billet flywheel and timming on engine

ruicunha

Member
A completly noob question.

I instaled and billet flywheel and sparks plug get really dry dark after some laps engine bogs at low rpm until it fails.

What is normal degree timming on a gx390? i have a 6 degree key installed.

my engine has stock crank, modified cam, 30 mm carb with big air filter, harder springs, rpms are prob 6000.

The flywheel already has 24 degree with stock key, should i change key to stock or just change carb low jet to a smaller one.

Thanks alot.
 
What is actual timing?
Is cam timing correct?
Verify cam and ignition timing first.
Degree wheel.

Most have trouble getting enough fuel to get off idle to get on main circuit.

Too cold a plug on gas can be problematic, especially with idle times.

Just some thoughts.
 
When i installed key the image on instructions said the notched part should be to the left, that means im changing the timming, from 26 .º to 20.º. Prob i should install the stock key and get 26.º.

Ill verify everything again. Thanks.
 
Nope thats right .
the flywheel turn too the right if you move it forward to the right thats advancing it .
visualize the piston at the top tdc with out piston movment . then the flywheel turning forward or back.
ahead of the piston or behind the piston .
 
What is actual timing?
Is cam timing correct?
Verify cam and ignition timing first.
Degree wheel.

Most have trouble getting enough fuel to get off idle to get on main circuit.

Too cold a plug on gas can be problematic, especially with idle times.

Just some thoughts.
 
What flywheel are you using? I've never built a 390, but I know with the 212's, in general the ARC flywheels are designed to use a stock key, so if you're using an offset, that in and of itself may be your issue. Again, never done a 390, so I could be completely wrong. I'd check the installation instructions that came with the flywheel though...
 
Even with stock flywheel and stock key i get black smoke out of muffler, and engine bogs at low rpm when i rev up.
changed coil and have same issue.
Flywheel doesnt seem to be the problem.
will try a diferent plug, can some tell me the ngk plug reference for a hoter plug?
 
Even with stock flywheel and stock key i get black smoke out of muffler, and engine bogs at low rpm when i rev up.
changed coil and have same issue.
Flywheel doesnt seem to be the problem.
will try a diferent plug, can some tell me the ngk plug reference for a hoter plug?
Once your timing key install is verified to be correct then you can start work on the carburetor. If this is an aftermarket slide carb you're very likely gonna have to do some tuning. Something fuel related is causing your issue. That "black smoke" is a sign your engine is getting way too much fuel. If you're new to this, there are many videos online about how to set up your carb.
 
I had to learn by myself how to solve the problem, the 30mm carb had a 48# pilot jet installed, way too big, installed a 42 and then a #40 and the problem is fixed, still testing and probably ill install a #38 jet.
 
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