I have a mess on my hands?

Take the head off, Slide the cylinder off and start inspecting. You say you already have scratches in the cyl. wall. Well, that sounds shot already. If the cyl. is scratched up then the rings are probably shot also. If the piston doesn't have too many deep scratches in it you might save it. (only maybe,) But if it looks all chewed up too, replace it.
Next, VERY GENTLY, so you can feel it. Take the connecting rod and see if there is ANY up and down play in the bearing. Sometimes it's hard to feel, But ANY play, Even just a little is WAY too much. If so you're looking at a new crank.
If you're sure there's NO PLAY in the lower crank bearing then you might get by with just a top end rebuild. But you also need to check the play in the piston, wrist pin, rod connection. Sometimes you can just replace the wrist pin and bearing, but if theres a lot of play in that then you're looking at a new crank again. If you have ANY play in the bottom end or some play in the wrist pin you are looking at replacing the crank. If so, It's just a couple more bucks for a new "ENGINE ONLY" and a LOT less trouble. I know, I've rebuilt more than my share of them. You'll spend more money on parts and shipping then you would for a new motor. Check out ebay for the best price. Motovelo is over priced, BGF is cheap but thats what you get, A cheap engine. I've used his engines and had no problems. Others hate his guts. To each his own I guess. EVERYBODY has an opinion on who has the BEST motors, I just buy what I can afford.
However it turns out for you I wish you the best of luck.
fatdaddy.

Couple things. When you said that it started to bog down when you release the throttle, I'm just wonderring if you realize that you're supposed to pull the clutch in when you release the throttle. If you leave the clutch engaged when you release the throttle, you'll get what is called compression braking, where there is too much compression for the low rpms of the engine and the force of that compression can be hard on the engine over time. However, the ht engines usually stall after a minute of being engaged with no throttle. Now when you say you see scratches on the cylinder, it sounds like one or both of the piston rings broke and scored the cylinder. If that is the case, the cylinder is shot. Other signs of piston ring damage are extremely hard starting, as in trying to start it 4 or 5 times and it wont turn over, and then maybe the next time it finally catches. When it finally does catch, it may also seem like it takes a lot longer than usual to warm up completely. Another sign of ring damage is excessive amounts of oil dripping from the exhaust after a few attempts to get it started. As far as seeing a gap where the head gasket is, tightening the head bolts should seal the head gasket properly. If your rings are damaged, this wont make any difference, but it will on the next engine. Tighten the head bolts each a little at a time in an x pattern, until they are evenly tightened. Use a torque wrench for this. I cant tell you the proper torque specs because I never used a torque wrench to do it, but its a good idea. Now as far as what to do about your current engine, I wouuld recommend getting a replacement engine on ebay. I believe you can still get them for $90 or less. You could get a top-end rebuild kit, but if there is any other damage to the engine besides the piston rings, a top end might be a waste of money. I wasted over $100 on two top end rebuild kits once for the same engine, not knowing at the time that my crank bearings were also shot and both times the piston seized as soon as I tried to start it. If you want to try a top end rebuild kit, you can. But if it doesnt work, I'd just get a new engine before wasting any more money trying to fix this one.

Dont take apart your clutch, its hard to adjust for a first timer
Just pull the head and check out how your cylinder and walls look like.
Also check your plug color, if its white its running lean. if its a nice choco brown your good. if its black and oily your running rich

Either lean or rich can cause you to bog down.

Are you running an inline filter? crap from the tank can clog a good carb

ocho ninja said:

Are you running an inline filter? crap from the tank can clog a good carb

Click to expand...

This is excellent advise / suggestion. My bike recently started bogging on hills and just crapping out a lot, i looked at everything but could not find the problem. I drained the tank and pulled the petcock and low-and-behold it was filled with china crap. The flow coming out of it was about 1/4 of what it should have been. problem solved.

the obvious sign was the oil coming out of the head gasket.

that would be a head gasket leak and would rob you of your power.

if the leak is big, it shouldn't run at all.

a very small leak can seal up as the engine warms up, at least enough to keep running.

it also creates a hot spot that can damage the piston, rings, and cylinder.

some small scratches can be "normal," meaning the chrome on the cylinder walls is wearing off, and usually the engine will keep running more or less normal. i've had many engines lose a lot of chrome and keep running fine.

any deep scratches you can feel with your fingernail will rob you of compression, as the combustion charge sneaks passed the rings, and will need parts replaced.

after you pull the head and jug, you'll know for sure. if it is gouged up bad, you need to find the source. replacing the top end won't do any good if there's chunks of metal in the case, or a bad bearing...

Check your carb, if you can move it you may have an intake leak but certainly check the head gasket, torque is supposed to be 15# but I usually torque to 20#.

If the head is leaking oil try a new head gasket and piston rings, make certain the head is torqued down enough to seal. If you decide to get a new engine and can't find someone to sell one to CA residents, try thatsdax.com (reasonable prices, good engines) and he sells top and bottom ends for only $60 each, also, rosa on ebay sells cheap china girls to CA residents. Motovelo is way overpriced.