Cheaper to rebuild an HT engine or buy new?

[Will'smotobikes19]

My neighbor has an engine from 2016 and it has some miles on it now. There was some obvious blowby on the piston and the crown is pitted. He thought his bearings were bad but they seem ok. He had something like 1,200 on the engine. I will rebuild it for him as a Christmas present but I was just wondering if rebuilding is worth it versus buying a new one. I already have a fresh piston that would work and an unused cylinder although it's black instead of silver. Think i'm going to go with replacing all 4 6202's with Japanese ones all new gaskets as well. The half moon keys took a little beating from my screwdriver so thought I should replace those too. Ideas?

 

[Tyler6357]

Yes, I think it will be cheaper to rebuild it if you just count parts and don't count your labor. A new engine will cost $100-$150

 

[Will'smotobikes19]

What type of bearings would you say are better rubber shield or metal shield?

 

[LewieBike]

You don't want to leave those shields in place on the engine's new bearings. The outer crankcase seals are for that job. You want the bearings to have access to the full flow of fuel/oil mix.

 

[Will'smotobikes19]

Do you mean both seals? I already know about removing the sides inward. Ordered 4 Nachi 6202 nse9's, 4 woodruff keys and a gasket kit.

 

[LewieBike]

That's how all two stroke engines with ball bearing supported cranks mount theirs. Never leave the seals ( even the metal shielded ones..) on those bearings, The thin combination metal/viton shields the bearings are shipped with are for use in dry conditions. The actual engine seals are the separate spring reinforced variety that sit outboard of the ball bearings behind the CDI magnet and pinion gear. You want the fuel and oil to circulate freely from both sides of the bearing, take both sides off, that extra seal on the outside doesn't help in any way and could melt and mess up the engine's bearings.

 

[Will'smotobikes19]

Well the guy I'm rebuilding the Ht for insists that I leave the seals on the bearings. I have tried explaining this to him and in my mind the gas would eventually wash the grease from the bearings and they would get even less lubrication as the bearings expand and contract but the rubber seals would be blocking the oil in the gas. I just try not to argue with him about stuff.

 

[FNTPuck]

You can leave the outer facing shield for the crank and clutch bearings, but have to remove the shield for the inner facing ones to allow them to be oiled.

 

[Will'smotobikes19]

I would like to leave the outer seals on the crank ones since it would be extra protection against leaks since I mean they’re Chinese seals. I don’t know about the bearing seals melting never had or heard about that issue. I kind of want to start building HT engines as they are capable of 50+ mph and a lot lighter than a predator 212cc but can go just as fast and aren’t a foot wide. Easy to rebuild too I think I will try porting and maybe get into the timing stuff as I’ve seen some fast bikes with not too much work done. Right now I’m trying to setup a vm18 for the black engine. I got a 90 jet but think I need a 22.5 pilot jet. The engine has 6mm mount studs though so if anyone could send me a link to a black crankcase with 8mm studs I’d appreciate it.

 

[Spare_Parts]

https://zedamotorsports.com/collections/cases-and-cranks/products/zeda-engine-case-8mm-studs
You have to paint it.