new engine seized, what went wrong (pics included) [Archive]

sbjones73

10-13-2008, 12:59 AM

ok people. i am just pissed to the extreme right now. a little history here.

84 250r engine has been totally gone through about 10 hours ago (riding hours) took it out today for just a little fun and do another plug chop. got her into 4th gear about 3/4 throttle and the whole things just locks up on me. took it out of gear and brought back home. just for giggles i tried to kickit over again and the thing started, i shut it down immediatly (ifigured damamge was already done). removed the plug. looks a little darker than card board, a little lighter than the rust colored car primer. took the head off and saw scoring in the cylinder. removed the cylinder and this is what i found.:cry:

as you can tell the plug color is good in my opinion. fins for the cylinder and the head have been plasted clean and been painted with ceramic pj1 paint. stock exhaust. 20:1 for mixture with 92 gas and belray oils through out the entire engine (including 2 stroke oil) engine is bored 70mm over stock, no porting or anything else done to it.

as stated above. i have ran this thing several hours prior to this happening. it has been up in the throttle a couple of times in the lower gears (3/4 throttle, but only wide open 1 time for plug chop, which was good just the like the picture)

i would like to know what in the heck you guys think caused this. i am baffled:confused: , and i don't want this to happen again when i redo it. please let me know. pics are below.

Autophysn

10-13-2008, 01:06 AM

Wow, that sucks! I am very interested in what the guys have to say!

Erics350x

10-13-2008, 01:07 AM

lean...............
That plug looks like you had a head gasket leaking water in.

mdunn

10-13-2008, 01:08 AM

What piston to bore clearance were you running with what type of piston?

jlharrison3

10-13-2008, 01:18 AM

Lean! Not enough clearance
could also cause this problem.
Mic the piston and the cylinder .
A wiseco piston requires more
clearance than a cheap cast
piston. That thing got hot! Pretty
sure it didnt have enough fuel.

KASEY

10-13-2008, 01:22 AM

LOOKS LIKE A COLD SIEZE was it warmed up ????? oh by the way eric... its an 84 so i highly doubt it is leaking WATER... when you seize a piston on the intake side it usually indicates cold seize... also i don't think thats the right plug either,,,,,, threads look to short

sbjones73

10-13-2008, 01:25 AM

ok i will go and mic up the piston and the cylinder real fast here. i am running a wiseco. this is an air cooled engine. no water in the engine at all.

i will be right back with the measurements.

sbjones73

10-13-2008, 01:26 AM

kasey what is a cold sieze?

KASEY

10-13-2008, 01:29 AM

an aluminum piston expands at twice the rate of a steel cylinder,, if you don't warm it up with a new motor you can in some cases sieze a piston when its cold,,, like what just happened to you,,,,,,

jlharrison3

10-13-2008, 01:30 AM

What is your main jet size? Did u
take your new piston to the
machine shop so they could bore
your cylinder to that piston?

sbjones73

10-13-2008, 01:37 AM

ok i did my measurements as good as a i could with a dial gauge. bore and clearance are right on as far as the box for the piston says.

yes i took the piston with the cylinder to the machine shop and the box.

my main jet is 130.

sbjones73

10-13-2008, 01:46 AM

so you think i cold siezed it. man, i still am about to puke. i ran it for about 20 minutes or so before i got on the throttle like that. !@#$%%^^&**()(*&^%$#@! this gets me so mad!!!!! but it sounds like i did it to myself.

other than letting the engine warm up, how do you prevent this? and also, after the engine has been thuroughly broke in, will this continue to be something i need to watch out for. meaning get her warm then ride it hard after warmed up?

jlharrison3

10-13-2008, 01:46 AM

Im running a 300 big bore now
on my 84 but, when it was a
250 i ran a 140 main jet. Your
plug isnt dark enough for my
liking. Im leaning towards the
fuel being the problem. . A
clearance issue would have
shown up before now if u have
ten hous on it . Jmo

jlharrison3

10-13-2008, 01:50 AM

If that trike was running 10
minutes *Edited**Edited* u nailed it . . It was
warm enough .

sbjones73

10-13-2008, 01:54 AM

i changed my mainjet from a 140 to a 130 becuase i fouled out 2 plugs before this. my last plug chop looked very similar to this one.

Twilight

10-13-2008, 01:56 AM

Looks like an air leak, there are proper breaking in procedures for all engines. I think that maybe a gasket leaked or even that your cylinder didnt get enough oil.

im only good with 2-strokes. but when a piston looks like that, i would say air leak, or you put a dry piston with no oil into the engine it expanded too quickly.

sbjones73

10-13-2008, 01:56 AM

and ya know something. before this happened i got on it about 1/2 throttle going down the road for about 1.8 mile through all of the gears. it ran great, till this happened.

jlharrison3

10-13-2008, 02:04 AM

That pic of your plug. . To me. .
Looks lean. I'll take a pic of my
plug and post it on this thread
tomorrow . Is it possible that
you have an air leak
somewhere ? Intake boot?
Reed cage? What slot is your
clip on *Edited**Edited* needle in? My guess
is lean. . Those pics are just a
prime example of what happens
when you dont have enough
fuel.

sbjones73

10-13-2008, 02:33 AM

please take a pic. i would like to know what it should look like when running properly. because when i redo this darn thisg. i will be putting an 85 or 86 carb on it and i would like not to go through this crap again.

thanks!!!!!!!!

Autophysn

10-13-2008, 02:41 AM

take it back to the machine shop if they bored it to that piston, should be warranty, but hide the plug

By the way, may sound like a stupid question, but was the plug tight when you removed it?

sbjones73

10-13-2008, 02:42 AM

i am looking at my engine right now. ya know, the main cylinder gasket does not look as though it has been crushed on one side. also i have fuel under the gasket in the 2 valleys up front. think this could be my problem?

sbjones73

10-13-2008, 02:43 AM

auto, that actually sounds like a good idea. thanks. but wouldn't they know that it has been ran with the carbon or soot on the top of the piston?

3Razors

10-13-2008, 02:53 AM

IMO you have too many variables going on with that engine. Piston to bore clearance, weird spark plug, jetting, air leaks, ect. When you build a motor everything has to be just right for it to last. One wrong thing and you will find yourself as the same position as now.

sbjones73

10-13-2008, 03:07 AM

i thought that i a was paying attention to everything when i put this together, and it ran for approx 10 hours worth of light riding. your probably right. but i guess why would it last for even 2 hours of riding under 1/2 throttle if things like air leak and piston clearance where the problem. also shouldn't jetting have shown up on my first plug chop? or even the air leak?

well this time when i build it, i am going to be a fanatic about all of it!!!!!!!

sbjones73

10-13-2008, 03:09 AM

auto, yes plug was tight. that was a good question though, i checked that first believe it or not.

ceaserthethird

10-13-2008, 04:35 AM

what's the plug Number ?

Make sure you get a '86 carb

Also run it rich on the main jet, (next time) i just carry a extra plug around in case it foul's.

Keep us posted !

Erics350x

10-13-2008, 08:37 AM

I didn't notice the 84 part. lol Anyway, it was lean. Did you clean the carb before running it? Carb and petcock cleaning are regular maintenance on 2-strokes that is commonly over looked. A good way to judge the amount of fuel it is getting is by, looking at the edge of the piston for the amount of "piston wash". There should be a clean area just around the outter edge of the piston. No clean area means lean and too much is rich. Or maybe its the other way around, im still half a sleep
That spark plug looks like its out of a car.

atctim

10-13-2008, 09:03 AM

What is the name and numbers on your spark plug? The threads look way to short.

maggiesboy

10-13-2008, 09:08 AM

lean...............
That plug looks like you had a head gasket leaking water in.

:banned: LOL

sandpuppi101

10-13-2008, 09:37 AM

Which way is the arrow pointing on the top of the piston exhaust or intake? You should run an NGK BR9ES or something of that liking.That look's like an Champion L82 plug or something along those line's.Like the other's said also that plug look's way lean.Was it reving unusual or did it idle irratic?

300rman

10-13-2008, 07:14 PM

overheating due to detonation?

otherwise, probably too lean a main jet.

dont forget, the needle and ppilot jet play a role too. pilot jet controls startability/low throttle. needle 1/4-3/4 and jet 3/4 to WFO.

Daddio

10-13-2008, 07:53 PM

Is the cylinder scored up that bad or is that melted aluminum smeared on it? Also were the edges of the ports beveled properly?
I doubt if it was a main jet issue. A 130 doesn't sound that far off to me.

1upfront

10-13-2008, 08:17 PM

If the jetting was lean it would have burned the crown of the piston but it appears to be fine, it looks like tight tolerance in just a couple areas of the cyl maybe it wasn't honed correctly.

250RNUT

10-13-2008, 09:10 PM

I believe your problem might be from running it down the road like you said. What happens is if your mixture is not a little rich when you scream down the road, The oil does not have time vs. the RPM of the engine to properly lubricate it. I would guess it is the almost 2 mile ride down the road that might of caused this.Not good for 2 strokes sometimes.

POS 250sx

10-13-2008, 09:18 PM

Daddio

10-13-2008, 09:28 PM

If you were running at half throttle when this happened it would be a problem with the pilot jet.

1upfront

10-13-2008, 09:36 PM

Wow that sux. Im so glad diesel engines arnt that big of pansies. Imagine if i had just spent $1400 on a rebuild for my truck and 10hours of labor and it blew up? holy shoot id be pissed. Good luck with *Edited**Edited* 2stroke im soooo glad i dont have one lol.

It's not because it's a 2stroke, 2strokes are some of the most reliable motors ever made and hold up better to high performance mods than a 4stroke IMO, just like any other powerplant if theres a tolerance problem or other problems it can cause damage but it rarely happens.

POS 250sx

10-13-2008, 09:45 PM

It's not because it's a 2stroke, 2strokes are some of the most reliable motors ever made and hold up better to high performance mods than a 4stroke IMO, just like any other powerplant if theres a tolerance problem or other problems it can cause damage but it rarely happens.

Gas engines in general piss me off lol. In the world of diesel everything is so EZ. You give it fuel you give it air it runs. you want more power you add more fuel. If want more power you add more air and then even more fuel. And theres no mixing no intake leaks no jetting none of these crazy variable to worry about destroying your engine. HaHa 2strokes dont have shoot on diesels for reliability. And 4strokes in general own in longevity.

Daddio

10-13-2008, 10:13 PM

Gas engines in general piss me off lol. In the world of diesel everything is so EZ. You give it fuel you give it air it runs. you want more power you add more fuel. If want more power you add more air and then even more fuel. And theres no mixing no intake leaks no jetting none of these crazy variable to worry about destroying your engine. HaHa 2strokes dont have shoot on diesels for reliability. And 4strokes in general own in longevity.
You're showing your age. I take it you've never heard of a 2stroke diesel.
This guy is asking for help from people who may be able to help him. I would suggest that if you don't have anything useful to contribute to this thread that you leave it alone.

DeePa

10-13-2008, 10:16 PM

does the piston have to be burned from being lean?

Oh, and if you think you can avoid gas engines for your entire life, youre wrong

whipit

10-13-2008, 10:41 PM

Erics350x

10-13-2008, 10:47 PM

He already said the head gasket was showing signs of leakage.

Erics350x

10-13-2008, 10:48 PM

does the piston have to be burned from being lean?

Oh, and if you think you can avoid gas engines for your entire life, youre wrong

No...................

POS 250sx

10-13-2008, 10:56 PM

Im fully aware of diesel 2strokes, their only modern use is as generators on large trains. No i dont avoid gas engines I ride a CB400t everyday and hate my leaky intakeboots that make it run like *Edited**Edited**Edited**Edited* and i cant afford $120 for new ones. I wasnt trying to start a fight i was commenting on how crazy it is to pay for a rebuild then have *Edited**Edited* motor blow up. And comparing his situation to a rebuild a did a few months ago, which cost much more time and money. I was being thankful that my rebuild was on a diesel which are much more simply and hassle free.

hondawasaki

10-14-2008, 12:07 AM

I'll give my 2 cents, That is a 4 corner seize, which more than likely means you ran lean at full throttle. make sure you ck the engine for leaks before you run it again. (cap the intake, exhaust, and use a cylinder leakage tester at about 8lbs to make sure crank seals, base gasket, intake boot arent leaking) That base gasket definitly could be your issue. If the cyl isn't scored, muriatic acid will take the aluminum off the bore. so all you would need is a new piston, as long as you get your intake leaks fixed. good luck!

sbjones73

10-14-2008, 05:13 AM

thanks for all of you comments and opinions here, i think i may have it solved. i took my piston and everything to a couple of long lost friends of mine that have in the past raced snowmobiles and go carts (all 2 strokes) the figured that it was a clearance problem. one of them took out some tools and checked it for me. it is about 3/4 what it should be. also, they looked at the plug. all of them said that it was slightly lean, but not enough to do this type of damage. wait there is more!!

i took it to a machine shop (not the one that did the boring) and they confirmed the clearance issue, but they mentioned that i should have seen this prior to this. i asked them if they do small engines like m ine and they don't. they are mostly big engines like detroits and cummins semi engines.

so tomorrow i will take it back to the machine shop that performed the boring for me and see what happens. i will keep you guys informed.

but now i have a question for dadio, what do you mean beveling on the ports. the only port that is beveled in any way is the exhaust. do i need more work to be done? any one with pictures that would be great.

i found a site that has good pictures of 2 stroke piston problems. let me find it again and i will put it up here. one of my snowmobile buddies told me abou it.

sbjones73

10-14-2008, 05:21 AM

ok the web site that i found for piston diag is this....lloydy.org. then go to diagnosis and click on 2 stroke pistons diagnosis. they have some good pics of damaged pistons like mine.

tecat-z

10-14-2008, 07:31 AM

It's referred to as champher. It's done at time of bore/hone. It would be clearly evident if you snagged a ring. Ring snaging is not siesure, and often times catastrofic for the cylinder and rod.

3Razors

10-14-2008, 08:24 AM

Sbjones you friends cannot acurately diagnose that plug because the plug isn't even the correct length to sit in the dome. A plug that is short like that and probably the wrong heat range will give a false reading so whatever color it is makes no difference because it is viod.

leokendall

10-14-2008, 01:15 PM

sbjones73

10-15-2008, 05:07 AM

3 razors, yea they said that also. i do realize that it is the wrong plug. should i have used it? no. i do know that. and i am sure that it didn't help the situation. will i do that again? HECK NO!!!!!!! i guess it was just me being impatient like i can get some times.

can anyone show me a good plug as far as coloring? i would like to see what i should have when i get this thing redone.

thanks for all your guys help!!!!!

88 Turbo Coupe

10-15-2008, 07:22 AM

too lean. a cold seizure happens if you run outside, start the machine and immediately take off flying down the road. it will seize in that case.

I would let it have lots of fuel (big main jet) next time and try to tune the blubbering/fouling out with the air screw

I gotta laugh. You don't know how many times I've seen riders at the track start their quads and rev the shirt out of them when there stone cold and then take off on them. I just shake my head.

atc500x

10-15-2008, 09:38 AM

I had the same problem with my 87 cr500,exactly the same problem....I had a wiseco .80mm...plug was brown/gray.... I change the cylinder and put a HONDA piston in it without changing the jet ,problem solved.Wiseco expend more than honda

ThinktwiceZ71

01-12-2009, 02:43 PM

how did you ever make out on this ? did yuo get it up and running again ?

Tech23

01-13-2009, 12:34 AM

I may be jumping in too late here, but make sure the cylinder head studs are not pulling out of the cylinder. I had to heli coil the studs on my "83". It was running fine...and over a small jump the engine seized. It restarted after it cooled. The studs where pulling the aluminum threads right out of the cylinder. The nuts took proper torque on assembly too. When I took it apart I was also at at loss, so I tried to remove the studs and the threads came out with the studs on many of them. Still had compression but enough to cause a vacuum leak. May want to check the cylinder base studs too. Also I am not sure you have the correct spark plug, the plug gasket is missing too.

Tech23.

sbjones73

01-27-2009, 09:27 PM

ok guys. i know that this is an old post, but i do have a new piston to install.

now i am getting to the jug boring. my box says .020 clearnace. i called wiseco and they said that it needs to be .030? so what is the right number.

remember this is on a 84 250r air cooled trike. let me know please asap. jug is at machine shop right now waiting for me to call back.

thanks

Daddio

01-27-2009, 09:45 PM

Is the piston cast or forged? That makes a difference.

2quicktecate

01-27-2009, 10:24 PM

i think wiseco's are all forged so go with the .030" my wiseco is pretty loose in my tecate but it runs really strong. you can hear it slap at low r's

sbjones73

01-28-2009, 12:16 AM

they are forged pistons.

Tri-Z Pilot

01-28-2009, 01:29 AM

had a lil incident like that before, only it was a rv125 dirtbike. i was drivin along and next thing was the trottle stuck wot and i jumped off, the bike went towards some trees snapped the chain and reved high for 5 or 10 min, then stoped. tryed to crank her over no go. i guess since the bike was high riving for a period of time and the bike was in one spot air really wasn't cooling it down because it wasn't blowing through the air fins on the head and she over heated. pulled the top end of and everything was melted, and a cracked piston skirt.

Why in the world would you let it just sit there waiting to melt itself down? I mean I'm sure the killswitch wouldnt work, (or pullin the plug cap for that matter), but you could have shut the fuel off, and put your hands over the airfilter to choke it out.

SB, a word of advice for you. Nothing but NGK, ever!

cr480r

01-28-2009, 02:08 AM

now i am getting to the jug boring. my box says .020 clearnace. i called wiseco and they said that it needs to be .030? so what is the right number.

i think wiseco's are all forged so go with the .030" my wiseco is pretty loose in my tecate but it runs really strong. you can hear it slap at low r's

I think you guys mean .002"-.003" not .030"... I would run .003 minimum on a wiseco.. I have never had any problems with wisecos at .0035-.004"....

2quicktecate

01-28-2009, 02:23 AM

you know what i meant. 30 thousandth's or .0030

cr480r

01-28-2009, 02:45 AM

three thousandths is not the same as thirty thousandths...

2quicktecate

01-28-2009, 02:50 AM

so we were right in the first place. you want 30 thousandths. three thousandths like your saying is way tight.

2quicktecate

01-28-2009, 02:52 AM

i don't know i'm confusing myself. but thirty thousandths is what we run forged pistons in our race vw engines and more when were on the bottle...

cr480r

01-28-2009, 03:21 AM

so we were right in the first place. you want 30 thousandths. three thousandths like your saying is way tight.

thirty thousandths(.030") is huge... you want three to four thousandths(.003"-.004")

i don't know i'm confusing myself. but thirty thousandths is what we run forged pistons in our race vw engines and more when were on the bottle...

maybe you are thinking of it like "thirty" ten-thousandths(.0030)... which is reduced to three thousandths (.003)... no automotive engine runs .030" bore clearance....thats a whole piston oversize

oscarmayer

01-28-2009, 10:18 AM

if weisco said .030, that's what you go with. they mde the piston and thus know what it should have. actually pretty mcuh ever weisco should have .030 clearance.

Nick_R_23

01-28-2009, 12:41 PM

thirty thousandths(.030") is huge... you want three to four thousandths(.003"-.004")

^This. I run .004" on anything aircooled with a Wiseco in it.

.030 is the 3rd bore size, which is wayyyy too much clearance.

Stock > 1st bore: .010 > 2nd bore: .020 > 3rd bore: .030 > etc

-Nick :TrikesOwn

Dirtcrasher

01-28-2009, 02:10 PM

.030 or 30 thousands is double a spark plug gap :lol:

.003 or 3 thousandths is what your looking for or whatever Wiseco suggests.

Don't you guys remember your decimal points?? :D

tri-Z ripper

01-28-2009, 02:29 PM

what's this math stuff? jk decimal place very important!

sbjones73

01-28-2009, 02:39 PM

oscarmayer

01-28-2009, 02:57 PM

ok sorry i meant .0030 forgot an extra 0. sorry.

Dirtcrasher

01-28-2009, 03:08 PM

ok. i called wiseco 2 times here. one last night and one today. one guy told me .003 and the other today told me .002- .0025. i am going to run the .003 clearance since i had this thing lock up on me once before.

thanks for all your help. :D i hope this thing will run ok. i cann't afford to rebuild it one more time. already got 2times my budget in it.

wish me luck!!!!!!!!!!

Good luck!! and I too would go with the larger clearance (.003)......

Those 2 stroke air foolers need time to warm up and expand properly. I always sat and warmed it up a bit for about 1 minute and then rode easy for 3 or 4 minutes before I beat the snot out of it :naughty:

WOW, imagine if you had asked them for .030?? :lol: machine shops don't always know pistons, but they know sizes very well!!

Turned and milled for quite a few years myself :D

Nick_R_23

01-28-2009, 04:02 PM

I dont know the air cooled 250r cylinders very well, but if it has a bridged intake or exhaust, I would have those bridges chamfered out slightly more then the rest of the cylinder. Reason being is that those bridges tend to expand inward toward the piston and can cause seizure also.

-Nick :TrikesOwn