Diaprame carbs

[Redeye]

Hi all- I have diaphrame carbs on my Hirth 2 stroke in my glider- The dont have bowls or fixed jets- Two scews marked H & L

Can anyone tell me how to adjust these carbs for altitude please

[John Young]

Phone David S. on oh 83 262 83 six 7

Think that he is a lurker anyway.

Time to bring David S. in.

Regards
John ZU-CIB

[Duck Rogers]

They're also known as CV or CD carbs. Constant Velocity or Constant Depression, same thing (almost)

They generally are altitude compensating carbs (to a point) Some may not have any external adjustment capabilities.

Give me the carb make and model and I may be able to help.

[Redeye]

Thanx- The carbs are Tilitsons- There is a an H anf L adjustment- The Glider came from CapeTown- I srewed the H needles in a bit andthe power increase was dramatic but at 3/4 and low throtle settings it runs a bit rough now-

[Duck Rogers]

Sorry Redeye.....they are not CD or CV carbs. According to my old documentation they are also referred to as pumper carbs. Apparently so called because they can be used at any angle.
They are NOT altitude compensating and can't be adjusted for altitude (not externally anyway)

You set them as follows:
You adjust them by running them at full throttle and turning the high speed needle in and out till it runs best. Same for the idle. Let it idle and turn the slow speed needle in and out till it runs it's best. The high and low speed needle adjustments will effect each other a bit. In other words, richen the low speed and it will also richen the high speed just a bit, and visa versa.

Hope this helps you understand them a bit better.