K&B .45 doesn't need pressure tap???

Andy, Not all engines need the muffler pressure to operate. It will help in most cases. It makes up for low fuel draw or tank installations that aren't on or near the centerline of the carb. If you have a break in stand, you can try it both ways and see which way works best. Generally the pressure will win out, but I don't run pressure on my ST3000 and don't have any problems (with the engine anyway!).

Good luck with it and have fun.

Fred

On 5 Jan 2004 12:34:57 -0800, snipped-for-privacy@hotmail.com (Andy) wrote: Andy, I assume that this is the K&B 45 Sportster. The tap is on the muffler extension and not on the muffler. Look at the extension and you will see a where it goes. You could drill and tap this. I have used it with and without the pressure and found very little if any difference in performance. good luck Gene

HI Andy, The K&B sportster 45 does not require muffler pressure, in fact muffler pressure can cause premature wear of the bearings and very rich running in the air.(this straight from K&B). They told me that it causes the engine to go over rich and wash the lube from the bearings. The venturi in the carb is small and gives the engine good fuel draw without muffler pressure. A few years ago I took up this issue with K&B due to poor running of my Sportster

45 and they told me to immediately discard the muffler pressure. I did and it cured all the engines ills. Ok this being said I now have my flame proof cyber shield up so let me have it!

Tom Wales AMA435536

I didn't think the K&B "Sportster" series had any bearings.

Mike

Interesting that K&B would say that. My first two Sportsters broke apart in the air. They had no pressure taps. Not that they are related. The replacement engines do have taps but I haven't used them much. Maybe they sent me the old design as replacements. Oh well. Still a fair engine in it's day. Now days, over priced for what you get. I will disconnect the pressure tap even though without a pressure tap, a remote needle engine is a little hard to start because it takes a finger over the exaust to pump fuel to the carb. Can't always choke it. Maybe someone has a good idea how prime the remote needle. Happy flying Gene

Interesting that K&B would say that. My first two Sportsters broke apart in the air. They had no pressure taps. Not that they are related. The replacement engines do have taps but I haven't used them much. Maybe they sent me the old design as replacements. Oh well. Still a fair engine in it's day. Now days, over priced for what you get. I will disconnect the pressure tap even though without a pressure tap, a remote needle engine is a little hard to start because it takes a finger over the exaust to pump fuel to the carb. Can't always choke it. Maybe someone has a good idea how prime the remote needle. Happy flying Gene ==================== A few drops of fuel directly into the carb might give a starting burst that draws fuelthrough the remote needle setup.

I have an OS .15 that flat won't run with pressure...Runs great without it, though.

Roger

Mike wrote:

Muffler pressure is a 'modern thing' brought about by increasing the carb throat size to raise HP - with the result of poorer fuel draw by reduced venturi vacuum.

A modern .40 carb has a larger throat than either my 1970 OS MAX .60 Goldhead or ST G60 Bluehead.

I have a 1968 Enya 45TV in which the carb throat is only about 0.15" ! Measure the hole in an OS 40FX and I think you will find that it is about 0.25" !

An end result of the HP race is.... the original Jensen Ugly Stik was a ' .60 size plane', the same size today is a ' .40 size' !

David

Well, the consensus seems to be that the tap is not required. I will be breaking it in in the spring - without the tap. If I have trouble

- I'll scream here :)

Thanks all,

Andy

We all have flame suits and ear plugs..... BIG GRIN

David

Engines with smaller diameter carbs will develope faster airflow in the venturi. This will give better fuel draw if designed properly. Many earlier designs did not use or need muffler pressure to draw fuel. Many early designs didn't even have mufflers!

And the early mufflers did NOT have pressure taps ! I have several

1970/71 vintage OS MAX engines that I purchased while in Korea. None of them came with mufflers - they all had 'butterfly' exhaust restrictors (except the .40 which had a barrel type restrictor). I did purchase the optional mufflers for them, tho.

David