There is a guy on ebay that sells a new cyl/piston for like 180 bucks.
You can compare that to approx 130 for a bore/piston.
Upgrade:: you can shave the head .030 to bump up the compression slightly.

 

Good news - I now have my head back rebored and shiny new piston.

Starts well - but now I have another problem.

Because I messed around with the carb the engine is now racing - so much so that if I start it on the ground without the wheels in the air it goes off at well over running pace (striaght into the side of the barn!).

What would cause the engine to race so fast. I have turned the idle srcrew to both extents in and out - it makes no difference to engine speed / pitch.

Engine is running clean with little / no smoke. Sounds great too.

Have checked throttle cable and all ok.

Even attached throttle cable to carb while carb removed and checked action - seems good.

Why so fast then?

Please help with any suggestions

Dave

 

2 things come to mind.
1) The slide is in the carb incorrect. It may look and act fine but not be so. Align the groove in the slide to the lil notch in the carb.
2) loose the o-ring inbetween the carb and reed cage (air leak)?
Just to make sure:: Arrow on the piston toward exhaust, right?

 

Arrow definately to exhaust.
Checked action of cylinder carefully and definately aligned to groove.

Must be O ring - will check first thin in the morning.

Thanks for your help LT80 - you're a true gent!

 

ok LT80 .... it was an air leek between the carb and the reed box . you are a genius.

Fixed it all up with new trottle cable, new air filter and new brakes on front and runs like a dream .. at least for the first half an hour.

Now it runs fantastic until the battery loses charge and then slowly loses power and eventually dies.

I put the battery on charge and tried again - ran for 2 minutes at full power and then died

It starts from the starter motor ok when battery charged.

I thought it was a combined starter / alternator - if the starter works does that mean the alternator must work?

Could this just be the battery? or is there another electirical bit that has gone!

Dave

 

It's not charging.
The stator has 2 pickups, 1 for charging, 1 for ignition.
Look under the hood, you'll see the wires comming up from the motor. The white/red is the charging side.
There is a small chance that it came unplugged. If not, you can do a ohm test on the charging side. Sorry don't know the correct ohm reading.
OK, read the book. LOL
Disconnect the w/r wire. Set the tester to volts. Run machine at 5000 rpm's. If reading is under 28 volts, it's a bad stator. Test with ohms (not running) should read .63 +/- 20%.
It says to check the rectifier also. Apparently the w/r wire goes to that then it sends charge to the battery. ACK, I can't explain that, it shows a graph of what tabs in the rectifier to check. I'd think if the stator checks out OK, then it would be the stator.
Hope that helps.