoke because the cylinder is still warm, its very odd but none the less i dont want any of my bikes at less then 100% im a little anal lol

[ac300]

Hey Vinson581, I am having the same issue, I just did a complete rebuild on my machine, new piston/rings/valves, etc. I went 50mm over on the bore and it smokes for about 2 min after I start it cold. I have torn it down 4 times and cannot figure out what the issue is. I have only run 2-3 tanks of gas through it… I see you had this problem a couple years ago, what ended up happening?

[CJM]

Did you replace the valve guide seals?