GX270 Kickback

[jshep1102]

Hi guys, I need your help again. I'm working on a friend's pressure washer with a Honda GX270 engine (GCBGT-2225859) and his complaint is kickback when trying to pull start it. He said it just started doing this a few weeks ago. He has had the unit since new and has not replaced any parts on it. I figured is was a sheared flywheel key that screwed up the timing. My experience is that it's uncommon on a pressure washer and more likely on a mower that has the blade direct coupled to the crankshaft but I told him I'd check. I confirmed the complaint before doing anything.
Upon inspection, the flywheel key was not sheared, the ignition coil looked gapped correctly but I reset it using a business card (~0.010), the valves were a few thousandths loose so I reset them to 0.006 inlet and 0.008 exhaust (at TDC on comp stroke + 1/4"), I can visually see the decompression mechanism burp the exhaust valve on the compression stroke. After reassembly, the engine pulls over normally when the spark plug wire is disconnected but once I hook up the plug wire, it snatches the pull cord out of my hand violently when trying to start it (pressure washer hose not connected so it's not water backpressure causing a problem). In my mind, that confirms a mis-timing issue but hoping you guys have some ideas on a troubleshooting path forward. New coil? Seems like the most likely cause but that's a strange way for a coil to fail (fire early). Picture attached.
Thanks, Jerry

 

[Rivets]

First, please don’t try to start the unit without the water connected and on. Should you get it to start with no water, you could very easily burn out the pump seals. I’ve seen this more times that I care to count, as it doesn’t take long for the pump to overheat with no water for cooling. Second, with water hooked up try starting the unit, try starting the unit with the gun control engaged, water should be coming out with normal hose pressure. I’ve seen on some units that pressure on the pump slows down the flywheel. Let us know what you find.

 

[jshep1102]

Thanks Rivets, I spent the afternoon playing with chalk and monster trucks with my 2 year old granddaughter. I'll teach her small engine repairs soon so she can fix her boyfriends truck someday in high school.
I'll try starting it with water attached tomorrow after my doc appt and let you know the outcome. I'm also very stingy with any runtime without water attached. Those plastic check valves in the pumps don't like heat.

 

[jshep1102]

First, please don’t try to start the unit without the water connected and on. Should you get it to start with no water, you could very easily burn out the pump seals. I’ve seen this more times that I care to count, as it doesn’t take long for the pump to overheat with no water for cooling. Second, with water hooked up try starting the unit, try starting the unit with the gun control engaged, water should be coming out with normal hose pressure. I’ve seen on some units that pressure on the pump slows down the flywheel. Let us know what you find.

I hooked up water to the pressure washer today and disconnected the spark plug wire again. Like before, it pulled over normally several times with no issues (wand trigger held to relieve pump pressure). When I hooked up the spark plug again, on the first pull the cord snatched out of my hand so violently that it broke the pull cord plastic handle when it hit the recoil housing. Ouch!

Any other recommendations for the GX270?

 

[jshep1102]

I checked everything again. Attached is a picture of the flywheel and coil (cooling fan removed for clarity). The piston is on TDC, both valves are closed with the proper lash adjustment, the flywheel key is intact (checked a second time). The flywheel magnet looks way too far advanced to me. If I put the magnet back at inline with the coil, the compression stroke will not have completed when it fires which will cause it to reverse direction and give me the kickback I'm experiencing. I know the engine will be turning at 3600rpm so there has to be some time delay but this component alignment looks off to me. Am I correct with this assessment or does the alignment of coil, magnet and piston look correct to those of you with MUCH more experience than me?

 

[jshep1102]

Is it possible that the crankshaft is a 2 piece component that somehow spun to throw off the timing?

 

[activelife92]

Could it be the compression release? Had that issue with my new GCV200. It was replaced under warranty.

 

[jshep1102]

Could it be the compression release? Had that issue with my new GCV200. It was replaced under warranty.

I can visually see the compression release mechanism burp the exhaust valve when I have the valve cover off and turn it over by hand. It also doesn't kick back at all if I have the spark plug disconnected. As soon as I restore spark, it kicks back on the first pull.

 

[activelife92]

I can visually see the compression release mechanism burp the exhaust valve when I have the valve cover off and turn it over by hand. It also doesn't kick back at all if I have the spark plug disconnected. As soon as I restore spark, it kicks back on the first pull.

Got it. Well if it’s only kicking when there’s spark, it would seem that there is something off with the timing. Plug might be firing too early or too late..? Just a thought from my non-professional opinion lol.

 

[StarTech]

It may just be a bad ignition coil. It rare but I have seen the electronics in a coil to cause a similar problem on one engine I repaired years ago.

Now I do just one question in reference to your image of the coil aglinment. Did you verified the piston was at TDC when you took the picture? I never seen a flywheel that far off at TDC.