flygilmore

I have a paticular 50cc engine that has been taking about 30+ flips (cold with choke on) to get a pop when starting after it has been sitting for a week or so. When it does pop, it will run for about two seconds and then quit. Four more flips and it is running great. In the air it runs great. I know that it should not take so many flips to draw fuel........I am wondering what is the issue is. Tank/lines etc. are all new but the engine is about 3.5yrs. old with about 14gal. through it. I just got it a few months ago and it seems as though it is taking more and more to get the carb primed. Is it time for a carb rebuild to solve this?

Thanks.

BarracudaHockey

My Feedback: (11)

Maybe. Could be the choke butterfly isn't seating fully either. Have you tried it with the cowl or hatch off so you can see the fuel draw?

What engine/plug?

soarrich

My Feedback: (98)

Close the hole or notch up in the choke plate, I do it with soldiering the hole close, some use glue or a bolt.

After you modify the choke plate the way to start the engine is:
a. Close choke completely.
b. Open throttle half way.
c. Flip engine with ignition on until the engine coughs.
d. Take choke fully off.
e. Set throttle just above idle, flip until it starts, usually 3 to 5 flips.

smarks

Wonder if the carb diaphragm is old and stiff thus not drawing fuel very well during priming?

spaceworm

Maybe look here and consider installing a primer bulb? http://www.rcuniverse.com/forum/m_11...m.htm#11140093

But the other hints are good also and all of them can be used together. Likely a carb rebuild will help the most.

Charlie P.

Disagree. A priming bulb will just get you airborne before the engine konks out. If your carb diaphram is not working on the ground to get fuel moving it will not get any better in the air. Check the strainer screen for gunk and make sure the rest of the fuel delivery system is OK.

Pump the prop until you get fuel dripping and then start.

If you have an enclosed cowl and don't know when the fuel has reached the carb barrel - then how do you know when to stop thumbing the primer bulb?

spaceworm

...In the air it runs great. I know that it should not take so many flips to draw fuel...it seems as though it is taking more and more to get the carb primed...

I saw nothing about a cowl, I did see where it runs great after getting a good prime. He said the plumbing was all new. I agreed a carb rebuild was likely the best resolve. What is your point Charlie P.?

captinjohn

Charile did not think that post out too good...that happens...no biggie ! Capt,n

Charlie P.

Happens plenty. 

I didn't read the whole other post.  I got about as far as "But in other cases, there is no access to the carb when the engine is fully cowled . . . " and came back here.  I'm home from work now and have read the other post.  If you have a tap and space - by all means use a bulb if it adds to your flying pleasure.

I rock the prop from about 5:00 to 2:00 to draw fuel to the carb.  You don't have to spin it full circle.  Maybe that doesn't work on all gas engines, but it works faster and easier on all mine.  Bulbs are handy on equipment that doesn't have a handy way to pulse the diaphragm - like weedwhackers and pushmowers.    My engine mentor taught me: "anytime you splice into a fuel line you introduce the potential for air leaks - and air leaks stop engines."

ahicks

My Feedback: (2)

Charlie - I do the "rock" thing on mine routinely as well. Lot's of guys try that and end up flooding them out though...

The only thing I'm wondering is if the engine might be running a bit lean on the idle - which can make it a complete PIA to get started?

High time plugs and reed valves that aren't seating very well (or are chipped/broken?) can make an engine difficult to start without an electric assist. Once started though, they can run great....

pe reivers

With the carb down instead of sloping down toward the engine, it sometimes takes a lot of choked flips. Just make sure the choke plate closes well, and flip as needed to get that first pop (all other things being OK)