LCGB Forums

Currently running an RT195 lightly ported with Bgm clubman v4 on a series 2 Spanish. Dellorto 28 phbh carb,Ram air filter and Gearing set up at 18/47. Runs beautiful through the range but the maximum top end is about 56mph which it doesn’t hold for very long especially when coming to any kind of incline. I’m just looking to get a little more up top. Would a decent expansion do the job with a little adjustment of the jets or would I have to have some work done to the cylinder head? I just need some opinions on which way to go with this.

Sounds like your gearing is too tall for the configuration you’re using which will take much of the pleasure out of riding always having to drop to 3rd to build revs.
I’m using an RT195, BGM and 25 PHBL and it’s great running final drive ratio (FDR) of 4.8

Personally I’d sort the gearing for your engine configuration.
Once that’s right take it from there.

You’ll have to take your gearbox out and count the teeth to determine what gearbox you have (if not already known)
Then with the sprocket sizes you’ve listed use a gearing calculator to work out your FDR
https://www.afrayspeed.co.uk/media/other/50188402/45-tooth-gear-chart1..pdf

Once you know that update this thread. However aim for between an FDR between 4.8 to 5 for your configuration is my suggestion which may mean changing sprocket sizes.

I completely agree with nsaints, there probably isn't anyone on here who builds their own motors who hasn't over-geared at some point to learn that lesson; I certainly have.

Also, I'd go a little further and say that most expansions would exacerbate the problem by shifting power up the rpm scale. There are exceptions to that, notably CST3, but rule of thumb is expansions need more revs, so lower gearing.

I'd suggest changing to a 16 tooth front as your first step.

I run a RT 195 using A LI 150 GEAR BOX STANDARD SPROCKET S AND USE 30MILL DELLORTO CARB DOES ABOUT 70 TOPS AND CRUISES AT 60 . THATS WITH A BGM CLUBMAN.

Thanks for your inputs guys. Definitely food for thought.

My Rt 195 reedvalve , 25 delly, bgm sport, sx200 box 16/46 does around 73 flat out and cruises at 50/55/60