Heat riser valve setting help 71 fj40 (1 Viewer)

[jikser]

Anybody know which position is open or closed for the heat riser flap on my stock 71 1f. I no longer have parts 55-58 and even if I did the thing is rusted enough you can only turn it by hand. I want to open this vs having it restrict exhaust flow, and boil the fuel in the carb. It will move by hand and stay once it is moved, I just don't want to pull the pipe to see which way is open if I can avoid it.

Thanks
Les

 

[IDave]

Flap horizontal is how it is supposed to be when the engine is hot.

The counterweight (63 in the figure) parallels the flap. In the picture it is oriented for being cold: directing the hot exhaust gasses to the underside of the intake.

 

[jikser]

Thanks IDave, think I will run it horizontal.

Les

 

[IDave]

That's what you want to do. Leaving it in the "cold" position when the engine warms up can cause problems, like intake cracking.