Drag Specialties Minitach

[BoulevardBoy]

I purchased a Drag Specialties Minitach for my 2005 C50 Boulevard. I had the dealer install it because I am lost in electrical wiring schematics. On the ride home, I noticed that at 70 MPH, I was indicating only 2100 RPM in fifth gear. That seemed about half of what I was expecting.

According to Drag Specialties, I need a single fire adapter, basically three wires, two diodes, and some resistance. I was told that a bike that has one ignition coil to fire both cylinders is a dual fire and a bike that had a coil for each cylinder is a single fire...the reason I need the adapter.

However.....a few guys with older Volusia's say they didn't need an adapter. Could the additional of fuel injection have caused Suzuki to also add another coil, one for each cylinder? I have already ordered the adapter, tach is on and reading half of actual and waiting to see if the adapter was worth the money. Any help will be appreciated.

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[drgibson]

Yup it is only reading half of your rpms. I can't believe the dealer didn't know this.

[BoulevardBoy]

dr,

Did you design that cool Suzuki rider under your post name?

[drgibson]

dr,

Did you design that cool Suzuki rider under your post name?

The logo is from the sixties I cleaned it up and stylized it a little.
Below is the original.

[Clint]

Those things really rev that high? That's as high as my four!

[drgibson]

Those things really rev that high? That's as high as my four!

Hmm Your bike redlines at 4200 rpms? Man my cruiser redlines at 6000

[oldtimerwrenchturner]

what does it idle at?
if the idle is correct then it is reading rpms ok

[BoulevardBoy]

No, the idle RPM is half, too. The tach is an 8,000 RPM tach. Running 2100 RPM at 70 MPH would put the needle nearly always in the lower quarter of the tachometer's range, if correct. And at a idle speed 1000 RPM, it would be nearly on the the bottom peg. But it's not correct.

Several folks on another forum have had the same problem and have given up and were saving up to buy a $200 tach.

But, a guy with a Baron's ($199) tach had the same problem. He got his to read correctly using the Drag Specialties adapter (because it was half the price of Baron's same adapter) and by adding a 33K 1/2 watt resistor with the adapter. The website called for adding one to two 10K 1/2 watt resistors for a VTX 1800. I don't know how he came up with the 33K, but he said he had a power commander and could read the RPM'S on his laptop. With the resistor he added, his tach was now reading correctly. Anybody else ran into this?