2004 RM-Z250 Starting Trouble

Old Yesterday, 07:14 PM #1 (permalink)
tigmaster
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2004 RM-Z250 Trouble
Well, I don't take my bike to the shop and I hate to even ask advice, but I can't get my bike started. Heres the breakdown. Bike started and ran perfectly, last time I rode it it started on the first kick. We rode at the track for a few hours. The next day, I washed my bike with a hose. No water got into anything. Filter was dry and cleaned and re-oiled. Pipe also has a plug in it when I wash my bike. So then I proceeded to start my bike up like I always do, NOTHING. It would not fire, however 45 minutes of work later it randomly started with no trouble. I warmed it up for a sec with choke and took the choke off too soon and it died. I was able to start it right back up with no trouble. I let it run the rest of the gas out of the carb and it shut off. I never keep gas in the carb. So I put it away and a week later tried to start it to no avail. Another week and I spent 4 hours trying to get it started. During that time I tried to kick it and pop start it behind my friends quad. It did not start, but I got plenty of backfires and it would idle for about half a second. Thats all. These two things happened multiple times. So it was time to get into things. Started out with spark. New plug, checked stator and excitor coil voltage, checked coil resistance and checked the spark. Then I began checking sensors. TPS was perfect, neutral switch good, crankshaft good, kill switch good. All electrical circuits checked out. So electrical system appears to be good unless the CDI unit is blown out. Carb is next. After kicking for a bit I drained the bowl, let it fill back up and checked again to assure gas was there. That rules out float height and float needle. After that I kicked it over again and pulled the plug to check for gas, which it had. So now I know nothing is wrong with gas and spark, last is compression. Pulled the valve cover and check valve spacing. A little off, but not out of spec, but I made spacing perfect. Still wouldn't start. Next on my list was valves. Pulled them out and poored gas into the ports and saw some seepage around the seat. My buddie and I then lapped the valves twice. Good results from that. One valve still showed a little trouble but everything was good. Still no luck, so next was piston. Bore was perfect, no cracks in the piston, ring gap was good, and ring thickness was good. Well bike still wouldn't start and we couldn't figure out why. Took another compression reading yet something was funny because all we got was 25psi. No good, yeah I know. So I knew something was up with the compression reading because my bike had gone from starting on the first or second kick to nothing at all. How? Well there was nothing wrong with the cylinder and the last thing we had thought about was the decompression valve. We checked that and it looked strange so we pulled it out and tried to start the bike. Well, first of all couldn't kick the bike over because of ridiculous compression, we then knew compression was good. So since we couldn't kick start the bike we went to pop start it. Still wouldn't start. So we put that back in, so ignore what I said about the compression reading because with the decompression valve, readings don't work right. So learning that everything was fine with compression is really annoying because it doesn't leave many problems. Also the head gasket was good. So, I have GAS, COMPRESSION, AND SPARK. What more is there. Well last of all that we had to question was timming. Not that we din't do it right. We put the cam chain on right and eveything, but one little thing caught my friends attention. When putting on the cam chain, he turned the engine over until the second mark was there. When putting the exhaust cam in, to get the chain on the alignment mark didn't line up perfectly. I know I can't exactly explain it, but my friend had to move the crankshaft a tiny bit. I know it just sounds like we put it on wrong, but it was in the right spot, the stuff just didn't line up. So we turned our attention to the the flywheel and and the cam sprocket. We thought that maybe the cam sprocket may have been tweeked slightly, but I don't think so. So I turned my attention the the flywheel. I wondered if the keyway may have sheared. I tried to pull the flywheel with my home made puller, but after using excessive force I couldn't get it, which makes me question the keyway shearing. I am going to get a puller on Tuesday or I'll make a better one tommorow. If the flywheel keyway would have sheared then timming may be off slightly, explaining the impossible to start and backfiring. If this isn't it then I don't have anymore ideas. I can't even take it to the local shops, because while talking to their mechanics about this, they told me I knew more than them. Hmmm... I guess I'm glad I don't take my bike to anyone. Any way so I looking for any help I can get. My bike ran perfectly at the track and the next day I couldn't start it. I hate to ask for help, but I really good use all your help. Sorry for the length I've been working for three days straight and have done a lot.