[R Powell]

Am just taking the engine out of my 900 SEI that I have owned for the last 33 years to give it a much needed rebuild. It has been using lots of oil and smokes quite a lot! As well as the compression on the no 1 cyclinder being 60 psi and the others 120 psi.
i have purchased a new barrel and 6 Pistons from Germany and intend to have these and many other parts fitted in the engine.

Will take engine out of the frame with the help of 2 friends during the week! And then I intend to take it to Selwyn Motorcycles for rebuilding. This will include various improvements that Selwyn has made to many of his Benellis. I rode Liz's Benelli six on a trip to Germany and told Selwyn that it was the smoothest bike I had ever ridden!
I hope I get mine to run like that, I will keep you posted on the progress.

 

[R Powell]

The Barrell and pistons are the best part of £1000, some of the improvements Selwyn makes are carburettor rejetting, electronic ignition, making all the conrods the same weight, replacing the drive chain from the crank to the gearbox and smoothing the inlet manifolds. Mine has always sounded like a bag of bolts when it is cold and has always had some hesitancy in the rev range . The bike I rode in Germany had none of those issues and ran well from cold. Am hoping know that the bike will serve me well until I hang up my riding boots!

 

[R Powell]

Hi just an update on my progress, I am picking up my rebuilt engine from Selwyn motorcycles this week. On close inspection Selwyn found various gears and shafts in the gearbox worn and wear in the clutch. This has all been rectified and the balanced crank has been refitted with the new barrel and Pistons. The cyclinder head has had the valves ground in and all new valve stem oil seals fitted. As I use the bike a lot I thought it was prudent to have any part worn parts in the engine sorted. This bike should now last me till I die!
will post some photos on refitting the engine and let you know how it runs!

 

[R Powell]

The 900 Sei oversize pistons are impossible to get, Kawasaki gpz305 pistons fit with some light machining but are again impossible to find. I bought a standard barrel and 6 pistons from Benelli de in Germany a few years ago so they might be able to help. I also heard someone there may have found alternative pistons. The 900 Sei and Benelli 604 shared the same piston but were made in smaller numbers than the 750 and 500 which can use Honda parts.
if you do source some pistons let us all know there are lots of owners who may need them in future,

 

[R Powell]

Those pistons may get fit a 750 sei but not a 900 sei. The 900 has a different stroke as well as bore and the pistons have a shallower deck height!

 

[R Powell]

Hi Tornadoboy, I agree that reducing another piston in height might not work, Allen Millyard used a piston from a watercooled bike in an aircooled engine and had expansion rates on the piston that damaged it!
I think Selwyn and the other German suppliers have looked into getting JE pistons to make them but this was not cost effective without a large order!