Following on from the successful production of pistons for OHV 500cc Sunbeam models Chris Odling and I thought it would be useful to produce some high-quality forged pistons suitable for the Model 6 side valve long-stroke. The Model 6 was produced from 1922 until 1939 becoming known as the Lion after takeover by ICI. With its 77mm x 105.5mm bore and stroke this was the last side valve powered motorcycle to win a Senior TT.
There were of course changes along the way and the piston produced is nominally compatible with models produced from 1925 until 1929. Before 1925 a 5/8″ gudgeon pin was used rather than the later 7/8″ type and the change to a scavenge pump from total loss oiling in 1930 means a different piston ring configuration is required. It is possible that these pistons could be adapted to suit.
I have limited availability of pistons in 77.0mm +0.000″ and +0.040″ sizes. An all-up weight of 434g has been achieved for the 77.0mm which is within 2g of the target weight that we set out to achieve.
Once we have given the new items a good look-over I’ll be contacting those who have reserved pistons already and adding them to the Sunbeamland shop.
I noticed that Steve over at Racing and Investment Motorcycles has a rather nice looking 1928 Model 90 for sale in sports trim. Race pipes with Bentley and Draper dampers complete the look. These bikes don’t come up very often so I don’t suppose that it will hang around. Could be worth a look if you are in the market?
Don’t forget to checkout the Sunbeamland shop where there are a variety of items in stock including a limited number of these vintage tax disc or license disc holders. They are replicas of an original late 1920’s Pennant item that was loaned to me some time ago and would make a great addition to any quality vintage motorcycle i.e your Brough Superior, Sunbeam, Velocette or cammy Norton.
There are also various other vintage motorcycle spares that are left over from various projects that might be useful. For example, we have quite a number of different controls and levers including items from Amal, Amac and Bowden. Decompressors, valve lifters, magneto advance/retard control.. that sort of thing. Have a look round and let me know if there is anything you might be interested in.
There’s not much left in the seat department, so grab a bargain whilst there is anything left in stock. I’ll accept sensible offers on most items just to clear the space.
I was short of a set of handlebar clamps for the ’28 bull nose Model 90 that we are working on and so had a few sets cast and machined-up using an original Marston clamp from the ’30 bike as a pattern. They came out quite nicely in high-tensile brass and will be serving in place of decorations over the Christmas period.
Handlebar clamps for Sunbeam motorcycles with Druid rather than the later Webb-type forks.
I had a few extra sets produced and will put them on the shop in due course in case anyone out there is also in need of a set.
I’m pleased to say that we now have the recently manufactured high-quality, lightweight forged 7.5:1 pistons available on the Sunbeamland Shop in +0.020″ and +0.040″ oversizes. Modern materials and CNC machining mean that all-up weight is within a few grammes of the original Marston’s item and I’m enjoying the experience of running one in on my own 1930 Model 90. They should fit any of the late 20’s early 30’s 500cc OHV bikes and we hope to be following up with production of a small batch of 6.5:1 pistons aimed more at the Model 9.
Forged piston for Sunbeam Model 9 and Model 90 7.5:1 compression ratio
This little beauty arrived today and I couldn’t wait to put a post up on the blog here at Sunbeamland. It is the first from the box of a batch of forged Sunbeam Model 90 pistons. It is modelled on an original Sunbeam 7.5 : 1 piston and, unlike some alternatives that are available, weight has been controlled so that the combined weight of piston, pin and rings closely matches the original.
Next job is to bore a spare cylinder to suit either of the +0.020 or +0.040 sizes we have produced and get some testing done before winter sets in.
A new development here at Sunbeamland is that we now have a vintage motorcycles for sale section added to the shop. To get the ball rolling we have this rather interesting 1929 BSA sloper. Being 1929 vintage, it is of course eligible for VMCC events such as the Banbury Run. If you’d like to know more, drop us a line and we’ll put you in touch.