Why only CG builds?

[JerboaJohn]

I think ppl are boggled by rebuilding them with real bearings. my 48cc runs like new after 850 miles. but then it's entire life has been under 5200rpm.
I'll probly do crank and clutch bearings before i run my next 2 CG's w/ my 42.5mm jug and this 45mm (60cc) I'm thinking of getting.
oh and stainless fasteners. anyone can do that at least for like $15.
yall built your bike, so you gotta have Some mechanic skills haha. you don't have to be a rocket scientist to fix em up,,

 

[Steve Best]

I think ppl are boggled by rebuilding them with real bearings. my 48cc runs like new after 850 miles. but then it's entire life has been under 5200rpm.
I'll probly do crank and clutch bearings before i run my next 2 CG's w/ my 42.5mm jug and this 45mm (60cc) I'm thinking of getting.
oh and stainless fasteners. anyone can do that at least for like $15.
yall built your bike, so you gotta have Some mechanic skills haha. you don't have to be a rocket scientist to fix em up,,

A lot of truth in what you say JerboaJohn, but I don't think you NEED to go so far on modifications. I ran the stock Grubee Skyhawk for many, many miles without problem just following the manufacturer's recommendations and doing routine maintenance. After a break-in period I did start a program of trying to get more speed out of the engine and eventually ran in to problems at 10,000 rpm after several 1000 kms on the stock bearings. It wasn't the stock bearings that failed, it was the circlip on the piston pin! That engine is still running on the same crank and clutch bearings.

So, what do these China Girls need for daily reliability?

• Respect the design parameters, 25mph bicycle assist
• Put the engine together as designed, respecting mechanical principles, ie: clean, torque, aligned
• Good quality 2 stroke oil in sufficient ratio (32:1 or more)
• Clean and grease the main gear and chain every tank of fuel
• Daily inspections before and after riding; bolt torque, alignment, operation, cleaning, spark plug
• Immediate attention to defects; loose bolts, worn tensioner bearing, chain wear, spark plug

That is pretty much it. I rode 50 kms a day to work on this sort of maintenance on the stock engine, clutch, chain and tensioner.

I see people on here who do not understand basic mechanical principles, yet are trying to modify their bike and engine. FIRST understand what the designer was trying to do. There are many areas on these engines that can use improvement (at cost!) but trust me gentlemen, these engines will run for thousands of miles if you know your stuff!

 

[Spare_Parts]

Steve's last paragraph is what I have been telling the OP only not in a very nice way lol.

These engines are simple and the forum has all the information needed to keep one running for many miles, even a performance build.

 

[JerboaJohn]

yeah,, best bang for the buck.
I'm just trying to build up to a warm 1hp per 10cc on the cheap

 

[mark20]

mine had around 1800 miles on it before i took it off (still runs perfect, might use if for another build). only thing i did was grease the clutch gears. and ran it on 32:1
break-in is the most important part inho.
and if accept the engine for what it is, it will last you!

 

[Steve Best]

yeah,, best bang for the buck.
I'm just trying to build up to a warm 1hp per 10cc on the cheap

The formula for making power is simple. PLAN = Pressure*Length of stroke*Area of the piston*Number of pulses per minute
Increase any of these and you increase power. Ahhh, how you do it, that is the challenge.

 

[LewieBike]

I made a post-mod comparison video that shows an old good clutch, a new defective one, and a fresh rebuilt/upgraded bearing one side by side but never did a step by step. Once you get it apart its all self-explanatory though. Clean the race/backing plate, if its a blown clutch you may need to gently sand out any bumps and grooves,

lightly grease the race to hold the BBs in place, then use tweezers or clean hands to place the bearings back on the race 1 at a time, keeping it all as clean as possible.



Putting it back together isn't hard, just hold the bottom part in the vice and use a pipe of the same diameter as the outer ring on the race and tap it in with a small hammer. If you don't have an identical sized pipe, in a pinch you can use just a flat square bracket like from the U-Bolt mount to tap it in an "+" pattern (first tap it spread across top/bottom, then across left/right). You need something that will only push on the race on the left side in this pic - the race sits inside the bevel gear then gets pressed on the backing plate. You can also see the damage on the backing plate from the bearings that turned themselves to paste within 50 miles.
View attachment 86627

This is the back of a bevel gear with fresh bearings in it. They don't actually touch the backing plate, but that plate still needs to be sanded and cleaned to not get junk inside the nice clean new bearings. The race and backing plate stay connected while the bevel gear rotates around it.
View attachment 86628

Doesn't describe how you removed that race that hold the bearings in place or did I miss that part.

 

[LewieBike]

Steve's last paragraph is what I have been telling the OP only not in a very nice way lol.

These engines are simple and the forum has all the information needed to keep one running for many miles, even a performance build.

Honda already beat you to that with their 4.5 hp pushrod 50 cc engine when they introduced the C-100 Supercub in 1958.

Frankly, I'll be happy with a couple h.p. if it holds together for a few thousand miles.

 

[FNTPuck]

Guys, guys, guys... I don't know what you are talking about. Admittedly I have been running 2 strokes for many decades. I used to curse 2 strokes until I learned what they needed. Yes, the China Girl is cheaply made, even the bearings in it, but isn't pricepoint what the customer is asking for?

But if it self destructs in 100 miles? Hey, I've taken 100 mile daily rides on mine, what's up with yours?

These motors are perfectly designed for what they are supposed to do: 25mph universal bicycle assist at the lowest cost.
This is why they sell so well.

Years ago I was into 4X4 off-roading. Most of us bought an old truck or SUV and put $$$ in to rebuild it. I had a buddy buy a brand new Lada Niva. It was cheaper new than our old 4x4 trucks used. He brought it home, ignored the warrantee, and completely dismantled it. New SKF bearings and seals, Painted and undercoated the inner fenders, and many other fine touches let this Niva run trouble free for many years. Doing this to a China girl could not hurt.

Please re-read the post.

The 100 mile self destructing was just on the defective batch of clutches from Zeda China that came in CDH and ZedaMotorsports kits ordered from ~October through December of last year. I had 5 of them and all 5 ate the bearings between 10 and 100 miles. I rebuilt them and haven't had a single failure on any of them, and one I pulled to test after 600 miles.

The information was straight from Zehe Chen, the Owner and CEO of Zeda China where the majority of kits come from who admitted about the defect.

 

[FNTPuck]

Doesn't describe how you removed that race that hold the bearings in place or did I miss that part.

Place it resting in a vice with the spacing adjusted to just hold the bevel gear above it, then tap it out with a socket that fits in the center. Comes out in three pieces - the bevel gear, back plate, and bearing race.