One for Burnerman - tractor / mower

[Harry Bloomfield]

I had a breather issue with my first tractor /mower, which I never got to the bottom of - instead I sold it on and bought another one. This was around 5 years ago and that first mower is still doing excellent duty, mowing around a private fishing lake regularly - complete with my breather botch.

The problem was that the B&S engine blew lots of oil out of its breather pipe, back into the intake. So much that it would short the plug and stop the engine, plus lots of smoke from burning oil out the exhaust.

As what was intended as a temporary botch, I found a small glass jar with a metal screw lid, pierced two holes in the lid, then hot glued pipes in it - breather from engine leading almost to the bottom of the jar, pipe to intake near the top and filled the jar with stainless steel scourer pad. The jar never filled with oil, as I expected and the engine ran and still runs I am told, without an issue. I even tried fitting the breather back a before and back came the problem.

I just wondered if you might have some explanation?

 

[Burnerman]

Thats a curious one Harry!
First, I’d think that the oil level was too high in the sump.....was the dipstick the correct one for the engine?
Next, the oil grade needs to be somewhere near the 30 grade.
There is a possibility that the oil control ring at the bottom of the piston was cracked ( if there was one) or maybe the lower of the piston rings broken?
If it was a side valve engine, there should have been a baffle plate behind the tappet cover that only allowed air out when required - this was supposed to minimise pressurisation of the crankcase.
With your modification I would have expected there to be some oil deposit in the jar, but if this wasn’t the case then the length of the breather system maybe helped to minimise crankcase pressure? After all, it wasn’t too long ago that closed circuit breathers became the norm - before that any fumes just vented to the atmosphere.
John

 

[Harry Bloomfield]

With your modification I would have expected there to be some oil deposit in the jar, but if this wasn’t the case then the length of the breather system maybe helped to minimise crankcase pressure? After all, it wasn’t too long ago that closed circuit breathers became the norm - before that any fumes just vented to the atmosphere.

Curious is right. It was the correct dipstick and the oil level was correct - I'd had the tractor for a few years, before the problem began. No, there was absolutely no oil deposited in the jar. It was a single belt drive, single blade MTD, like almost all of them. I was just curious to know if you might have some explanation which I might have missed.

I replaced that with a slightly more compact twin bladed MTD Lawnflite. That is suffering from wear on the bottom steering bush, for the bottom end of the steering shaft where the pinion meshes with the steering quadrant. Try to turn left - the steering wheel just forces the pinion to just click out of mesh so the tractor goes straight on. I am having to plan my cutting to only make only right turns

The bush is only like a large, thin hexagon, where it locates in the chassis, bored out to 5/8". I did think to make one on the lathe, but found they were only £4 so ordered one a couple of weeks ago and waited for delivery from a UK stockist - I'm still waiting for promised 7 day delivery. I ordered some electronics from China, the day after and tracking shows that is already in UK Customs.

 

[Burnerman]

Maybe the length of your breather system reduced the pulse effect from the crankcase gases so it didn’t discharge oil into the jar?
You may be aware of the site diyspareparts.com which is good for part numbers and identification.
John

 

[Harry Bloomfield]

You may be aware of the site diyspareparts.com which is good for part numbers and identification.
John

No I wasn't aware of it - thanks. The problem I have found with tractor mower parts is that there are so many models and different names for basically the same machine. The bush I needed, was used in many MTD machines, with multiple part numbers and the tiny parts diagrams don't help much to identify the bit you need.

One problem which soon showed up soon after I bought my present Lawnflite 703 was the PTO clutch slipping and not reliably driving the blades. It just developed more slippage as time went on, with horrible noises. Replacement PTO clutches were silly money, as complete unit replacements - no plates - so I pulled it out to investigate. I had no details on it, but found it was just bare metal on bare metal - whether that was how it was intended to be, I don't know.

I decided to try an home made clutch lining and superglued some gasket material to one of the plates. After a bit of bedding in, it worked absolutely great.

My components from China arrived this am, but I'm still waiting for the bush to be delivered from the UK

 

[Burnerman]

I have to admit, those electric pto clutches are pretty vicious but I haven’t replaced one just yet!
I find the top column bushes wear quickly too, but they are much easier to replace.....once you’ve knocked the roll pin out holding the steering wheel on
John

 

[EddieM]

John, I think you need to set a website up. honest John's mower maintenance. Charge a small subscription fee.

 

[Harry Bloomfield]

I have to admit, those electric pto clutches are pretty vicious but I haven’t replaced one just yet!
I find the top column bushes wear quickly too, but they are much easier to replace.....once you’ve knocked the roll pin out holding the steering wheel on
John

No, it's an entirely manual clutch, operated by a release bearing. It's take up is very smooth.

 

[Burnerman]

Ah yes, that will be similar to the Jonsered / Husqvarna type - quite a good idea I think.
John

 

[Harry Bloomfield]

The bush arrived at last, this morning. So I took the cutting deck off, got it jack up enough to get under and investigate it properly. The shaft was very sloppy, but not much wear on the pinion and none on the quadrant it drives, to turn the wheels. Taking the pinion off to get at the bush, I noticed I wasn't the first to go in there - someone had fitted a thick large washer in the past, in there attempts to maybe sort the steering slip out before. The bush fits / just drops in the chassis member from above with panels an inch above it. Pushed up and out, thinking it was steel like the new bush, I tried to fish the old one out with a magnet on a stick - it didn't work, it was a plastic bush. I eventually fished it out with a bit of wire.

Rather than risk loosing the new bush in the chassis, I fished a bit of string through between chassis and panel, then out through the hole, put the bush on the string, then made it into a loop. A bit of fiddling about and I managed to get the bush near enough to the hole, to catch it with some small hooks and pull it down into place in the hole. A bit of grease, then I dropped the steering shaft back in place through bush, refitted the pinion, the nut and tightened it up - which locked up the steering solidly

After a bit of checking and measuring, I realised the new steel bush was thicker than the plastic one which I had taken out. Instead of the pinion nut tightening against a shoulder on the shaft, it was tightening against the new bush instead and locking it all up. So I took the pinion back off, popped it in the lathe and ground a couple of mm off one face of it. All seems fine now, I just need to drop it down on the ground, and refit the cutting deck.

New on the left, worn out old on the right....

 

[Burnerman]

It makes you wonder about the design teams for these machines, if there is such a thing....most of them seem to be constructed as an afterthought!
John