OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions on Other Engines TROJAN MAJOR - Motor Fitted To Ogden Rotamatic

Just curious on looker...Have you checked the compression? I know borderline minimum compression can give me fits sometimes on 2 cycles here.

Hi AVB,

Found a broken ring and cracked rear seal. Giving it an overhaul now and will see how it goes from a fresh.

Secured the crankshaft seals today, looking for piston rings now. 46 mm bore, 2mm ring. Anyone bought rings for a Trojan/Tor before, mine is 75cc engine with Std piston ?

Ive Not seen New parts for Trojan Paul, I think you'll need to find a collector or club who may have old stock, if no one here has a set.

Ive had success with JP before for impossible pistons and rings, if all else fails check em out. Pretty sure they do A fair bit of Villiers as well....like the 7F.

Send them a sample ring and they may be able to match them.

http://www.jp.com.au/JPPistons.html

Thanks Mal,

On to them and sent a few emails back to the Mother country. 46mm rings are a common size and even the gap profile can be found but 2mm thickness is what I need. Still trimmers use 46mm and there's loads of them, just a bit more digging required.

Lucky the gaskets are only paper type, wonder how thick though ? Corn Flake or Weet Bix type :-)

Rings are sorted, coming from JP Pistons, odd thing with the crankshaft bearings. I have another motor for spares which I stripped down, found that the two cranks use different bearing sizes.

One crank has a 20mm I.D. Bearing either end but the one used on the Ogden mower has a 17mm on the blade end and a 20 mm on the magneto end. Wonder why they went to using a different size bearing on the stressed up end of things. Perhaps this is the reason for the fancy clutch ? Above the blade plate as the crank is thinner down there.

Well done Paul on the Rings Paul, they've helped me a few times.

Not sure on the bearings?

Gasket size Im unsure of. Basic rule for crankcase to barrel is, fit the barrel and measure the distance between barrel end surface and piston to find your thickness,and use the appropriate material allowing a few thou for crush. Crankcase halves are usually dry,sealant or of the thinnest material...eg paper thickness.

As for the head, see if there is any salvageable material to measure,or just run std Victa 125 thickness?

Anyways glad you got your rings, cant wait to see it running:)

Thanks Mal, Bearings are all sorted, crankcase and base gasket are just paper and sealant. The crankcase has an inner lip to seal the halves, very clever. I can salvage the head gasket but I may make a new one. I will put up some pics soon.

A few pics of the progress

First for Jack some better pics of the Ogden cast alloy cowl
Gallery images include:-

Remnants of Ogden logo
Carb side
Underneath
Engine progress
Sealing lip on one side of crankcase
Engine number
Piston
Look what I found
I am hoping it will clean up for a good spare :-)

Hello Paul and ODK Members & Guests

First, thanks to HT6 for recommending JP Pistons.
They appear to be the premier company for sourcing pistons, rings and etc.

Paul, thanks again.
These are invaluable photos in recording this Ogden version of the Trojan 75cc.
The yellow (not gold) cowling would have looked absolutely stunning on this
moon-buggy mower.

This mower was painted in green and yellow for a single purpose: the Melbourne
Olympic Games, in the year this rare mower was introduced. I hope this motor
will mate with a chassis ... some day.

p.s. I love the lipped seal on the crankcase. It was kismet!

All very significant.
---------------------------------
JACK

I have to Agree with Jack...I'm really hoping you can complete this little gem with the aquisition of a base and parts.

Thankyou also for breaking down the engine, as engine building/restoring is one of my main passions,and this is one I've never had the chance to build. I really like the fact the casings still retain alot of their original casting lustre after so many years.

Im quite excited about the restoration,as this is one very elusive mower id really love to see complete.



Please keep your progress info coming.

Spent most of the day cleaning parts, the spare magneto cleaned up nicely. It has no condenser, I am wondering if anyone knows what one will do the job, I have plenty of spare Victa ones. Would one of the Victa ones do the job ?

Victa condenser should be fine...I occasionally use the later Special conds on the Rotomo wipacs,when I run out. Never had a problem.

Do you have an image of the original condenser on your good engine? Should be the brass one with screw on connection.

Thanks Mal, no original condenser to view. My other magneto already has another in its place, I think they were a long thin one with a nut on the end from memory. I will put a Victa one on for now.

New rings arrived today and there spot on, tried them in the bore and they are perfect. Made some gaskets while my son looked on, he was very interested as to why there needed to be a gasket and so the lesson began. I have all the bearings and seals so on Saturday I will take my time and enjoy putting it back together

:-)

Hi Paul and ODK Members

Thanks for this exciting update. This posting has attracted a lot of interest.

For one thing, It has been most helpful in Mal's recommendation of JP Pistons.
Clearly, for rare piston or ring needs, JP is probably the first point of call in OZ.
For another thing, the larger Trojan was rarely used on AUS lawnmowers.

I digress now, because I am compelled to say something about photographs.

I know that most images that appear on these forums here are illustrative.
But - some images - do a little bit more - they tell a more rewarding & complex story.

This narrative tells the 'ring story' and the 'son story' in such a nice way; and this is
reflected in the composition of your excellent photograph.

It is an exploration in geometry - circles and squares - but with a twist. Note:
- the rings on their package, but the package is on the diagonal.
- the circles and half circle (almost) of the c/case, cylinder, rings and can.
- the contrast of light table to dark background.
- the gasket that appears on the cylinder base.
- the hammer, with circular head, has more complex connotations.

This photo reminds me of the importance of images as part of the words in
telling the story of members' machinery. For example:-

https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=59799#Post59799

Sorry for the indulgence here.
My message: photographs form part of the provenance of members' restorations.
They can clearly add value to machines down the track - but also act as an historical record!

All very interesting.
------------------------------------
JACK

Hi Jack, your comments are always interesting and much appreciated. So many circles in one picture, the crankcase has 11 alone ! I had a look at the post in your link and have added it to my watched topics to enjoy later, I also realise that I haven't posted a pic of the crankshaft. I took one but didn't post it as it is blurry, it's a very interesting build so I will take another one.

Tapped the crankshaft seals in this afternoon, just a note on the back seal. It goes in the reverse way, why I am not to sure but that's how the original seal was fitted on both of my motors. It does have an alloy cover that keeps the rubbish out though

Hi Paul

That's an interesting observation on the seals.
Crankcase seals are, I guess, unusual; in that they have to work
both ways: the upstroke creating vacuum, and down-stroke creating
positive pressure. I wish I knew more in this area but I don't.
Can these seals be driven in from either side?

All very interesting.
--------------------------
Jack

I drove them in from the inside but I guess you could fit them from either side.