Top end advice

[Egee]

These photos are of my SX200 barrel which many year ago was bored out to 225cc. It has sat in the garage for past 40 years, and now in the light of day, I'm not sure if the set up is compatible with todays scootering and fuels. It was a runner when it was dismantled! The barrel has the lower fin chipped below the exhaust port. The cylinder head has an impact area at the 8 o'clock position on photo - will this polish out? How are compression ratios these days, if I remember this was a high compression engine. Not sure how to clean the rusty areas, the bore measures 69.97mm - will linishing increase this dimension greatly?

Chipped barrel.jpg

[Captain Pugwash]

I've bored 200 barrels out to 71mm and they've worked well. Your barrel might be better with a local engineering shop giving it a very light hone or you could use a flex hone with fine stones fitted.
If you get the bore measured you will know how much wear there is "or isn't"

I think You might be better off with a new lower comp head, something like the AF 225 head as used on Rapido and TS1. Keep it below 9-1 compression ratio and it should be ok on modern fuels.

Wouldn't worry about the missing fin it's at the cooler end of the cylinder.

Only my thoughts

[Egee]

I've bored 200 barrels out to 71mm and they've worked well. Your barrel might be better with a local engineering shop giving it a very light hone or you could use a flex hone with fine stones fitted.
If you get the bore measured you will know how much wear there is "or isn't"

I think You might be better off with a new lower comp head, something like the AF 225 head as used on Rapido and TS1. Keep it below 9-1 compression ratio and it should be ok on modern fuels.

Wouldn't worry about the missing fin it's at the cooler end of the cylinder.

Only my thoughts

Thanks for that, I want to keep it as original as possible, and not go overboard with the spend. I'm in mid Wales, not many local engineering firms around here (mainly tractor focused). Would a large flap wheel remove the glaze in the cylinder, or does this risk possible eccentric shaping? Good to know about the fin.

[Captain Pugwash]

I wouldn't use a flap disc, your best getting a flex hone like these.

http://www.osborn.de/english/products/h ... _tools.htm

These are the easiest to use in a barrel with holes and a spigot with cutouts.

Engineering shops that do rebores and that kind of stuff would use a spring loaded parallel honing tool to clean the bore and prepare the barrel surface. .

[Egee]

I wouldn't use a flap disc, your best getting a flex hone like these.

http://www.osborn.de/english/products/h ... _tools.htm

These are the easiest to use in a barrel with holes and a spigot with cutouts.

Engineering shops that do rebores and that kind of stuff would use a spring loaded parallel honing tool to clean the bore and prepare the barrel surface. .

Didn't know about these, will try and track one down. Thanks again