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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

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.

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.

Rivets said:

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.

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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?

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?

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

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

activelife92 said:

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

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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.

jshep1102 said:

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.

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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.

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.

StarTech said:

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.

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Yes, the spark plug was out and I verified that the piston was at TDC. It really has me stumped. Do you think a new coil can compensate for the flywheel being off that much? I didn't measure it but it looks about 30 degrees off to me.

I just wish someone would take the time to look at one their GX270 for us. I don't have one in the shop right now nor does the service manual show an image of the flywheel to coil timing but 30 degree a lot to be off by in my opinion.

I took a screenshot of a youtube video by Autotech (thanks Autotech) of him removing the flywheel from a GX390. It shows the magnet at about the 12 o'clock position and the piston down about 1" in the bore. With my GX270 magnet at the 12 o'clock position, the piston is at TDC. If I put the magnet even with the coil, the piston is about 1" down in the bore. Not the same engines but something is definitely different (i.e. wrong) with mine it seems.

Thanks to all for weighing in and giving me some things to try. Still stumped though. Looks like I need to tuck my tail between my legs and tell my friend I got my butt kicked with this one. Unless you guys can reach a little deeper into your bag of tricks one more time, I'll admit defeat.

Remember that the spark has ADVANCE so happens BEFORE the piston is at TDC
Typical advances are 25 to 35 degrees of crankshaft rotation

Thanks Bert. Looks like mine is advanced about that much but I still haven't figured out why it's kicking back. I put it all back together today and it started twice with one pull. Woohoo!!!
On the 3rd start, it snatched the cord out of my hand again. It's just teasing me now. Dang it!

Increase the air gap between the magneto & flywheel
This will retard the spark
You can keep on making it wider till it stops snatching provided that it runs fine WFO blades on.
Start with double and see how you go.
The amount of retard will depend upon the sensitivity of the coil & the strength of the magnets
It could just be you lucked in a very sensitive coil + a stronger magnet

Just a wayward thought. Could the compression release return spring on the camshaft be weak and give the appearance of working when turned over by hand but be kicking out too early when cranked by starter rope .leading to kickback.

bertsmobile1 said:

Increase the air gap between the magneto & flywheel...

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That's a great idea! I'll try that today after my bloodmobile donation appointment. Thanks!!

ILENGINE said:

Could the compression release return spring on the camshaft be weak

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I wondered that myself but if I disconnect the spark plug, I can pull it over all day without any kickback. As soon as I reconnect the plug, it kicks back when I try to start it. That points me back to a timing issue.

Has compression been checked on this engine. More for excessive compression not low compression Normal is 85-121 with decompress without decompress is 114-170 Also the other choice is a ignition module with a faulty spark advance.

Grasping at straws here. Make sure whatever is attached to the end if the crankshaft is tight. I have seen mowers with a loose blade kick back.

jshep1102 said:

I wondered that myself but if I disconnect the spark plug, I can pull it over all day without any kickback. As soon as I reconnect the plug, it kicks back when I try to start it. That points me back to a timing issue.

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When the plug is removed, there is 0 compression. To truly test without the plug, use a compression tester in place of the plug. That way you get compression and a reading of how much.

SUCCESS!!! Bertsmobile1 win the prize (if I had a prize to give away). I had the original magneto gap set at 0.010". I set the gap to 0.020" and it jerked out of my hand at 1/2 of a pull. I set the gap at 0.030 and it starts every time and runs great. I wouldn't have ever figured that out on my own. This forum comes through again!!

I'll put a label on the engine cover to remind me (or anyone else that may work in this pressure washer in the future) to set the gap at 0.030 to prevent this kickback issue.

Thanks again to all those who offered advice. Thanks most to Bertsmobile1 for figuring it out for me. WooHoo!!

With a gap of 0.030" there is something that is wrong.
Illingine is probably right & the timing chip in the coil is bad
But the old saying "If it is working don't try to fix it " comes into play

Have a close look at the exhaust for black smoke and check the plug for soot.
If the spark is too late then you get a build up of soot on the plug & exhaust valve .
You can fix the plug by going one or two grades hotter ( with NGK's ) but you can not fix the valve build up other than by turning the fuel off & starving the engine rather than using the ignition switch .
OTOH mower engines are very low tech lazy engines and will usually run quite happily over a massive range of mal adjustments
Also be watchful for signs of overheating but if it works then go mow .

For those who are unaware , the spark timing vs air gap is an inverse square relationship so 3 times the air gap is around 1.2 deg of crank rotation.
Those of you who play with Runtronics ignitions in your model aircraft will be familiar with this method of timing .
Yamaha also used it on some of their flywheel magneto motorcycle engines till they developed a much better ( thus expensive ) control module

bertsmobile1 said:

Have a close look at the exhaust for black smoke and check the plug for soot.
If the spark is too late then you get a build up of soot on the plug & exhaust valve .

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My buddy picked up the pressure washer today and will keep an eye out for these issues. If they appear, we'll order a new magneto and go back to 0.010 gap. Thanks again for all the help!!

Update - the pressure washer started fine for a while but recently started kicking back again while trying to start it. My buddy ordered a new ignition coil and set the gap back to 0.010". No change with the new coil. Still kicking back. I think I need to order a book of matches and some gasoline.

move the coil back another 0.005"
This will retard the ignition a poofteenth .

If its like the GCV200 mower the cam timing is off and there is a video on youtube showing how to adjust this. I had two brand new Honda HRX217HZA's both fail within 4 days of the first mow. Cam not working with automatic compression release so its firing too early. I also talked a honda mechanic that has 35 years and he said even though the service manual says adjust valves at TDC, he said go a hair past that because at TDC sometimes the automatic compression release still won't function. He's repaired dozens and dozens and that is the adjustment he makes. There is also a couple of videos on honda pressure washer valve adjustments.

All, the GX270 and corresponding GX390 et al have a compression release issue. There is a new camshaft available to remedy this concern. If under warranty, any capable Honda dealer can replace the camshaft. I monitor these issues daily, so this is a fairly common occurrence.