Hayter With Swiss MAG 7hp Engine

[Wendelspanswick]

I have been given a Hayter cylinder mower, this thing is massive with a 30" cut and built like a tank. It has a 3 speed and reverse gearbox and even has the roller with the cast seat on it to tow behind the mower and a bolt on rotary deck. Kids could play hide and seek in the grass box!
Its the kind of mower they use for cricket pitches and its in a really good condition, the bummer is the engine refuses to start. Its a Swiss made MAG engine, 4 stroke 7 hp pull start. I am normally a dab hand with small engines but this one is beating me.
Part of the problem is a lack of info on the engine i.e. correct plug and points gap etc.
Anyone got info on this engine? I have tried on the VHGMC forum but no luck.
Perhaps another one for LawnMowerBoy?

 

[grandads_shed]

got some pictures ? people tend to remember them that way

 

[DrNik]

does it click loudly when you turn it over??? i had one here for repair and had a funny magneto setup

 

[Wendelspanswick]

does it click loudly when you turn it over??? i had one here for repair and had a funny magneto setup

No mag, it's stator,coil, condenser and points. It's a side valve engine and the current plug looks too short to me, the end dosen't project into the combustion chamber.
There is a reasonable spark and good compression, the fuel gets drawn into the combustion chamber. It does fire sporadically.
Ideally I need:
Correct plug and gap.
Points gap.
Ignition timing BTDC. (Although there is only minimal adjustment on the stator plate).
Carb settings.

 

[Wendelspanswick]

got some pictures ? people tend to remember them that way

I will photograph and post after the weekend. Off to the Goodwood Revival for some retro car and motorbike racing.

 

[AndyStobbs]

Can you test the spark in a tube type tester? A spark at atmospheric pressure isn't much indication of a nice healthy burn voltage and burn time, when placed into the engine its got to be good enough to overcome compression pressure. Can you check the condensor out too?

 

[wristpin]

Possibly a MAG 1026-SRL ? Should be on the spec plate on the engine cowling.

Points 16thou
Inlet 4-6th
Exh 6-8th
Ign 22degrees btdc
Plug 20th
Bosch W 95 T1 light running
Bosch W190 T 1 continuous full load
NGK B6HS
Champion L86C

 

[Wendelspanswick]

Possibly a MAG 1026-SRL ? Should be on the spec plate on the engine cowling.

Points 16thou
Inlet 4-6th
Exh 6-8th
Ign 22degrees btdc
Plug 20th
Bosch W 95 T1 light running
Bosch W190 T 1 continuous full load
NGK B6HS
Champion L86C

Spot on, your a star! Just the info I need.

 

[DrNik]

ive had them before where the spark plug is indeed too short to be in the combustion chamber, although it would fire occasionally it took ages to work it out

 

[wristpin]

Spot on, your a star! Just the info I need.

That's fine, if it's not a 1026 I can probably find the gen for whatever it is.
Been to Goodwood nearly every year since it started but left it too late this year and they were sold out!

 

[Lawnmowerboy]

I'm no longer a member of the VHGMC after the utter ringpiece of a chairman made a rather rude remark...

The MAG engine is very similar to the kubota and suzuki 7HP

is yours electronic ign or an impulse magneto. The one I had on a brushcutter thing was a BTH mag bodged on.


Wristpin has answered about all I could say. If you know you're getting fuel though then the next place to look is a spark. I'll write up the list of checks with a multimeter on the coil depending on what ignition you have.

 

[wristpin]

Fairly certain that yours will be an "original MAG" before the tie up with Kubota and will have a flywheel magneto (Bosch) with coil, points and condenser. If you go into the magneto don't be alarmed if you find an extra coil - quite a lot had a lighting coil even though not used in that application.
If you've got a decent spark I would leave the magneto well alone but if you do need to pull the flywheel, hopefully you have one with two tapped holes for puller bolts but some did have a recessed internally threaded centre into which screwed a purpose built puller. I have never come across one of those on a MAG engine, only on a Bosch flywheel magneto on a JLO engine but the matter was raised on another forum and I subsequently found that type in some MAG literature.
Whatever, beware of trying to pull the flywheel with a two or three leg puller as there is a possibility of distorting it and in an extreme case leaving the boss still attached to the crank!

 

[Wendelspanswick]

She lives!
Got a chance to look at the MAG engine today, sorted out a new plug of the correct length and gapped the points (a big thank you to Wristpin for the correct engine data), a splash of fresh fuel and she started 3rd pull.

30" cut, a 3 speed and reverse gearbox

Here's a pic of the Swiss made MAG 7hp engine.

Anyway it ran for a few minutes while I tinkered with the slow running, I cut the engine to put the air filter back on and went to restart it and minimal compression!
I guessed correctly that the valves were not seating, the exhaust valve gap was non existent! The valve was heating up, growing in length and not seating causing a loss of compression when hot.
The problem I have now is that I cannot see how to adjust the tappet gap, I took the cover off the valve chest, I can see the tappets rising and falling as I turn the engine over but no adjustment?
Is it a case of whipping the valve out and grinding the end of the stem or is there some adjustment inside the tappet? Either way I guess I will have to remove the head and draw the valve out.
Another one for Wristpin or Lawnmowerboy methinks.

 

[ChrisJ]

no thats a mower!! definately needs flames down the side

 

[Lawnmowerboy]

Most likely there's a cap over the lifter with shims in it. If you take all the shims out and still not enough gap then you need to file or grind the bottom of the valve stem.