Mech

Right.. I forgot about them..

Try turning the heaadlights on and see if it revs better. And check the charging and regulating. That can make them sound like a rev limiter but usually at much lower revs.

Well done. Perseverance always wins, giving up never does. To check the rod bearings you put at the top and move it side to side. That shows up play in the bearing. It will probably move about three mills side to side, but five mills is too much. The manual will probably give specific measurements. Then, to check for wear on the crank pin you rotate the crank a few degrees after top dead center, about fifteen degrees after, and then holding the crank from moving you push down hard on the rod and rock it forwards and aft feeling for any roughness. Then turn the crank again a little to about twenty degrees and check, then turn it to about twenty-five degrees and check it. If there is roughness on the crank pin it will be in that fifteen to about twenty five degree range.. perhaps even up to thirty degrees after top dead. I think I see some black aluminium oxide in the bore which is caused by an over heated/ near seized piston. Turn the piston so we can see both sides of the skirt and show us what they look like.That carbon build up isn't too bad and could be left there. As Gw says, check the ring fit in the grooves. Check all the way around looking for any part where the rings have more clearance that the other way around. The bore looks a bit scratched but that may buff out with a hone or wet and dry paper. If you can get it so you can't feel the scratches with your finger-nail it will be ok if the piston is reusable still. Put a top ring in the bottom of the bore and square it up with the piston then measure the gap. Then put the ring at the top, not right at the very top but just below where the top ring was rubbing to in use, and measure the gap again. The difference between top and bottom measurement, divided by three, will be close to how much wear/taper the bore has. If everything checks out ok I'd probably put it back together with new gaskets, rings and a valve lapping and valve seals..

Ok. It's your money your money. For anyone watching and interested, and for their future reference.. Engines, single cylinder engines, that only have 35Lb compression, don't start. They start getting real hard to start when they get down to about 80Lb. Also, if an inlet valve is leaking, then they don't like idling.. This engine we are discussing both starts and idles. The most likely reason for such a low compression reading is either that the throttle was closed while doing the test, or the gauge is faulty. The one thing that has the most dramatic effect on exhaust temperature is ignition timing being retarded or not getting advance. That will cause it even at low revs or little throttle settings. Lean mixture can cause exhausts to get hotter, but they have to be ridden with the throttle open to do that, and even then you seldom notice the exhaust red hot unless it's night time. A red hot exhaust in daylight is ignition timing..

Yup, replace the head-gasket and a new O ring doesn't need sealer.

#101 Yeah I've noticed that it doesn't seem to get packed in the syringe in USA. Here though, the syringe is the most common way of finding it. And yeah, it seals just fine case to case, with no gasket.

Yeah. You need to use a timing light and check it's idle ignition advance angle, and that the ignition timing advanes as you rev it up. It should probably have about ten degrees of advance of top dead center at idle, and should go up to between twenty-five and thirty degrees of advance at full revs. If it goes up by about ten degrees more advance than what it had at idle, then it should be ok...The flywheel is probably marked with a ignition timing mark, possibly full advance, and possibly idle advance. The manual should probably have specific figures..

They will generally turn easier than pull out. What you need is a modified screwdriver. The plunger metal is soft and if you use a regular screwdriver it will spread the plunger and make it jam. Get a screwdriver that has a tip the thickness of that slot, it will be too wide to go in but you should be able to move the cable to one side, then grind the width of the screwdriver down so it's going to fit down beside the cable, then, carefully grind the flat of the screwdriver so it is concave and the tip is the thickest bit. You need to grind it a long way back so that the tip can go right to the bottom of the slot. Then, because the tip is putting the force on right at the bottom of the slot, you can apply quite a bit of force. Get it turning and turn it till it turns easily, then start pulling up gently while you turn it. The slots will grind the gunge away and it will slowly come up. If it gets tight, push it down and lube it plenty with runny oil to flush the gunge away then keep turning and pulling. I've got plenty out like that. Make sure you've ground the screwdriver enough that it's only touching at the bottom of the slot..

Like the manual says, the ignition timing can't be adjusted, but things can go wrong that will put it out..

Yup, and if you gently tap the aluminium on the side of the plunger it might help the oil creep in.

Try driving it. You can't test the awd on a jack, it needs the back wheels to be turning faster than the front wheels to make the clutch engage. It might be that it needs the opposite process to disengage When it's on a jack, and the first wheel disengages, then there might not be enough torque/rotation between the second wheel's wheel and axle to disengage it.

Yup, with that blueing it will be lack of oil getting to the top end. And it must have been running short of oil for a while. Since the other rocker and the cam bearings don't look as bad I'd suspect that rocker is the last place the oil gets to and so it ran dry. A lot of over head cam engines have a restrictor/restriction in the oil supply to the head to stop it taking all the oil pressure away. The restriction, because it's a small hole, can get blocked. The restrictor is generally down on the crankcase.. A manual or a parts diagram should show it.

#27.. Lol.. Jap stuff uses six mills or eight mills, which are the same a one-quarter and five-sixteenths. The clip will be eight mills I'd be pretty sure.

Yeah I was going to suggest hitting the top of the bolt.. But Gw has covered it well.. And like he says, if you can get it to move, even the smallest amount of rotation, only five degrees even, then tighten it down that five degrees and then try undoing it by five degrees again, keep working that five degrees till if feels a bit freer then try for eight degrees, work that eight degrees.. Keep doing that, a lot of small gains. Even if it takes an hour to get it free before you can start winding it up, it will be better than breaking the bolt off. And when you are winding it out, keep winding it back down again by at least a half turn every full turn or the bolt will cause galling and wreck the threads.. Oh.. and only wind it slowly by hand. Power tools will wind it too fast and can cause galling even on good threads. Impact tools should only be used to loosen bolts, not wind them off.

It's always best to fit the piston to the rod first, then center the rings on the piston, then lower the cylinder down onto the piston. As long as you hold the piston square to the cylinder the rings will compress and go in with just a bump of the hand on top of the cylinder. One way to make sure the piston is square on to the cylinder is to put two bars across the crankcase under the cylinder and sit the piston down on them. The bars aren't generally required for a single cylinder but they help a lot on twin cylinder engines. For gasket sealer I highly recommend loctite master sealer 518. It doesn't start to harden till you actually clamp the two surfaces together. That means that if you have a hold up, or want to stop for a few hours, it will sit there waiting for you to bolt things up.If you buy a small syringe of it. it will last for years on the shelf, and it's extremely economical and clean to apply and wipe off. Most sealers, once you open the tube it starts going hard in the tube and so you need new a tube if/every time you need bit more a few months later. If you do a search in here for loctite you will see me enthusing about it at length.. I never use anything else. A possible reason for the engine leaning over might be that it's rubber mounted and the rubber bushes are worn.. That would be unusual but..