Is the new engine I just bought dead?

[Nahom]

I'm so fuming right now- I checked everything outside the engine and it was all fine spark plug, magneto, carb, spent ages learning how to make one from scratch replaced everything new and now I finally realise (if you've been following the thread- "troubleshooting engine start fail") that the spark plug wasnt wet so not enough fuel was reaching the engine.
So I open up the damn engine- take the top off then slide the fins up and the piston looks like this :

the dents and scratches I am just clueless as to how it happened- it never started properly once and the fuel ratio was perfect the cylinder seemed to be mostly ok but there were still marks near the bottom and I can feel a few ridges.
This kind of stuff was precisely the reason I bought a new engine in the first place.
I have no idea what I did wrong this time but if this engine is unusable this has been such a waste of money and I'm ready to give up if that's the case
Could someone please confirm if the cylinder/piston is damaged?

 

[Steve Best]

Nothing wrong with piston or cylinder.
Ports could use some deburring.
If you don't know what you are doing in there, why are you taking it apart?

Steve

 

[Nahom]

Nothing wrong with piston or cylinder.
Ports could use some deburring.
If you don't know what you are doing in there, why are you taking it apart?

Steve

I had help from another motorhead on this site who suggested when I used no oil in the previous engine that it might be destroyed- so opened up and there were many scratches going down the cylinder which apparently meant it was damaged and should be changed so I used a new engine from a new kit. I just couldn't think of another reason other than that because I tried everything and it still wouldn't start- didn't know what else to do...
The following is a pic of the old cylinder- would you say this one is damaged then? Was I right to change it?

 

[Street Ryderz]

That cylinder will work fine! those lines are quite common in these engines.if when you run your finger nail across them and your nail hesitates and you can feel it,then no not good but if its still smooth they are fine.

 

[Nahom]

That was the old cylinder and I could feel them with my nail- so I decided to forget about that one. I couldn't feel anything with my nail in the new cylinder.
what about the small roughly circular dents in the current piston? I think I could feel those. You agree with steve they are fine?

 

[Street Ryderz]

yes that part of piston doesnt touch the cylinder wall or anything just the rings and the cylinder still shows signs of being brand new with the factory cross hatch still visible.

 

[Street Ryderz]

not a good real cross hatch but thats how they do it!

 

[Nahom]

yes that part of piston doesnt touch the cylinder wall or anything just the rings and the cylinder still shows signs of being brand new with the factory cross hatch still visible.

If the actual metal piston doesn't touch the metal cylinder and only the plastic rings then why is it necessary to add oil? I thought the purpose of oil was to lubricate so that the piston doesn't grind too much witht the cylinder- if it's never in contact what's the point?

 

[butre]

If the actual metal piston doesn't touch the metal cylinder and only the plastic rings then why is it necessary to add oil? I thought the purpose of oil was to lubricate so that the piston doesn't grind too much witht the cylinder- if it's never in contact what's the point?

the rings are iron, not plastic. there is metal on metal friction. plastic rings would never survive in a combustion engine. plus, the bearings need to be lubricated or they'll wear out and grenade on you within a couple of minutes.



if you don't understand why an engine needs oil, then I would suggest not touching anything motorized until you do some reading on the subject.

 

[crassius]

you really need to find someone in your area to help you with these - your new one looks OK, and I'd even give your first one with the small scratches a try to see how it ran (might run fine with only a 2 or 3 mph loss)

these are dead-simple motors, but some amount of the 'aspect of the mechanic' is required