Re: Carb upgrade for stock-ish qt50 as first mod.

Bill Mazzacane /
This single post is part of a larger thread. Start from the top or view this post in context.

> Rob LaFreniere Wrote:

> -------------------------------------------------------

> I just bought what I hope is a stock 1984 qt50 and want to upgrade it to

> eventually be fast enough to safely commute to work. I think that 40mph

> would be bare minimum.

Sounds fricken dangerous too me :)

If you don't increase the amount of air the engine consumes, you will create a lean condition because you increased the diameter of the carb. The carburetor's venturi reduces the air pressure inside the carb, so that atmospheric pressure can push the fuel (from the float bowl) and air (into the carb) into the engine.

But if you don't increase the engines demand for more air, or find a way to increase air pressure, the pressure inside the carb will increase, and less fuel will be pushed into the carb, and that is how the lean spot is created.

It has been 100 years since I worked on a QT :) They have a great stock exhaust pipe, and it works well the stock cylinders porting. A tuned pipe does not, or at least in my opinion, the power gains of a tuned pipe are not worth the money unless the exhaust ports blow down time (BDT) has been increased to 21 to 23 degrees. 18 degrees of BDT is the absolute minimum, but I wouldn't waste my time building or selling a tuned pipe unless the customer knew that changing BDT was essential to the performance of the engine.

I don't know these companies, but if you are under the opinion that you can bolt a pipe on to any stock cylinder and get decent HP, that isn't true.

With a stock cylinder, you are better off with a 1/2 pipe that only improves the engines scavenging abilities.

Bill M.

This single post is part of a larger thread. Start from the top or view this post in context.
Subject Written By Posted
  Carb upgrade for stock-ish qt50 as first mod.Topic by: Rob LaFreniere Rob LaFreniere 04/10/19 04:14PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/10/19 08:16PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Rob LaFreniere Rob LaFreniere 04/11/19 11:49AM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Bill Mazzacane Bill Mazzacane 04/11/19 07:06PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Bill Mazzacane Bill Mazzacane 04/13/19 04:38AM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/13/19 10:03PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/11/19 07:16PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Bill Mazzacane Bill Mazzacane 04/11/19 08:54PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/11/19 07:26PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/11/19 11:53PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/12/19 12:06AM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Rob LaFreniere Rob LaFreniere 04/12/19 09:33AM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Bill Mazzacane Bill Mazzacane 04/12/19 07:24PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/12/19 10:50PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Rand Jacobson Rand Jacobson 04/13/19 07:02PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Bill Mazzacane Bill Mazzacane 04/14/19 04:37AM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/15/19 07:26PM

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account