Harmony 215 stalls easily - low power?

[relative4]

I just bought a HRM215SXA (vintage 1993) at a yard sale. I fueled it up, and it started on the first pull. So I changed the oil and spark plug, checked the air filter, and ran it for a bit. Everything seems to work perfectly, except it seems to have low power - stalls easily under any load. When I engage the blade, it almost stalls. If I engage the blade in contact with grass, it definitely stalls. If I run it into high grass, it stalls.

I haven't rebuilt the carburetor, as I'm not seeing any clear evidence of mixture problems. It cold starts fine with the choke, hot starts fine without the choke. No surging. Throttle response is normal, and engine sound is smooth. No smoking.

What are my next steps to figure out why this thing is so weak? Thanks!

 

[jp1961]

I'd say check the compression, but if the engine has a compression release system, I'm not sure that would work. One item you could check is your valve specs.

 

[robert@honda]

What are my next steps to figure out why this thing is so weak? Thanks!

Make sure the throttle is all the way open, and the engine is spinning at 3,150 ~3,300 rpm with the blades engaged. Use a tachometer to be sure. If running slower, you won't have enough power/torque to prevent stalling.

Inspect the blade brake system and ensure it is not dragging, binding, or worn.

Could be the governor, linkage, etc. are sticking...carb could have debris/slime, carbon build-up in the cylinder head, worn valves, etc. Lots of possibles on an older, used mower with no service history.

A shop manual is well worth the investment if you want to bring the mower to top condition:

Honda Power Equipment Shop Manuals on eBay
Honda Power Equipment Shop Manuals on Amazon

 

[relative4]

Engine speed is pretty good, steady around 3200 RPM. Compression is not so hot - 60 PSI dry, 65 wet. Valve job time? Anyone know if these things have a compression release system as jp1961 mentioned?

 

[relative4]

I disabled the compression release and got a test result of 94 PSI. Is that acceptable? Depending on where I look, I see minimum acceptable compression of anywhere from 80 to 110 PSI on this engine (GXV140). I live at 5300 feet, if it makes a difference.

While I was in there, I checked the valve clearances, both right at spec.

The governor arm moves smoothly, I don't detect any sticking or anything. Anything in particular I should look for?

With the blade clutch engaged, there doesn't seem to be any dragging of the brake pads on the rotor. Anything else I should check there?

Assuming 94 PSI is acceptable, is there anything else I should look at before I pull the carb?

 

[robert@honda]

Engine speed is pretty good, steady around 3200 RPM. Compression is not so hot - 60 PSI dry, 65 wet. Valve job time? Anyone know if these things have a compression release system as jp1961 mentioned?

Yes, pretty much all modern Honda engines have a compression release, but it is disengaged above a certain RPM, generally far lower than you will get when briskly pulling the recoil starter. The release holds the exhaust valve open, so you'd get zero PSI if it was engaged during the test.

The Harmony HRM215 came was made with early and later versions of the GXV140 engine. Early models have a compression spec of 85~121 psi, while later production were only 58~85 psi. (both are @ about 800 rpm) If you could share either the frame serial number (back of mower deck) or engine block serial number, I can see if your mower is early or late production.

 

[relative4]

Frame MZBB-6073972, engine GJAB-6430326 - early run, I guess? Sounds like the compression is fine, so time to clean the carb, unless you see anything else to check before I pull it?

I've been reviewing the gaskets to order before pulling the carb. I see two gaskets (16212-ZG9-T00 and 16221-ZH8-801) I'll pretty clearly need to replace; should I also replace spacer 16220-ZE6-010?

 

[jp1961]

Hmmm,,,some engine manufactures offer an available carburetor jet for 'high altitude' operation. In checking my Intertec manual, it doesn't list a special main jet for Honda engines, but it does use the word 'standard'. If you can still get a new main carburetor jet, I might try experimenting with boring (the old one) it to the next size, not talking much just a few thousandths.

 

[jp1961]

I Googled how much power is lost for every 1000 ft elevation, this was one search result:

When I worked at a new car dealership in Colorado, the "accepted" rule of thumb was a 3% loss for every 1000 feet of altitude.
That was with carbureted engines. The default practice for every "new car prep" we did was to advance the ignition timing at least 5 degrees to try and compensate for some of that loss.

Check my math,,,3% X 5000=15%. Assuming your engine produces 3.5 hp the reduction would be .525 hp, quite a reduction.

 

[robert@honda]

Frame MZBB-6073972, engine GJAB-6430326 - early run, I guess? Sounds like the compression is fine, so time to clean the carb, unless you see anything else to check before I pull it?

I've been reviewing the gaskets to order before pulling the carb. I see two gaskets (16212-ZG9-T00 and 16221-ZH8-801) I'll pretty clearly need to replace; should I also replace spacer 16220-ZE6-010?

Gaskets and spacer only need to be replaced if damaged, torn, cracked, etc.

Before you committ too much time to cleaning the carburetor, consider replacement of the entire carb...it can often save a LOT of time and frustration vs. trying to perfectly clean an old one. You want Honda Part Number 16100-ZG9-M01.

Google any part number to find a Honda Dealer selling it online, or use this link to find a Honda Dealer in your area:

Find A Honda Dealer