MPG has decreased since Dayna tech ignition install

[yarin]

im not sure what happened but. although my 92 runs much stronger with my New Dynatech ignition.  my mileage is terrible.  ive not adjusted anything else.  idles great runs great, blip test good.   Ill try leaning out the idle mixture screws.  could it be my timming is a bit advanced. i followed instructions and got TDC.  it is a ten year old ignition i found on ebay.   has anyone else had this problem

Tom

[Pat Conlon]

Couple of Q's:
How much of a decrease?
What setting are you running for the advance?
Are your riding habits the same?

[yarin]

decreased roughly from 50mpg to 30mpg
there are 3 advance curves, ill check does it matter, which is best
habits are the same

[Pat Conlon]

50mpg is very high. The only one I've heard coming close to this was Monkey Mark.
30mpg is much too low, something's wrong.
Most FJ's run in the range of 38-44mpg, depending on jetting and riding habits.
Last I checked the Dyna had 5 ignition settings and IIRC folks have been happy at setting #3 (Frank, others, help here) regardless, your ignition advance should not be the cause of your poor mileage unless you had it advanced too much and damaged your engine thru detonation or preignition. You would have heard it.

Start with the basics.
1) Do a warm compression test (throttle open) post your numbers.
2) Check your valve clearances. Re shim any tight valves.
If your compression numbers were low and you had any valves that were tight, retake the compression test and see if the numbers come up.

3) Sync your carbs. Tell us if you any that are way out of sync. This is very common.

Then check your mileage again. Tight valves and/or badly sync'ed carbs will affect your mileage.

Hope this helps. Pat

[FJmonkey]

As Pat suggested my mileage is better than average. It does vary. My fill-ups between mid Oct and Last week. The average is 45.1 MPG. This is after Suppertraps, re-jet & UNI pods.

47.6, 45.8, 50.9, 50.9, 45.0, 38.9, 39.2, 45.7, 46.2, 41.0

Before the changes:

43.8, 55.0, 45.7, 53.7, 44.1, 45.3, 46.9, 43.5, 50.0, 46.8 (AVG = 47.5)

[FJ_Hooligan]

As Pat said, unless the ignition had too much advance and damaged something, I love to hear ANY reason how adding a new ignition can cause a decrease in mileage (given riding style hasn't changed).

It has no control over fuel flow (on a carb bike).  All it does is provide a spark.  Maybe the "runs much stronger" statement is a clue.  You know it's running stronger because you're using more throttle?  :-)