My Monkey bike won't run properly

[Honda Al]

Hi all,

Now I know this normally isn't the type of bike we talk about on here, but I have problems with a Monkey bike that I'm hoping this fantastic place can help me with.

It's a 1978 Z50J bike with a slightly later 1984 4speed manual engine.

The bike ran normally, no problems and good as gold. Started first kick and accelerated nicely up through the gears.

Then suddenly one day the carb started leaking through the over flow. No problem I thought, I'll pull the carb and obviously something stuck in the needle valve. Did that, re assembled the carb and that problem solved.

Since then it struggles to accelerate, bogs down, stumbles, back fire and die. Then it's not as easy to start up again.

The bike idles fine, will be ok if you very, very slowly open the throttle up.

I've re checked the carb, checked the passages and ensured pilot jet is clear. Used wire and lots of carb cleaner. All clear.

I've checked fuel flow to the carb from the tank and all fine. Also opened up the drain screw on the float bowl and fuel pours out.

Checked for a strong blue spark from the plug and that's ok. Sparks nicely against the engine when I turn the kick starter over.

Any suggestions as to what I can look at next, or what I have missed so far?

Many thanks, Alan



Sent from my iPhone using Tapatalk

[hairygit]

Try revving it with the choke on, or partly on. If it improves, something is awry with the fuel supply, float too low, jet obstructed. Have you got a filter in the fuel line anywhere?

[zebedee85]

Hi Al - Do you know if the carb is perhaps flooding, is it still leaking from the overflow? I don't know these models well but a float height check can't hurt.

[totty]

Also sounds like fuel supply to me.
Fuel hose could be breaking up internally, float height could be wrong, whatever blocked the float valve could have also got elsewhere.

Good to see another monkey bike post, I ride a Jincheng copy.

[Honda Al]

Checked float using clear tube method and fuel line settles 1-2mm above bowl gasket level.

Doesn't leak out of the overflow anymore, that problem was fixed.

Using choke makes it worse and stalls even quicker.


Sent from my iPhone using Tapatalk

[hairygit]

That fuel level is TOO HIGH! I don't know offhand what the level should be for your carb, but it should no way be above the joint face, so the motor is flooding. The float height for a 1984 C50 is 10mm, and is almost certainly close to where yours needs to be. Make sure you measure it correctly. [ Guests cannot view attachments ]

[mike the bike]

That sounds like it's too rich.  What's the air filter and the airways like?

[hairygit]

Also, when you set the float, make certain that the tang on the float is JUST touching the spring loaded tip of the valve, and NOT compressing the internal spring. [ Guests cannot view attachments ]

[kevski]

Use the tube method and take it down below gasket level between 3 to 4 mm and see what happens from there.

[Honda Al]

I took the carb off, checked the float valve and float. The float is a plastic ring shape (like a piles cushion!) and has a fixed tang. Not adjustable as far as I can tell.

Anyhow I ensured everything clean and replaced. Did the clear tube method again with the carb level in a vice and it stayed below gasket level.

Replaced everything and started first time with no dramas and revved properly with no hesitation.

Seems fixed. Although not really sure what I've done. I'll road test it tomorrow.

Thanks everyone for your help. This place is brilliant. Better than planet minis!! Ha ha




Sent from my iPhone using Tapatalk

[hairygit]

It could be particles of crud in the fuel, from a dodgy petrol station, or a dodgy can, or crap in the tank. Try putting a small filter in the fuel line to stop it happening again. Glad you got it running again, try and convince your sister to have  ride on it, she doesn't know what she's missing!

[Honda Al]

It could be particles of crud in the fuel, from a dodgy petrol station, or a dodgy can, or crap in the tank. Try putting a small filter in the fuel line to stop it happening again. Glad you got it running again, try and convince your sister to have  ride on it, she doesn't know what she's missing!

My sister on a monkey bike! Ha ha ha.


Sent from my iPhone using Tapatalk

[hairygit]

Oi, she's scared of bikes, what better or safer way to get her over her fear, you should encourage her to try!

Sent from my X6pro using Tapatalk

[Honda Al]

Ha ha. I wasn't being rude, I can just imagine it in a hedge with my sister sticking out of it!


Sent from my iPhone using Tapatalk

[hairygit]

She'd probably not want to give it back after a go on it!

Sent from my X6pro using Tapatalk