NEED Help BAD!!

[mcboomport]

Ok guys, I seized my top end 3 times in the past few months. I have not got to ride my freakin bike besides for break in cycles. The second I ride it for about 10 minutes it seizes the piston for a second, then loses compression.

I thought a bad radiator was the culprit for the first two pistons, but after putting my stock one back on, I just found that the radiator wasnt the problem.

The place that built my motor has it jetted fat as hell for break in.(I checked the plugs after/ during each heat cycle when I first got the bike and it was wet low-mid (fouled plugs during mid) and golden brown 3/4 to WOT). It loaded up so bad in the mid that it would go from no power to rail 3/4-WOT without hessitation and stay in a wheelie through the gears staying 3/4 to WOT.

The bike isnt seizing at necessarily WOT ......
They almost said by looking at the piston that it looks like a cold seizure, but this isn't possible either.

They did leak down tests, compression tests... grrrrr...

I run kLOTZ 32:1, 92 octone
I have stock cylinder, ported mid to top, 88 rod, 4mil stroker crank, 38 A/S. Wiseco Piston.
They shaved the head, I am not running a spacer plate.
WHAT could be causing this?!!?!?! HELP!! I NEED TO RIDE!!

[LONG-ROD]

you need a preasure test, I let mine idle for at least 5 min and run 20% on off throttle for the first 2 miles before I even think of getting in to it.

[C-LEIGH RACING]

Ok, its probably what you dont know, thats causing the problems, like.

Piston the cylinder clearance.
The borer, when they bore the cylinder, are they mounting the cylinder to the boring bar table at the base of the cylinder or at the head.
You sure the jettings fat or could it be skipping & having wet plugs because its sucking coolant. Coolant in the cylinder can seize a piston just like running lean.
You can seize a piston from a pilot jet being to small just as easy as from a main.
Ignition, old ignition system can cause a skip that by ear sounds just like a main jet is to big, but realy its not.
When the shop did the crankcase presure check, how long did they do the test. If it was a good amount of time, was there any leakage.
Neil

[mcboomport]

When we did the electrical, we tested everything with a meter, and everything was within the Honda manual specs.

I did not see any coolant in the bottom end, how else would I know if coolant was getting to the piston.

WHen I thought it was my radiator, (i bought a used AFCO) The coolant was leaking, but i didnt really notice it boiling out the overflow. IT seemed the cap wasnt seeling. (i don't have an overflow bottle, but have it ran below pipe)

As far as jetting, I trust these guys 100% (which may be the only thing I trust them for now). Before my bike was built, I had stock bore motor with cleanup porting and I bought the 38 A/S and I rode it for two years with not a single problem. The jetting was spot on.

I'm not sure of the time and pressure loss.

[jhtrx250r]

Ok, first I would check jetting as stated earlier in the forum, did they change any thing ? the main jet size only matters if every thing else is right as in, needle 1st, pilot 2nd, then fine tune with needle clip, air screw and last main size

with a 38 striker I would call sudco customer service, that is most likely where your carb came from and was most likely pre jetted for stock porting.

when an engine is ported it is very important to get the pilot jet size increased.



Then check for a air leak, most likely center of the cases or the LH crank seal



It is very possible you got a crooked bore, or a bad port job, on the R if the exhaust port is to high or to wide then you will get extreme temps that will stick rings or burn piston skirts.



I would start with the carb double then triple check your jetting and call sudco they have good customer service and sell there carburetors to every major and minor shop out there

( make sure you check your jets and needle #s before you call them)



Then check for air leaks; cylinder base gasket, LH crank seal and center case gasket .

[custom R]

how much compression do you have if your running 93 octane make sure your not running over 180 psi

[machwon]

Based upon the motor set up you described it has way too much compression for 92 octane (stock cylinder, 4mm crank, milled head). Even on 110 octane and if you're using the wrong head gaskets it could be too much compression becuase they milled the head too. I'd ask whoever did your motor, how much they milled the head and what is the compression ratio and fuel octane requirements? They should be able to confidently tell you where they set it up at, otherwise find someone in the know. If they won't/can't help you pm or e-mail me. I'd never go by static cranking psi to determine the octane required.

Also, double check the cylinder bore to make sure they relieved the exhuast bridge.

[mcboomport]

I told them when they built the motor I just wanted to run pump gas with this motor. They recommended Klotz at 32:1(which is what I have always run in my bike and my wifes bike) They told me they could cut the head down more down the road to run race gas. I was going to wait for my big bore until I did that route though.

I asked them right away if they made sure the exhaust bridge was relieved and they said yes.

They also told me it was CR head gasket. I will ask them how much they milled the head... I am probably gonna take it over to Arlan to have him look at it.....

[machwon]

The CR head gasket is nice for a stock stroke motor but has no business in a stroker motor with a milled head.

Try a squish test with a piece of solder and I'm guessing you will not get it to turn over (unless the head is recessed after milling). You likely have about .010" squish unless they did something more than what you described to the head.

Of the 4mm set up's I've done I would mill the head to correct the squish angle, but ultimately you will end up making the combustion chamber bigger to get the right compression. The stroker adds cc displacment so it will need a larger dome size than a stock stroke R to still run on pump gas.

[2-330s]

if you post some pics of the pistons it would help if your piston looks like this all the way around its a tight bore like neil said. if it's melting on the exhaust top of the piston its lean. if you back out of the throttle and it sticks it's your piolot. post some pics and it could help the piston i have pictured came from a great motor builder every one has a off day. (curtis sparks) nobody is perfect. some times the small stuff gets over looked