Kickback

[dennis]

I have a log splitter with a Briggs and Stratton 10.5HP. Mod..215802, Type 0114-E1, Code 050726ZA. Sometimes when I start it cold the starter rope kicks back hard. The intake valve clearance is .005 (specs .003-.005) and exhaust is .006 (specs .005-.007). I checked and double checked, and triple checked this at 1/4" past TDC on the compression stroke. It still kicks back when starting cold. No kickback when warm. It runs very well. I have not checked the flywheel key, I admit, but before I do, I would like to know what else may cause this. Thank you.

[bgsengine]

cold hydraulic fluid? can be an issue with direct drive hydraulic pump.

a compression test done cold can maybe tell the tale if it was valves, you'd see higher compression. Other than that it would have to be timing (key) try changing plug gap a bit .020, .025, .035 and see if there's any difference... Plug gap can have some effect on timing.. also volatility / quality of the gas (low octane winter blend ethanol blended fuel that had water in it and drained making super-low octane gas, plus higher compression = preignition)

[smallen]

maybe MCR, compression release, watch exhaust rocker arm for slight movement just before tdc, pull slowwly as you watch, try closing exhaust adjustment to min, .oo3

[dennis]

Thanks bgsengine and smallen. I will check those things out.

[Skywatcher]

Hi Dennis

Another trick to starting some of the heavier pulling engines is to set the crankshaft position before attempting to start the engine. By this, I'm referring to the trick us British motorcyclists used to use. Turn the engine over slowly until you feel the piston coming up on compression. As the piston goes over TDC, you'll feel a little bounce in the starter cord - stop pulling right there.

Now let the starter cord retract to home position. Pull the cord just enough to engage the starter dogs, grasp the grip with both hands and give the cord a firm but not violent full length pull. By doing this, you're giving the flywheel 1½ turns to gain momentum before the piston hits compression. This is usually enough momentum along with the rotational force of the starter to carry the piston over the first compression and get the engine started.

I had one customer who picked up an old (with the wrap around starter rope) 15 hp B&S at a farm auction and had me give it the once over to get it running. After he got it home, he complained that it was the devil's own game to get the brute started. I instructed him to turn the engine backwards by hand until he felt compression, then wrap the starter rope round the pulley to start it. He phoned me back 10 minutes later saying it started great. Hope this helps and all the best,

Sky

[RoyM]

The compression release mechanism on the cam shaft may have failed in which case you need to replace the cam. I learned quickly on high compression engines such as in large chainsaws to slowly bring it up to where compression stops the piston, let the rope retract, then give 'er a firm pull. If it hit compression using Skywatcher's method, the kick back would leave my fingers smarting. A BSA Gold Star parked me on the handle bars, thought I broke my leg.