Postby Workshop Help » 04 Jan 2008 14:08
Hi! It's me again. I hate to be a 'buttinski', but this issue of what should be a simple and inexpensive part being overpriced by some parts stores is beyond irksome.
What many fail to understand is that the Z-S carburetors function best when the temperature of the carburetor is about 100 degrees Farenheit. This is why hot air from the exhaust manifold is needed until the carburetors have warmed up. Then the sensor in the air cleaner closes the flap door and outside air is admitted thru the air filter. This opening and closing of the flap door can be a continous process, depending on the outside air's temperature.
The hose from the manifold is a key element. Removing it delays the warm-up of the carburetors. It is important that a carburetor be heated so fuel in the float bowl can atomize and be drawn into the chamber where it is blended with the incoming air. Thus an efficient mixture is combusted. If, and more often when, the hot air hose is absent, the fuel is in the form of large droplets and blended with cold air producing a less than efficient mixture. This gives an uneven performance as misfires occur until the carburetors eventually warm up from the proximity of the engine heat. In cold weather, that warm up will take a long time.
The flip side is during warm weather, the need for hot air from the exhaust manifold is non-existant and the air cleaner flap door opens to the outside air very quickly as the carburetors reach 100 degrees Farenheit. Please understand, the heating of the carburetors is to warm the fuel only. Once at proper operating temperature, an engine functions best on warm fuel and COLD air. This is why modern cars have dedicated hoses directed thru the fenders to draw in unheated air. The TR7 stock air cleaner draws in air from the heated area under hood area. It would behoove the engine if a hose was attached to the air cleaner spigot and channeled to the unheated air thru the fender.
I am amused and bemused by people that wrongly think eliminating the stock air cleaner for accessory 'pancake' or 'Longflo' style air cleaners are improving the efficiency of their engines. They may look good, but they fly in the face of the proven results a cold air intake hose. Perhaps if you're interested another post can explain how easy a cold air hose installation is accomplished.
So, the engine needs that hot air hose.
In fact, there are a couple ways to get around the overpriced hoses out there. The brand from 'Mighty Flow!' has part number 96032, which is a 1 3/4" by 36" hose that can be stretched to fit. Or, as we have done, get two 1 3/4" by 18" hoses and a 1 3/4" by about 3" to 4" steel exhaust connector, along with two 1 3/4" hose clamps. The advantage of the two hose technique is that when one section of hose is damaged, it is easier and less expensive to to replace that one section. These items are found at the local automotive parts houses.
Mildred Hargis
