Seasoned Builder Needs Help

[dougsr.874]

I have bought & installed over a dozen of these 49cc 2 stroke Chinese kits.....But this last one has me whupped.....It will start and run somewhat, but will not take the gas unless you keep fidgeting with the choke, then it will only run about half throttle,will try to die, etc...This kit was new out of the box,,, I replaced the new carb. with a new carb.....replaced the piston rings, checked for spark, can't find any air leaks , and it still won't run right......I'm to the point of throwing it away..unless someone knows more than me....

 

[gasbikeproject]

Perhaps a bad crank seal, clutch side?

 

[GearNut]

Remove the pinion gear and magneto rotor. Securely cap the intake and exhaust ports. You can use a metal plate with gasket on the exhaust, a rubber cap and hose clamp on the intake manifold.

With the piston at BDC pressurize the engine to 6 PSI through the spark plug hole. No more than 6 PSI or you will blow the crankshaft seals out.
Spray both crankshaft seals and all gaskets with a soap and water solution while the engine is under pressure. If you see bubbles you have found your leak.

Here is a PDF with more info: http://www.duncanracing.com/TechCenter/2stk_presstest.pdf

 

[BigBlue]

Jaguar did a nice post on testing for leaks:
http://www.motoredbikes.com/showthread.php?39860-preventing-power-loss

Good Luck,

Chris
AKA: BigBlue

 

[Fabian]

You need to have a chat with Zulufoot.

I am sure both of you can have a good heart to heart "man talk"

but these are some notable parts the thread conveying Zulufoot's emotional state:

All the research isn't helping, the SOB will not run!
So i'm ready to ditch this pos soon, I just cant be stuffed wasting all this time on it when my two perfectly good motorcrossers in the shed could be doing with my TLC
Ive also used 1/2 can of quick start which appears to do nothing really, the floats are set fine, needle & seat clean, clip set 3 from top, so everything is set for it to run, so why isnt it?
Come this morning dead as a dodo!
stripped it all down again, put a second o-ring inside the carb throat because the connection seems real crap tried clip at top and bottom and shes dead as a dead thing.
POS I say. life is too short, the Chinese can stop laughing at me now, they have me beaten with their utter crap.
What a total waste of time and money
judging by the hrs and $ people are spending on these garbage cans, its a full time dedication which i will reserve for my current passion
2 weeks of my life wasted and I'm calling it, Its to the tip tomorrow.
Couldn't sleep last night trying to work out why this thing wont start, it has to start!


My Chinese bicycle engine runs just perfect, giving me perfect reliability and enjoyment that's well, all i can say is that it's perfect.

Now where is Zulufoot to weigh in on the conversation, discussing the joyful merits of the Chinese bicycle engine

 

[Deleted member 12676]

They obviously don't test the engines before sending them out of the factory. Do you think a chinese laborer getting paid $1 per hour is going to care if the right side crank seal has caught on the shaft lip while installing and isn't sealing?

 

[Fabian]

Why does my Chinese bicycle engine run so well: maybe the Jaguar CDI and Rock Solid Engines intake system and the CR Machine Manufacturing billet cylinder head might have something to do with it !!!

 

[BigBlue]

They obviously don't test the engines before sending them out of the factory. Do you think a chinese laborer getting paid $1 per hour is going to care if the right side crank seal has caught on the shaft lip while installing and isn't sealing?

It is amazing that these engines cost less than they did 10 years ago. The cost of labor, materials and the value of the Yuan have gone up in recent years. It must be the minimal quality control that was eliminated due to the lower profit margins and the use of cheaper materials. It is very evident in the number of bearing failures and seal leaks reported with new engines by members on this forum and the other forum.

Here's some pictures of quality control from Grubee's website:


I am wondering if the crankshafts are stacked in a pile like those carburetors. How many fall on the floor? That might explain why some are so out-of-balance.

You have wonder what happens to those rejects?

Chris
AKA: BigBlue

 

[BigBlue]

Why does my Chinese bicycle engine run so well: maybe the Jaguar CDI and Rock Solid Engines intake system and the CR Machine Manufacturing billet cylinder head might have something to do with it !!!

O.K. I have a 49cc 2 stroke that I bought in 2004 and and still runs great. I think that the older engines are better than the crud being passed off today, even if you do the minimal preparation. Adding other parts to make a more reliable engine maybe the only alternative for other parts of the world.

Here's a cost comparison:

Happy Time with additional components:
Flying Horse engine: $155
RSE Intake: $165
Jaguar CDI: $75
CR Machine head: $80
Total: $475

You also have to consider the purchase of a shift kit. I know some people claim that is an essential item for a Happy Time engine. So you have to add another $145 to $239 to the total. So now you are talking $620 to $714 for a completely reliable 2 stroke. Oh, and don't forget to add the cost of bearings and seal replacements. This is becoming a real issue with new purchasers of these kits.

You also have to consider the cost of replacing the crappy chain, acorn nuts, engine studs, spark plug, spark plug wire and milling the head.

Lastly, you have to consider the amount of time replacing parts and walking your bike home or waiting for someone to pick your a*s*s up after breaking down - Priceless!

79cc Predator 4 Stroke:
Engine: $96
Engine Mount: $25
AGK Jackshaft kit: $135
Clutch: $34
Gas Tank: $24
Throttle kit: $12
Sprocket kit w/ Rag Joint: $17
Kill Switch: $5
Throttle/cable: $24
Header: $44
Total: $416

I know I've left out chains and maybe some other minor parts, but for the money and reliability, a 79cc 4 stroke for those living in North America maybe a better deal. You can also add performance parts to the Predator down the road if you choose.

Sure you can always start out with a 2 stroke basic kit and upgrade as money permits, but in the long run, I think it is a better deal with the 79cc predator.

Some one else may have a different opinion and that's O.K. I am not trying to start a flame war, but just stating the facts that maybe relevant to your situation.

Good Luck,

Chris
AKA: BigBlue

 

[Fabian]

You have wonder what happens to those rejects?

They go straight in the shipping container bound for Australia and South Africa.

Australia has always been a dumping ground for poor quality product.