TWM140 is beating me!

[Paxman]

As I wrote: both valves felt pretty good when I spun them and after spraying some lubricant along the stems it felt like they freed up even more.

Good to know that there is a decompression feature. That means that as fas as I can tell the valves are good to go. Now I only have to source a new head gasket so I can move along with the trouble shooting. I have emailed my local small engine shop with the part number but they haven't replied yet.

 

[jp1961]

The head gasket doesn't look bad, I would reuse it.

Don't try to remove it from the block as you'll undoubtably tear it.

Your engine looks like it is a vertical shaft unit, so the penetrating oil won't trickle down the valves like a horizontal shaft engine (unless you can tip the mower on it's side).

 

[Paxman]

Part of the gasket was stuck to the head so a new one is a must. The valves are fine.

 

[jp1961]

Hello,

With the head off how is the condition of the cylinder walls and if there is a ridge at TDC?

I realize you don't want to sink a ton of money into it.

Jeff

 

[bertsmobile1]

Find tdc on the compression stroke
Two ways from here
1 shine a strong pencil beam torch into the intake & exhaust ports while looking down at the valves.
If you see light then the valves are not seating.
Or tip the engine cylinder down and pour water into both ports one at a time.
If the valve face / seat is good it will not leak out.

 

[Paxman]

Today I had some time to inspect the head and the head gasket. To me it looks like it was blown.


Gasket on the bottom (turned upside-down) and mating surface on the top. The cooling fin is much greasier than any other. I think it's the one facing downwards when installed on the machine.




Same placement here. There is a clear track of black from the combustion chamber to the bolt hole. The two bolts that where grimy was in these respective holes.

A new head gasket is ordered. It'll be interesting to see what the compression is after I put everything back together.

The bore is so so...there is no lip, but there is an area that look a little different on one side (right side looking into the cylinder). I suspect this is from the side force the con rod puts on the piston. I can't feel anything when I run my fingertips along it. The same goes for the whole cylinder surface. The hone marks are still visible except on that side area.

 

[Paxman]

OK, so today I replaced the head gasket and reinstalled the head. Weirdly enough the compression was lower now! The torque spec I found was lower than I could dial in on my torque wrench, so I went a little higher. I thought f*ck it...I'll just put everything back together anyway.

Before I reinstalled the carb I squirted some gas straight into the intake and pulled the cord. It started straight away and revved up and died. Encouraging!

With the carb back, without the plate (that sits on top with the choke linkage), I pulled the cord again...nothing. A little squirt into the throat and the d*mn thing started! With a little fiddling with the mix screws I had it running well enough to put the plate back. That thing is not that intuitive, but I have seen a video of how to set it up and was able to get it pretty good. More fiddling with the main and idle mixing screws and it was running sweet! :biggrin: I ran it back and fourth on the street doing small adjustments on the main mixture screw, stopped it and started it again with no effort! I think it's fixed!! :thumbsup:

The only thing that I'm not super happy with is the governor. When I engage the mower deck the rpms dives and I can't really see the governor arm moving that much. When I had it running before all this fixing the arm moved much more and you could clearly hear that it worked the way it's supposed to. It's not super critical, with enough throttle there the engine copes with the load but it would be nice if the governor kicked in when needed.

 

[jp1961]

Hi Paxman,

Good to hear you got it running, without too much invested.

Regards

Jeff

 

[Paxman]

Thank you Jeff! :smile:

In retrospect maybe the new carb was not needed since the head gasket seems to have been the culprit the whole time. I will not try the old carb now that the engine seems to be running well. I'll keep it for spares for future machines. The new carb was around $35 to my door and I think it will be a good selling argument when it comes to selling the mower in the spring.

Goes to show that not all from China is sh*t, even if it's cheep.

I will do some more testing tomorrow. I have a patch of grass that is on the higher side that I can mow. I found some youtube vids regarding the governor so I'll see if I can adjust that a little better.

So far I think the mower owes me around $150. I'm hoping to get $350 for it in the spring so a profit of $200. It won't make me rich, but so far I have had some good fun and learned that a blown head gasket can give symptoms that points to carburetor issues and even give good compression numbers! :thumbsup:

 

[jp1961]

Hello Paxman,

Yep, working on engines is a work in progress. No matter how much you think you know, you still learn with each project. Nobody is an expert.

Good luck in flipping the mower for a profit.

FWIW, I installed a Chinese carb on a Troy-Bilt tiller and it performed well as the original carb was corroded beyond repair/rebuilding.

Regards from the U.S.

Jeff