Chinese Engines Are Worthless

[MikeJ]

Worthless? Nonsense! They are good for something.

Tore my engine apart today (a second purchase), down to the last single piece I can pull out. The engine is a Nantong (NT) 80/66 cc. Manufactured in April 2009. $119 kit. I thought "cheap". Both top and bottom of connecting rod are needle / roller bearings.

Why tear it apart? I snapped two (2) head studs from over-torquing the puny 6 mm studs to 12 ft-lbs. I should have stopped at 9 ft-lbs. Today, one darn hole stripped clean out. Made engine totally useless. Tomorrow, I drill out and tap to accept real studs... 1/4 inch (or larger) Grade 8 fine thread bolts. This is an experimental engine; I plan on experimenting!

My first engine started just fine and is putting along just fine. Don't have enough miles on it to have real problems.

What I learn from this engine will be applied to my next project: Assembling from parts and pieces a Chevy V6 for oval track competition.

Inexpensive or top quality? Almost never can you have both.

 

[Pablo]

Good post MikeJ! See if you can go 8mm. (larger than 1/4)

 

[Dan]

Worthless? Nonsense! They are good for something.

Tore my engine apart today (a second purchase), down to the last single piece I can pull out. The engine is a Nantong (NT) 80/66 cc. Manufactured in April 2009. $119 kit. I thought "cheap". Both top and bottom of connecting rod are needle / roller bearings.

Why tear it apart? I snapped two (2) head studs from over-torquing the puny 6 mm studs to 12 ft-lbs. I should have stopped at 9 ft-lbs. Today, one darn hole stripped clean out. Made engine totally useless. Tomorrow, I drill out and tap to accept real studs... 1/4 inch (or larger) Grade 8 fine thread bolts. This is an experimental engine; I plan on experimenting!

My first engine started just fine and is putting along just fine. Don't have enough miles on it to have real problems.

What I learn from this engine will be applied to my next project: Assembling from parts and pieces a Chevy V6 for oval track competition.

Inexpensive or top quality? Almost never can you have both.

Awesome Mike and well said. Is true. "fast, good or cheap. choose 2 of the options"

 

[Bryan Smith]

I snapped two (2) head studs from over-torquing the puny 6 mm studs to 12 ft-lbs. I should have stopped at 9 ft-lbs. Today, one darn hole stripped clean out. Made engine totally useless.

Mike, you could put some JB Weld in that hole and re-tap it if 1/4" studs don't work.

 

[matt167]

Idk about worthless.. cheaply made, it's obvious, but with all the successful engines running, it's obvious there not worthless in general

 

[the willi]

Worthless? Nonsense! They are good for something.

Tore my engine apart today (a second purchase), down to the last single piece I can pull out. The engine is a Nantong (NT) 80/66 cc. Manufactured in April 2009. $119 kit. I thought "cheap". Both top and bottom of connecting rod are needle / roller bearings.

Why tear it apart? I snapped two (2) head studs from over-torquing the puny 6 mm studs to 12 ft-lbs. I should have stopped at 9 ft-lbs. Today, one darn hole stripped clean out. Made engine totally useless. Tomorrow, I drill out and tap to accept real studs... 1/4 inch (or larger) Grade 8 fine thread bolts. This is an experimental engine; I plan on experimenting!

My first engine started just fine and is putting along just fine. Don't have enough miles on it to have real problems.

What I learn from this engine will be applied to my next project: Assembling from parts and pieces a Chevy V6 for oval track competition.

Inexpensive or top quality? Almost never can you have both.

you can gbweld and put some stock bolts back in it try it let me know it should work!

 

[Junster]

I don't know if fine threads with more per inch or coarse threads with a deeper cut would hold better in the soft aluminum. My motor has 8mm x 1.25 (coarse metric) they are holding well. Both the motors I have bought were shipped outta china so fast the plastic wrapping left marks in the uncured paint. That production rate is going to pump out some lemons. As far as the a nuke war? I hope the first one lands on my house. I'd just as soon not live in/thru an aftermath. I have just over 1000 miles on my bike now. I had to charge the battery in my 4wd the last time I drove it cause it had been so long since I even started it. I'm having a great time on my bike, really am sorry your not WW.

 

[geoffmaree]

Welcome to the world ...its just a learning curve.
We do..We learn...And gain more knowledge from our mistakes.
As with this site it will help dramatically & increase our knowledge.

 

[MikeJ]

Good advice from recent readers.

Here is some more of my findings. JB Weld is good for compression loads; for filling in gaps like between an engine mount and the bike frame tube. It works great there. It is very poor for tension loads. It does not hold together like real metal when being pulled apart. After all, JB Weld is a plastic compound, not metal, regardless of what its name implies. As for as a stripped thread fix - One entry I read on this site or its sister site said that JB Weld did not hold for more than a few minutes for a head stud fix attempt. Maybe it got soft with heat.

8 mm head studs... I am sure 8 mm studs are a suitable replacement for stripped 6 mm holes. The real reason why I am going with Grade 8 5/16 -24 bolts is because they are locally available in multiple hardware stores. The drill and tap are available off-the-shelf. NF (National Fine) theaded bolts are usually called out by design engineers for high vibration environments (like these engines). NF threads tend to stay tighter longer. I also read that applying a little engine oil to the threads and bolt heads help them stay in place. I never knew that; I have to try it.

My next thought... Somehow balancing the rotating crankshaft to lower vibration. I got that concept from a gentleman who has already been able to lower vibrations, but is not currently pursuing that endeavor. I may try it, simply because I have an engine already in little pieces.

Thanks for your time,
MikeJ

 

[motorbiker]

I have done real well with the 48cc engines. The new ones look way updated. Steel sleeves.

I am going to try one of these next. Anyone tried one of these ?

49CC motorized BICYCLE ENGINE KITslant steel motor bike - eBay (item 150356325607 end time Jul-31-09 23:50:06 PDT)

 

[Cabinfever1977]

looks like a good deal.

 

[Stickshifta]

I am curently haveing alot of the same problems, but i have not givein up yet, The next thing i want to do is pull the crank and try to balance it. does anyone know a good way of getting the crank out? i have the case split but the crank will not come free of either side. Should i try taping with a hammer? am i missing a retaining clip hidden on the crank? sorry i do not mean to jack your thread.

 

[MikeJ]

Stickshifta -

Here is how I got my case open (other peoples' techniques may vary). The manufacturer put the crankshaft ball bearings case into a holder that is a fraction of a millimeter too small. That tight fit will not let you take the case apart. Don't beat on the end of the shaft with a steel hammer like I did. That was just a waste of time and slightly deformed the end of the shaft.

Here is what worked for me: Get a hair dryer or a propane torch and slowly and uniformly heat the aluminum case. I heated mine to the point where it was barely able to be handled by bare hands. (At higher temps I use cloth gloves.) Then take a soft non-steel hammer or use a piece of wood as the shaft protector and give the end of the shaft a good sharp blow. I had to hit mine twice, but the crankshaft did pop out of the hot case. (It's kinda brutal.) Make sure the crankshaft lands on a clean soft surface to avoid damaging the connecting rod and piston. You will then see the ball bearing case and the holder and get a better picture of what I tried to describe.

If you had a table vise, use it in a more graceful and controlled way for separating parts. Personally, I would still use heat to assist.

I am finding out that heating some parts with flame and cooling other parts with ice is becoming a useful method to disassemble and re-assemble this engine. Aluminum expands at twice the rate of steel for a given change in temperature.

I'd like to hear about other techniques that other engine builders use. If you are going into the engine, I assume you will order a complete set of replacement gaskets as well.

Thanks,
MikeJ

 

[Outrunner]

When we used to rebuild Triumph and BSA engines, the only way
you could remove the ball and roller bearings from the aluminum case
halves, was to heat up the immediate area surrounding the bearings with
a oxy-acetylene torch and then use a broom stick diameter wood dowel to
tap it out.
Generally,you should never force steel into or out of a pressed fit aluminum case.
It will cause tearing of the tight fit tolerance and possibly ruin the engine case!

 

[MikeJ]

Recall that my "worthless" Chinese engine had a stripped crankcase hole for a head stud. I decided to try to fix it. Just for everyone's future reference:

I got my engine back together. Keep in mind this is an experimental engine for me. Trying odd-ball techniques is all part of this effort.

I installed Grade 8 5/16 inch - 24 NF threaded bolts from Ace Hardware. I had to drill out the old 6 mm head holes and tap the crankcase hole. I now know that 5/16 inch is the largest you want to go for the head bolts. The drilling process broke through a small section of crankcase wall. I can see the bolt threads. There are still eight good threads holding the bolts in place. Each are tightened to only 9 ft-lbs. I will keep an eye on gas blow-by to determine if higher torque is needed.

Purchased a metric tap and die set from Autozone. Used it to clean up the magnet shaft and nut. Both shaft threads and nut threads were beat up really badly during the disassembly process. They were like-factory-new in just a few minutes.

Placed the crankshaft assembly in the home freezer to minimize diameter of crankshaft. Heated the aluminum housing to just above handling temperature. Poured 2-cycle oil on all bearings of the crankshaft. Placed new gasket around housing. Placed the two together on first effort. (Next time, will not freeze the crankshaft. Condensation on it produced a very light coat of rust on the flywheels. Probably negligible; will see.)

While I had the clutch plate off, I scuffed it up a bit with emery cloth to bite into the clutch pads a little better.

Adjusted the clutch arm to my liking. Had to grind out the center of the 20-tooth drive sprocket with a Dremel sander drum to get it to go on the crankshaft. Have to wonder if that little woodruff key will hold up when driving the gear off the crankshaft.

Tightened down it the frame without rubber or leather isolation. Carburator, muffler, cables, chain, and wiring went on as well as could be expected. It looks good and "feels" right. But the proof will be during break-in.

Tonight, double-check all external nuts and bolts. Then fire it up and see what happens!

 

[ylionb]

anyone have experience with bike berry 80cc?

 

[MikeJ]

Hi ylionb -

My 80 cc engines (two of them, Nantongs each) are from BikeBerry. I ordered mine through Jack. He is a good guy to deal with. My first engine was placed in a 24 inch frame. It was a really tight fit. The ladyfriend rides it. Assembly was by the numbers. The very first fire-up took a few efforts, but now ladyfriend (very mechanically inept) can start it up anytime without problems. I am still running a 24:1 oil ratio through it. It runs just fine. She rides it like an old lady, though.

The second engine... My previous posts tell about it. It should be called Frankenmotor. I am surprised it runs at all, let alone that it runs well. The various parts were beat on by a claw hammer, frozen to below -0F, heated to above water boiling point, drilled out, reamed out, tapped for non-metric threads, bolted with bolts you can find in a Chevy engine, and otherwise attacked at points with a Dremel cutter and a file. Crankshaft threads under the magneto needed to be re-threaded and the bolt re-tapped. I used water pipe joint compound to seal the neck of the carb intake to the carb output. The very first start was accomplished by spinning the crankshaft directly with a 3/8 inch drill. (I definitely do NOT advise that! I rounded the corners off the nut.) My engine was a little cranky to start, but I learned to give it some choke before starting, and it starts every time. The muffler was disassembled for inspection, then later the bottom pipe fell off during a ride. I reassembled it and still use it. You would think nobody in their right mind would do all this. For a while, I was ready to throw the whole thing into the trash can. But I decided to give what was salvagable a second chance.

After all that, I broke it in on 24:1 oil and will stay at 24:1 for my altitude (average of 6,500 feet). I tested it on hills that, in early runs, required pedal assistance. Now, the same hills are conquered without pedal assist. If the engine did not overheat and seize by now, that is one tough little engine. My max speed has been 30 mph, but I am a larger-than-average rider. If I weighed only 150 lbs, wind drag would be significantly less. And max speed would go up. I use a jackshaft kit from Sick Bike Parts - a challenge to put on, but it can be done with care.

Get the engine, but consider a good motorcycle helmet and bright yellow bicycling jacket as part of the riding experience. Stand out to traffic like a sore thumb! Your future potential income is worth much more than the puny cost of good head protection. (I paid $128 for my helmet and $70 for the jacket. If I am not hurt, my future income can exceed one million dollars. Yours can be much more, but only if you don't get hurt!)

Have fun! And thanks for reading my very wordy history!
MikeJ

 

[Dan]

Very well said Mike! TY, Great advice.

 

[geeksquid]

Robin,

I got mine from Herdan Franco Morini KickButt Engines . It came a couple weeks ago and I am impressed. You can see the flawless quality all over it. It is a little wider and heavier than I expected, it is the 6S-T 5.6hp. I will have to mount it high to clear the pedals, get I really wide crank made, or go with no pedals at all. It is legal here in Colorado to not have pedals and I am cosidering it. I'm building this bike as a prototype and the first stage is to come up with a drive system that is simple and can handle that much power. Later I will work on the ideal mounting position.

Hedan also has a 28cc engine that is much smaller and they tell me it is made for a bicycle. It makes as much horsepower as the 50cc Chinese engine.

I'll be posting pictures and a video when I get it rolling again.

Cherokee, here's a youtube video of a guy that made a very cool bike with a Moto Morini some time ago. It got my attention immediately when I first saw it. Only thing holding me back is the price for now. Wouldn't it be great if Morini started making bike kits to compete with the chinese ones. Or maybe if someone like Manic Mechanic would start making motor mounts and other hardware for these engines. It would definitely give a shot in the arm to the bike engine biz. Now what's confusing me a little now is the name Morini. The genuine Moto Morinis were truly Italian made. The engines on many of the well known mopeds were from Moto Morini. Now I'm seeing the name "Morini Franco", so there may be differences in engines carrying the Morini name. Last I heard, actual Moto Morini sold and was now being built in China.

YouTube - Motorized bicycle with Italian moped engine

NEW MORINI ENGINES

 

[geeksquid]

I've read every post and I understand all sides. What no one has mentioned that there really are high quality alternatives to the cheapo happy times motors. They are Tanaka, Robin Subaru and Honda. Lots of kits are made that include these quality engines but what has kept me away is that I highly prefer a center frame mount, not the rack mount that is used in those kits. I could care less about looks and I know that many prefer the happy time because of it's a simulated motorcycle looking engine. You don't get this engine shape in the quality engines. Unless a quality kit based on a Morini engine is developed by some enterprising, creative individual, my ultimate dependable ride would be a Tanaka, Robin or other quality engine on a center frame mount for the ultimate in weight balance and with the Sick Bike Parts type transmission/gearing setup. Manic Mechanic could come up with this type setup without much trouble. I'd buy it.