Two speeder barrels and piston questions

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13th March 2009 at 9:00 pm #2315

Deleted User
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Hi all,

Today I lifted the barrels of my two speeder to find some surprises. Or at least to me as I had only seen Flyer engines from the inside so far. So I have a few questions:

PISTONS

On the right the TS piston and on the left a spare SS Flyer 500 piston. Note the differences (the TS piston is oversize, about 75,15 mm at bottom of skirt):

– I thought vintage Scott pistons always had those grooves cut all around like the Flyer piston. The TS one has none..
– I thought Scott pistons had rings with a diagonal cut slot. The TS piston has wider rings with a modern style slot
– the TS piston has inserts in the gudgeon pin holes. Allthough this could be done to fix oval worn holes but it looks to be very original.

BLOCK

The block has some strange looking holes on the sides. It are just holes with no ports in it. What would be the purpose of this holes?

PORTS

RH outside

LH outside

RH inside

LH inside

I was surprised by the round holes on both the outside as the inside of the barrels. Somehow they seem homemade and out of place. Or am I wrong and are those holes original?
On the LH inside two of the three round holes have been connected to form one larger hole. This seems someones handy work. Any ideas on this? Could this have to do with the in balance in the incoming mixture due to the RH side mounting of the carb? But the LH cylinder already gets more mixture than the RH one…

Elsewere on the forum a deflector is mentioned that should be fitted to balance out the gasflow but I found none.

I hope some of the two speed experts can shed some light on this.

Cheers,
Erik

28th March 2009 at 9:26 pm #7987

Deleted User
Participant

No one?

Just back from a two weeks holiday and I kind of hoped there would have been someone that could shed some light on this…

I did some thinking on my holiday and the thing that puzzles me most is the round ports and the “pockets” on the sides. And of course the missing deflector (if there shouls be one in this engine anyway). I guess the pistons are oversize replacement items.

I went to have a look at the Pioneer run last weekend and spoke to quite a few Scott owners but no luck on the above questions…

Did however greatly enjoy the bikes on the run!

Cheers,
Erik

29th March 2009 at 6:45 pm #7988

Ian Parsons
Participant

The 1926 2 speed Super I once had and my 1930 Sports both have pistons like your Flyer one with the oil grooves and the diagonal piston ring stops. I suspect that this is typical of all Hepolite pistons. I do not know whether there is a difference between 2 speed pistons and short stroke Flyer pistons. There may be something in Technicalities.

Your other piston may be an earlier Scott one or made by a different manufacturer. Bushing the gudgeon pin bosses may have been done as a repair for wear. I would not have thought it would have been done from new.

My 2 speeder block has the relief like yours. The circular holes are definitely the work of an owner in trying to improve the breathing.

Hope this helps you,

29th March 2009 at 8:18 pm #7989

Deleted User
Participant

Thank you Ian.

Your answer sure is a start. Looking at the ’27-’36 spareslist I also see pistons with oil grooves in the engine drawing. So the non grooved pistons must either be older (my engine is ’24) or non original…

I will have a good look at Technicalities again to see if this tells me more.

Cheers,
Erik
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