Scored cylinder

[CaptainLunatik]

So I have a slightly scored cylinder it's really not that bad at all I actually thought it would be fine without any modification however seems my compression is suffering due to the scoring. Question is can I simply sand the inside of the cylinder smooth to fix issue?

 

[The_Aleman]

Most 2-stroke kit cylinders have a flimsy chrome coating, so no, you cannot simply sand the score out. All you'll do is make compression worse and the cylinder will wear much faster. You pretty much need a new cylinder jug.

Even if you had an iron/steel sleeved jug, simply sanding the score out wouldn't be advisable. It needs to be honed for precision.

 

[inspectorcritic]

So I have a slightly scored cylinder it's really not that bad at all I actually thought it would be fine without any modification however seems my compression is suffering due to the scoring. Question is can I simply sand the inside of the cylinder smooth to fix issue?

Go on line buy a new jug some sell them with new piston rings bushing and spindles for under $20.00 and your probably going to need them new rings they might have been sanded down too!

 

[CrazyDan]

Unless you are prepared to electroplate your cylinder (if you do, remove all chrome lining and nikasil plate it) then it is far cheaper to just buy a new jug. I wish I had junk cylinders to try electroplating myself, but alas, I have an iron sleeved 4 stroke... never had compression issues with it...

 

[CrazyDan]

Get a new jug and give electroplating a try, if you are adventurous. You will need to use the part you are plating as the cathode, and the metal you want to coat it with as the anode (almost like you are making a homemade battery). You will need to submerge them in an electrolyte, and pump dc+ into the anode (the metal you want to coat the cathode) and close the circuit with the cathode being the negative end. Leave it sitting in solution till it's built up past what you need, then bore and hone it to the required size. The electric current will strip atoms off the anode and transfer them to the cathode.
This is the exact same process that kills an old lead acid battery, if you open it up, you'll see the anode is almost gone and the cathode is covered in it's remnants.

 

[Frogslayer]

Do a God damned compression test already Jesus.

 

[LewieBike]

If you know anything about how engines work and you have a 'feel' for checking for spark, fuel and compression, you generally will have a good idea what is wrong.

By kick pedaling the bike on a center stand, left crank arm forward and level, you standing on the left side of the bike, place your foot on the pedal with the clutch released. Put some of your weight on the pedal. Does the engine resist your effort or does it easily rotate going "plut plut plut plut."

Low compression should be obvious if it's easily rotating with just a small amount of weight on the pedal. When these engines have good compression the pedal will resist your weight strongly. But even an engine with somewhat weak compression will attempt to run if all the other fuel and spark factors are in good order.

 

[Karl Snarl]

you need to figure out why it scored before doing anything. if it was just a bad ring, or something like tht. replace damaged parts and get back to riding. if it was a fuel/oil problem, figure out why. if you are running one of those sha clones, the atomizer tube is not calibrated correctly for the 66cc engine and has to be replaced or sealed and remachined with two tiny holes and one larger hole over the one small hole and one large hole it comes with. figure out tht scoring before moving on, so it doesn't happen again.

 

[Frogslayer]

Found in another thread you did have a reading of 80 psi. I'd think it would run but maybe not.