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Dave

2024-06-11, 20:02:05
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Dave

2024-06-08, 18:30:04
For Sale
xman has two very nice 1950's machines available - a green 1950 mk4 and black 1951 mk5 - both in good condition and running well.

Dave

2024-06-07, 02:13:36

Dave

2024-06-03, 08:23:05
For Sale
Duncan has just listed his green and cream 1957 Dragonfly for sale with spares and documents.

Dave

2024-06-02, 08:34:05
Parts avalable
alistair still has parts available - barrels, carburettor, castings - see all listings.


Dave

2024-06-01, 18:33:27

Dave

2024-05-28, 00:09:46
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valve guide clearance 2 3/4 hp

Started by a1mick, 03 Nov 2020 at 04:48

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a1mick

does anyone actually know the valve/guide clearance figures for a 2 3/4hp mtr, are the valve springs sold by the club any good? has anyone else had valve sticking issues, valves from club also, guides cast iron. i'm getting over reaming my guides bigger on the side of the road, any advice apreciated.

EW-Ron

What clearances are you presently at ?
You must eventually arrive at a happy medium !

Its pretty common to take old motors down and then marvel at the huge clearances they were running at.
But I know not where 2 3/4hp motors would/should be ...

Are your guides chilled cast iron, these give a modicum of self lubrication.
If they are not chilled, all bets are off ?

eddie

Mick,
          When we were involved with postwar spares, we were re-stocking with valves suitable for use with the then new unleaded fuel. G & S Valves told us that if the valves in the new material were going to be used in cast iron guides (rather than bronze), they would need an extra treatment to prevent them 'picking up' in the guides. One of the options was to have the stems hard chromed.

   Hope this helps,
                             Regards,
                                            Eddie.

Black Sheep

"they would need an extra treatment to prevent them 'picking up' in the guides. One of the options was to have the stems hard chromed."

Must be missing something here, but does this not render the valves useless for the ordinary tinkerer using cast iron guides? And does the humble 2 3/4 need high spec lead free valves? They have been running for 100 years on original spec steels and of course the petrol in these days didn't have tetra ethyl lead added anyway.

eddie

I mentioned the advice the valve manufacturers gave us because the repro valves that are available today are very unlikely to be of a similar spec to those produced pre WW1 - and may even be modified valves from a modern engine - hence the possibility of a mis-match of valve and guide materials!

  Eddie.

tck

I have been told that k-line bronze guides can be used has anyone tried this?
one link http://www.sbintl.com/KLine.html

a1mick

thanks eddie,   getting my valve stems coated was where i was thinking of going, what u said its anoying because i keep the bronze for guides here to and normally use it but for doug i thought i'd use cast iron! and the ''experts'' on other brands r allways upping me for using bronze! but it definetly seems like the guide material and stem material don't like one another. i have had other new no oil engines stick a valve on that 1st run, but ive never had to re ream them and its only happened that 1st ride, but doug, i keep reaming, they keep sticking. and yes i think the k line sleeves is a option to, i know lots of racers use them now and thats the advice they give me. it seems the general opinion [though nobody seems to really know] on clearance is around .003'' - .004'', seems a lot, having said that, i dont want to admit the clearance i'm at now.

Jonathan

I have been using K-line bronze guides for many years.
Never had a valve stick.  The beauty is that when it is worn, a new guide can be put in with very little effort.
They run at .003" from memory.

Regards
Jonathan
Jonathan H.