Pistion Clearance in ESR 330

[Burns310r]

For you guys running an ESR 330 PV,

What should the pistion clearance be set to when rebuilding.

Wiesco says on the box it should be .003

ESR says it should be set to .0045-.006 becasue the wiesco pistion is forged and grows more than a cast piston.


I have built 3 motor this year, 2 of which where set to .003 and siezed the exhaust/intake sides of the pistion very very quickly.

One motor was one that i blew up and honed, and its clearance was more like .0055 or something. It lasted and ran well.


Is there any truth to this?

[2-330s]

i have been running .0032 on my 330 and .0036 on my 350 with the wiseco. the wossner pistons didn't make it that tight,so i don't use them anymore

take the time to break the motor in good.

i'm also running 110 oct and klotz super techniplate at a 40:1 blend

hope this helps!

[Derrick Adams]

We run .003 on our ESR330. Anything more than that and the engine seems to rattle too much. Tuning is everything and personally I do NOT like wossner pistons.

[C-LEIGH RACING]

I'm thinking same as Rick on Mac Dizzy, .0045 or .006 is way to big.

I beleave, theres got to be some type of issue other than piston to cylinder clearance causing your problem.

I've done all sizes of big bore Rs & never set one up any larger than .0030. Normally many times will request the bore man to set it a tight three at that.

Back in I think it was 01 or 02, I had two engine to seize, both at the same event same day, a 330 & a 350.
The 350 just had a new piston installed & good long break in & seized on the second hot lap of practice.
330 which was back up for the 350, two riders had to use it & it was just plain ran hot what caused it to seize.

The 350, once tore down, cylinder bore was .0035 at the deck, .0030 at the skirt & .0020 just under the transfer ports.
What caused this, was me needing it bored in a hurry & not using my normal bore guy, but, an auto engine rebuilder that had a D A kid in the back training & didnt have a clue what he was doing, other than trying to make a dollar for Saturday night hang out.
Needless to say, that bit me in the ***** & the team ended up loosing the season championship getting last place points that one weekend.

Other than, ill adjusted carb, running to hard to fast, air leak issues, leaking coolant into the bore, running to hot or a bore job gone wrong, a 250r reguardless of the cylinder being used shouldnt seize up.

The only 250R engine I probably have ever got to .0045 or .0060, was the 330 I built back in 04 & raced the poop out of untill 07 before anything was touched on it. I never checked it, but dought it ever got that big.
Neil

[2-330s]

i agree with neil on the .003.

i have found that when we run at 10* or less i can't keep heet in my cylinder even with most of the radiator blocked off.
a hot aluminum piston and cold steel sleeve don't seem to work.

[Honda 250r 001]

I have a 310, which is slightly smaller. But i have had problems with it seizing constantly when bored to .003. I have had to bore to .0045 to keep it from seizing! Jetting was good and compression was in check! But my motor seems to run much hotter than anyone elses. About 225 constant running temp. Does yours run hot also Burns310r? More heat = more expansion which requires a bigger clearence? Am i correct or wrong on this neil?

[Burns310r]

Yes when my clearance was .003 my bike was always around 225-245. I checked everything.

Jetting was spot on if not on the rich side. I watch my jetting like a hawk. Between ever moto, and ever break i check the plug and pay attention to the engine.

I ended up putting the BB pipe on, that has cooled the engine down to 200-210, but i feel its robbing me of power.


I dont know what to say. I have had the same guy bore it ever time. He works and an arnolds machine shop that bores engines. I dont know what more to say.

Im almost scared to do anything, with the engine as far as tighting it up. I have been towed off my local track 3 times this season because of the damn engine.

I have switched to 112 race gas and 215 psi compression. But have only broke the motor in and rode around the yard hard on it. so well see.


Also when i build motors, i basically do this.

Start it up and let the engine heat up to full temp with small 1/4-1/2 throttle blips to keep it cleared out.

Cool Down

Re torque head, base bolts

Start it and heat it up and give it 1/2 throttle blips.

Cool down

Start up and get it to temp then go out and ride around my place for 15 minutes fairly easily and get harder and harder on it.

Cool down check plug. And then dial it in on jetting.

Multiple Hard runs through the gears, up and down, and then a long 5th or 6th gear throttle chop to get a good reading on the engine.

I will ride it like this for 15-25 minutes no issues.




Then after dialed i would go race it and it would blow up in the first lap of the heat. Sometimes make it to the first lap of the main.

Oh and my warm up before a race is very good to, the engine is always to 170 before i get to the gate.

[wilkin250r]

What is your relief on the exhaust bridge?

[Burns310r]

I cant remember, but seems to me the PV engine doesnt have an exhaust bridge.

[jcs003]

is it possible you got a bad batch of pistons?

was the honeing done correctly?

what condition are your base studs in? i assume your head studs are newer...

[Burns310r]

cylinder was brand new when this started in march.

so where the base studs.


I doubt it because the pistons where over 4-5 months.

[C-LEIGH RACING]

You know when something like this is happening, you got to look into everything, study closely to find the problem or problems.

I've not had a chance to use or run one of the new ESR jugs yet, but I will here shortly once I get caught up enough to set it up.

Theres a bunch of those new jugs out there being used & from what I'm reading only a few have or are having problems with seizing.
It could be something simple as where you live, like a 2 stroke would be set up & would run different down on the coast than one set up to run up in the mountains.
Fuel, it might be you would need a higher octane gas, to make it run cooler just because of where you live.
It is many things that can cause a seize & you cant let any stone be unturned to find out what it could be.

We all can suggest things for you to do & check, things we have been through & know first hand that is what caused the problem, but we are not there to see how your bike runs or to put our hands on it checking things, so we are kind of grabing things in the dark, guessing.

One thing I know for sure, some things I know that will cause heat,
high ignition timming,
to low octane gas for compression, which can change as heat changes,
carb jetted wrong= to lean trying to get that last hp out of it,
air leaks,
sucking coolant from somewhere & it getting into the cylinder bore,
pipe not sealed at all joints,
silencer messed up inside, coming apart & blocking outlet,
radiator fins clogged with silt so no air flow or either core clogged half way up.
water pump impeller worn on the end & not pushing enough flow through the cylinder.
That is just a few I can go over real quick & theres a bunch of other little small stuff to cause it.
You need a lazer temp gun so you can check the cylinder to see where it is getting the hottest at.

Those ESR jugs are cast different from the Pro-x.
The Pro-x has a coolant cavity around the exhaust port so coolant encircles the exhaust.
The ESR is cast solid around the exhaust port so no coolant in that area & has more material over top of the exhaust because it is a pv casting.
That being as it is, you would need to do what ever it takes to bring the temps down around the exhaust area be it through ignition timming or larger jets.
Neil

[machwon]

ESR will send a new 330 or 350 out with .0055 or more clear. Pretty sloppy to me, but that's how they make them survive. I guess you get to the next bore size faster that way too?

[C-LEIGH RACING]

That is just unbeleavable.
What on earth would be the problem, that piston to cylinder clearance would need to be over .0030 to survive.

If any of my cylinders ever got to .0050,, no let me change that, cause I've never ran one worn out to .0050 & if it got to .0045 it was way past time for a new piston fit.
Neil

[machwon]

Yea, I did 2 of the new 78mm cylinders last year and that's how they came to me. .003 is pretty tight on a 78mm bore, the tightest i've done is on a 68mm bore with a pro=x at .0022, that cylinder lasted a long time.