Small engine backfiring through intake.

I was working on a Kohler Command 18hp v twin. It was running terribly and was backfiring through the intake, shooting gas 4 feet in the air out of the carb.
I tried everything, until I pulled the valve cover and noticed the exhaust rocker arm was loose on one cylinder.

[@kevwills858]

Im searching youtube to discover a similar puzzle .. A friend wanted me to service a 2nd hand machine he bought and said it Backfures .. Serviced engine plugs oil n air and has 150psi both cylinders. But this 27hp Kohler backfires through exhaust and carby on Deceleration all the time .. Previous owner obviously had replaced entire carby(evidence by shine) .. So I am searching web (Not much info) and will check valves next couple of days.. Its a 2004 engine on a concreters ride on power trowel (we cal them concrete helicopters here in oz) Thanks for posting after the grief/frustration that you experienced 👍👍

[@kevwills858]

I found the problem, which was hard to discover ... It was a bad wire joint that goes to the 'fuel cut off solenoid' on the carby. I accidentally found it when removing the flywheel cover plates ... someone had joined it (possibly years prior). It was sitting in the crimped connection, but easily pulled out when I was checking wiring. The backfiring was being caused by fluttering on/off solenoid actions ... The flow of air in the cowling covers must have pushed it to connect at high revs, but temporarily disconnect on quick deceleration .. It started fine and ran on full throttle ok ... It just always backfired on deceleration 90% of the time... Rare fix Im sure .. but check carby Solenoid wire connections are all tight.

[@chriscostlow4210]

Good rule of thumb is backfiring out of intake is valve timing or valve related. Out the exhaust fuel related.

[@masongettman1687]

what if it’s both

[@chriscostlow4210]

@@masongettman1687 I would first pull the spark plugs and see if raw fuel is on either. If on 1 plug I would check coil for that cylinder. If on 2 plugs the needle in the carb possibly stuck. Then for intake backfire I would pull valve covers and verify all pushrods in place. If so adjust valves. Many issues involved with a engine just not having a regular valve adjustment.

[@bartdelege929]

By getting bigger exhaust Lash, you get real good backfires, but a bit Richer mix does help

[@hbeezey]

I was expecting your camera to show something at some point but you're just filming your bench I guess.

[@jonhsmith2706]

Lmao that's funny

[@kevwills858]

He's just providing information that youtube doesn't have. Kids that want pictures always struggled at storytime

[@johncue9971]

Excellent advice!!!

[@mattclark2784]

I'll do that thank you I appreciate your help

[@Whitestrash]

No problem!

[@valentasd8217]

Hi, goog video. But i have question. After i repair engine head (polished valves and seats, adjust valves gaps and so on) end engine not start properly, misfiring from carb. Compresion in this engine is 12bar. Timing is corect. So the questions are or its posible that intahe valves are leaking but i have good compresion? Can this misfiring are becouse my ignition coil is bad? Thans

[@Whitestrash]

Maybe double check the timing. Even 1 tooth off could do this.

[@Snowmonkeypablo]

I have a 40's chinese gen , it is doing same thing ,very small 40cc will get to it today ,its Always a process of elimination isint it ,with possible suggestions on the way,thanks for reassuring my suspicion.

[@ArizonaKid]

First but can’t back fire sometimes be rich gas ?

[@Whitestrash]

If it's a rich mixture it typically backfires out the exhaust. A lot of times if it comes out the intake it's a timing issue. In this particular case, the exhaust valve wouldn't open and everything was coming back out of the intake.

[@ArizonaKid]

@@Whitestrash ya I’m no mechanic, thanks for info , some times the quad can do light back fire on heavy rev up and then quick fall back fires lightly and I was told rich gas , so you confirmed it for me , nice knowing smart pepper on KZbin . Thank you my friend

[@Whitestrash]

@@ArizonaKid In no professional, but I tinker for sure. My Honda rancher backfires slightly on decelerating, this is a lean condition. Hondas are generally very lean, ya know, to save the polar bears. And it's always good to have people in your corner for the zombie apocalypse!

[@santaclause2875]

@@Whitestrash Greta would be proud!!!!

[@kevwills858]

Backfiring can be lots of things (excess carbon in combustion chambers, timing etc ..) Start with the simplest things first and not 'the KZbin guaranteed fix' Valve adjustments are easy, but often overlooked or just shunned off.

[@NoPeoblem389X]

It had to be missing

[@Huero805]

It would of helped if you had the Valve train in front of you??

[@Whitestrash]

I hear ya. I worked on this remotely and i had no way of filming it on site.

[@Huero805]

@@Whitestrash you should of waited till u were able too otherwise this video sorda useless sorry

[@kevwills858]

@@Huero805 Not useless if you understand description .. and what he explained in steps ...

[@kevwills858]

A thousand words can paint a picture to the blind. Listening is vision without sight ... n better than no information at all .. just my opinion ..

[@Huero805]

@@kevwills858 well thankfully I'm not blind

[@losmoore3358]

It would have been nice if u could actually video yourself step by step working on that problem. I like to learn instead guess what is being said.

[@mattclark2784]

I have a Koehler command 25hp, the left side plug get black with carbon and the exhaust on that side get fire hot in a short period of time. I check rocker arms both on good. any ideas? Thank you

[@Whitestrash]

I wonder if the exhaust port is restricted on that side? Maybe pull the exhaust off and take a look?