Honda Engine Surging

[KennyG]

This may sound pretty trivial, but I get frustrated when I can't see the problem. I have a Troy Built push mower with a Honda GCV160 engine I use for some trim work. It's one of those cheap ones without a throttle. It's been trouble free for seven years but last week it started surging. It continued to get worse. Obvious problem would be a plugged carb.

I took the carb apart and it looked perfectly clean. I blew it out, confirmed the float and valve were free, put a thin wire through the main jet and put it back together - no change. I repeated the cleaning - no change. It will run smoothly but slowly if you manually hold the choke on. Gas line is flowing well.

I can't think of any other causes besides carb and a new one is only $15 but I'd like to have some clue as to why it's not working. Any ideas?

 

[flyerdan]

It could likely be a bit of obstruction in a passage, or maybe even some varnish buildup on a jet that causes turbulence; a wire might pass through but it will still be irregular. It doesn't take much to put small engines off their game, and the corn gas causes all sorts of issues like this.

 

[tomplum]

Agreed. I've cleaned them the same way and had to get a bit more aggressive to get the results I needed. I did a GCV190 on a pressure washer 2 days ago and it took zipping the tip cleaner trough to smooth it out. Another thing to consider on these is that the valve springs are very light and that does make them susceptible to sticking a bit (or can stick open) due to varnish on the stems. That creates less of a surge,- more of a skip- but it is open to interpretation.

 

[hawkeye08]

My Honda generator surged when I bought it (used) and some SeaFoam and Lucas injector cleaner and all better.

 

[Gunny]

Dose it up heavy with Seafoam and run it, I do it about every other year on my Honda engines, haven't had to tear into a carb since I started doing that.

 

[BleedingOrange]

Check to make sure the impulse line isn,t cracked causing it to suck air in instead of fuel.

 

[KennyG]

Just a followup here. There were a lot of good suggestions on carb cleaning but I decided it wasn't worth it and splurged on a new carb ($20 for Honda OEM). I put it on, it started right up and surged just like before. If I hold the choke on about halfway, it will run smoothly but slower than normal. If I manually hold the throttle open it will rev up and sounds normal.

There was a suggestion to check the impulse line but this engine only has two external lines, the gas line in and the crankcase breather into the air filter.

It seems there is something not working right on the governor but I don't really understand how that works on this engine. It is just a shaft coming out of the side of the engine. At this point I've come up with a short term and a long term work around. Short term I think I will just wire the throttle open in place of the return spring. Long term I'm thinking of disconnecting the governor completely and installing a manual throttle.

Any other ideas?

 

[tomplum]

" If I manually hold the throttle open it will rev up and sounds normal." So by this comment, do I understand that it really runs well if you hold it to speed? If so, you aren't really dealing with a carb issue at all. You will want to know that both the throttle linkage and the little barrel spring around the link is hooked up properly and somehow things didn't get bent or are binding from the past repair. Next, do a static governor adjustment. 10MM wrench, loosen the nut on the clamp part of the governor rod where it comes out of the block. Be sure the throttle is wide open and move the shaft gently in the same direction with a pair of pliers. Hold in place and secure the nut. You may have to adjust the RPMs when you are done. It is best done w/ a tach, but should you need to do it by ear- listen to another mower and get it as close as you can by ear. The RPMs are adjusted by holding the top of the governor arm and bending the lower part of the arm slightly rearward to increase the RPMs. Wiring open the governor is not an option.

 

[KennyG]

OK, round 3. I checked all the linkages/springs/levers and everything moves freely and seems to be in good shape. I didn't expect a problem there since this issue started while it was being used and it's never had any repairs. (In fact, I hate to admit it but the first thing I did was change the spark plug. I've had this mower 7 years and never had the spark plug out. The only times it's been touched has been annual oil changes and blade sharpening.

I followed tomplum's instructions and adjusted the governor. It started right up and ran smoothly for a minute or so and then began surging again. Again, if I hold the lever it runs smoothly and sounds normal.

Tom, I'm curious about the statement that wiring open the governor is not an option. Not an option in that it's a dumb idea or that it won't work, in the spirit of "Hold my beer and watch this." Is there any reason not to add a manual throttle to these engines and disconnect the governor?

 

[flyerdan]

The governor is what keep the engine from exploding due to over revving, which would happen if running it unloaded. If it's still surging with a new carb, the problem could be an issue with the fuel delivery (bad part out of the box, sadly not uncommon anymore), or a weak spring on the governor. Since it seems to smooth out with a little help, see if there is another anchor hole for one end of the spring which will allow it to operate under a bit more tension.