stumped neil take alook at these

[2-330s]

burnt 2 pistons this winter. 350 pv 1st is at three thou clearence 2nd is at three and a half. did a leak down test it was fine. i was running a 40.5 kehin 230 main 62 pilot deg needle 1st time and a eeg the second 260 comp. plenty of break in. lrd big bore pipe ftz drag ignition ported rad valve 110 torco 32:1 klots supertecno. slapped my 330 cylinder back on had to come down to a 215 main 58 pilot. ran fine ???:confused:

[2-330s]

2

[2-330s]

3

[Honda 250r 001]

Now im not neil, but i do have something to add...

are the ports beveled in the cylinder? I read on macdizzy's website if there not it acts like a scraper and removes the oil from the piston and then its aluminum on steel... whats the bore look like?

[2-330s]

the bore is round ports are chamfered

[thedeatons]

I have seen fuel injected engines squirt too much gas in (too rich) and wash the oil ring out, resulting in aluminum piston melting across the rings.... Just throwing that out there....

[tt racer]

The brand of piston, or ring gap? Just a guess.

[2-330s]

it wasn't washing the plug. the plug was black but not wet.ring gap was fine. these are the first wossner pistons i used?

[86 Quad R]

you give plenty of warm up time. i'm no expert but based on your piston to cylinder clearances, it appears to be a cold seizer. :confused:

[2-330s]

we keep the trailer 70-80 deg to keep the shocks and fluids warm(us to) and i let it warm up atleast 5-10 min in the staging line

[Aceman]

Originally posted by 2-330s
we keep the trailer 70-80 deg to keep the shocks and fluids warm(us to) and i let it warm up atleast 5-10 min in the staging line

What was the water temp? I bet my 310 takes at least 5 mins. to reach 120 degrees in warm weather, winter time it might not ever warm up just idling, blipping the throttle. I usually have to take some low speed passes just to get the temp up to operating range before I really pour the coals to her.

[norcalduner]

What throttle opening were you at when it seized ? WOT, 2/3, decel after being on WOT, etc. ?

[fulltiltrider]

That looks like a classic 4 point seizure if you ask me. The combination of cold winter temps and what seems to me to be a very rich setup is not allowing that big bore to heat up, imo

[2-330s]

it stuck both times under wot the first time i thought it was a tight bore. i don't know the water temp but haven't had this problem with my sparks or lrd 330 motors.

[fulltiltrider]

Originally posted by 2-330s
burnt 2 pistons this winter. 350 pv 1st is at three thou clearence 2nd is at three and a half. did a leak down test it was fine. i was running a 40.5 kehin 230 main 62 pilot deg needle 1st time and a eeg the second 260 comp. plenty of break in. lrd big bore pipe ftz drag ignition ported rad valve 110 torco 32:1 klots supertecno. slapped my 330 cylinder back on had to come down to a 215 main 58 pilot. ran fine ???:confused:

You were changing 6 main jet sizes for a 20cc difference in cylinder size. Now I know that depends on porting but, if your plug is black it is WAY rich. Jetting that is running close to spot on will be light tan on gas, and have little color on race fuel until you get down in the plug a bit. You cant go by that exactly but you get the idea. My 310 started to run good on the top end at 190 but the plug was still black ended up at 178 and could probably go to 175 but its close enough for me. 90% of all 2 stroke owners dont have them tuned correctly. The rich jetting has everything to do with your issue imo. I think it is rich at every circuit to tell you the truth. Especially the needle and pilot. If it is rich at those two circuits you could putt around all day and not get it warm. First wide open run its gonna seize.

[2-330s]

i guess that could be it. but i was trying to keep some of the heat out of it until i knew the piston was tempered. i ran alot of heat cycles at diffrent loads,but i do like to get 1 weekend of racing on a fresh motor before i jet it out. i do know how to jet my motors been doing this for a long time. spent plenty of money on the dyno and building motors. my sparks motor runs 2 pilot sizes and 3 or 4 main jet sizes bigger than my lrd with the same carb and needle. using a digitron you can get them spot on for the main. i will run my plug almost white if i need every last hp out of it .(depending on the competition that shows up)

[fulltiltrider]

I really dont believe in "break in jetting". If the heat is right its right, new or not. I've broken in lots of engines, 3 heat cycles, a putt around the yard let it cool and have at it. I've done some drag engines with 3 heat cycles and run it down the track. Not optimal but sometimes you gotta do what ya gotta do. I think that rich breakins do way more harm than good.

[2-330s]

i know what u mean u can get away with that when u moto or drag race but flattrac you are puting the motor under extreme loads for a long period of time building alot of cylinder temp.

[jon370r]

I ran into the same problem with my 370cc. I had at least 2 hrs of break in time on it and when I actually put some power down it had a seize just like your pics. The only other time I siezed it was on the ice and that was definatly a (4) corner cold seize that also looked the same. Unless you have a temp. gage on it an know how warm it is, don't beat on it. When the air is cold you would be suprised how long it take to warm up to operating temp.

[2-330s]

i guess it could .be ftz is telling me it's that a kehin can't supply the fuel needed. i have been running 2 differnt pro x cylinders for 6 years on the ice and this is the first one that is giving me any problems.

[SuperSherman]

If FTZ says a Kiehin can't supply the fuel needed, they need to go back to school. PWK all the way....

[machwon]

2-330's, I'm sure Neil at Sabertooth racing can tell you exactly whats wrong. You definetely have an issue with the cylinder set up and your motor guy should help yo take care of it. Who did the cylinder set up anyways?

[2-330s]

ftz

[250r grave yard]

Originally posted by SuperSherman
If FTZ says a Kiehin can't supply the fuel needed, they need to go back to school. PWK all the way.... kiehin carbs are easy to tune , mikuins are more for fine tuning

[machwon]

I'd replace or rework the dome, too much comp. The 3 thou was a little tight but 3.5 should work awesome. After the dome is fixed the jetting will be way too rich. Hope this helps.

[fulltiltrider]

Originally posted by machwon
I'd replace or rework the dome, too much comp. The 3 thou was a little tight but 3.5 should work awesome. After the dome is fixed the jetting will be way too rich. Hope this helps.

I just saw the 260psi comp. I completely agree with the above statement.

[Honda 250r 001]

Originally posted by fulltiltrider
I just saw the 260psi comp. I completely agree with the above statement.

:eek2: 260???? i didnt notice that either. wow i have NEVER seen anyone run that high i bet that machine had a bunch of power until she went.

[2-330s]

yeah it was fast. i know that the comp is high. but i know of 4 or5 of there motors that run the same comp and last for a season or more.

[Honda 250r 001]

Originally posted by 2-330s
yeah it was fast. i know that the comp is high. but i know of 4 or5 of there motors that run the same comp and last for a season or more.

you were running the best fuel money could buy right?

[2-330s]

yes i was running race fuel. doesn't look to be a detonation problem.

[All250R]

Originally posted by 2-330s
yes i was running race fuel. doesn't look to be a detonation problem.
Does the head have coolant flow designed into it or are you running an exhaust gasket with flow metering (e.g. stock or cr gasket)? What is your coolant mixture set at? Is the radiator blocked by a number plate, or mud? If the cylinder gets hot enough it will kill off the oil film between the piston and cylinder. Is there aluminum on the cylinder wall too? If so, the oil was no longer present when it seized.

[2-330s]

it has the o ring head,i run engine ice for coolant.no number plate and no mud. there is 1 little strip of alumnium on the right exhaust side 1/8 " wide. i was WOT 6th gear 14/34 gearing when it started to loose power.

[headache]

what about the Klotz supertech? I've read that you aren't supposed to run that stuff in cold weather. just a thought..

[2-330s]

i know that you arn't supposed to run the benol but i haven't had a problem with this before now. so???

[250r grave yard]

cracked sleev or leaking head something could be warped the piston on the right looked like mine did when it had a leaking head problem
i had 240 psi with my 145lb butt kicking it over i dont think it was leaking till i was getting on the throttle

[All250R]

Originally posted by 2-330s
it has the o ring head,i run engine ice for coolant.no number plate and no mud. there is 1 little strip of alumnium on the right exhaust side 1/8 " wide. i was WOT 6th gear 14/34 gearing when it started to loose power.
My guess is your cooling system is not able to shed the heat that it needs to. Reduce heat, or improve your cooling system.

[2-330s]

i don't think it was a cooling problem.

[machwon]

Originally posted by machwon
I'd replace or rework the dome, too much comp. The 3 thou was a little tight but 3.5 should work awesome. After the dome is fixed the jetting will be way too rich. Hope this helps.

2-330's I build ATV motors and could help you out if interested. Otherwise, explain the picture or send it to your motor builder. Like myself, they should call this one right away. 260 psi is not going to get you the fastest motor out there. It probably snorted like a pig with torque and then couldn't run fast due to its short legs. The motor guy either sent you the wrong dome or simply made a mistake when building it. Without a dome change I'd bet this motor will continue to gobble pistons. Let me know if I can help you out.

[86 Quad R]

hey machwon, are you saying that the dome isnt "profiled" correctly for the way the engine is setup to run?

[machwon]

Originally posted by 86 Quad R
hey machwon, are you saying that the dome isnt "profiled" correctly for the way the engine is setup to run?

Yes, the dome is what the problem is here but I'm being vague on purpose as to what is wrong with it. If I was to do the work, I'd fill them in on what the issue was. Thats just part of being a good motor builder/tuner guy. Sometimes shops and the experts don't fess up to what is going on. 2-330's could call them and insist they fix it.

[86 Quad R]

oh i know what your saying. juss wanted to make sure i was on the same page. ;) the technology in that area phenominal < sp

[C-LEIGH RACING]

2-330s check your PMs
Neil

[2-330s]

no pm neil?

[C-LEIGH RACING]

Check now, took me awhile typing.
Neil

[2-330s]

reply thanks

[All250R]

Originally posted by 2-330s
i don't think it was a cooling problem.
It sounds like you got some offers to help already, but with super high compression like you probably have, a byproduct is that more heat energy is going to build up locally in the metal. When you compound that by running the engine as fast and hard as it can you're really asking the cooling system to pull a lot of heat from the metal to the water in a short amount of time. If it can't, the aluminum and iron will get hot enough to flash the oil and cause direct contact between aluminum and iron causing aluminum to shed off onto the iron surface. If oil were still present, it might seize due to interference, but not transfer aluminum because oil is still carrying a barrier between the two.

Your cooling system may not have a "problem" in the typical sense, but it sounds like it's not matched to amount of heat you're creating locally in the cylinder and piston. The easiest thing to do is pull the compression down, but there are ways to extract more of the heat into the coolant in a shorter amount of time as well if that's your game.

How did your setup run when in the upper rpm range with your overall setup - just curious?
Thx

[2-330s]

it pulled hard off the corner and reved higher than my spark or my lrd. it was a real arm stretcher. i will like it when i can keep it running.i'm going to try what neil told me and then put it on the dyno. thanks for your reply
ken