Rotax tach question!

[Ironman Al 35]

Has anyone ever had a Rotax tachometer that didn't read correct rpm? Mine will only go up to 3500 rpm., Engine runs smooth and seems to be at full power, good fuel supply with 5pd of pressure, throttle on carbs is all the way to max position, little room left before stop. Prop is set at mid climb/ cruise. Just thinking it's got to be a simple problem or faulty teach reading. Any thoughts appreciated! Thanks!

[EDMO 1078]

From what I have been reading, MOST of the tachs are reading wrong - Get a Tiny Tach or one of the knockoffs on ebay with replaceable battery for about $13.  EDMO

[chopndrag 226]

I had one off by 800 rpm at cruise and 600rpm at idle . I bought a tiny tach knock off and ended up buying a new rotax dash tach . They both read the same now . 

[EDMO 1078]

Don't some of the Rotax Tachs have a switch on them to change from Points ignition to CDI, and others do not?  I've got an auto tach that has a switch on the back to go from 2,4,6 or 8 cylinder engines.   Bought an imitation Tiny Tach too.   EDMO

Edited 17 Sep 2017 by EDMO

[chopndrag 226]

That I couldn't tell you . I can tell you the knock off tiny tach works great. 

[1avidflyer 1983]

I never saw a rotax tach with a switch on the back.  Points ignition only fires one spark per revolution, Rotax/Ducati 2 stroke ignition fires two sparks per revolution.  Is this a new install, or did it just start to happen?  JImChuk

[Ironman Al 35]

It just started! Its only a thought that maybe my engine is running up right and my tack is off. Ill be doing a strobe light test on the prop to tell for sure.

[akflyer 1427]

never trust a rotax tac.  They are also well known for putting dream o meters in the snowmachines.  When a stock 600 says its doing 130 you know its lying   Ive been on hard pack and dream o meter said I was doing 126 but the GPS said I was doing 97.  The tacs seem to be just about as accurate.  Most poor performing avids and kit fox can be traced to bad tac readings. 

 

[chopndrag 226]

If you get the blue dot rotax tach it's pretty much on point . It matched almost exact to my tiny tach . I noticed way better cruise and landing wasn't like the ground was coming at 1000ft a minute anymore . 

[akflyer 1427]

there has also been documented issues with the rotax signal wire coming off the stator.  Best thing one can do is just use a tiny tach or at least have one as back up for when the rotax tach / signal stop working.

Edited 19 Sep 2017 by akflyer

[Ironman Al 35]

Sorry for the delay on up dating this. After adjusting the warp drive prop 1.5 degrees the rpm went up to normal static running rpm.Oddly the Rotax tach was off only after it reached 3500. The TinnyTach and lazer confirmed that.