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I just got my 21HP Intex engine rebuilt and put back together. After putting oil in it and turning on the fuel I attempted to fire it. Standing to the side of the mower I pushed the brake lever with my foot and turned the key. It started!! and ran great for 30 seconds....then died!!! I turned it over again and nothing!! Then I thought about it and it should have never started to begin with because I was not on the seat and there is a pressure switch in the seat that prevents it from running without someone sitting in the seat! So I got in the seat and nothing! It is actually backfiring through the carb now!!

I am positive I lined up the timing "dots" on the crank and the cam!

I pulled the plug and I have plenty of spark!

Any ideas what could be wrong?

HELP!!!!!

My first guess is that the flywheel nut was not torqued properly. Now you have a sheared flywheel key. I would start there, pulling the flywheel and checking the key.

You nailed it!! The key was sheared.

Ok, what is the torque on the flywheel nut supposed to be? I will get another key tomorrow and hopefully have this thing running again!

Thanks!

Jeff

Two grunts & a groan.
If you are using normal hand tools you won't be able to overtorque it.
If you break the top off the crank, then let me know there is a place for you in the Mr Universe quest:laughing:

Around to 70-80 Ft/ lbs is where most go.

Without knowing your model number there was a few models that used a bolt for the flywheel, and I can't find it right now but seem to remember the torque was 75 lb/ft and the single cylinder intek engines with the nut have a torque of 100 lb/ft and the intek twins with a 1-1/4" nut is 150 lb/ft.

bertsmobile1 said:

Two grunts & a groan.
If you are using normal hand tools you won't be able to overtorque it.
If you break the top off the crank, then let me know there is a place for you in the Mr Universe quest:laughing:

Around to 70-80 Ft/ lbs is where most go.

Click to expand...

Sound like he didn't put the groan in after the two grunts :laughing:

Note there are two 21 hp B&S Intek engines with different specs.

Walt Conner

Ok, so I replaced the flywheel key yesterday and it pops over with ether but will not run on gas. Is it possible the carb might have been damaged when it backfired?

I still have last years gas in it so I think I will drain it and put some fresh gas in it tonight.

Any other things I might try? Running out of ideas!

Thanks!!

Jeff

jmartin99 said:

I still have last years gas in it so I think I will drain it and put some fresh gas in it.

Click to expand...

You have just answered it!

The thing is the first time I tried to start it when it sheared the key it ran great for 30 seconds without any ether!!

Jeff

Check to see if the fuel solenoid is opening on the bottom of the carb.

jmartin99 said:

Ok, so I replaced the flywheel key yesterday and it pops over with ether but will not run on gas. Is it possible the carb might have been damaged when it backfired?

I still have last years gas in it so I think I will drain it and put some fresh gas in it tonight.

Any other things I might try? Running out of ideas!

Thanks!!

Jeff

Click to expand...

No you can not hurt the carb from a backfire.
You can cause the fly wheel key to break ( as you have already found out ) it can cause engines with plastic timing gears to break off a tooth and go out of time and on engines with belts to skip a tooth.
However on yours, because it runs on starter fluid it most likely has a fuel supply problem.
Slip the float bowl off and confirm fuel is flowing into the carb
Check that the fuel shut off solenoid is fully retracting
and while the bowl is off squirt some fluid up the main jet and watch for it spraying into the carb venturi.

jmartin99 said:

The thing is the first time I tried to start it when it sheared the key it ran great for 30 seconds without any ether!!

Jeff

Click to expand...

I have already said there is more than one B&S 21 hp Intek. IF people don't know what engine you have, how do they know what advice to give? Model number.

Walt Conner