Does it smooth out if the throttle is moved back? Sounds like the choke may not be open in the run position.

Is this on a Honda mower with hand throttle or just a Honda engine on some other mower? The generic GCV has an automatic choke, and the Honda mower has a manual.

Thanks guys for the feedback.

Actually the choke was my first thought. I removed the air filter and ran it through it's paces while watching the choke. The choke butterfly stayed open the entire time. The rich running is something other than the choke. It's also something associated with two separate carburators.... both act exactly the same. When you manually advance the throttle plate, the system goes rich and begins to spew black smoke and cough. shutting off the fuel allows the engine to smooth out and run normal until the gas runs out.

This engine had been operating flawlessly and whatever happened, occurred during normal operation. That is to say, no one had been working on or changing anything prior to the start of the trouble.

I'm really puzzled on the fact that two carbs perform the same. I simply cannot imagine what could cause this other than the carb and it's difficult to believe a new carb would "the same" problem as the original one.

Is the fuel clean and fresh or is there any dirt in the tank? This does seem odd.

I flushed the tank out when I replaced the carb. Inspection of the old fuel revealed nothing. It looked clean.

Odd is right...

Ghostrider,
Did you ever find the problem? I found your posting while searching for the solution to the same problem with my GCV 160. Mine runs rich, too. It is new this year and ran great for the first 15 hrs, after that it started running rich. I purchased the mower in the States and had it shipped overseas, so I can't go to a dealer for parts. I've checked the obvious like bad fuel, corruption in the carb, etc. I even pulled the flywheel off wondering if the key was partially sheared which would cause the timing to be late and therefore causing it to run rich. I'm going to work on it again tomorrow, so I'll let you know if I find something.

When ghostrider and boomerang feel like answering my question, perhaps I or others may be of assistance. We have to know if the Honda engine is on a Honda or other mower.

Mine is a HONDA mower HRC216PDA.

Both of you may want to check the gaskets and insulator block orientation between the carb and head. Vent blockage on the backside mounting of the carb can affect running.

Pete-
Your problem MIGHT be caused by a weak spark, either plug or coil.
My thinking for this is-
When you open the choke, the engine can get its full air supply. This causes the compression to raise to its "normal" operating range. A bad plug/weak spark may not fire under these conditions.
I'd replace the plug for a start.
Will the engine run OK if you throttle it back to idle speed? That would tend to substantiate my theory.

My only similar issue I've seen on one these was a valve sticking slightly. It was an early spring tune up a couple of years back. This one ran but stumbled. It's worth a shot to remove the tappet cover , bring it to Top deadcenter and push on the valves by hand. Double check that you still have valve clearance. If a valve is gummy on the stem, a little gumout followed by lube will do the trick. Beyond that, I would check the flywheel key. As Bill had pointed out, a coil is possible- tho these aren't really noted for it. Maybe the cd in the coil went kerfluey. SIgned, grasping at straws.

Hi Guys
Thanks for the input. I've just had another tinker with the mower this afternoon. I've attached a timing strobe to the plug lead to check the spark (the strobe flashes on each spark) and the strobe still flashes ok as the engine dies right up to it finally stopping, so it seems that the spark is ok. I'm assuming this engine sparks on the compression stroke and also on the exhaust stroke (the wasted spark principle) as there is no spark distributer just the coil with plug lead attached directly to it.
I've also completely removed the muffler from the engine just incase it was blocked and causing some back pressure, but the fault still persits. The air filter is also removed so I can see the choke butterfly is fully open when I push the lever forward. After 10 to 20 seconds the engine splutters backfires a few times with black smoke from the exhaust then dies. When the engine starts I've also tried turning the fuel off just to prove the carb is not flooding. Still the same black smoke and backfiring. I'm assuming there is a spark on the exhaust stroke which is causing the backfiring of the unburn mixture from a previous misfired compression stroke.
The idea of a valve problem is interesting as I'm beginning to think this fault is not a simple one. Is the cover easy to remove, as the engine is OHC, can the valve clearances be adjusted easily with locking nuts and screwdriver type adjusters, or are the valve lifters shimmed.
Thanks Pete

The spark is timed via a capaciter in the coil pack- hence, you can have spark- but be out of time or fire erratically. This is not real common on these, but possible. A timing issue would more likely be the flywheel key. The valve cover is sealed with sealant and sometimes has to be chased to remove. Tappets are adjustable at least on some of these. I've never had a timing belt jump- but aw, what the heack- let's throw that into the mix too!

Spark plugs are TOO CHEAP NOT to replace when having engine problems. Worst case is you have a new plug on a 5 year old engine!

I've had a similar if not identical problem with my Honda mower going on 3 years now. It will start and run great then start to miss and die. It seems like a classic fuel starvation problem but it seems to be getting fuel fine and the float is non adjustable. I can see that the float needle is not stuck. Soaking the carb in carb cleaner seems to help sometimes but the problem is always quick to return. Sometimes when it starts to sputter and die I can move the throttle around and revive it for awhile before it finally dies for good. The gas in the float bowl looks good and things look clean. I pretty much hate this lawnmower now and usually end up thinking about get a corded electric one as my yard is not that big. When the thing runs it runs great so I doubt there are any valve or timing or spark plug problems. Its almost like there is some throttle feedback that goes haywire and ends up closing the throttle. This mower is about 5-6 years old and gets light use and is kept in the garage.

I just finished ordering a bunch of parts from Plano Power equipment. I will post my results once all the parts get installed.

Hi again from the sunny Uk (that makes a change, and also makes the grass grow !!)
Bill is quite right and it's certainly worth changing the plug which I'll do this weekend and report back.

Does anyone know if there are any ignition timing marks I can strobe while the engine is running to see it's staying withing limits, or am I down to locating TDC and making my own.
If the above fails then it looks like getting serious and it's off with the cam cover.

Thanks and regards Pete

Hi dflowers I noticed exactly the same problem on the weekend. My honda mower has around 15 hours on it and the initial symptom was running for about 20 seconds then it bcakfires and dies. The spark plug was black with coke which I cleaned off. The gap looked a little large but I left it. I also drained the bowl and sucked through the jet to ensure it was clear. This helped a lot but it still dies when it hits heavy grass, always accompanied by backfiring which may result in the air filter being blown off. when under load, if I manually accelerate the throttle on the engine body the engine will die (as if it is starved) but if it is not under load it will rev.

I thought this would be indicatinve of lean mix bought about by a blocked jet but the blowing-off air filter makes me wonder if it is mis-firing or has a sticky valve?

I had a small problem with idling about six months ago which was due to a really dirty air filfer which has since been rectified. Could it be just coked up inside? Are there any "mechanic-in-a-can" products that would help out with this?

thanks for any advice.

Josh.

Hi

I've just had another go with the mower for an hour this evening , I bought a new plug today and installed it. This has not cured the fault; after 20 seconds or so the same problem, black smaoke, a couple of back-fires and dies, as it's dying the regulator advances the throttle and this seems to increase the smoke and assist the dying process. Neadless to say there is a good coating of carbon deposits over everthing to do with the exhaust and of course when the plug is removed it has a good black coating on it.
Has anyone has the cam cover off this engine ?
Is the cam driven by a toothed rubber type drive belt similar to a car engine, or is it a notched flexi steel belt of perhaps even a chain ?
Are any special tool needed to adjust valve clearances, and remove the cam or even the head (Torqx or star drivers ect)
By the way you'll be pleased to know the UK weather has resorted to it's usual rainy self today so at least that's back to normal.
Cheers Pete

Hi Guys
Further update, IÂve had another hour with the mower this evening. Before attempting the cam cover removal I thought IÂd check the ignition timing. To do this I removed the red plastic cowling removed the plug and turned the engine by hand to TDC,inserted a thin metal rod to touch the top of the piston, and turned the engine to measure the down stroke (I make it approx 55mm). This gives 55mm X 2 =110 mm for the total down and upstroke of the piston, this is achieved in 360 degrees rotation of the crank.
So a bit of maths (please correct me if IÂm wrong on this one)
360 degree of crank is 110mm piston movement
1 degree of crank = 110/360 piston movement =0.3mm piston movement
10 degree of crank = 110/360 x10 piston movement =3mm piston movement.
( I took 10 degrees as an optimum ignition timing for an engine).
I marked a position on the started ring with fluorescent paint and marked TDC and 10 degrees before TCD and 10 degrees after TDC on the red plastic cowling adjacent to one of the slots in the cowling so I could strobe through it to the starter ring fluorescent mark.
Re-attached the cowling connected the strobe and the engine ran with the timing showing about 10 degrees BTDC on this crude measurement. Increasing the engine speed did not alter the timing after the usual 20 seconds at about 2,000 - 2500 RPM the fault reoccurred but the ignition timing stayed constant until the engine stopped.
I think this has eliminated ignition problems.
Have I missed anything before removing the cam cover ?
Cheers Pete

"(please correct me if IÂm wrong on this one)
360 degree of crank is 110mm piston movement
1 degree of crank = 110/360 piston movement =0.3mm piston movement
10 degree of crank = 110/360 x10 piston movement =3mm piston movement."

OK, I'll correct you:-)

The piston moves much more at the midway point down/up per degree of rotation than at the ends of the stroke.
It moves VERY little near the extremes of the stroke. Just visualize the positions of the crank throw as the piston travels from one end of the cylinder to the other.
Been a long time since I did Trig, but the function that equals 1 at 90 deg. and 0 at 0 deg. is the one to use.

You took the words right out of my mouth Bill. It's for this reason that the highest torque output is at roughly mid stroke where the connecting rod is at 90 degrees with a theretical line between the centerline of the crank and the big end.
A much more accurate way (and a hell of alot simpler) would be to locate TDC and use a protractor to measure off 10 degrees.
when it starts to die, with the air cleaner removed, spray some ether in the intake, if it picks up again for a few seconds with the shot of ether you have at least narrowed down the problem to fuel related.
try not to blow yourself up. :)
So far we have 3 countrys working together to solve this problem! (I'm from Quebec, Canada)Are there any I'm missing?. Forgive my bad spelling
On top of being a Frenchman. I am going on 32 hours with no sleep.(I Don't count the 5 seconds I got while driving here this morning.)

I got all my parts in and my mower seems to be running fine now. I bought a new carb for $30 and installed that first and that fixed it. So something must be plugged or broken in the carb somewhere. I took it apart and cleaned out any parts I could. I also soaked the old one in carb cleaner but that must not have been enough. Once it started running right with the new carb I also changed the spark plug and air filter and that didn't seem to make much difference. I have had such problems with the engine dying over the last couple of seasons that I am still not 100% sure that it is fixed. Only time will tell. But it sure seems to be running normal for two days which is a good start.

OK so it sounds like carb related so not too much dismantling! BTW I am in Australia so you can add a fifth 'provence' to the list! Also mine is a GCV190 (6.5hp)

I will be mowing again in the weekend, I'll report back on how it goes. I am still concerned about the backfiring blowing off the air filter - could this be a serious problem?

Cheers,

Josh.

I have used mine twice since cleaning out the carb and on the second use it appears ot run fine. There was some crud in the carb, and coupled with the coke on the plug I am lead to conclude that the whole thing was coked up. Once I cleaned the carb things started to improve and on the second use it was running really well. So problem solved for me too I think!

Cheers and thanks to all.