gregrob Posted June 23, 2009 Author Report Posted June 23, 2009 UCCR is uncorrected compression ratio. Cranking PSI alone is not enough to setup a motor. Squish band is how thick the solder is smashed, from tip to where it's no longer smashed. Get a set of alky domes from Kevin.... How do you check/calculate UCCR? I take it this is similar to what we call dynamic compression ratio in the smallblock chevy world. I'll check the squish band on the good cylinder before I tear the engine apart. Methanol domes from Kevin are what will be going back in it. Probably 18's, shooting for 170-180psi cranking(static) at this altitude. Quote
gregrob Posted June 23, 2009 Author Report Posted June 23, 2009 (edited) How long were you riding it? Its possible the float got stuck up and starved the engine for fuel on that one side. I've seen it happen before. About 10 mins total ride time after I putted up the road to the dunes to let it warm up. We made a few runs drag racing a long stretch and on about the 5th run is when it let go. Kinda hotlapped. Edited June 23, 2009 by gregrob Quote
dajogejr Posted June 23, 2009 Report Posted June 23, 2009 http://www.sacoriver.net/~red/uccr.html Quote
Bansh-eman Posted June 23, 2009 Report Posted June 23, 2009 Depending on your porting your results may differ but on my cub drag ported by K&T I got 185 psi running 18cc domes at sea level. Not sure if you Quote
dajogejr Posted June 23, 2009 Report Posted June 23, 2009 I can all but guarantee with 18cc domes at 8500 feet it will be no where near that. If they want to run dunes and hot lap bikes, I'd shoot for mid 50's on the squish, 160 or so PSI and about a 17:1 UCCR, give or take. You will lose probably about 10% performance or so, but the motor will hold together longer because there won't be as much heat. Quote
gregrob Posted June 24, 2009 Author Report Posted June 24, 2009 When my duner was fresh the 19's gave me 160 psi. This was out 6k ft, where I live. Thats why I was thinking 18's would probably get me at least into the 170's. Bigreds little kt bike has 180 with 17cc domes up where he lives at 7k ft. Its more of a drag port than mine though I think. Kevin kept my exhaust duration pretty conservative for my weight elevation pipes fuel choice etc at the time. Walden @ 8500 is just one of the places we ride, and is definitely the highest. Quote
gregrob Posted June 29, 2009 Author Report Posted June 29, 2009 (edited) Well I promised I would post neat-o carnage pics when I tore it apart and here they are. My theory on what happened from looking at the piston is that the bowl sucked dry and started a lean condition, which caused the cylinder temps to sky rocket. The high cylinder temps started uncontrolled detonation, and that's what burned a hole through the piston. The reason I say that is because you can see two distinct and seperate areas of damage on the piston. The first being melting / deformation of the aluminum on the crown of the piston on the intake side. The other being the damage directly beneath the spark plug and the exhuast side of the piston. I believe the intake side damage was from being lean, and the other from detonation. Thoughts? The good part about it is that it burned a hole so quickly through the piston, and made such small particles that it didn't hurt, scratch, or gouge the cylinder wall at all! The cylinder looks great, and the dome even looks great except for a small amt of aluminum powder packed in a few places that could be easily removed. As I suspected before teardown I dont believe this was a jetting or timing issue, as the other piston looks BEAUTIFUL. It was a nice light caramel color all the way across the piston, indicating a nice even burn. There is ZERO pitting the piston top, crown, or the dome. Everythin on that side looks awesome. Piston-to-bore clearance checked in at .0045 so it's completely runnable. Just gonna get a new piston for the right side, base gasket, domes, and O-rings and put it back together. Next chore is getting all the metal out of the crank. Been filling the crankcase and washing out with 16:1 premix and the crank smoothed up a lot and got lots of metal out, but theres still shrapnel in there. Guess I'll try some cheap 2 stroke oil from walmart and see if it will help suspend the particles better than gas. Here's the pics: Plug Plug again Piston - Top View Piston - Intake Side Piston - Exhaust Side Piston - In Bore Other piston in bore Note: I carb cleanered the top off the piston and wiped off the nice carmel brown color it had going on Edited June 29, 2009 by gregrob Quote
dajogejr Posted June 29, 2009 Report Posted June 29, 2009 I'd be splitting those cases with that bad of carnage. Quote
FireHead Posted June 29, 2009 Report Posted June 29, 2009 I'd be splitting those cases with that bad of carnage. Word......... The crank bearings are sure to be fouled. It looks like you had a water leak in there to create such a pronounced hole in the piston. Quote
gregrob Posted June 29, 2009 Author Report Posted June 29, 2009 I'd be splitting those cases with that bad of carnage. I had thought about it. I ran almost a gallon of premix through the cases and still getting metal shavings out... Would you clean the bearings out and run it or put new bearings in? Trying to get it going for this coming wknd. :-/ Quote
gregrob Posted June 29, 2009 Author Report Posted June 29, 2009 Word......... The crank bearings are sure to be fouled. It looks like you had a water leak in there to create such a pronounced hole in the piston. Water leak, hmmm... There was no sign of that on the dome and the O rings were in good shape, but it's possible. I wouldn't be surprised with the way the aluminum powder packed into the edges of the dome and sprayed on top of the rod. Almost like it has moisture to make it stick.. Quote
FireHead Posted June 29, 2009 Report Posted June 29, 2009 Water leak, hmmm... There was no sign of that on the dome and the O rings were in good shape, but it's possible. I wouldn't be surprised with the way the aluminum powder packed into the edges of the dome and sprayed on top of the rod. Almost like it has moisture to make it stick.. If you get the plasma cutter looking effect going on, then you certainly had some water getting in there...... :geek: Quote
gregrob Posted June 29, 2009 Author Report Posted June 29, 2009 If you get the plasma cutter looking effect going on, then you certainly had some water getting in there...... :geek: Good to know, Thanks Other than new domes and O-rings, is there anything else I should double check before putting it back together, that may have caused/cause a water leak? Quote
dajogejr Posted June 29, 2009 Report Posted June 29, 2009 I would split the cases and flush the bearings out of the cases. I'd spin 'em once out and see how they felt. You've got all that fluid gone through the motor and you're still getting shavings. When I popped a piston in my motor two years ago, it was only a little of the crown, above the ring land. That's a big hole smack in the middle.... Quote
KEVSWS6 Posted June 29, 2009 Report Posted June 29, 2009 New piston kit, o-rings, base gasket, needles and domes on the way. Quote
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