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pope59

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Discussion starter · #1 ·
OK just to give more info on the bike its a ct 330 pv with the Cr ignition 40.5pwk,v force 3 reeds, i took the bike to a builder here in Utah to have the top end rebuilt and bored there was the last over bore on the sleeve left 78mm i asked if it would be OK to go with the 78mm piston and they said yes so i paid for the bore hone and piston gaskets got it home gaped the rings to 14 thousandths and put the top end together they said to brake in the top end in nice and slow so i broke it in just as in the sticky said to i did 5 heat cycles on it the 1/4 1/2 3/4 and wot runs on it 3 of each with a cool down between each i thought it would be OK to ride after all this so i took it to the dunes and it seized up in about one minute of ride time after a good worm up my heat gage red 140-150 when i got on it and maybe run 200 yards wot on a little dune and bam the piston grabbed and shut off the bike so i was done for the day got home took off the top end to see all four Conner's of the piston had heated up and touched the sleeve called up the builder told him what happened he said to bring up the cylinder and the piston so he could look at it so i did got up there and he said i heated it up way to fast and to hot and it just grabbed my question is what should the piston be gaped at in the sleeve they said they had it set for 4 thousandths and that is good and i have a bad water pump and my weight dose not help either I'm 250+lbs to have seized that quick and i know that my water pump is not bad the bike ran fine before the bore and new piston there was no hot/hole in the top of the piston for a air leak i was jetted rich 50 pilot and a 182 maine dhg needle on the second from the top and the air screw was all the way in oil was red line 32-1 mixed with 110 race gas so i was rich my question is what would you guys gap the wosser duct piston piston/cylinder at it seems just to tight to let the piston grow at 4 thousandths they said they set the gap at 4 thousandths and that was enough should a gap of 5 thousandths be better they honed out my cylinder and said it would be ok with just a new piston but i think i should just re sleeve the piston is 180.00 alone i just don't want to throw money hand over fist at this if it should be resleeved they think i will be ok with just the new piston
i had a lot of hours on the top end and i was running low in comp so that is was why i rebuilt the top end the bike would run like a top at 200-225 i try hard not to get over 230 on the temp i coast the bike down the big hills and let it sit at the top to cool down I'm not hard on my bike i almost baby it
i don't know what to do any help from you guys will be a big help thanks
 
#2 ·
Bad news my friend…sounds like a cold seizure.

.004" is a bigger clearance than Wossner recommends. Wossner Big Bore pistons are set at .00276" or .07MM total clearance. Wossner pistons expand a lot less than Wiseco or ProX pistons, due mostly to the higher Silicone content in the Mahle piston material Wossner uses.

Assuming the builder truly did hone it to a 78.00MM straight & round bore, then the piston to sleeve clearance was more than enough and actually over the amount recommended by Wossner, therefore; time to look at other possibilities:

a).Not enough Warm Up time prior to WOT? (4 piston corners indicate rapid expansion)…Big Bores can take 3-5 minutes to heat up properly.

b ).Engine air leaks? Did you perform a full engine leak down test…

c).Bad Hone Job? The cylinder could have been honed to 78MM at the top and bottom of sleeve and much smaller in the middle, the area around the exhaust & transfers sometimes can only have .002" clearance or less if the honing stones had not been trued properly or the person doing the honing did not know what he was doing.

d).Look at the piston closely, does it have any dents on the top of the crown? Take a few pictures and post them up…

e).Was your fuel mixed correctly? Not enough oil or an error in mixture…

f).Are your port edges generously chamfered?

g). Exhaust port bridge relieve correctly?

h). Piston skirt edges have ample radius or chamfers all the way around?

Lots of possibilities; post some pictures of the piston & sleeve…and have an independent shop or machine shop gauge the sleeve in three locations; top, center and bottom all three locations at 90 degree intervals.

Carlos.

PS: I am sure Neil will add a lot of insight to your issue as well…
 
Discussion starter · #3 ·
QUOTE(acecarlos @ Sep 23 2010, 11:49 PM) index.php?act=findpost&pid=48223Bad news my friend…sounds like a cold seizure.

.004" is a bigger clearance than Wossner recommends. Wossner Big Bore pistons are set at .00276" or .07MM total clearance. Wossner pistons expand a lot less than Wiseco or ProX pistons, due mostly to the higher Silicone content in the Mahle piston material Wossner uses.

Assuming the builder truly did hone it to a 78.00MM straight & round bore, then the piston to sleeve clearance was more than enough and actually over the amount recommended by Wossner, therefore; time to look at other possibilities:

a).Not enough Warm Up time prior to WOT? (4 piston corners indicate rapid expansion)…Big Bores can take 3-5 minutes to heat up properly.

b ).Engine air leaks? Did you perform a full engine leak down test…

c).Bad Hone Job? The cylinder could have been honed to 78MM at the top and bottom of sleeve and much smaller in the middle, the area around the exhaust & transfers sometimes can only have .002" clearance or less if the honing stones had not been trued properly or the person doing the honing did not know what he was doing.

d).Look at the piston closely, does it have any dents on the top of the crown? Take a few pictures and post them up…

e).Was your fuel mixed correctly? Not enough oil or an error in mixture…

f).Are your port edges generously chamfered?

g). Exhaust port bridge relieve correctly?

h). Piston skirt edges have ample radius or chamfers all the way around?

Lots of possibilities; post some pictures of the piston & sleeve…and have an independent shop or machine shop gauge the sleeve in three locations; top, center and bottom all three locations at 90 degree intervals.

Carlos.

PS: I am sure Neil will add a lot of insight to your issue as well…

thanks for the info on the setup and the reply i will take it to another shop to see what they say thanks
as for putting up some pics the shop has both the piston and the top end so i can not put some up
 
#4 ·
Sure sounds like a 4 corner cold seize, but not being there I realy dont know.
0.004 should have been enough clearance, but is the bore straight what I dont know.

We lost 2 championships one season, because of two different engines with cylinder bore 0.004 top, 0.004 bottom & then 0.002 right in the center just under the ports & me in a hurry to hit the road & not checking close.
Same shop did both jugs at the same week & then later I found out a kid in training did the finish honing, man, talk about screwing us.

I guess what you need to do, is take the cylinder somewhere other than who you had fit the piston in the first place. It is very unlikely, with your cylinder in their hands, it will be their fault if the bore was not straight. In my years, I can count on one hand those that said it was & offered to replace the work.
Problem now is, only thing you can do is sleeve the cylinder & start over, that is if the bore is messed up to much after you boil the aluminum out of the scars.

I would recomend, taking that cylinder to another shop or machine shop & have it closely measured & then move on to the next step.
Neil
 
#6 ·
i had a lot of hours on the top end and i was running low in comp so that is was why i rebuilt the top end the bike would run like a top at 200-225 i try hard not to get over 230 on the temp i coast the bike down the big hills and let it sit at the top to cool down I'm not hard on my bike i almost baby it
i don't know what to do any help from you guys will be a big help thanks
Click to expand...


You need cooling air flowing through the radiator to cool things down. Prob not a great idea to just sit with the engine running.

Definitely sounds like a cold seize. Have the bore checked and if it's good, throw a Wiseco in there this time around. It would be a shame to resleeve if it didn't truly need it.
 
Discussion starter · #7 ·
You need cooling air flowing through the radiator to cool things down. Prob not a great idea to just sit with the engine running.

Definitely sounds like a cold seize. Have the bore checked and if it's good, throw a Wiseco in there this time around. It would be a shame to resleeve if it didn't truly need it.
Click to expand...

i would go that rought but is has the ct piston/mod so i can not run a wiseco
 
#9 ·
I like flat dome pistons if built correctly. Builders like CT have been pushing Flat piston tops for some time. The benefits (in my opinion) are not just less reciprocating weight, flat top pistons seem to have a better burn pattern at higher RPM’s…however; I would not bend over backwards to build a flat top engine unless it’s use was very specific…

Carlos.
 
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acecarlos
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