wjstarck wrote:
The saga continues....
Tried a replacement carb. Same result. Idles nicely and revs well but bogs down when riding and will never go any faster than 20-25. I tried the good slide from the new carb in the old one, and then swapped carbs. No joy.
I took the muffler off and there was no gasket. Only one spring present. There is a metal ring (see pics) on the exhaust port of the cylinder head that is 2/3rds circumerence. Not sure if this is correct.
The gasket had a tear in it but this may have happened when I took the head off.
I noticed there was a lot of gooey oil where I've indicated in the picture.
How does the piston and rings look?
Next step?
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Well based on what I see there:
1) The black goo I see in the red circle you made in the pic is coming from the exhaust. It is going past that broken ring on the exhaust manifold.
2) No way to tell if your rings are worn out based on just a picture. You have to remove them from the piston and put them into the cylinder and measure the end gap. Are they over spec according to manual ?? Also are they free in the groove or are they locked up right now ??
3) Your base gasket is not showing any signs it was by passing any of that black goo. That rip was probably caused when you removed the cylinder. Your base gasket is paper -- I don't like that. I think it should be metal. You will have to replace it anyway.
4) Your piston has a scar on it. Buff it off and re-use it.
5) Your cylinder has a scar on it. Hard to tell how deep it is based on a picture but I would just give it a light hone and I think your good.
6) Did you pressure test this
Engine before you tore it apart ?? That's important actually, because it would tell you if the crank seals are still good or if you had a leak somewhere else. I actually doubt you had an air leak right now because your piston does look good to me, but if the rings are locked in the piston grooves I would reconsider this theory.
7) That looks like an excessive amount of black poo in that red circle you made. It looks like it is drowning in oil and that would kill your power too. What oil mix ratio are you using ??
Edit: 8) While you have it apart check the big rod end clearance with a set of feeler gauges. Check the manual for max spec allowance. (It will probably be around .020 right now). Engine looks clean inside.
The down on power thing is probably worn out rings or a slipping belt or shivs not working (did you do the felt pen thing I recommended ?? )