How do you measure RPM's with out a tach?

busa186

Registered
My dad and I went in on a carbtune and we will need to adjust is idle after we are done but his bike does not have a tach. Now we can do it by ear, or buy a tach and install it, but his friend gave him a tool that you hook to a spark plug and to the coil? However, it does not get that great of reviews, seems to bounce around a lot (up to 400rpms). How would a shop adjust RPM's. (Probably on a dedicated machine).

Anyone adjust the idle with out a tach?

As always thanks for the help! :beerchug:
 
1. Bring engine up to operating temp (run about 10 minutes).
2. Turn idle adjustment screw out until engine starts to stumble.
3. Turn idle adjustment screw in 1/8 - 1/4 turn.
4. Engine should be idling smoothly, if not repeat step 3 until smooth idle is reached.
 
1. Bring engine up to operating temp (run about 10 minutes).
2. Turn idle adjustment screw out until engine starts to stumble.
3. Turn idle adjustment screw in 1/8 - 1/4 turn.
4. Engine should be idling smoothly, if not repeat step 3 until smooth idle is reached.

so kinda just by ear... thats what I told him but I think he is looking for a tool. I know he his going to want to set it 1100.25441 rpms:laugh:
 
My dad and I went in on a carbtune and we will need to adjust is idle after we are done but his bike does not have a tach. Now we can do it by ear, or buy a tach and install it, but his friend gave him a tool that you hook to a spark plug and to the coil? However, it does not get that great of reviews, seems to bounce around a lot (up to 400rpms). How would a shop adjust RPM's. (Probably on a dedicated machine).

Anyone adjust the idle with out a tach?

As always thanks for the help! :beerchug:

Go with the average of the high and low numbers. I wouldn't completely rule out the possibility the bike is idling rough either. Plugs, filter, fuel etc good? Vacuum leaks?
 
I found that out the hard way when the dealer said "I can fix that with a throttle sync" $140 later, still has pulse of the beast. Just bought the manometer and doing it myself. My dad has a royal star that we are about to sync but he has no tach so finding his rpm is challenging. We found a tool you clamp on but I think he will end up doing by ear.
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