Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties UH Gearing

UH Gearing

Moderators: Curt!, Pa

Post Mon Aug 07, 2006 8:28 am

Posts: 5
Location: Copenhagen
After driving 5000 km in 3 weeks, I found out that highways isn't that bad after all. But when i run at 110 km/h the engine rews a little more than I think it should, and therefore I was thinking about changing the gearing. I run with a standard 22 teeth sprocket now.

Any experiences and/or suggestions? 24, 25 or 26 teeth?


Edbbob :)

Post Mon Aug 07, 2006 9:46 am

Posts: 2677
Location: Los Angeles, CA
Are you asking about the engine or transmission sprocket?

Post Mon Aug 07, 2006 6:09 pm

Posts: 646
Location: Detroit
24/24 is nice all the way around.
New Knuckleheads? Thank, you, Jesus!!

Post Mon Aug 07, 2006 11:04 pm

Posts: 304
Location: oklahoma usa
I've run a 23T engine sprocket and 25T transmission sprocket for years with no problems. Dropped the rpms dramatically and thanks to flathead torque will even take off in 3rd gear from a dead stop.
(Keep an eye on the rear chain adjustment; the 25T gets pretty close to the oil tank. I rigged up a small nylon shoe to act as a guide and prevent flopping in this area.)

Post Tue Aug 08, 2006 1:37 am

Posts: 5
Location: Copenhagen
Thanks guys :)

Gotta be carefull not to chop holes in the oil tank. I need that one!

Is there any difference, wether I gear on the engine sprocket or the transmission sprocket?

Post Wed Aug 09, 2006 7:00 pm

Posts: 919
Location: RENO,NV. U.S.A.
KRAZY LOOP,I concur that's what we used to run years ago,there's no reason it shouldn't work now. BREWSKI

Post Sun Aug 13, 2006 7:26 pm

Posts: 1642
Location: Interlaken, NY USA

23/25 and 24/24 are almost exactly the same, 3.27:1 for 24/24, 3.28:1 for 23/25. Assuming a present engine sprocket of 23T and tranny is 22, your present ratio is 3.72:1. If you've a 24T engine, it's 3.57:1. You're really going to have to change the countershaft sprocket to get it geared up to a nice cruising RPM range.
Just my .02 worth.
Dr. Dick

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