Greetings all, The cylinder found on the 1970 Starfire currently scattered about my garage has a curious groove in the cylinder wall approximately 1/2" down from the deck. There was a standard piston in the engine as-found yet an oversize piston is due. My concern is if the groove speaks to a liner that may become too thin after the bore. What do you all think?
Bill
I would have a photo, but the file is too large. Will need to find a young person to diagnose my camera.
check out the bore size specified and what you have. you could take to get rebored and if too bad could be removed and replaced at the same time.
if you hover over your picture and right click, use the option "open with" and select paint.
from the top bar there should be "resize", you can either do percentage wise ( I normally go 50% to start with) or pixelwise.
once reduced save, if you dont want to save as the original I add small after.
then either open the same way and down the bottom it will tell you how many kb on the bottom bar (1084kb is the limit I think) or you can re submit by choosing the file again with Attachments and other options, if you need to re size again , alter the small named file.
edit.
there is also the option of using software but its something else I dont need to slow up my laptop
Chaz, Many thanks for the file compression guidance! I'll try and attach the photo now. While in revision mode, the groove is 1/4" down in the cylinder instead of 1/2".
Hi,
I have just surfed several images of B25 cylinders and none have this groove so not sure about the groove but 75 down is BLADE and 75 across is BONE.
Dave.
cant say I ve seen a groove like that before, If the piston rings dont get near at top dead centre it should be ok, but any chance of a ring catching would be a worry.
I know some 2 strokes have a squish band where the top of the barrel does have a relief , a section slightly bigger than the bore but upto 5 or 6mm long but not a groove.
If the barrel has a liner, maybe the liner has moved?
Well done with the crossword solutions!
Concerning the liner question, I'll attach a photo of the bottom end of the cylinder. There are a few tailcoats to be seen. I've been measuring with the calipers and trying to build a sketch that makes sense.
Hi Oliver,
All the B25 liners that I have found have the top spigot and a stepped skirt. The groove almost looks machined but for what reason? Is there any sign of the piston having seized?
To fit a liner it requires quite a bit of the original material to be bored away for the liner to be pressed in. My thought is that a poor quality fitting of the liner has resulted in a weakness at the point of the groove. A piston seizure may have caused enough force to fracture the liner allowing it to move. However it does look very uniform for a fracture.
A wild theory but perhaps possible!
Dave.
Hello Dave,
I agree the groove has a "purposeful" line of separation to it. Based on measuring the liners at the bottom of the cylinder, I believe the innermost liner has had to have moved. Beyond typical cylinder wear marks, I see no signs of a big seizure (I had an old OSSA that showed me that scene!).
I'm thinking new liner or a replacement cylinder is in order. Seems as though I've seen some cylinders floating around on e-bay.
Thanks to all for your time and experience,
Oliver
Where are you located Oliver?
Paul.
I live in the United States - in Virginia.
I have seen the odd liner move and I know Land Rover Freelander's suffer from spinning liners, I used to machine crankcases for railway brake compressors which were pushed in with little interference , cast iron into aluminium , but were counterbored for the rim and held in place with dowels.
looking at yours, it seems the cylinder has vertical marksthat line up and has not rotated.
if it has dropped, there might be a mark or oil line on the outside where the liner was held in place.
the other answer is, that a previous re sleeve or even an original was fitted and moved after fitting, someone took the barrel off saw it and got one elsewhere instead of getting it repaired.
here is Westwoods liner https://westwoodcylinderliners.co.uk/products/browse-by-application/bsa-motorcycles/b25-c25-250ss-247-249cc/ its a top hat style , maybe it was machined with the undercut under the rim too deep but would have been jagged not clean break
Hi,
The liners that I have come across are as in the image so it could be that someone bodged the relining with a plain liner.
Although this is the best BSA Forum in the world, 'Britbike Forum' may of help as there are a lot of American contributors and you should be able to get details of US unit single gurus.
Dave.
Dave and Chaz,
Many thanks for your technical history and insight. After 50+ years of motorcycling, this Starfire is my first go at a British bike and it is a fun learning experience. I couldn't agree more with the appraisal of this BSA Forum; straight forward, honest experiences delivered in good spirit and camaraderie. So many forums seem to be showcases for the rude.
I will check out Westwoods and BritBike Forum – thanks for the references.
Onward, through the fog!
Oliver
Hello Folks,
I've attached a photo of the "groovy" cylinder after being bored to fit a +0.020 piston.
Oliver
Hi Oliver,
That has cleaned up really well with no sign of the groove. I suppose the cause will remain a bit of a mystery. Good luck with the rest of the rebuild.
Dave.