Honda GX160 won't run without choke on

[m_c]

Neighbour asked me to look at a rotovator. Says it was running fine, then started running rough and cutting out.

I have so far stripped the carb as much as possible, left in the ultrasonic cleaner for a while, and checked all jets were clear giving everything a good blow out with carb cleaner and air.
Tried a new spark plug.
Cleaned out the tank and filter as there was a little dirt in it, even though plenty fuel runs out the float bowl drain.
Tried fresh petrol.

It will start first pull, but with the choke off hunts at full throttle.
A little bit choke and it runs nicely. At idle, it will just die unless the choke is on.

I'm not sure what to check next, as every major engine fault I can think off, would either make it hard to start, or run continuously poorly, unless there is something cracked/holed/gasket blown between where the carb bolts on and the cylinder head, but there wasn't anything noticeable when I had the carb off, but there was still another cover in the way.

So anybody got any suggestions?

 

[Kram]

My engine auger had simlar sounding problems, It was an air leak where the cyl head bolts were vibrating loose and running lean, eventually damaged the piston and barrel. For a while it would only start on choke or with a spray of brake cleaner, and only run with some throttle.

 

[Blue Boy]

I've always found that hunting under load with those engines is a dirty/blocked pilot jet. Would be worth cleaning again IMOA.

 

[m_c]

My engine auger had simlar sounding problems, It was an air leak where the cyl head bolts were vibrating loose and running lean, eventually damaged the piston and barrel. For a while it would only start on choke or with a spray of brake cleaner, and only run with some throttle.

I've just found a parts diagram, and it appears that it's a heatshield with a gasket either side, that goes between the carb and cylinder head. The outer gasket was fine, but I wonder if the inner one has split. I might try some brake cleaner with it running tomorrow to see if it's sucking in air where it shouldn't.

I've always found that hunting under load with those engines is a dirty/blocked pilot jet. Would be worth cleaning again IMOA.

Done it once with the carb still on, then again with the carb off.
It's a basic fixed jet, which you can see daylight through.
Idle adjustment is done via an air bleed adjuster with limited adjustment, but if that was blocked, it would be running too rich.

 

[addjunkie]

Complete carb can be had for 20 quid…

 

[Blue Boy]

Have you taken the pilot jet screw out to clean? You would need to cut off the lug that limits it's position or prise off the cap as in the link below. I've a few off these engines and they all get blocked pilot jets/passages/screws when left for a while, they all start and run when that happens and hunt at throttle. I normally have to strip and clean them every spring and I've never got one clean and stopped the hunting without pulling out the pilot screw to clean it effectively, often needs a couple of attempts as the passages in the carb are small.
GX160 Fault Finding
With the lug off the pilot screw you can tune the engine to tick over and run better, by ear. Just count the turns to seat the screw before unscrewing and set it back to that once cleaned as a starting point, 1 1/4 turns from memory.
Good luck.

 

[Smallfry]

Got to be fuel. Honda are brilliant engines, and the ones I have always start first pull, even if they have not been used for months.

Water/condensation in the fuel system would be my first guess, so clean the fuel tank and lines, and completely strip the carb and clean the jet/s.

Or just buy a new carb.

 

[julianthegypsy]

I once overhauled an old Suffolk colt mower. Simple engine but wouldn't run right. Jets were completely clear, I could see through the pilot jet, clean as a whistle. Then I got a piece of wire, poked it through and there was a piece of totally transparent plastic stuck in it. I don't even know why I decided to try poking a wire through it since it looked fine. Anyway, problem immediately solved and ran sweet as a nut.

 

[m_c]

Had another go with this this evening.
I hadn't bothered taking the idle air adjuster out as I could blow carb cleaner and air through it. However to make sure, I got the die grinder out, ground down the lug, and tried adjusting it. Still wouldn't idle with adjuster fully closed. Tried winding it out a few turns, but little difference.

Took the rocker cover off to make sure valve clearances were good, which they were, and everything seemed how it should be.
Rebuilt and no difference, so left it in frustration.

Done some other work then tried it again, and it's now running fine .
I'll give it proper test tomorrow, but I have no idea what the problem has been

 

[KemppiFrog]

After you ground it's lug off, it got frightened of what you might do next

 

[dobbslc]

It identifies as a female so it will do what it likes when it likes.

 

[Keith 66]

I recently hada similar problem with an outboard motor, two things, blocked jet & crankcase mounted vacumn fuel pump. Diaphragm had perished with the new unleaded fuel. Now both things are sorted it runs like a dream.

 

[m_c]

AARRRGGGGHHHH!!!!
£&£$*$&£ thing ran perfectly for me during a 15 minute test, so dropped it back, and it's playing up again.

New carburettor has been ordered.

 

[MattF]

Complete carb can be had for 20 quid…

AARRRGGGGHHHH!!!!
£&£$*$&£ thing ran perfectly for me during a 15 minute test, so dropped it back, and it's playing up again.

New carburettor has been ordered.

You should've listened to him.

 

[m_c]

New carb hasn't fixed it.

It now won't even run for more than a couple seconds, which is what it was apparently doing when it got delivered to me the first time.
Even pouring petrol in the spark plug hole makes little difference.
Spark is nice and bright.
But with the air filter off, it does seem to pop back through the carb, but not in a back firing kind of way, so I suspect there's a sticking valve issue.

Compression leakage tester seemed fine with no major leaks, but if it's just a sticky inlet valve, it might just be slow to close.

 

[GRW]

I'd still think that @Blue Boy is likely to be correct.
Ive seen any number of small Honda generators with thus issue, and my own EX1000 was just the same.
The cause - is usually the machine being left with unleaded fuel in the carb. You must drain or run the carb dry unless its in regular use.
Unleaded fuel when it evaporates or dries up.... leaves behind a hard varnish like residue. On bigger cars it's usually not enough to cause a big problem - but on dinky engines the varnish gums up pilot jets yes, but also the small galleries in the body and the tiny holes in the brass atomiser tubes above the main jet etc.
It took a dull strip-down, & couple of sessions in the ultrasonic cleaner using proper carb cleaner to get my ancient EX1000 running properly off-choke without hunting.

 

[julianthegypsy]

It may want the tappets setting? Common problem with old side valve lawnmower type engines, they tighten over time then leak when they get hot. On those engines that meant grinding a bit off the end of the valve stem...

 

[m_c]

It's an OHV engine, and I've already had the rocker cover off to check for anything obvious.
Next step is to remove the cylinder head to see what is going on.

What I do find notable, is the new version of the machine now comes with a bigger engine, so I suspect the GX160 is possibly being pushed a little too hard.

 

[m_c]

Now that it's warmed up a bit again, I found some motivation to have another look at this.

Opted for one last try before dismantling, so dragged out the venerable LPG and Sievert torch to fire some gas in it.
Flames were most definitely fired the wrong way, so much it even lit the torch at one point.

Opened up the inlet valve a few extra thou, but no change, so removed the head.
Inlet valve seat is burnt/worn/pitted around the bottom.
I wouldn't have said it was bad enough to stop it from running completely, but gave it a clean up, dug out the Gunson valve lapping tool, and gave it couple minutes with the rough paste. Looked like good contact from the paste, but cleaning it off showed a definite lack of contact around the lower third of the seat.

A closer look at the bore revealed staining and a bit of pitting, so I suspect it's been sat getting water in it. It does life in a poly tunnel, and the air filter housing has been damaged at some point.

If I can get somebody to cut the seats locally for a reasonable cost, I'll give that a try.

 

[qwakers]

why bother?

Pardon our interruption...

or

Genuine Honda GX160 T1 Cylinder Head - TKI-7 | eBay

Goos quality head, perfect for modding.

www.ebay.co.uk

or

https://www.amazon.co.uk/Hippotech-Cylinder-Assembly-5-5-6-5HP-Gasoline/dp/B086R5BNJT/ref=asc_df_B086R5BNJT/?tag=googshopuk-21&linkCode=df0&hvadid=641663919012&hvpos=&hvnetw=g&hvrand=10642093090634083149&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1007099&hvtargid=pla-1597651730342&psc=1&mcid=bda081090acc3991b705a1d7b89f47ef

etc