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Old 28/01/2016, 07:00 AM
Dogsbody Dogsbody is offline
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Join Date: Oct 2013
Location: North West. RAS, RCS,RDS & RES Silverstone, RFS Oulton, Super Cub, Burgman 400
Posts: 408

Originally Posted by Bearingman View Post
If I remember correctly, I attempted to put an MX5 gearbox on the early MX1 cases and the primary chain would not fit. My only guess is the gearbox mount on the early engine cases are slightly longer.

Kenny Sykes
Silverstone with GPA2 or GPA5 cases with cam barrel box and Griffon clutch takes 72 link chain not 70 as I found out recently. Colin
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Old 28/01/2016, 06:47 PM
Stan Nicholson Stan Nicholson is offline
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Join Date: May 2010
Location: Nr Ottawa, Canada
Posts: 64

Thank you Druid and Rob.

As both the transfers and exhaust port are farther down the bore on the RES vs. the RBS/RCS it does look like the it was intentional that a portion of both ports remain covered by the piston at BDC. Strange! Now all I have to find will be the original overall length of the sleeve so I can determine the port timing measured from piston TDC.

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Old 30/01/2016, 07:49 PM
Stan Nicholson Stan Nicholson is offline
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Join Date: May 2010
Location: Nr Ottawa, Canada
Posts: 64

Thanks to the information from Druid and Rob, plus the stuff in Derek Pickard’s book, I have put together what I think is the history of the Silverstone cylinders from the RBS onwards although, as an ex jig & tool draughtsman and after a 36 year career as a production engineer, the lack of any revision control on these drawings does make me wonder how they controlled drawings and the subsequent parts manufactured from them:

The name Liner seems to be used as the term for the heavy wall, cast in liner and the drawings do show pictorially a thicker wall than those for the Sleeve titled drawings, used to reclaim cylinders that have reached the max oversize of + .010” before exceeding the 250cc capacity limit for racing.

G1089 (dated 9/5/64) Titled RBS Liner: This is probably the original porting for the RBS as the first RBS left the factory in May, 64 according to Derek.

G1089 (dated 3/6/65) Titled RBS Liner: Exhaust and inlet port sizes increased. According to the available drawings these sizes remain constant from this point through the RES. Both G1089 drawings call up the same H&G sleeve part number as material. I checked the cylinder from my RCS and that, as far as I know, is original and it has the same porting as the earlier revision of the drawing. So it would seem that the RCS had the same porting as the RBS. As this version of the liner drawing is dated after the last RCS left the factory that would make sense, although why Greeves would produce revised porting in June 65 and not introduce it until the 1966 models is a mystery. The cylinder from my RDS matches the porting sizes and positions shown on this 3/6/65 version of the drawing.

G1169 (dated 17/1/66) Titled RBS Sleeve: This drawing is for the thin wall sleeve used to reclaim oversize cylinders and carries the same porting dimensions and positions as the 3/6/65 version of drawing G1089. This would make this sleeve suitable for use with RDS cylinders.

G1168 (dated 17/1/66) Titled RBS Sleeved cylinder: Companion drawing to G1169 showing the machining dimensions for fitting the G1169 sleeve into RDS cylinders.

G1235 (dated 3 Feb 67) Titled RES Cylinder Sleeve: Pictorially this drawing shows a thin wall sleeve and the title, sleeve, indicates this was for reclaiming oversize cylinders if the same drawing convention was being followed. However, the material call up is the same thick wall H&G sleeve as used for the cast in liners, G1089. Either this was an error or the same drawing was used for both the cast in and thin wall sleeves but using the different H&G sleeves, as the RES cylinder carried this part number. While the port dimensions are the same as those of the 3/6/65 version of G1089 the ports were all moved down in the bore by 1.75 mm (or the imperial equivalent as the transfers were dimensioned in inches), including the transfer windows at the bottom of the bore. My RES cylinder stamped G1235 conforms to the porting shown in this drawing.

According to Derek Pickard, the RDS was considered by many to be the fastest of all the Silverstones and this would make sense as the cylinder had the larger ports without them being moved lower in the bore as per the RES, which resulted in less duration for the exhaust and transfers while giving increased duration for the inlet but leaves the exhaust and transfer ports partially covered by the piston at BDC. I have used all 3 versions of cylinders over the past 33 years I have been racing my Silverstone but have never run it on a dyno to see what power it developed. I changed cylinders as each was damaged, was awaiting reboring or had reached the max size and still needed further boring to remove ovality, etc. When I was running with the original Hepolite pistons with the Dyke top ring, any tightening up would usually result in a broken top ring and subsequent damage to the top of the exhaust port. I went through a lot of pistons and rebores over the years. Luckily we are allowed up to 5% oversize engines in classic racing here so 2mm oversize is just within the limits. I have just had a new sleeve fitted to the RES cylinder to repair the damage caused by the broken rod and need to get my RDS cylinder resleeved again (it was done here in Canada per drawing G1168 many years ago) and has now reached the point where the inner sleeve is perilously thin. As Greeves never expected these sleeved cylinders to be bored out more than + .010” I was not sure how far to push my luck.

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Old 11/07/2017, 06:02 AM
hawkie197 hawkie197 is offline
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Join Date: Jun 2011
Location: Melbourne Victoria Australia
Posts: 68
Default Crankcase differerences

I was just about to post a photo showing different challanger type crankcases when I stumbled across this thread which answered my question, but I will post them any way as a picture speaks a thousand words.
Cheers Pete from the Antipodes:
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