I just finished installing a S&S 106" big bore in my Dyna Low Rider now my speedo pegs out till I get past 300 rpm then it reads 20mph faster than im going plus the odometer is running very much fast like a 5 mile trip is 50 miles now. Do i need to change the transmission gear to a bigger( more teeth?) Or try a different map in my thundermax?

 

Sounds like you made some changes you shouldn't have.
A big bore kit should not have any effect on your speedo.
Did you change the gearing?
I have never used a tuner like will change the speedo.
I ,use the baker cabel to correct my speedo's
Perhaps someone with more knowledge about this than I do.

 

Do you have a code reader? I'd scan it. Not everything shows up on the OBD dash light.

 

Your ECM(Thundermax) is way out of whack. Delete everything and start over.

 

+1, if you have not changed gearing/pulleys, then check the TMAX. They have settings to correct speedo if you did change the above. So maybe those are out of whack.

 

Definitely sounds like the map you chose for the tmax has the wrong speedo calibration. Make sure the map is for your bike then use the speedo calculator to determine what your calibration should be.

 

Exactly. If you didn't touch the gearing (30tooth front & 68 or 70tooth rear) the only problem is in the speedo cal setting in the tmax. As long as you chose the correct map for the 106 you simple didn't input the correct code for you bike in the speedo cal window. In TMax the speedo is separate from the map, so you can choose whatever map and dial in your speedo on its own.

Just hook up a laptop to your bike and link the unit. Then go into Basic Settings and speedo cal section. There it will list the code you should be using for your year bike. Done.