| Author | Message | ||
     Cupcake_mike |
You guys may or not remember but about a year ago, my m2 ate it's rear piston.  Never really figured out what happened other than maybe a Bad piston from the factory. Anyway, I sent the head off to nrhs to get cleaned up and bought a 1250 kit. I installed everything a few months back, did all my heat cycles and rode it for about 250 miles. Ran great. I was getting ready to change the oil when I noticed my head bolts had loosened up and the front head gasket had blown out. I put her in time out for the last couple months and rode the hell out of my uly. Got around to changing out the head and base gaskets and starting her up...she is running like crap. Front cylinder isn't firing. I have checked that both intake and exhaust valves are moving. Put new plugs in, have spark at both cylinders. No intake leaks. Timing is good and even swapped cps, coil and ignition brain cause I had spares on the shelf. No change. I checked compression, 200 on the rear, 60 on the Front. No gaskets have blown out. Anybody think Of anything I might be missing? I can't imagine it's a problem with the Front piston cause it ran so great the first time and it was in fine shape when I replaced the gaskets. I am dumb founded. | ||
| Two_seasons |
Try swapping out spark plug wires with a longer one and send front spark to back. | ||
| 2003xb9r |
Swapping high tension leads isn't going to gain you 140 psi on the front cylinder! My guess is broken ring/s or valves not seating correctly. A sticking lifter will do it or incorrectly set adjustable pushrods for instance. | ||
| Cupcake_mike |
Never had a lifter problem, anyway to diagnose that? I pulled the exhaust and intake manifold and watched the valves while turning it over with the starter and the valves appeared to move the same amount on the front and the rear head. I am going to put a air chuck in the spark plug hole and see if the valves are leaking past out the intake or exhaust, but that's the only thing I can think of I haven't looked at. I did notice I had a small amount of oil blow by out the front cylinder exhaust port (leaked past the exhaust gasket), which makes me think maybe I have a ring problem buts its so little I wonder if that's just not normal and is usually burned off in the exhaust? | ||
| Mmcustoms |
I would do a cylinder leak down test to see where your losing compression to see if it's going out the exhaust intake or crankcase Maybe you got a piece of that piston or carbon stuck in a front valve | ||
| 2003xb9r |
I had a lifter stick on an S1W once. No warning, just wouldn't fire up right the next day. It put a very slight bend in the pushrod & valve stem resulting in valve not closing properly. For sure do the leak down test & be prepared to lift the front head & cylinder. | ||
| Cupcake_mike |
xb9r how did you determine it was the lifter? | ||
| 2003xb9r |
Mike, I removed the lifter to check it thoroughly after finding the bent valve & pushrod. It was 8 years ago since I replaced it, been perfect since. Your problem may not be the same, just putting it out there as a possibility if something is bent. Have you done the leak down test yet? | ||
| Brentx1 |
I had the same thing happen when I installed the 1250 kit on my X1 long ago. The stock pushrods were too long due to machining of the heads. Bent two valves and cracked 2 valve guides. Ran for about 90 miles, then imploded. Adjustable pushrods fixed the problem. | ||
| Lakes |
Cupcake mike, did you use same ignition, same carb same jetting that motor had before you went to 1250 kit? | ||
| Cupcake_mike |
lakes, yes | ||
| Cupcake_mike |
Finally found some time to tear into it some more and I am even more unsure what is going on than before. I have no leakage past the intake or exhaust valves or into the crankcase. Even pulled that front rocker box to inspect pushrods, they are not bent. Put everything back together and now I have 80psi on the front cylinder and 30psi On the rear (which I didn't touch). I think my gauge might be screwed up? If i put my finger over the sparkplug holes each cylinder feels about equal. Cranked it 8 times, with it choked and worked the throttle, at about 30-45 seconds each time, couldn't get it to light off. Pulled the air cleaner and could see and smell the gas going in the engine-but I pull the plugs and they aren't even wet. I am probably gonna set this m-fer on fire. | ||
| 2003xb9r |
Don't burn it!! (yet!) Are you checking the compression with wide open throttle? You won't get an accurate reading unless you do. Then try it again with a couple of squirts of oil down the spark plug holes. If this raises your compression results dramatically then compression is most likely escaping past the rings. If the compression stays much the same, then it is getting past the valves, head gasket. |
