03-26-2009, 08:50 AM #1
Need some help reading my cylinders
I posted something on my little project thread, but I figured it would get more exposure over here.
I finally got around to opening up the engine to see what was the matter, and this is what I found:
#1 Cylinder dome
#2 Cylinder dome
#3 Cylinder dome
Looks like some detonation in cylinder #2. Looking into the cylinders themselves confirms this, plus the possibility of a mild seizure in cylinders 2 and 3:
Cylinder 2 DEFINATELY ran lean at some point in time, and a compression test before I opened the engine indicated zero compression in that cylinder, with #3 a bit low, but not too bad.
So, I think the story went like this: I put on a freeflow without rejetting, and so, got the dreaded lean spot due to the accelerator pumps, resulting in the piston getting fried and a mild seizure.
Should I replace the #2 cylinder AND piston, or would I be able to get by with just a piston? I'm not sure how long the scuffed spot (seizure?) was there on #3, as it ran fine all summer.
03-26-2009, 09:10 AM #2
If you clean the aluminum galling on the walls of the cylinder, and there is no damage to the plating you can get by with just a piston. I have used acid to remove this when it is a light seize. Looks like you had something else in #2 besides deto, there is some damage on head and piston top from either broken ring or worse a bearing.
03-26-2009, 12:28 PM #3
#2 sure looks like you had something foreign in there bouncing around. Did you check to see if you had a broken piston ring ?
03-26-2009, 12:39 PM #4
For what its worth....I would take it all the way down to the crank @ least for an inspection.
03-27-2009, 10:39 AM #5
Thanks guys! I'm going to remove #2 and #3 jugs today and have a look at the bottom end.
HallPass sent me one of his spare cylinders and pistons just in case I need it, otherwise, i'm going to pick up a pair of new pistons and rings, as well as a powervalve retainer and WaveEater clip (both disappeared mysteriously).
03-27-2009, 10:46 AM #6
I saw those HP cylinders - You should be able to use those pistons with no problems.
03-27-2009, 10:31 PM #7
Can you rotate the motor by hand? if so, does the #2 piston move up and down? Reason I ask is because if you have 0 compression on #2, then that usually means a rod broke or something else happend to the crank. I have found on these gpr cranks that when they seize they get knocked out of whack and need to be inspected. For the peace of mind at least, but you'd be surprised at what can happen to these crank and how quickly they can get out of balance.
Just some food for thought for you.
03-27-2009, 10:44 PM #8
in piston number 2 in the pic where the piston is down in the cylinder...is there a milky substance on the piston? if there is ten that's water intrusion....but it looks like something like a bearing came out and was hitting. you need to check the cases to make sure that pin isn't in there or whatever it was that was hitting. and check all your bearings. this looks like flyboys piston when his bearing rod came out.
03-27-2009, 11:03 PM #9
Removed all cylinders and the #2 and #3 pistons today. Wrist pins looked good on both, as did the needle bearings. Rods looked good as well.
I'll have some more pics tomorrow, but the culprit of all of the aluminum debris looked to be caused by a ring catching against one of the smaller intake ports, which took a good groove out of the side of the piston, possibly due to a lean condition (maybe? SOMETHING got hot, at least). Both rings were stuck pretty well in position along that groove line.
Thanks for all the help, guys!!!!!!
03-27-2009, 11:45 PM #10
there is loose metal debri in your motor somewhere. This is what might of happened.... A needle bearing came out and was hitting the top of the piston and your head causing those dings. Then the bearing dropped down the side of the piston causing the rings to stick which then cause it to catch a lip on the port. Hopefully flyboy or pistonwash will chime in. I'm actually the one who found 3-4 needle bearings in flyboys ski and it was right in front of them. If you can't find and metal in the motor it may have exited the exhaust port and out your exhaust
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