D17 Governor adjustment

dhermesc

Well-known Member
We were working on my FIL's D17 Series IV over the weekend and my son commented how the tachometer doesn't work. I spent a few minutes checking the issue - the tack works fine it turns out the engine is over revving and pegging out the tachometer. Is this a common issue with a common fix? We haven't run it enough to know if the governor is working.
 
Engine off. Hand throttle set wide-open. Remove the cotter pin from the link rod to the vertical governor arm directly behind the generator. Pull the link rod out of the arms hole. The governor arm shouldn't move. If it moves to the rear, reconnect the link rod and pull down on it in the middle to make it shorter. Re-check your link rod length fit to the governor arm. If the link rod is too long, RPM's will be higher than they should be. The link rod should just slip into the arm hole and not be too long. A drop of oil on each end of the link rod is a good idea. Tachometers usually read 150-200 RPM high when they get old.
 
Seems like if that was really pegging the tach. it would be screaming! While proper governor/carb. adjustment will effect speed, that adjustment is more for correct operation/response/etc. I would think you'd need a stiffer gov. spring to get the kind of speed you're indicating. I have an electric eye type tach. which works on anything which will hold a piece of reflective tape. Last year I found my friends' D15II tach. reading 400 RPM off.
 
A properly tuned D-17 gas engine and correct governor link rod length can only yield about 2100 actual RPM at the very most on a D-17 with the gov spring stop screw clear out. If that link rod adjustment is too long it's easy to gain any 100 RPM or more. Like I said, the factory tachometers tend to read high in their old age at full throttle.
 
It has a new tach and by ear it seems about right. I am guessing it's running 2800 RPM when wide open.
 
And you haven't checked the linkage adjustment?? If it truly is 2800 RPM's you must have one governor weight broken/cracked. Keep on running it and you'll be tearing the front off of the engine repairing timing gears.
 

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