Troubleshooting a 2 Stroke Engine: Tips for Starting and Fixing Common Problems

[Jones1987]

So I'm back home from uni for afew days during summer. My dad has a little bike 2 stroke engine that won't start, so he has given me the job of attempting to get the little thing to start.

The spark plug works. I've taken off the top of the engine block and fitted a fresh seal ontop of the cylinder head. I've made new seals on the connection to the carberetta. I intially thought there was a compression problem. However the engine will still not start.

Any tips where else I should be looking

 

[Q_Goest]

Have you tried starting fluid to see if you can at least get it to turn over? If it runs momentarily on the starting fluid, you can rule out spark problems.

 

[brewnog]

Have you tested for compression? Is the spark timing approximately correct? If both of these are okay you pretty much have a fuel issue. Is the plug getting wet?

 

[turbo]

How long has the engine been sitting idle? Gasoline (at least in the US) with ethanol seems to degrade more rapidly than the straight gasoline available in the past. I put fuel stabilizer in every can of gasoline or diesel that I buy, and that seems to help. My 2-stokes include leaf blower, weed-whacker, small tiller, and chain saw, and they all start up fine and run well. That was not the case before I got "religious" with the fuel stabilizer. It can get pretty tedious to yank on a starter cord for any length of time.

 

[Jones1987]

I'm not too sure exactly how long the engine has been idle. Nothing is rusted for seized. I get a pressure build up when I pit my thumb over the spark plug hole and kick start the engine. I have no idea if the timing is correct. How would I test this?

I havnt tested if the plug is wet however this will be my first job in morn. I will be taking it apart again tomorrow and testing.

When I kick start, sometimes it does give out a small bang asif there is ignition but the engine does not tick.

So if it's a compression issue, what are my next steps?

Timing issue, I'm not exactly sure how I can correct this as to my knowledge this requires
software to change

 

[Q_Goest]

Try starter fluid. Report back.

 

[Ranger Mike]

i been here before..

remove the air filter and check to see if it is clean or clogged..leave off until you get the engine to fire..there is only three things that can go wrong on and engine that has been running..
lack of spark
lack of gas or lack of spark at the proper time...you got spark so squirt some starter fluid in the spark plug hole , replace the spark plug and see if it fires..if it does, chances are the timing is ok so now we have a fuel problem..most likely the line or filter is clogged
if the carb is a float bowl type
the needle and seat may be gummed up not permitting fuel to enter the float bowl..hence no fuel can enter the carb throttle body...if the carb is a diaphram type.. you may have a cracked or broke membrain and again not fuel will enter where it needs too..lets address the simple stuff firts

drain the gas tank by removing the fuel line from where it connects to the carb and place the line in a catch can to collect the fuel. open the petcock under the tank to permit fuel flow...if you got flow thur the filter to the catch can this is a good sign..if it drips out, the filter may be clogged or the little wire mesh filter at the petcock may be gummed up..

se air hose to blow the fuel line to the empty fuel tank before refilling with fresh fuel..
if possible drain the carb and fuel filter..if you have a float bowl carb it should have a drain screw..use it to empty the bowl..if no fuel is present when the drain screw is removed complete the fuel tank fuel filter cleaning described above and replace the fuel i nthe tank..make sure you got a steady fuel stream tot the catch can after the new fuel is added.
close the fuel petcock and reconnect the fuel line to the carb
remember the fuel bowl drain screw is still removed..open the petcock and the fuel should run out of the carb bowl drain hole..if not..you probably have a stuck needle and seat and carb rebuild is in order..you got the idea of how to trouble shoot
pls let me know how it goes