Someone asked almost EXACTLY the same question about a GX160 (ProKart) engine only a few days ago. The answer is to go back to the BASICS and do this systematically:
Engines fail to start for MANY reasons and you should be able to start the diagnosis steps for yourself.!
(If you HAVE done these steps, why haven't you TOLD us?)
Engines need four basic things:
1) Fuel
2) Air
3) a spark!
4) Compression
after that comes:
5) Exhaust
6) more esoteric things like 'timing' etc.
Start with the EASIEST:-
However, note ONE safety rule! If you spin a motor with the plug out, you MUST ensure that a plug IS connected and is pressed against something that can 'earth' it! E.g, rest it ON the cylinder head! We have been told that NOT having that connection can damage the coil! There are arguments about if that is true or not but why find out the HARD way?????
Check the spark
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Remove plug
place on cyclinder head with plug lead CONNECTED
'spin' the motor and look for spark
If it DOESN'T have a spark..... guess where to start!
Then check for fuel
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Remove plug
Inspect plug, if it's 'wet' with fuel (i.e., wet with thin liquid and NOT covered with oil) then the FUEL is getting there or else it CAN'T be wet! Secondly, smell the plug, the plug hole and the exhasut, if they ALL smell of PETROL, then it MUST be getting there
If it DOESN'T smell of fuel...... guess where to start!
Check for Air
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Remove plug
Spin the motor and OPEN throttle during the spin. If the note is significantly different open/closed, then it's likely that the air IS passing through the engine.
Need I say more?
Compression
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Remove the plug
Jam your finger over (not "INSIDE"!) the plug hole and spin the motor. If you finger is FORCED off the hole, you have a fair amount of 'compression'. This will tell you if a valve (on a 4 stroke) is JAMMED open, a holed piston, broken con-rod etc.
Now, put the plug BACK and spin it again. Does the engine FEEL as though there is 'compression'?
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The lack of 'exhaust' (i.e., blocked exhaust, by a rag etc..... it's all TOO common in karts!) is a different problem. This usually will allow the engine fire but not to RUN!
So.......
Tell us the 'score' from the above tests and we'll have SOME hopes of helping you!
**********
Remember, I wrote this for someone who had just rebuilt his motor but didn't seem to undersstand the simplest 'basic' of diagnosing the 'area' of the problem! Hence the 'grumpy' tone of my reply!
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Obviously, I haven't covered it ALL. E.g., if the plug is COMPLETELY dry, then you need to check the fuel SYSTEM. Again, start THAT with the 'basics'!
Is there fuel in the tank?
Is it leaving the tank and flowing along the fuel lines?
Are there HUGE bubbles in the line?
Does the fuel GET to the carb?
Does the Float chamber (in your case) have any FUEL in it?
What happens if you CHOKE the engine when spinning the motor? (Do you KNOW how to choke the motor by using your hand? It's NOT just sticking your hand OVER the hole!!! You MUST (must, must, must, MUST!!!) open the THROTTLE or it does almost NOTHING!)
Is the Plug WET after choking?
Etc.
Etc.
If you can answer those, we can help. However, in 95 times out of 100 times, the very ACT of doing those BASIC checks will diagnose the WHOLE problem for you!
In your specific case, it's likely to be FUEL as you've been fiddling with the carb. So;-
A) Is the plug WET
If it is, then you ARE getting AT LEAST enough fuel. If not, then you know ehere to look!
B) Is the plug TOO wet?
If so, remove the plug, remove the carb and spin the motor over VIGOROUSLY! This can easily help to eject (as a sticky mist) the excess fuel/oil that's sitting in the motor. Now, fit a NEW plug, refit the carb, squirt a SMALL amount (under 1cc) of petrol through the carb and try to start the motor WITHOUT re-connecting the fuel lines (if you have an external pump, make CERTAIN the fuel line is fed BACK to the tank F*I*R*S*T!!
If THAT doesn't make it fire, then use 'Easy start' (Yellow and Blank spray-can of damned-nigh neat ether, bought from Halfords, etc.) into the carb while spinning the motor! If THAT doesn't do it..... I'd go BACK to checking the spark!
Easy-start has a VASTLY lower 'ignition point' than does the fuel and often, even if the engine is FLOODED (but the plug is clean) then it WILL fire! That can be enough to kick-start the process.
It also has the advantage of being a FABULOUS cleaner of 'oil' off things.... e.g., wet plugs! Use the stuff to 'wash' the tip of the plug and let it dry. You'll then have a 'not flooded' plug.
Ian
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Rotax Max engine not starting. by 'PaulClarke' (24 Sep 2008 @ 9:32)
