Newbie with problems

stv1jzgte

New Member
Feb 11, 2009
489
0
0
australia
Hi All, My name is Steve is my first post and i have to apologize as im starting out with a question.
My mountain bike was stolen this morning!, i was looking at a friends Gasman bike a few days ago, now i own it!
I pretty sure it is 48cc, there are a few problems with it as it only likes to run with the choke on.
As i ride and turn the lever the sweet spot is with the lever 1/2 to 3/4 closed. im going about 25-30 kmh though!
am thinking there is a lack of fuel when fully open, does this sound right.
i did pull the float bowl off and there was a heap of crap in it! i fixed a few air leaks but the problem remains.
Any help you may have is most appreciated
Regards,
stv
.wee.
 

svc

New Member
Jan 10, 2009
43
0
0
sydney australia
Sounds like you still have an air leak if its running better with the choke on after its warm. To find out if you are rich/lean at wide open throttle take a good run on the bike and hit the kill switch and clutch at the same time. Let the engine cool down and read the plug. Black indicates rich/too much fuel. white or grey lean/not enough fuel.You want a brown color. Any air leak will throw the results off though and could cause damage.

What color is your plug now? If its grey or white it would pay to richen the mix a bit before you experiment.

Fuel mix up to 3/4 throttle can be adjusted by moving the clip on the end of you're throttle cable.
 

stv1jzgte

New Member
Feb 11, 2009
489
0
0
australia
Um it doesnt have a kill switch! thanks for pointing that out, i will have to get that fixed asap.
the plug is black colour a bit sooty looking.
I will have to get another head gasket as it is all mangled and will not seal properly and this is the only leak i can see hear and feel would this cause the problem? blown head hasket.
Thakyou again svc! i will do some more investigating!\
Regards
stv
 

svc

New Member
Jan 10, 2009
43
0
0
sydney australia
i Have heard of people using no head gasket. Just RTV silicone or hylomar and torqueing down the head bolts. Form what you have said it sounds like you may be running a bit rich and can probably raise the clip 1 setting (lower the needle). Rich is safe anyway so its a good place to start. Get a kill switch on and do some plug chops to be sure.
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
235
63
up north now
The blackness is from running with the choke on.

Clean the carb again, check the intake manifold for leaks, and re-seal with RTV or silicone. Then, if it still runs lean, move your "C" clip on the slide needle DOWN a notch. Try it again and report back.

I don't know if RTV will work for a head gasket though....
 

stv1jzgte

New Member
Feb 11, 2009
489
0
0
australia
Hi Guys, well i stayed up late tweaking away at the bike and made a new inlet and exhaust gasket, When i went to work it was a bit better! choke on 1/2 way!
Pedaling it takes me 20 mins, i got there in 9 today! and i was not sweating and stuffed

when i got to work i poped the head off and made a new head gasket and really cleaned the carby out. When i left work it was 100% better, choke off! and when i put it on it wanted to stall. sweet.
I have to get a speedo as my last one was on the bike that was pinched, so i can see how fast im going.
Thankyou Svc and Bikeguy Joe