tonyown Posted April 24, 2010 Report Share Posted April 24, 2010 Happened at WOT after 6-10 seconds wot... the right piston's near to have a hole too right at the same place... I suspect detonation... I ran 50/50 ratio of 91/110 octane last year with no problem and this year I checked compression and squish... 130 psi both side with a non reliable gauge and .050 squish so I tryed only 91 octane and I think it's what caused that... Other suggestion? 160 main in 33mm pwks at 40-50 degrees 1000 ft altitude modifs: fmf fatty's, vforces 3, noss head with 21 cc cut domes, 795 series pistons, 4mm stroker 5mm long rod, fast wood/trail port, port matched case, +4 timing, 33mm pwks, 6'' K&N style pods could it be cuz i was Lean on main jet or a air leak? Does it cause hole in piston? cylinder wall looks nice no seizure... piston skirt have some scratches but didnt affect the cylinder Quote Link to comment Share on other sites More sharing options...
blowit Posted April 24, 2010 Report Share Posted April 24, 2010 Yep, thats a hole..... I suspect octane as well on this one. Keep in mind that sometimes 87 octane comes out of the handle, even when 91 is selected. With 21cc, +4*, +4mm, and cold temp, you are at the edge there. Keep in mind that cold air is dense air, this raising the dynamic compression ratio over what it might be at say 80*F. I think you would be fine just going back to a 50/50 blend. MIght take a quick peek at that main jet to make sure nothing else is going on but I think you are all over it. B Quote Link to comment Share on other sites More sharing options...
tonyown Posted April 24, 2010 Author Report Share Posted April 24, 2010 Ok ty I'm gonna run 100ll av gas... 100 octane when I get my pistons Quote Link to comment Share on other sites More sharing options...
toolman Posted April 24, 2010 Report Share Posted April 24, 2010 Just my 2 cents Looks lean. If you look at both pistons one is clean the other has carbon on it. If it was detonation would not both pistons have some damage (pitting). Looks like it went lean on one cylinder at WOT jetting or a sudden air leak. Bad crank seal or base gasket. I would do a leak down test if you just put pistons back in, to rule out the crank seal. Quote Link to comment Share on other sites More sharing options...
toytech Posted April 24, 2010 Report Share Posted April 24, 2010 Happened at WOT after 6-10 seconds wot... the right piston's near to have a hole too right at the same place... I suspect detonation... I ran 50/50 ratio of 91/110 octane last year with no problem and this year I checked compression and squish... 130 psi both side with a non reliable gauge and .050 squish so I tryed only 91 octane and I think it's what caused that... Other suggestion? 160 main in 33mm pwks at 40-50 degrees 1000 ft altitude modifs: fmf fatty's, vforces 3, noss head with 21 cc cut domes, 795 series pistons, 4mm stroker 5mm long rod, fast wood/trail port, port matched case, +4 timing, 33mm pwks, 6'' K&N style pods could it be cuz i was Lean on main jet or a air leak? Does it cause hole in piston? cylinder wall looks nice no seizure... piston skirt have some scratches but didnt affect the cylinder looks lean on that side possible air leak carb boot,crank seal, and possibly to hot of spark plugs Quote Link to comment Share on other sites More sharing options...
tonyown Posted April 24, 2010 Author Report Share Posted April 24, 2010 both side were near to have a hole... and I think right side have a lot of oil cuz I started the enigne after it happened so the right side got a lot of oil running on 1 cyl at idle Quote Link to comment Share on other sites More sharing options...
tonyown Posted April 24, 2010 Author Report Share Posted April 24, 2010 I'll do a leak down test for sure... Quote Link to comment Share on other sites More sharing options...
dlnoss Posted April 25, 2010 Report Share Posted April 25, 2010 What do the domes and plugs look like? It looks more like a 'melt' than a 'break' making me suspect running lean. Detonation might pit the dome or break the plug electrode. -David Quote Link to comment Share on other sites More sharing options...
tonyown Posted April 25, 2010 Author Report Share Posted April 25, 2010 domes looked great and plug too just real dry... right side have a lot of oil probably cuz I started engine after it happened... But I washed domes in ultrasonic solution and machine and they now look like crap so I must buy new one lol didnt know that ultra sonic would damage aluminium like that Domes after removal dome after ultra sonic wash... they look like crap Quote Link to comment Share on other sites More sharing options...
bbluebanshee Posted April 25, 2010 Report Share Posted April 25, 2010 130 compression seems pretty low for detonation. Quote Link to comment Share on other sites More sharing options...
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