Solved: 50cc Engine hard to start when still hot. Common?

[Tseg]

My son's 2015 Super 8 has been running great.  Starts with the first press in the morning.  However after the engine gets hot on a short ride and then trying to restart it within an hour or two it can take 2 or as many as 6 or 7 presses to get it going... but it always gets going.  Once running, no other issues.  This has been an ongoing issue.  The work-around is to give it a little throttle when starting it and hold the throttle slightly open for 10-15 seconds and then the motor will keep going.  When idling, the rear wheel, like when brand new (a 1/2 year ago) rotates slightly. 

What is the correct fix?  I'm guessing it is something simple (slight screw turn somewhere?).

[Redk]

Yes !

A simple twist of a screwdriver will probably improve things quickly.

There are series of scooter carb adjustment vids on the youtube..
They are listed here on the forum.
redk

[Tseg]

After a lot of Internet research just about all "problem solved" posts related to 'hard starting when the engine is warm' relates to a leak in the intake manifold... either not screwed down tight enough or hairline cracks.  I probably cannot check out until this weekend.  Hopefully this will solve the issue.  In the mean time, giving it slight throttle when starting when warm seems to continue to be the work-around, starting with the 1st or 2nd press of the starter button.  I actually found a Kymco thread back to 2008 where several owners came to the same work-around conclusion and just accepted that is the way it is.

What has been interesting for this specific issue how the scooter owners try 10+ different things, some based on forum recommendations... everything from electrical/battery to carb to spark plugs... and nothing works, until they finally land on the intake manifold issue.  I've found 4 'problem solved' threads on this issue and each one landed on the same issue/solution.  Hopefully I am number 5.  Of course, since I'm pro-actively writing this post I just hexed myself.

[Redk]

A carb should only draw air in through it's snorkel which should accordingly be securely attached to the airbox/filter.

Locating intake leaks may be done by spraying a shot of ether at various portions of the intake tract before the filter.
WD40 penetrating spray is probably a little safer...

If the engine races, you have found the vicinity of the leak.

The smallest of the scooter motors are Very sensitive to temp and fuel/air ratio.
I would not feel it extra-ordinary that a hot engine might require a partial throttle position when starting.
redk

[Tseg]

I would not feel it extra-ordinary that a hot engine might require a partial throttle position when starting.
redk

Good to know.

[MJR]

Why I so like fuel injection.

[Tseg]

This morning I removed the seat to get into the engine and loosed then tightened the intake manifold at the 3 contact points (2 flange screws + hose clamp).  I also turned the idle screw about 1/8 of a turn clockwise increasing the idle.  Now with the engine hot it will start up on the 1st or 2nd press without any throttle... tried it several times.   The starter also seems to punch harder than I recall.  Another observation is the scooter seems to pull through acceleration smoother... no flat spots.  Who would have thunk 2 almost non-changes to the system would make any discernible impact?  Anyway, I'm not complaining, neither is my son, the primary user.

[Mr. Paul]

Thanks for the update. Many times on a scooter the smallest of things can make a big difference.