Boring a FCR MX 39 to 41mm?

[Svery]

I see some people have done this - I can have my 39mm straight bored out to 41mm as far as I know (physically can be done). Is this advisable or not? Will it mess up the flow characteristics or is it ok to do?

[Wayward Son]

as long as its done but someone familiar with boring carbs its no problem.

[Svery]

Thanks Eddie.

[hinksy]

Svery , you are lucky that there are a few people on this site who already use the 41mm FCR , so you shouldn't have much trouble re-jetting with there help . In the 80`s I bored out my dellorto carbs from 32mm to 36mm , on my laverda 1200 . It took me a couple of months to work out the jetting by trial and error . The good thing was that we had leaded fuel , so it was easy to do a plug chop . But the dellorto`s have a fuel pump just like the FCR , so try getting 3 carbs to pump in unison , and the supply of needles were difficult to get , Had no problems with the pilot air and mixture though , they were the easiest . I was lucky that I found a local firm , that specialized in the boring out and resleaving , so they were able to do it for me . They used to linebore the arms on loaders once the pins wore out and they also had quite a few fitter and turners who could use this type of equipment and a lathe aswell . Let us know how it goes , if you do get it done , as that would be a cheaper option than buying a whole new carby , greg

[Svery]

Thanks Greg, I'll post back when I have some progress on this.