Need Help with 48cc centrifugal engine pull start with speed carb

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dirk005

New Member
Dec 15, 2012
14
0
0
Ft. Lauderdale
Now i took it to a guy who knows something about those bikes and he says that it is flooding something and something else isnt getting enough.
He said its getting alot of gas but that is because i spilled gas on bicycle.
Now I changed the sparkplug thinking that was the problem but still same problem.
My biggest problem is that when it does start the back whell doesnt move.
Why does the engine rev high but the back wheel doesnt move.
Is the engine broken
is the centrifugal clutch causing a problem
The back wheel will move after being raised off of the ground.
I took the pin and move it down one notch but then today put it back in the middle.
If I take off the choke the air suffocates the engine with alot of air and it shuts down immediately.

It only starts with alot of engine starting fluid.
It starts but then cutts off after 10 seconds.

Why does it not stay started.
Also the bowl when I unscrew the bottom is always full of gas.
Also do the bikes need to have the chain tensioner.
 
Last edited:

wan37

Member
May 29, 2011
354
4
18
Illinois
Well let us know more engine size and gas and oil mixture?Try this before messing with any thing.Loosen gas cap and try to start it,some time vents bad.How old is it?
 

dirk005

New Member
Dec 15, 2012
14
0
0
Ft. Lauderdale
48cc engine with speed carb. The old gas cap was stopping gas. New gas cap doesn't stop it as bad.
If it starts then that means it could work right.
It starts after a lot of engine start fluid.
The speed carburettor is a trouble maker for it to start.
Also when the choke is open it shuts down very quickly.
I have caught it trying to stay on but it struggles then dies.
I don't know how to turn the idle screw for what it wants.
The jets at the speed carbs are at the bottom of the carb beside the bowl.
Are there any jets they sell for those speed carbs.

I am going to check if the speed carb came with an o ring.

Its a pull start but the damn thing doesn't start without engine start fluid.

Also could the cdi be bad.
 

dirk005

New Member
Dec 15, 2012
14
0
0
Ft. Lauderdale
Also I went down the hill to ride start it but there was no pop that time but no fuel and new oil in tank.
Down the hill it just dragged.
I don't want to always put engine starter in it . Also the choke shouldn't have to be completely closed for it to start.
What is a good screw setting for idle.
I have seen on youtube, 3 turns to 4 from all the way screwed in..
 

dirk005

New Member
Dec 15, 2012
14
0
0
Ft. Lauderdale
The problem is the speed carburetor. I took it to a scooter mechanic that they have to deal with carburetors all day because that's how scooters work and he said the carb has a problem.
When the choke is open it wants to die and when it is closed it works but dies as well. So he did some thing where he kept playing with the throttle and the choke at the sametime constantly and it worked but he told me it would work but you have to keep moving the choke valve nonstop up and down for it to work while moving throttle up and down which is impossible to do while driving. How does a person reset the speed carburetor to work. Both mechanics said the speed carb they gave me with bicycle engine is no good. And would take many hours to reset.

Solved.
Problem was speed carb needed o-rings.
It was leaking air.

New problem.
The bicycle rear wheel is locked up.
Only moves when I turn wheel by hand really hard.

It feels like sludge in it.
When clutch is release rear wheel locks.
It was running for two days decent then I got paranoid and put iin more oil when I thought my gas and oil mix was off.
Then it locked like sludge.
I also put back my old 2 stroke oil.
Could be reason.

My question is

I have newly bought a 2stroke pull start centrifugal kit.
The engine wouldn't run then I got o rings and it runs.
Then when riding there was clanking around centrifugal area.
Eventually the second day of riding by the time night hit the rear wheel locked up.
When I push the clutch the rear wheel it is free.
When I release clutch it is locked and very hard to turn back wheel.
I have to do it by hand with strength.
Also the pull start broke sometime before this. Some plastic piece under the screw metal part.
It wouldn't catch. I super glued it. It worked then melted and broke.

Anyway the rear wheel is locked up with clutch released.
It is very very hard to turn almost like sludge is in there.

What could have happened. Is my gas oil mixture off.
Is the motor ruined in break in time...

So my question is if I buy a 4stroke 48cc engine only can I use the 2stroke throttle and cdi on the 4 stroke.
Do I need a different kit...

I have two 2 stroke 48cc. One is 48cc skyhawk from late 2011.
Been rained on and rusted.
The other is the new 48cc
Pull start chinese engine w/cent clutch.
I now have two new carburetors one speed and the other same type but doesn't say speed. And has a black round back.(Looks like "punisher logo"), plus two 2.5l gas tanks both brand new, one has an old gas cap though.
I want to get rid of all those listed for a 48cc 4 stroke engine only.

It is worth it to me cause I don't want to mix gas and oil again and have a problem.

Can 4 stroke fit on a roadmaster mountain bike. Is it same size as 2 stroke engine. I had the top bar on roadmaster bike cut and rewelded to fit 2 stroke engine.
I want to remove that and buy a cheap 48cc 4 stroke engine.
I want to know are the electronics of cdi and throttle different on 4 stroke kit.
Also is anyone interested in getting all that stuff for a working 4 stroke engine.
The 4 stroke would have to fit the roadmaster though.
I dumped to much money into bike.
Cause I bought a hub adapter the 1.003 size I think and that alone costs $50...

Are there 4 strokes small enough to fit there, a roadmaster.
What is the dimensions 4 stroke 50cc or 48cc to replace 2 stroke and also would the monting kit fit in there also.
 
Last edited:

wan37

Member
May 29, 2011
354
4
18
Illinois
Well do you know if a NT speed carb,I don't know what kid speed carb you got or what you are call a speed carb.If it's only got a idle screw it more that likely to be a nt speed carb hence if got a fuel/mixture screw and idle screw it the cns carb.So I can try to help that info is needed.I think you need to find which one it is.When you do that you can type it in the search bar and theres alot of info you can read on here.That can really help you.I will check back and see whats up and help you as much as I can.Plus there's a lot of others on here that know a lot more then me.
 

dirk005

New Member
Dec 15, 2012
14
0
0
Ft. Lauderdale
The 1st problem was the speed carburetor needed o-rings. O-rings stop air from escaping. They should send a set of o-rings with the speed carburetors and any carburetor that any bicycle engine place sends.

2nd problem was the cylinder head top. I had to take it off cause when it is on the engine top with the sparkplug in it supposedly no air can get out and it locks up rarely.
I had to unscrew the top, move the wheel by hand and then it was very free.
I retightened the cylinder head top with spark plug in it and the engine returned back to normal.
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,837
252
63
up north now
You have some serious problems.

I would suggest spending some time to get a basic understanding of the engine and bicycle so as to communicate you issues properly.