New here! 50cc build

[Atvrunner2]

Hey all!! Just wanted to introduce myself and my new build.

I bought the cheapest ebay hit at the time which was a 50cc for $88 shipped. I am NOT NEW to 2-Strokes. I have been building pocket bikes and GoPeds for a long time.

It seems like everybody goes for the 66/80 CC Motors, I've been trying to read through a bunch of threads with not much luck.

With that said this 50cc has as far as I know on these engines and upgraded cylinder. I also opened up the gaskets to match as well as the intake a little bit and the exhaust and exhaust port.

I just want to do a little bit of work to it and I will be doing some endurance running, and I know these engines don't like wide open throttle for long times. We'll see how it goes. Here's some pics.

I have a mountain bike I bought for $40, the whole goal of this project was a $150 budget or less. Minus safety items. What's to do this what is a competition with a buddy but he's not going to be able to compete.

I actually spent $138 including bear coil and CDI and tensioner, which the kit actually came with a 4 bolt tensioner. I have spare chain links and spark plug. I'll be slapping the motor back together here soon also polishing the exhaust port and piston head.

I am glad to hear about running 32 to 1 because with pocket bikes you can do 40 or 50 to 1. Glad I checked.

Like others on this forum I don't expect a lot of miles on this, I know the quality, I'm all about a little bit of corrective power and we'll see about the rest.

A few pics of the current situation. There is definitely information on here that has been great about certain oiling and greasing certain parts.

 

[Chainlube]

Every kit I've received with the alloy intake has looked like that, chamfer the inside edge of all ports to look like what you've done with exhaust port.

 

[Atvrunner2]

Yeah, thanks. I did some work on the intake post, tried to match the gasket after I matched the gasket to the intake. Couldn't believe the obstruction in the intake, I also had debris in the cylinder and intake.

I always pull apart chinese motors to clean them out, check everything over. One of my pocket bike engines had the Piston backwards. Funny stuff.

I polished the transfer ports and exhaust port. Opened up the actual exhaust intake to try to match the cylinder exhaust port.
I know little improvements go a long way on these tiny chinese 2-strokes.

 

[Chainlube]

The chamfer is the best ring saver. I don't do much porting, but do take off all casting flash. The important part is the squish area, match that to the piston.

 

[Atvrunner2]

Yes, I hear that. Now with these motors, I have been reading the high compression on these can wear them out fast. What is the comfortable squish for these? Assuming 50cc and the 66/80 would be similar. I will eventually get a nice, 66/80.

 

[Street Ryderz]

Yes, I hear that. Now with these motors, I have been reading the high compression on these can wear them out fast. What is the comfortable squish for these? Assuming 50cc and the 66/80 would be similar. I will eventually get a nice, 66/80.

What high compression, these engines are 6:1 stock and maybe 8:1 modified, 50-60% of the bore for squish area to get the proper msv and .7 clearance is standard.

 

[Atvrunner2]

Ha, I never checked. Honestly thought these had more. Probably won't mess with that too much. Just wanted to clean it up make sure everything flowed properly.

 

[Atvrunner2]

I build a lot of pocket bike engines, squish is over 0.060" stock and I have taken them down to 0.035". That mod alone makes great power over stock.
This is my first bicycle engine, hoping to learn a lot. What is stock squish and how far have you guys gone with the squish?

I know these start around 6:1 which I consider low but seems to be just fine. I obviously haven't finished the motor yet. This winter as I have been cleaning up the intake and exhaust ports, I might widen the exhaust port as well.

Now, this is a budget build, $150 with bicycle, I am at $135, just wanted a few free mods to run a few buddies bikes. One will have a 66/80. Eventually I will build a 66/80 just so you know.
Thanks in advance.

 

[DieselTech]

Yeah I've heard that there's guys out there with great results with the 50cc engines, some with 50cc that are faster than there 66cc counterparts.

 

[Street Ryderz]

I build a lot of pocket bike engines, squish is over 0.060" stock and I have taken them down to 0.035". That mod alone makes great power over stock.
This is my first bicycle engine, hoping to learn a lot. What is stock squish and how far have you guys gone with the squish?

I know these start around 6:1 which I consider low but seems to be just fine. I obviously haven't finished the motor yet. This winter as I have been cleaning up the intake and exhaust ports, I might widen the exhaust port as well.

Now, this is a budget build, $150 with bicycle, I am at $135, just wanted a few free mods to run a few buddies bikes. One will have a 66/80. Eventually I will build a 66/80 just so you know.
Thanks in advance.

Stock the squish is kinda non existent, it can be over 1mm and have no band width or matched to the domes radius, .7 of a mm is recommended and some will go as tight as .6 of a mm which really is just bumping the compression if there is no band width to utilize.