PA090119.JPG;bike won't start|||PA090120.JPG;|||PA090121.JPG;hmm, where is that oil drain plug|||PA090122.JPG;its on the side, you don't actually need to remove the skid plate|||PA090123.JPG;|||PA090125.JPG;|||PA090126.JPG;|||PA090127.JPG;|||PA090128.JPG;|||PA090129.JPG;|||PA090130.JPG;|||PA090131.JPG;|||PA090132.JPG;|||PA090133.JPG;|||PA090135.JPG;|||PA090136.JPG;|||PA090138.JPG;|||PA090139.JPG;crusty old carb, the original Mikuni VM20SS|||PA090140.JPG;|||PA090141.JPG;what a strange choke|||PA090142.JPG;|||PA090145.JPG;|||PA090146.JPG;|||PA090147.JPG;|||PA090150.JPG;|||PA090151.JPG;this thing is actually pretty heavy|||PA090152.JPG;float was adjusted way too high, it was certainly overflowing fuel slowly|||PA090153.JPG;|||PA090154.JPG;|||PA090156.JPG;|||PA090157.JPG;|||PA090158.JPG;first cleaning|||PA090160.JPG;float level set properly|||PA090161.JPG;|||PA090162.JPG;|||PA090164.JPG;Reinstalled the carb and the bike still wouldn't start. Proceeded with top end rebuild|||PA090165.JPG;|||PA090166.JPG;|||PA090167.JPG;|||PA090168.JPG;|||PA090169.JPG;|||PA090172.JPG;|||PA090174.JPG;|||PA090175.JPG;|||PA090176.JPG;|||PA090177.JPG;|||PA090178.JPG;|||PA090179.JPG;|||PA090180.JPG;|||PA090181.JPG;|||PA090183.JPG;getting the head bolts out requires removing all but one engine mounting bolts|||PA090184.JPG;|||PA090185.JPG;|||PA090189.JPG;|||PA090190.JPG;|||PA090191.JPG;|||PA090192.JPG;|||PA090193.JPG;|||PA090195.JPG;|||PA090197.JPG;|||PA090198.JPG;|||PA090200.JPG;|||PA090201.JPG;lots of carbon on head|||PA090202.JPG;|||PA090204.JPG;|||PA090205.JPG;|||PA090206.JPG;original cylinder looks pretty good. I will hold on to this cylinder|||PA090207.JPG;|||PA090208.JPG;|||PA090209.JPG;|||PA090210.JPG;|||PA090211.JPG;|||PA090212.JPG;new cheapo cylinder on the left|||PA090213.JPG;|||PA090214.JPG;|||PA090215.JPG;|||PA090216.JPG;|||PA090217.JPG;|||PA090218.JPG;|||PA090219.JPG;|||PA090220.JPG;|||PA090221.JPG;|||PA090222.JPG;|||PA090223.JPG;|||PA090224.JPG;|||PA090225.JPG;|||PA090226.JPG;|||PA090227.JPG;|||PA090228.JPG;gasoline does slowly leak past valves. Would likely be drained in about 90 minutes|||PA090229.JPG;|||PA090231.JPG;|||PA090232.JPG;|||PA090233.JPG;|||PA090234.JPG;|||PA090236.JPG;|||PA090237.JPG;|||PA090238.JPG;|||PA090239.JPG;|||PA090240.JPG;|||PA090241.JPG;|||PA090242.JPG;Removed carbon from head. |||PA090243.JPG;|||PA090244.JPG;|||PA090245.JPG;|||PA090246.JPG;removing rocker arm requires slide hammering out a bushing|||PA090247.JPG;|||PA100249.JPG;The pilot jet that I believe was still clogged after the first cleaning|||PA100250.JPG;still clogged in this photo, though even once clear the hole is microscopic|||PA100252.JPG;new slide hammer required to get rocker arms out|||PA100253.JPG;|||PA100254.JPG;the camshaft is so cute|||PA100255.JPG;|||PA100256.JPG;|||PA100257.JPG;|||PA100258.JPG;|||PA100259.JPG;|||PA100260.JPG;|||PA100261.JPG;|||PA100263.JPG;|||PA100264.JPG;|||PA100265.JPG;|||PA100266.JPG;exhaust valve looks very dirty|||PA100267.JPG;|||PA100268.JPG;|||PA100270.JPG;original valve seal|||PA100271.JPG;|||PA100272.JPG;|||PA100273.JPG;|||PA100274.JPG;|||PA100275.JPG;valves cleaned up, ready for lapping|||PA100277.JPG;|||PA100278.JPG;lightly lapped valves, intake looks great, exhaust is better but not great|||PA100279.JPG;after lapping the exhaust valve still has some pitting|||PA100280.JPG;removed original valve stem seals|||PA100281.JPG;installed new genuine yamaha valve stem seals|||PA100282.JPG;|||PA100283.JPG;|||PA100285.JPG;|||PA100286.JPG;|||PA100287.JPG;|||PA100288.JPG;|||PA100289.JPG;|||PA100291.JPG;|||PA100293.JPG;|||PA100294.JPG;|||PA100295.JPG;|||PA100296.JPG;|||PA100297.JPG;|||PA100298.JPG;|||PA100299.JPG;|||PA100301.JPG;|||PA100302.JPG;|||PA100303.JPG;|||PA100304.JPG;|||PA100305.JPG;|||PA100306.JPG;|||PA100308.JPG;|||AlbumDescription;<p>We bought the bike in Wyoming and immediately took it out for some light off-roading. I was dissapointed to see that it was burning oil and stuttered at high RPM. Burning oil has to be rings or valve stem seals so I bought the parts to replace both. I didn't plan on doing that job right away.</p>
<p>Unfortunately for me, right before our next off-road outing I couldn't get the bike the start. It had spark so the problem was either compression or fuel. I pulled off the carb and cleaned it but the bike still wouldn't start. My compression tester doesn't have a threaded end small enough for this bike so I couldn't measure compression. I decided to tear down the top end and install those new parts.</p>
<p>I installed a cheapo cylinder and piston kit. It came with a new cylinder, piston, rings, head gasket, base gasket, cam chain tensioner gasket, wrist pin, and valve stem seals. I nstalled all that stuff except the valve stem seals. Those I chucked in the garbage and used genuine yamaha seals.</p>
<p>The combustion chamber had a lot of carbon built up. I cleaned up the valves, intake manifold, and exhaust manifolds. The original cylinder actually looked pretty good so I flipped the head upside down, filled the chamber with gas, and waited to see if it leaked past the closed valves. It did leak past, though not too quickly. I didn't have time to get new valves and seats, so I opted to lightly lap the valves and seats. Too may be lapping suction tool was too big for valves this small. Bummer. So I did all the lapping by twisting the valve at the stem by hand. That was tedious and couldn't put much pressure on it. I think the intake valve and seat look great. The exhaust valve seat still looks a little rough.</p>
<p>The head on this bike is annoying. You need a slide hammer to get out the pins that hold the rocker arms in place. While waiting for my new slide hammer to arrive, I was doing more research on this bike. The carb is not well liked and it seems that the pilot juet can get clogged in just 2 weeks of not running. Even though I had already cleaned the carb in my ultrasonic cleaner, I cleaned it again. This time I actually removed the pilot jet which did appear to be blocked. It is hard to say for sure because that jet hole is the smallest I have ever seen. Ultimately I think the fix for the bike not starting was cleaning the carb and pilot jet a second time.</p>
<p>I put everythign back together, changed the oil, adjsuted the valve clearance, and gave it a kick. A few kicks later it was running, just in time for our trip the next day.</p>
<p>I am happy to report that the bike is running well. It might still be burning a tiny bit of oil, but nothing like before. You really have to look for the smoke. The bike still breaks up a higher RPM. It feels like it should keep pulling but it sputters. I think the carb is at fault. But for typical RPMs, it is running strong.</p>
<p>I also installed a tachometer and hour gauge so I start keeping more detailed maintenance schedules.</p>|||