OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Two Stroke Lawn Mower Frames Masport 632 - Tecumseh Powered - Issues

Hi All

I found an old Masport 632 mower (circa 1980's) with a Tecumseh TVS600 two stroke engine (model with vertical pull start). I took it to the local mower shop for a quick service to make sure that I could sell it on quickly. The mower did start when you sprayed 'start ya bastered' down the air intake and seemed to run well.

The mower shop has since informed me that the mower has a badly scoured piston and needs new rings as the old ones are shot. They said the damage was due to carbon build up and not lack of oil. It also has a few issues with the on/off switch on the engine.

I wanted to know if it was a easy or hard fix to repair these issues in a Tecumseh engine as I have never worked on one of these before. Also the shop said that it would cost around $600NZ$ to fix! Is this price right.

Hi VC Victa, Geez,$600NZ to fix the prob....you could probably buy a brand new machine for that price.
However, let's look at the prob. You say that it will start ok with "Start Ya Bastard" These ether based starting sprays are definately not recommended for small engines and damage can result from continued use.

The workshop has indicated that the piston is badly scored; well, if that is the case, what does the cylinder bore look like....it could be badly scored as well and will require a re-bore/re-sleeve plus an oversize piston.
As for the rings, are they still intact or broken (which could have caused futher damage to the bore.
And you would have to look at the condition of the head, seals, bearings, gaskets etc...You can see the $$$ piling up plus labour costs.
Plus the fact that Tecumseh engines are no longer manufactured (they went into liquidation)...are spare parts going to be available in the future?

In my opinion, you may be better off looking around for a good second hand engine that would suit, and can be had for the right price.....especially if you are going to sell the machine.

Hi Darryl

I have had a look at the engine and there is no damage to any part of the inside of the engine bar the piston, which is not too badly scored. The rings seem stuck, they are not broken though. There is alot of carbon build up that needs to be cleaned. Otherwise internal of engine seems great.

When the engine was running it runs very well.
I suspect the starting issue is to do with the carby needing a good clean as the mower had been sitting under a house for many years.
What do you think? Engine repairable or a throw away?

Hi VC Victa, Well, mate, that throws a new light on it; if there is no other damage than the piston and rings, here's what I'd do.....I would measure the inside of the bore to determine if an original size piston can be used, if so, see if Bruce can source one for you, plus new rings to suit, plus any new gaskets that will be required.

Whilst waiting for them to arrive, de-coke the engine, clean up the head; dismantle and thoroughly clean the carby, check and clean the inside of the fuel tank....there could be heaps of crud in it after sitting for many years.
When your parts arrive, re-assemble, give it a new plug, check for a good spark, fresh fuel, (check for good fuel flow from the tank) and if all is well, fire it up....
I'm sure that grumpy might have further good advice for you when he comes online.
Hoping this helps,

Hi Darryl

Thanks for the help so far, I guess the shop I took it to charges alot in labour. It must be alot of work to do though. I will have a look in greater detail to make sure there are no other obvious issues, but it looks pretty good though.

Hi VC Victa, yes mate, there was another thread on the forum recently that touched on the issue of "It's stuffed, mate, and will cost $600 to repair; but we can suggest for a few dollars more, you could buy one of these!"
In other words, they can't (which is a worry) or don't want to spend the time on the repair, so they load up the labour costs to make it an unviable enterprize....
Repair by replacement in a "throw-away" enviroment is their catch-cry. And, more of a worry is that new apprentices are embracing this line of thought....
Anyway, I'll get off my soap-box now.
Please let us know how you get on.Best of luck with it,

I'm not clear on why you would want to fix an engine that is rare without being good. Unless you hope to make a collector's item of this mower, it seems to me to make more sense to pick up a decent full-crank Victa 2 stroke or a B&S 4 stroke (around here, at least, they are usually free and as close as the surrounding nature-strips) so that you end up with something worth having after investing time and/or money in getting it up to scratch. However if you want to fix the one you have, just out of sheer cussedness, there is a fairly good chance that you can get a reasonable result with a new piston and rings. I'm not denying the legitimacy of cussedness: when my father died he had left a non-running 1960s Supaswift with a Villiers engine under his house, and for no sensible reason I repaired it (new rings, second-hand magneto, and rebushed the throttle butterfly in the inlet manifold). Even more foolishly I then used the horrible thing as my one and only lawnmower for a dozen years or so. OK, so it would invariably start first hit of the impulse starter even after months in the shed, but I doubt it had much more than 1.5 hp, and being a 2-stroke I often had to clean the spark plug. Fortunately the replacement magneto finally packed up last year and I had an excuse to junk the machine and buy a beautiful 1976 Victa 4 stroke, which has improved my quality of life immeasurably.

I think you will have to replace the piston in the old Tecumseh if it has broken, stuck rings. I've been known to resuscitate car pistons with those problems by cleaning the ring-grooves on a lathe then fitting spacers beside the compression rings, but it isn't worth the effort for a lawnmower, and anyway 2-stroke rings are usually pinned to keep them from rotating, which stymies the idea of cleaning the grooves on a lathe. Since your piston is also scored, which matters on a 2 stroke, a new (or at least better) piston seems essential. If you are going for a new piston you should consider having the cylinder bore honed if it can be done cheaply. Overall though, I can't understand why you would want to do these things. I had that awful Villiers thing recently enough to still abhor its memory, and I'd expect a Tecumseh to be worse. (I had a 4-stroke Tecumseh for a decade or so, and that was definitely worse.)

Grumpy, what would running the engine in its current state be like? I have used it once to mow my lawn and the mower seemed to run fine, starting was a bit of an effort though. But once warmed up it was one of the best running mowers that I have had.

The problem that keeps it from starting is probably just lack of compression due to the stuck rings. I had misread your post when you said the rings are not broken - I thought you had said they are broken. Stuck rings cause fairly massive blow-by, carboning up of everything, scoring of the piston, and pretty soon, scoring of the bore as well. Do not run it with stuck rings.

If the rings are stuck but the piston scoring is not bad, I'd try to remove the rings without breaking them, clean out the ring grooves - carefully - as well as possible with a hand-made scraper, and try the old rings in the bore to check the ring gap. The gap will probably be bad: that will be what caused the blow-by that caused the carbon build-up that caused the rings to stick. If the gap is big, you need new rings. Unless the piston scoring is bad, that is all you need. Clean the ring grooves, fit new rings, put it back together. If you want to be thorough, check the gap in the new rings by trying them in the bore - but it should be OK, even if not perfect.

Old guy's trick: once you have verified that you can't re-use the old rings because the gap is really outrageous, break one of them, grind the broken end square, and use it for a scraper to clean out the ring grooves.

One good way I have found to clean the ring grooves is too break one of the old rings and use the broken edge to scrape around in the groove.

Personally though, its great that your having a go at repairing it, but for the effort now I would generally strip the motor of everything good and keep them for spares.

Hi All

I took the engine apart and cleaned it all throughly. Got hold of some good second hand rings and replaced the existing ones, cleaned the carby and generally serviced the engine (new spark plug, air filter etc..)
Put engine back on base and it now runs mint. Starts first pull and sounds great. Idle speed is a little high but that is of no concern to me.
All up cost me about $20 to fix.
I still can't understand the money the mower shop said it would cost.

Ok while $600 may be high, I wouldnt be doing it for bikkies either.

Generally these days I charge $200 plus the cost of rings for the job, to do it proerly it can easily take a couple of hours and you know that 'Time is money'

your right Joe, it does take a while and I expcect that it would cost a bit to get the job done right. I was just hoping to get a good price