huskyohilux Posted December 22, 2008 Report Share Posted December 22, 2008 I haven't been riding much this fall due to really bad weather, but the last couple of days it's been irresitible to take out the shee! It's still winter here in southern Sweden but 45F , semi wet streets and sunny :biggrin: This past summer I really fried my pistons; http://www.bansheehq.com/forums/index.php?...hl=seized+again Since then I've baught the pwk 28 Quote Link to comment Share on other sites More sharing options...
Bansh-eman Posted December 22, 2008 Report Share Posted December 22, 2008 if your pistons look the same as your first lockup, I would lean tawards something being wrong more then bad luck. What ratio are you using and what kind of fuel? The first seize looks like a cold seize like it didnt get enough oil and you went to town before it was warmedup. Before I saw the picts I was thinking possible air leak but that doesnt look like an air leak to me. What do the rings look like too? Quote Link to comment Share on other sites More sharing options...
GASSRX Posted December 22, 2008 Report Share Posted December 22, 2008 are the cylinders being bored to the correct talerances meaning the are different bores to piston fit... cast is different from forged pistons... are u holding it wide open for a long ways to town that will cause it to... oil ratio brand of oil.. Quote Link to comment Share on other sites More sharing options...
huskyohilux Posted December 22, 2008 Author Report Share Posted December 22, 2008 The pistons from the picture are the ones I busted this summer with my stock carbs. They had maybe 10 hours on 'em. I haven't had the guts to remove the cylinders yet to inspect the damage from the other day...gonna wait 'til it doesn't start anymore. From the beginning, when I baught the bike, it had the keihin 35 mms and I ran 1:20 with 95 octane. It ran a bit too rich but on the other hand the pistons and cylinders looked great after 30-40 hours. These days I run 1:32 with shell v-power 99 octane (not sure if you have the same octane rating in USA). It doesn't smoke much, hardly at all, once it's warmed up. I'm 100% certain that the bike is hot enough when I get on it and I believe I have no air leaks. The plugs look great. Gonna mix 1:20 from now on just to be on the safe side (it sais 1:20 in the Yamaha manua, right?) I think one problem is when I back down on the throttle the lubrication isn't enough...maybe I'll lower the needle clips to richen the middle...? Quote Link to comment Share on other sites More sharing options...
spurdy Posted December 22, 2008 Report Share Posted December 22, 2008 I haven't had the guts to remove the cylinders yet to inspect the damage from the other day...gonna wait 'til it doesn't start anymore. WTF!?! If you tear it down now you may be able to salvage without boring. That is the life of your engine. 10 hours every rebuild is crazy! But I guess if you have enough money to throw at it and that is what you want to do power to ya! I would really try to figure out what is wrong and fix it so you can ride it and enjoy it. Riding it not knowing when it is going to lock up next doesn't make for an enjoyable time.. SP Quote Link to comment Share on other sites More sharing options...
huskyohilux Posted December 22, 2008 Author Report Share Posted December 22, 2008 If you tear it down now you may be able to salvage without boring. That makes sence...gonna start by peeping throgh the exhast and intake ports to get an idea of where I'm at. Ofcourse it's stupid to wait until the cylinders need to be rebored if I can save them now and only get new pistons that's a whole lot better :thumbsup: And you're right about me worrying rather than enjoying... :sweat: Quote Link to comment Share on other sites More sharing options...
moneybags Posted December 22, 2008 Report Share Posted December 22, 2008 [quote I mix 32:1 mobil fully synthetic w/ shell v-power 99 octane Did I read this right, are you mixing your gas with mobil fully synthetic motor oil? Quote Link to comment Share on other sites More sharing options...
98_shee Posted December 22, 2008 Report Share Posted December 22, 2008 Pull the head off, check the cylinders walls and the pistons out, if they look bad pull the clyinders off. If you think its its not getting enough fuel at less than 1/2 throttle up the pilot. Quote Link to comment Share on other sites More sharing options...
seabass Posted December 22, 2008 Report Share Posted December 22, 2008 (edited) [quote I mix 32:1 mobil fully synthetic w/ shell v-power 99 octane Did I read this right, are you mixing your gas with mobil fully synthetic motor oil? I just read this and was thinking the same thing. Are you mixing your gas and oil with 2 stroke pre-mix oil or Mobil motor oil? Edited December 22, 2008 by seabass Quote Link to comment Share on other sites More sharing options...
deckheight Posted December 23, 2008 Report Share Posted December 23, 2008 Never mind... Was looking at the pics in the post below yours DUH! My mistake, sorry for any confusion... Europe uses a RON rating for octane, if thats the case with your fuel it would be equivalent to our 94 or 95 octane PON. Plenty good for 20cc domes even with 45 deg. air temps. Looks like multiple detonation seizures... Classic 180 deg. stick, probably stuck it and re-started and stuck it again... Carbon is cooked onto the piston crown, hardly any wash and it's burnt off in the center above the spark bolt. Better than average chance your way high on compression for the octane fuel your using. Small chance for a massive air leak and average chance for a combination of the two. That would be my guess for what it's worth. on edit: What fuel octane what cc domes? Quote Link to comment Share on other sites More sharing options...
huskyohilux Posted December 23, 2008 Author Report Share Posted December 23, 2008 I just read this and was thinking the same thing. Are you mixing your gas and oil with 2 stroke pre-mix oil or Mobil motor oil? Yes ofcourse it's the 2-stroke oil :biggrin: Will remove the cylinder head and inspect the damage Quote Link to comment Share on other sites More sharing options...
spurdy Posted December 23, 2008 Report Share Posted December 23, 2008 Yes ofcourse it's the 2-stroke oil :biggrin: Will remove the cylinder head and inspect the damage Good call! :thumbsup: Quote Link to comment Share on other sites More sharing options...
huskyohilux Posted December 26, 2008 Author Report Share Posted December 26, 2008 Removed the top-end and just like I suspected, a small seize on the right piston. Only two scratches on the side of the piston, say 2 and 5 o'clock when pointing forward. The cylinder wall seems to have made it with just some aluminium residue bashed on it. A simple hone will get rid of that. The lefts side is good to go. Since the pistons only had a couple of hours and no boring is necessary, I'll only need to replace one piston, right? I also think I found the casue of the seize...when I fastened the intake rubbers and reed cages them bolts were a tad to long. They came from the reed spacers I had with the 35's last season. So apparently they didn't fasten enough causing minor air leaks from the intake. The right cylinder had cracks from the bottom of the threaded holes showing the bolt wanted to go further in. In the mean time I've already mounted my stock jugs and pistons, they were in awsome shape. So I'll be able to hit some grabble raods this weekend :biggrin: Thanks for the help, guys edit: is it standard protocol to move the needle when it's colder weather to richen the middle as well? I've already bumped up the jets. Quote Link to comment Share on other sites More sharing options...
05Special Posted December 26, 2008 Report Share Posted December 26, 2008 replace them both, i wouldn't chance changing the one piston and then being back where you are now. Quote Link to comment Share on other sites More sharing options...
Bansh-eman Posted December 26, 2008 Report Share Posted December 26, 2008 If the piston is new and it only leaked on one side I would just replace the one. You might think about replacing the ring on the other that way you are fresh on both sides Quote Link to comment Share on other sites More sharing options...
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