Another Bogging at full throttle post

[Ruckenstein]

Long time lurker.


So I’m banging my head against the wall. 
49cc agility bogs at full throttle

120 psi compression
Valves adjusted .003 in, .004 ex
Kicks over and starts right up also starts up easily with battery
Cleaned carb twice.  Still bogs.  Then I put a new Chinese carb. Sounded exactly same as kymco carb.
Tried 2 different cdis.  Sounds exactly the same. 

Have sprayed for air leaks. Found none.

Tried revving with exhaust off.  Still bogs at wot.

Petcock tested great. Gas is fresh.  Oil level is perfect.

Stator is putting out 13.8 volts if I recall.

Tried 2 different coils. Still bogs.

Plug looked very new.

Anyone ideas are welcome!

[CROSSBOLT]

Air filter condition? Try with filter removed? By starter tested or inspected?

[Ruckenstein]

Thank you for the idea.  However…
I’ve tried it without the air filter and a better looking newish air filter.  Same results.

[CROSSBOLT]

Thank you for the idea.  However…
I’ve tried it without the air filter and a better looking newish air filter.  Same results.

Okay, ruled out air filter. What about the by starter? That is, the electric choke?

[Ruckenstein]

It was tested and is plunging properly. 

What would happen if it had jumped time?

[CROSSBOLT]

What is your plug gap?

[Ruckenstein]

Brand new plug .025 if I recall

[JJJoseph]

It may not be fuel.  Small engines can overheat at WOT, and start to seize up as the pistons swell from the heat.  This is common on small-bore bikes, especially if racing!  It's not unusual.  It's hard on these things to ride them at WOT for longish times..  It hurts!

[punktnet]

Long time lurker.


So I’m banging my head against the wall. 
49cc agility bogs at full throttle

120 psi compression
Valves adjusted .003 in, .004 ex
Kicks over and starts right up also starts up easily with battery
Cleaned carb twice.  Still bogs.  Then I put a new Chinese carb. Sounded exactly same as kymco carb.
Tried 2 different cdis.  Sounds exactly the same. 

Have sprayed for air leaks. Found none.

Tried revving with exhaust off.  Still bogs at wot.

Petcock tested great. Gas is fresh.  Oil level is perfect.

Stator is putting out 13.8 volts if I recall.

Tried 2 different coils. Still bogs.

Plug looked very new.

Anyone ideas are welcome!

Fixed it?
Sounds like lack of gasoline. Clogged jets / level needle issues, faulty petcock, clogged filter or fuel lines.

[Onekneedown]

What size is the carb and what size is the main jet?