Outdoor Power Equipment and Small Engines - Hydrostatic transmission doesn't engage.

Hi all.

I have a Honda HRB536C which has recently stopped working.
The engine starts ok, but the blade will not turn. It's not jammed completely, as I can turn in manually.
I don't know much about engines, but would like to repair it myself if possible. I have purchased the service manual but need to be pointed in the right direction.

Any suggestions as to what I should be looking for?

Thanks.

PS. Subject refers to "Hydrostatic transmission" but I have no idea what it is, or if it is the problem...

Since I'm not too familiar with Honda's and the model number does not show up as a valid ID, by my lookup ability, I can't help you well without knowing if this is a riding mower or walk-behind mower. And, if the model is, indeed, correct. FYI, generally, the wheel drive (hydrostatic unit) is unrelated to the blade drive.

HRB 536 CHX is probably more accurate, although it says HRB536C on the user manual.

It's a self-propelled walk-behind mower and is probably quite old.
I found very little info about it here: (just to show it does exist!)
http://www.mauriceallen.co.uk/1272/info.php?p=2&pno=0

FYI, generally, the wheel drive (hydrostatic unit) is unrelated to the blade drive.

In that case, the subject of this post is completely wrong as everything works as it should except for the blade turning - when I press the yellow button on the blade control lever, then push the lever forward, I don't get the usual noise and the bag doesn't fill up with air.
Hope this makes sense.

Ah ha, I now see you're from across the pond from us here in the US. This would explain why I can't identify this model since it is a Euro model and likely, specifically, a UK spec'd model. Based on your additional information and the link you posted, this does, indeed, have a blade brake clutch. The blade on this unit - similar to a lawn tractor - is driven by a belt. When you push the lever with the yellow button you are tightening a belt which engages the blade. Whether you have a belt that is worn or broken, or, a control cable (related to the lever you push) that is broken needs to be determined. There should be a plastic cover on the underside of the mower that you can remove (you must first remove the cutter blade) to give you a good view of the brake assembly and belt. Remove the spark plug, tip the mower up at a 45 degree angle (muffler side up), have an assistant work the blade control (at the handlebar end) and you can watch the action on the underside and see what is going on in the blade brake area. If you see no action (movement) when the lever is pushed foward, this would indicate that the control cable is broken and in need of replacement. If you see movement then you need to determine if you have a simple control cable adjustment issue or a belt in need of replacement. I'm going to guess that you'll find you need a new blade drive belt. Post back once you have inspected and determined the trouble.

Thanks puey61!!!

If you see movement then you need to determine if you have a simple control cable adjustment issue or a belt in need of replacement.

I'm really glad I found this site. This mower is my spare and I put it in the shed 2 months ago thinking it would have to be taken to the repair shop.
Last year I had been tinkering with it because it was "hunting and surging". I seem to remember adjusting the control cable, so I adjusted that first and it fixed the problem!

Still "hunting and surging" though but at least I can use it.
Thanks again.

The "hunting and surging" is related to the carburetor (being lean/restricted) and you will want to disassemble and, at least, blow out the passageways with compressed air. Depending on the condition, once disassembled, you may need to replace some components and soak the carb in a bath type cleaner. In the least, I recommend using a carburetor/choke spray cleaner.

In the least, I recommend using a carburetor/choke spray cleaner.

That was all I needed to do. This mower now goes better than the one I use normally. Maybe it needs some attention too...

It does seem a bit loud though. Would that suggest something wrong with the exhaust?

The muffler is certainly possible but is rare on Honda engines for this to rust/corrode. It may also be an off-time ignition and would then be either a flywheel key sheared or something else related to the ignition system.