Violent Recoil on Wheeled trimmer

[Bat57]

I have a B&S engine (10T502-0457-B1) that when I pull it a couples of times it seems ok but then when I go to pull it again it will violently snatch the pull rope back. I checked the flywheel key and it seems to be fine. What else would possibly cause this reaction. Any help would be appreciated, If I get it to start it will run but it will pop every now and then. Hope you guys can help. Thanks.

 

[Scrubcadet10]

could be valves out of adjustment, flat head engine so grinding the end of the valves a little at time usually opens the gap back up....

10A000 Thru 10M000

L-Head Aluminum/Cast Sleeve Single Cylinder

.005 / .007

.007 / .009

Intake 005 to 007, exhaust 007-009, thousandths of an inch.



the flywheel key should make a perfect a square in the key slot... if any doubt, remove the flywheel and l o o k.

 

[StarTech]

Slight change to Scrub's posted valve specs. The following is per Briggs Power Portal

Intake Valve	.004-.006 in (.10-.15 mm)
Exhaust Valve	.007-.009 in (.18-.23 mm)

Also camshaft that has mechanical ACR that can fail. So look for the bump of one of the valves (I believe it is the exhaust on this model) just TDC compression stroke.
Also has plastic on steel cam lobes that slip out of place.

 

[Bat57]

could be valves out of adjustment, flat head engine so grinding the end of the valves a little at time usually opens the gap back up....

10A000 Thru 10M000

L-Head Aluminum/Cast Sleeve Single Cylinder

.005 / .007

.007 / .009

Intake 005 to 007, exhaust 007-009, thousandths of an inch.



the flywheel key should make a perfect a square in the key slot... if any doubt, remove the flywheel and l o o k.

Thanks for the info, i will check that.

 

[Bat57]

Slight change to Scrub's posted valve specs. The following is per Briggs Power Portal

Intake Valve	.004-.006 in (.10-.15 mm)
Exhaust Valve	.007-.009 in (.18-.23 mm)

Also camshaft that has mechanical ACR that can fail. So look for the bump of one of the valves (I believe it is the exhaust on this model) just TDC compression stroke.

Also has plastic on steel cam lobes that slip out of place.

Thanks, I will check that.

 

[Fish]

Sounds like you are using an engine from a push mower. If so, you will have to find another flywheel for it, as the pushmowers have a much lighter flywheel.

 

[Hammermechanicman]

I assume you have the engine on a push mower with a blade on it. Things that can cause kick back are a partial sheard key and a loose blade. Valves in a briggs L head engine vary rarely need the lash adjusted unless valves are worked on. If the engine does not have a blade on it will start and run but can kick back trying to start and sometimes have a rough idle. The blade augments the lighter flywheel on mush mowers.

 

[StarTech]

It is a two wheel string trimmer. And that engine could have the light flywheel; although, I would think the OEM would selected the heavy version. Easy to tell if light weight weight as it will aluminum vs cast iron.

 

[Hammermechanicman]

I just reread the original post. I missed the string trimmer thing. It probably does have a heavy flywheel. I built my own string trimmer using a push mower engine with the aluminum flywheel. Works ok but a heavier flywheel would help.

 

[Bat57]

Sounds like you are using an engine from a push mower. If so, you will have to find another flywheel for it, as the pushmowers have a much lighter flywheel.

It is the Original engine that came on the Poulan Weedeater WT4000C.