PSC GP200 » Fri Jun 17, 2016 10:52 pm
I was talking to a well respected Yorkshire scooter tuner and dealer today and mentioned that I was thinking of putting A BGM on my Rapido 225. He said not to as the tail pipe is too small and stifles the top speed on capacities above 200cc. They modified one on a customer's bike with a bigger pipe and that cured a "loss of 10 mph from the top speed".
Anyone heard of this or had similar problems? I thought they were a good product and ,no, he wasn't just saying it to get me to buy one of his pipes.
As you happen to ask:
This is good to read as it confirms what has been stated previously on this Forum & probably read by some with cynical disbelief.
Bearing in mind that most Lambretta enthusiasts would agree that racing has been @ the forefront, generally, for achieving increased power from the engine, you can imagine that the tailpipe diameter is a fairly critical consideration. There has to be a trade-off between power/torque & reliability by ensuring that heat build-up is not caused by too small a diameter.
Having said that, the diameter gets to a point where it is not only the cause of heat build up but restricts power/torque as well!
I can recall a ‘top tuner/rider of the 1970’s @ the time advocating precisely the size I would consider unsafe nowadays! They were ‘different times…’
On a reasonably set up large block engine with a kit, bigger carburettor & efficient expansion chamber/Clubman type exhaust, I would imagine Ø22 mm bore to be restrictive. Yet, I hasten to add that is my own opinion based upon experience
An inch bore or Ø25 mm would be a much safer option.