Simple problem(s)?

[hoosierdaddy]

Hello all.  I have a firework and powersport store that I just started the end of summer last year.  I had a horrible winter as could be expected in this business, so I lost my mechanic for lack of business.  I am not very mechanical inclined but know some basics. 

I have two different people who have come in with what seems to be fuel issues on 49cc scooters. 

The first one is one I sold, the scooter only has 70km on it... It was hard starting and stalling, It had good spark and compression, and petcock was tested, so I put a new carb on,   It will now start fine and idle fine, but whenever you stop it dies?  If you try to start right away it's hard starting, but if you wait 5 seconds it will start right up, but then die again when you stop again every time?  (If you give throttle at stop it will stay running)?

The second one is a friend of mine who bought a used scooter for his daughter, at first it had about 80 psi compression, so I adjusted the valves and replaced the carb because it too had fuel issues... and still does.  It will start with starting fluid and run fine for a few miles and then die and then doesn't want to start?  It has new carb and I tested the petcock?

Any help would be appreciated. 

[hoosierdaddy]

Oh yeah I forgot to mention, I have the new carbs mixture screws set at two turns out, and have adjusted the idle screws for both.

[Rebel]

On both of them check for a vacuum leak. Also check the fuel filter.

Did you recheck the compression after adjusting the valves? 80 is very low, it should be about 120 - 125.

What do the plugs look like.

[hoosierdaddy]

I checked for vacuum leak, I'm not seeing anything. I did check compression after adjustment and it was 150

The used scooter I did put in a new plug, but I don't think I checked the plug on the new scooter, so I'll check that and the fuel filters.

Thanks!

[craisin]

Hi I am a 120kg New Zealander I use a NGK CR8HIX which is a colder than standard Iridium plug.
I use a manual petcock as vacumn drops at wide open throttle and restricts fuel flow to carb

50cc GY6 run 10.5 to 1 compression ratio so I run 98 octane

[Rebel]

Petcocks on these are controlled by vacuum. It may have a hole and is no letting enough fuel come through but they are pretty easy to check by putting a hose on and sucking on it. If it is working the vacuum opens it up and fuel comes out. Any kinks in the hose? Replacing the filter is easy and not expensive.