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Old 04-19-2012, 01:00 AM   #8 (permalink)
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honda cb125 - '74 Honda CB 125 S1
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Originally Posted by mikehallbackhoe View Post
I very rarely run it over 2,000 rpm. so I doubt I will have a problem running too lean. I could always choke down the 2" intake to match the 1 3/8" heated pipe. I would guess those having head gasket problems are running much harder than I drive.
The issue with running lean is not to much air but to cold of air, unless you have a remote thermometer probe in the air cleaner box to track the air intake temps because that little flap and the vacuum diaphragm is there to keep the air temp consistent so your air mass can stay steady, it gets rid of the need for a MAP sensor and a bunch of other sensors that you would have if you had fuel injection.
I know I've seen calculators before for figuring ideal intake size but I can't find one at this hour, but that 1 3/8" heated air duct is the same size as the Honda Accord used to supply air to their 1.8L engine of the same vintage as your car, so I really doubt that it's causing a lack of HP or MPG for your 1.3L engine running at 2,000 RPM, I just would hate to see you damage your engine because you ran it lean by disconnecting some of the controls on the carburetor.
On the other hand it might just keep the choke on if the air is not up to temp, so you might be safe from engine damage but would also be wasting gas and reducing the performance of your engine by having the carburetor keep the choke on.

Last edited by Ryland; 04-19-2012 at 01:52 AM..
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