Rich? Lean? Leaking? What's going on?

angryteabag

New Member
Local time
12:09 AM
Joined
Jul 28, 2014
Messages
7
Location
New Zealand
Hey guys, first post and i'm scratching my head on this issue.
Got my first moto bike the other day, second hand.
The bike didn't come with a carb, but with fuel in the intake, it turned over so I got it.

Replaced the spark plug and it fires fine.

Bought a carb the next day, attached it and it wouldn't start.
Moved the needle up one, nothing, down one, nothing.

eventually, I took the air filter off. Using a spray bottle, sprayed fuel/oil into the carb intake and started it (Pin in the middle).
The bike fired up with the throttle open, ran rough and would eventually just die. Tried to fire it up again and it didn't work.
Sprayed into the carb intake again and it worked so long as the throttle was open. As soon as I let go, the bike wouldn't idle and just die right away.

I have tried an O-ring on the carb. It is covered in silicon gasket goo. The intake manifold - the engine has fresh gasket goo. Exhaust has fresh cb gasket + goo.

Why won't it start/idle?

ZA3jEP6.jpg

as it stands - Also, Hi from New Zealand
 
you didnt mention pulling the new carb apart and giving it a clean because thats the one part they seem to skimp on at the factory...gfetting the gunk out.

if you cant see light through the jet...fuel wont have much chance of getting through it either.

anyway. its to do with the new carb ;)
 
you didnt mention pulling the new carb apart and giving it a clean because thats the one part they seem to skimp on at the factory...gfetting the gunk out.

if you cant see light through the jet...fuel wont have much chance of getting through it either.

anyway. its to do with the new carb ;)


Hey thanks for the reply. Yeah, took the carb apart. Can see through the fuel jet no problem, even blew through it for good measure. I'll try run a pin through it in an effort to clear it out incase though.

Does the float level have any effect on how much fuel the jet picks up, or is it just a marker that tells the carb how much fuel to store in it's float area?
 
marginal effect on the amount it picks up. think of it as a straw. its hard to suck anything through a two metre straw!

so, if the fuel level is high, it will tend to be rich, if its low, it tends to be lean, as its only the venturi effect sucking it up.

could just be blocked needle valve... is the bowl actually filling up?


go back to the carb that worked ;) after yay many years, im still using the plain old stock carbs, and trust me...ive done some fiddling with alternative carbs over the years ;)
 
marginal effect on the amount it picks up. think of it as a straw. its hard to suck anything through a two metre straw!

so, if the fuel level is high, it will tend to be rich, if its low, it tends to be lean, as its only the venturi effect sucking it up.

could just be blocked needle valve... is the bowl actually filling up?


go back to the carb that worked ;) after yay many years, im still using the plain old stock carbs, and trust me...ive done some fiddling with alternative carbs over the years ;)

Yeah, no problem with the bowl filling up. I'm using a new stock NT carb, just trying to get the thing running before I play with alternative carby combinations haha.
When you say marginal effect, would you go so far as to say that the effect is significant enough to prevent the bike from running?

Maybe I should try bending the float levers to raise the level of fuel in the carb
 
by marginal i mean its a good fine tune when the jets are right, but thats it.

unless it is SO low the jet isnt submerged, in which case...its excessive :giggle: so no, not critical.

pop carb, hold at same angle as its fitted, turn on tap... close, remove bowl carefully...and the fuel should be at least halfway up, a bit more with the float in there. most people say a few mm from the top, they just dont say how to measure it when you cant see it! (think about drilling a hole in a small screw, attaching some hose, and screwing it in where the drain normally goes ;))

hmmmm....


just a thought...now i read your first post closely...has the previous owner tried any home porting? like, chop the piston skirt?

cus that will make em really hard to start, if done wrong.

at TDC, you should normally see some of the piston skirt through the intake. can trim it away til its "just" flush with top of port, but anymore...oh dear.

if you have to rotate it a fair bit before seeing piston...its been overdone, and it will need a new piston. shoving fuel down the intake will get it going, but it doesnt produce enough suck for a carb to work.


thats a (really) messy silicone job there!
 
and pop the magneto cover/gear cover and just check for any suspicious looking oil/fuel around the crankshaft... if its got a leaky seal, once again...it might start with a load of fuel, but not with a carb.
 
and pop the magneto cover/gear cover and just check for any suspicious looking oil/fuel around the crankshaft... if its got a leaky seal, once again...it might start with a load of fuel, but not with a carb.


Piston is fine, no suspicious oil. that being said, the gasket in the clutch cover is destroyed and the cardboard the previous owner used for sound deadining was 100% saturated. Looks like gas that has leaked in from when my carb was leaking, there is no oil around/under the crank gear and no oil at the magnito side.
 
blown crank seals will make hard starts, usually it blows on the magneto side though
 
https://www.youtube.com/watch?v=Rt291A_C4KI&feature=youtu.be

Here's a video with me getting it to run.
It will only start when the throttle is open, and I have sprayed fuel in the intake. However occasionally it will turn over and draw fuel from the carb.

Got it running indefinitely (like crap) and it wouldn't idle.

Could one of the bearings or something have blown causing too much resistance?
I don't have the space or tools to feel confident enough to take the whole engine apart. plus the bolts that hold the engine to the frame have been bent outwards because the bar is too big....




IMG_20140729_145301.jpg
Dr can you please look at my piston?
 
Back
Top