Help me fix a 50cc two-stroke - AKA why i hate twostrokes - Pics now.

[CoronaC]

I've been looking around at pocket bike engines lately, for a little future project and i stumbled onto this site http://www.pocket-bike-racing.com.au/forum/ might be able to get some help there its filled with pocket bike nuts.

Cheers
Chris

[sheepers]

de-coke the exhaust.
sure to be the problem, youll need to get it pretty hot on the inside. i reckon oxy/acetelyene up its jacksy should do the trick.
dont bother taking the exhaust off to see if it makes a difference, it will most likely run worse without the exhaust on, no matter what you do.
hope this helps,
sheepers.

[styler]

well a basic test can start by taking out spark plug and grounding it on the chassis, then crank it over and see how strong the spark is, should be bright blue.

*health and safety to this method* - close up fuel sources before procedure so fumes dont ignite. also hold it on the chassis with some wire or zip tie if prone to health problems or dont like shocks (only will shock the shaky handed) not like the bastard who cranked it over before i could hold it properly!

[takai]

Heh, the main problem is that its a rolling start bike. So basically you run along looking like a retard and then release the clutch to spin over the engine

I think ill ziptie the spark plug to the chassis.
I have considered cleaning the exhaust. Maybe ill just take off the "secondaries" and run a wire brush through the "primaries"

[Vios-GT_07]

I've been looking around at pocket bike engines lately, for a little future project and i stumbled onto this site http://www.pocket-bike-racing.com.au/forum/ might be able to get some help there its filled with pocket bike nuts.

Cheers
Chris

oh that's just gold...

[brett_celicacoupe]

3 things for a 2 stroke to run. everything branches off them.

1.compression
remove spark plug and cover the hole with your finger....crank it over and make sure there is enough there to blow your finger clean off the hole. also check the main seals arent leaking (sealing crankshaft to motor housing).

2. spark

check the spark and check it can jump a gap of ~3mm.....should be nice and blue as well, not redish.

id also whack a new spark plug in as the old one is probly carboned up which will cause the motor to not run....they are only a couple bux.

next thing is fuel which sounds like the cause of your problem. sounds like not enough fuel is being delivered at higher RPM.

things to check;
-check the idle mixture screw is all the way in and the 1.5 turns out
-check the needle hasnt seperated from the slide...sometimes the circlip pops off the needle and so the needle stays all the way down and the motor runs on the idle circuit only.
-check the float level of the carby, ie the needle is closing fuel flow properly.
-remove the imulsion tube from the carby (tap out with punch) and clean all the holes....this part is often overlooked by backyard motorbike mechanics.
-double check all the other jets/nooks/crannys are clean and havent got growth in them.


ohh, and put your oxy in the exhaust....be prepared for an explosion though!

[GRUMPIRA28]

Hi,

My money is on the exhaust. It needs to be cleaned out every so often on these small motors. If it has a baffle pull it out and burn off the carbon with oxy/acet or similar device and check that the exhaust port and exhaust sytem is clear.
That's my experience with small motor cycle engines. This should be done periodically as part of a service. It can make a big difference.

Good luck!!

[takai]

Hi,

My money is on the exhaust. It needs to be cleaned out every so often on these small motors. If it has a baffle pull it out and burn off the carbon with oxy/acet or similar device and check that the exhaust port and exhaust sytem is clear.
That's my experience with small motor cycle engines. This should be done periodically as part of a service. It can make a big difference.

Good luck!!

BINGO
Thats exactly what it was, that and the clutch was stuffed, but i had already replaced that.

The only problem was that the exhaust was a one piece back to the muffler.... but its not now. The dropsaw made quick work of that.
Now just to get a 2nd part made up for it, its close to as loud as the race car in a 50cc 2stroke kind of way.

Thanks all, ill post vids soon of me riding it around.