andy m Posted February 17, 2014 Author Report Share Posted February 17, 2014 Having read Charlies thread on his site re the gearbox conversion and Woodys comments I will stick with std box. Couple of questions, are the gear ratios in the early and late engines the same? also what piston will be best for a soft engine ? Std or B25 ?? Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted February 18, 2014 Report Share Posted February 18, 2014 Hi Guy's Hi Andy. There are three sets of diffrent sets of gears, that will fit "Dizzy" engines standard, close, and wide. some you can swop! To be honest close is probably best if you don't do a lot of road trials? and you use the 18 tooth engine sprocket. My opinion. Are you building the bike for the "Britshock" class??? You know what I think about pistons BSA Otter Site, and I have researched this subject over the past couple of weeks, with several people, and we agree, that this is probably the best choice. Getting the ignition sorted, with the right timing curve for the job in hand is the most important thing to get right. a couple of systems spring to mind, but I am looking into other possibilities. Regards Charlie. www.bsaotter.com Quote Link to comment Share on other sites More sharing options...
davetom Posted February 18, 2014 Report Share Posted February 18, 2014 I had a standard piston after my last rebore, about 7.5 / 8:1. I turned 40 thou off the top and it became much better Quote Link to comment Share on other sites More sharing options...
andy m Posted February 18, 2014 Author Report Share Posted February 18, 2014 I want to stick to 250cc so won't use Triumph piston. Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted February 18, 2014 Report Share Posted February 18, 2014 Hi Guy's, Hi Andy, Why??? So you would use a +60 C 15 piston? But not a Triumph that is +80 say.?? And boosts the power slightly ,reduses the weight of the barrel, and adds to a better power characteristic . I know that this is a totally different concept ??? But what is the compression ratio on the New 4RT???? Are we thinking along different lines ,now a days?? Or has all this Trick stuff that has been put into "Britshocks" come to a close ??? And are we now Retro thinking??? Regards Charlie. 1 Quote Link to comment Share on other sites More sharing options...
andy m Posted February 23, 2014 Author Report Share Posted February 23, 2014 Got some advice at Telford. Using std gearbox 18 tooth primary, 14 tooth front spkt and 60 rear. Use std piston, n ot flat top and if I want to lower comp slightly use a 2nd base gasket. 1 Quote Link to comment Share on other sites More sharing options...
sickswan Posted February 18, 2015 Report Share Posted February 18, 2015 I had a standard piston after my last rebore, about 7.5 / 8:1. I turned 40 thou off the top and it became much better I also have standard bore an piston and am about to build this when you say 40 tho I presume you turned/milled 40 tho off the top? Is 40 tho maximum amount? Quote Link to comment Share on other sites More sharing options...
davetom Posted February 18, 2015 Report Share Posted February 18, 2015 Yes 40 thou off the top. There's more meat there if you measure it but not sure what the max you could remove is? Quote Link to comment Share on other sites More sharing options...
sickswan Posted February 24, 2015 Report Share Posted February 24, 2015 Do you have any idea what compression is with 1 mm off the top Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.