Carb float height wrong

Bob_pipedream · #1 11-14-2010, 05:45 AM

Hi all,

Finally whipped the carb off yesterday and now have it in bits on the kitchen table.

I have found that the float height which is supposed to be 7/32 (with gasket) on the 10-3678-32 is actually set in mine at 9/32 (with gasket) and that the floats are not equal height. So this means that the float was too low.

Question is would this 1/16" make a big difference? I could not get any idle rise on shut down at all, so hope this may fix it.

I also get an EGT rise on all cylinders when I apply carb heat...

By the way the 16-A31 gasket does not fit the 10-3678-32 MA-4SPA carb! I will post the correct gasket number here when I get it.

aerhed · #2 11-14-2010, 09:36 AM

With the float at 9/32 you should have been leaner than normal. Makes sense to have no rise at ICO. Also explains carb heat temp rise if you were running leaner than you thought (below stoichiometric). Is your idle mixture screw already way out?

Walt · #3 11-14-2010, 10:00 AM

I have generally found that carbs are not that sensitive to float levels being off a small amount. I don't think this alone is going to fix your idle rise problem.

Mel · #4 11-14-2010, 10:13 AM

I have to go along with Walt. The float level will not affect idle mixture much if at all. And with controllable mixture, it's not going to affect cruise much either.

aerhed · #5 11-14-2010, 06:49 PM

You guys think it'd have to be way off to matter? I haven't found many really that were very far off. Mostly just sinkers.

Bob_pipedream · #6 11-15-2010, 05:11 AM

Hi all,

Thanks for responses, just to make clear - she idles fine and starts fine, it is just that I can not get the revs to rise before shutdown and even though I have screwed out the screw 4 turns, still no rise (so I put it back where it was).

Of course she it a taildragger, so that may compound low fuel level as it is on a slant.