Unexpected air leak on HIF38!
Posted: Tue Mar 16, 2010 7:57 pm
This is a trap I fell into when setting up an HIF38 on my boys' 1100, but could easily apply to a Moggy1
I had been re-profiling the needle to get the mid range near to what was needed when I dropped one of the 3 damper chamber screws on the gravel under the back of the engine. As I was cold and it was getting dark, I put it back together with just two screws, in the rearmost lugs. I then had starting problems, richened the mixture to overcome this, and finally got it to run, but hesitant picking up. After much cursing and fiddling, I decided it was as good as it was going to get, moved the car back and retrieved the third screw. Imagine my surprise when on screwing it into the forward most lug, the tickover suddenly increased! A little leaning out and the engine was perfect! The reason- that third hole is drilled right through into the choke tube, so having the screw missing was bleeding a good bit of air into the carb downstream of the piston, upsetting the balance! Worth remembering for the future, but I bet I don't!
I had been re-profiling the needle to get the mid range near to what was needed when I dropped one of the 3 damper chamber screws on the gravel under the back of the engine. As I was cold and it was getting dark, I put it back together with just two screws, in the rearmost lugs. I then had starting problems, richened the mixture to overcome this, and finally got it to run, but hesitant picking up. After much cursing and fiddling, I decided it was as good as it was going to get, moved the car back and retrieved the third screw. Imagine my surprise when on screwing it into the forward most lug, the tickover suddenly increased! A little leaning out and the engine was perfect! The reason- that third hole is drilled right through into the choke tube, so having the screw missing was bleeding a good bit of air into the carb downstream of the piston, upsetting the balance! Worth remembering for the future, but I bet I don't!