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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 12592
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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HM100 new caburator, new coil, new air filter, new spark

Customer Question

HM100 new caburator, new coil, new air filter, new spark plug and new gas it won't start it has good spark and the lug is soaked with gas
Submitted: 25 days ago.
Category: Small Engine
Expert:  JohnF2015 replied 25 days ago.

Hi, my name is***** will be assisting you.

You have indicated that you have good spark and you are getting fuel to the plug since it is wet. What is the compression on the engine like? Have you checked the flywheel key? On this engine the flywheel key could be sheared and 90 degrees out of time but the ignition will still fire to the spark plug every time that the flywheel magnet passes by the ignition coil. It is not like the old point style engines that would not fire if the flywheel key was sheared.

Customer: replied 25 days ago.
I check the flywheel kids fine and it seems to have good compression but I didn't test it
Customer: replied 25 days ago.
Nothing about this makes any sense even with low compression that should start it won't even pop
Expert:  JohnF2015 replied 25 days ago.

What happened leading up to all of the parts replacement that caused you to replace the carburetor, ignition coil. Was the engine running prior and died? Fill me in on a little more background about what happened prior.

Customer: replied 25 days ago.
The engine is on a generator seven days after last use it just won't start I tried to get it to run and nothing so I change the coil still would not run so I bought the carburetor instead of putting a kit in it still would not run so I bought a new air filter drain the gas put new gas in and bought a spark plug it's still will not start won't pop nothing
Customer: replied 25 days ago.
I bought the generator used for $80 I have over $100 trying to fix it I should've thrown it away
Expert:  JohnF2015 replied 25 days ago.

I assume that the last time it was working it was running okay? You shut it off and now it won't restart.

You have verified that it has good spark and that you are getting fuel to the plug, the only other thing that could be an issue is the compression. If the compression is too low it will not fire. Odd however that you weren't having issues before.

Do you have access to a compression gauge?

Customer: replied 25 days ago.
No
Customer: replied 25 days ago.
It pulls over hard like it has plenty of compression
Customer: replied 25 days ago.
I unhook the wires to the switch in the oil and the Killswitch sure nothing is grounded
Expert:  JohnF2015 replied 25 days ago.

Since it is on a generator that can be misleading because you are having to turn the rotor on the genset which does have some resistance as well.

Customer: replied 25 days ago.
Even with low compression the gas should fire
Expert:  JohnF2015 replied 25 days ago.

You indicated that you were getting spark to the plug so I wasn't concerned with any grounds in the system. The only thing that I was concerned with is the flywheel key due to the fact that if it is sheared you will still get spark but just not at the right time in order to start the engine. Everything else can seem fine, you are getting fuel since the spark plug is wet.

Customer: replied 25 days ago.
I did pull the flywheel the key is fine
Expert:  JohnF2015 replied 25 days ago.

If the compression were too low it would not fire. This engine would normally run around 60PSI compression, if it fell to let's say 35PSI it is not likely to fire. You might get an occasional pop if you pulled the rope enough times.

Customer: replied 25 days ago.
I guess I will find a compression gauge
Expert:  JohnF2015 replied 25 days ago.

I am going to opt out of your question which will allow for one of the other experts here to add any suggestions that they might have. I believe that you are dealing with one of two issues but maybe someone else has a different suggestion or thought on your problem.

Customer: replied 25 days ago.
Thank you
Expert:  Curtis B. replied 25 days ago.

I concur with Jon, with spark plug being wet with fuel, and having good spark, and getting nothing . I think you are going to find your compression is too low to fire the cylinder. The valves may be too tight and are leaking, but to adjust, you have to remove the valves from the block and grind off the ends, to get clearance.