Hi All
A quick story so far. My F1 front barrel is cactus with the lining having come away from the bore of the barrel. The bike is a 85 model frame #83 engine #163.

I bought a replacement front barrel of the auction site we love to hate. The barrels that came out of the bike have a straight bottom end to the liner. The one I have bought has a cutaway on one site (I didn't notice this in the picture when I bought the replacement). The bore diameter is the same and everything else is the same including position of the belt runner mounts. The cutaway does not impact the stroke of the piston. I noticed in the parts book that the barrels actually have cutaways. The new barrel fits fine on the case as well. I am not sure that the replacement barrel has the same lining as the original and will check with the magnet tonight. It seems to weigh a bit less than the original too.

My question does anyone have any advice on why they are different? Has anyone experienced this as well?

Here are some pictures of the old barrel. new barrel and the parts book

Hi,
I am no help?? Out of curiosity, do the cylinders have casting dates on them??

I have seen both styles, even on the vertical twins I have seen that cutaway style.

Clay

Your bike being an '85 it should have a cast iron liner. If you have a liner with a peeling surface it is probably an aftermarket piece, chromed rather than Nikasil. More detailed pictures would be helpful. I don't know if it is just the camera angle but all the relieved cylinders I've seen are cut away on both sides of the bore, your picture looks like a chunk is broken off the liner. The liner itself can be replaced pretty easily if it is cast iron. Northwest Sleeve does excellent work. If the new liner you have is the black one in the pics it looks like a later 750 part,they have Nikasil lined bore which is a hard coating applied directly the the aluminum cylinder and is lighter than the one with the iron sleeve. It will likely work but ideally you should probably replace the vert. cylinder too, there could be cylinder temp differences with 1 iron and 1 alu. cylinder.