Mantis Tiller won't start

R

ritalz

Member
I have a Mantis tiller model 7222 something with the 2 cycle motor that won't start no matter what I try. I've been through this thing and just don't understand. Here is a list of things tried.
Exact model is unknown as the tag is damaged.

fresh aftermarket carb and fuel lines
new spark plug gaped at 25
compression is around 100 psi
checked flywheel alignment
verified the on/off switch
verified there is spark (thin and blue)
fresh fuel
preset carb adjustment to recommended settings

Not sure if there is a way to check spark timing.

Even tried a dash of starting fluid without getting even a sputter.
Removed the tines for testing and for my safety but that should not matter.

Any suggestions would be appreciated.

Al
 
I suggest you pull the muffler of and heat it up red hot with a torch and burn out the years of carbon buildup. Your compression is a bit low.

If exhaust cannot get out, air/fuel will not get in properly.

It helps to confirm you spark with an adjustable gap spark tester. If no spark, the first suspect is a failed coil. Second suspect is the off/run switch.
 
ritalz said:
I have a Mantis tiller model 7222 something with the 2 cycle motor that won't start no matter what I try. I've been through this thing and just don't understand. Here is a list of things tried.
Exact model is unknown as the tag is damaged.

fresh aftermarket carb and fuel lines
new spark plug gaped at 25
compression is around 100 psi
checked flywheel alignment
verified the on/off switch
verified there is spark (thin and blue)
fresh fuel
preset carb adjustment to recommended settings

Not sure if there is a way to check spark timing.

Even tried a dash of starting fluid without getting even a sputter.
Removed the tines for testing and for my safety but that should not matter.

Any suggestions would be appreciated.

Al
Click to expand...
Timing is set by the flywheel key. If partially sheared, or sheared, it will affect timing.
You need to remove the muffler and look at the condition of the piston, rings, and cylinder. Are they scored or smooth. Only experience will let you determine the amount of scoring unless they are totally trashed. You need a minimum of about 90 psi of compression on a 2-stroke to start/run. Not even getting it to fire for a brief period tells you it ain’t looking good (compression), or you have overlooked something.
 
Tiger Small Engine said:
Timing is set by the flywheel key. If partially sheared, or sheared, it will affect timing.
You need to remove the muffler and look at the condition of the piston, rings, and cylinder. Are they scored or smooth. Only experience will let you determine the amount of scoring unless they are totally trashed. You need a minimum of about 90 psi of compression on a 2-stroke to start/run. Not even getting it to fire for a brief period tells you it ain’t looking good (compression), or you have overlooked something. The only Mantis tiller I have not been able to get running over the years was one with bad compression. Echo makes the engine on a Mantis, and they are basically bulletproof.
Click to expand...
 
The problem is the compression. It has to be above 100 psi for two stroke to ignite the fuel load.

In 17 yrs I have only seen one chainsaw to start below 100 psi and then it ran like crap. Matter it is the chainsaw I have now which I rebuilt.
 
After reading the above comments I went back to test the compression again. Made sure I have a good seal on the tester it registered slightly above 130. I did check the muffler to be sure there was no blockage. The flywheel key is a flat spot on the shaft that matches up with same type of spot on the flywheel. I checked the flywheel to be sure it lines up with the piston being at tdc. Guess I'll keep looking.
 
Where is the plug from? I hear there's lots of clones out there that don't work well, and you should buy from local auto parts store. Don't test 2 stroke with starting fluid, there's no lube in it. You can spray mixed gas instead. Make sure all the gas/vac lines are run correctly.
 
I would make sure that the plug is a genuine one. What happens these days is someone lets a machine like a Mantis sit. It fails to run. They do the easy things first, replace the spark plug, replace or clean the air filter, replace the fuel. It still doesn't run. Then they replace the carb and it still doesn't run. If they had just replaced the carb and the fuel to begin with it would have run fine. The plug they got was counterfeit and kept the engine from running. it happens all the time these days. And it happens to the best. I would GUESS that there are even people who buy counterfeit that doesn't work, then buy a genuine plug, put the counterfeit in the box and take the box back. So, it could happen even if the plug is bought at a known good store.
 
I think I just proved that it's a fuel/fuel delivery issue. Was inspecting the carb and looking in the intake to be sure it was clear. With the carb completely detached I sprayed a little fuel down the throat and pulled the cord. To my surprise it fired and ran for a second before I could hit the kill switch. I have two carbs to play with, the original and a pos aftermarket. My next project will be to try to make one of them work using parts from both. Might still be an uphill battle but at least I have a clear direction.
 
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