Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Idle advance or retard

Idle advance or retard

Moderators: Curt!, Pa

Post Sun Aug 07, 2011 12:22 pm

Posts: 186
Hello all;
Is it more advisable to idle a 45 flathead, with slight retard on the spark, rather than just full advance.
Thanks Keith 8)

Post Mon Aug 08, 2011 3:52 pm

Posts: 575
Location: devon,england
retard will make it idle smoother as the engine wont be 'fighting' its self to run.
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years

Post Mon Aug 08, 2011 8:45 pm
Pa Site Admin

Posts: 5547
Location: Ohio USA

Auto advance timers only advance timing while engine rpm increases. At idle they are in the retard position.

Post Mon Aug 08, 2011 11:40 pm

Posts: 186
Well, it might seem like a dumb ass question, but,
as we all know, the spark timing on a bone stock WLA 45 flathead is not automatic.
With the timing set as exact as possible according to the manual, just wondering if the full advance position is just a minute amount early at idle (inherent in the design)
This would cause uneccessary knock at the gudgeon bushes, and other components.
Best to listen to the motor closely I guess.
After engine warm up, and choke fully open, my motor seems to run nice at full advance, but labors more when fully retarded. I just love that sound at low idle with full retard though.
As already advised, idling the motor just off full advanced would be best, as the spark would happen exactly at TDC.
Thanks for your replies.
Regard Keith

Post Tue Aug 09, 2011 12:22 am
Pa Site Admin

Posts: 5547
Location: Ohio USA

The 45 engine eventually went to the auto advance timer. The auto advance was to mimic the standard manual timer automatically. Think modernized. If I remember correctly, HD evovled two different 45 auto advance timers into production. Manual is not a problem if adjustments to rpm are met.

Post Tue Aug 09, 2011 4:09 am

Posts: 1604
I'm sure there will be a lot of differing views on this, apart from anything else it will vary with engine set-up, overall gearing and overall bike+rider weight, but as a general comment I would reckon to start the engine on full retard, warm up on 1/2 advance and wind up to full advance as you ride away. Ride generally on full advance, but apply maybe 1/4 retard for riding in traffic and 1/2 retard when idling.
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Tue Aug 09, 2011 4:33 am

Posts: 186
Thank-you all for good advise. Excellent!! That answers my question exactly. Happy riding always!! :D
Regards Keith

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