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Old 01 October 2018, 13:19   #1
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Suitable Tacho for setting up carbs???

Im doing the mixtures on my Honda90. Once done i was going to balance them, Any suggestions for a digital tacho, pref cheap, that would help me set it up. I was thinking of an optical tacho running of a mark on the cam belt. suggestions?? Anyone spotted one particularly good or even best avoided. Nik
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Old 01 October 2018, 13:32   #2
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Why not get one of the 10-15 tacho/hour meter models many of us use on our SIB OBs?

Such as the one I fitted shown on post #19 of this thread... Best Tiny Tach type
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Old 05 October 2018, 06:32   #3
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Thanks for that...from looking around ebay/web I think the Tiny Tac copies are not up to it long term ,so I think i'll fork out for the original Tiny Tac. Ta nik
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Old 05 October 2018, 08:32   #4
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Personal choice but I happily replaced the one in that thread bought 2yrs ago with an identical one when I changed OBs this summer.

Mine was 17-22 delivered and interestingly the Mariner dealer I bought the new OB from showed me a Mariner brand mini tach which was over 60... the exact same one as I'd bought for 17-22.
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Old 05 October 2018, 15:33   #5
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Originally Posted by Fenlander View Post
Personal choice but I happily replaced the one in that thread bought 2yrs ago with an identical one when I changed OBs this summer.

Mine was 17-22 delivered and interestingly the Mariner dealer I bought the new OB from showed me a Mariner brand mini tach which was over 60... the exact same one as I'd bought for 17-22.
+1 bought the same no probs does steam up mine but was ok for set up of props just steamed up over two years
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Old 05 October 2018, 17:48   #6
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Originally Posted by matata View Post
Im doing the mixtures on my Honda90. Once done i was going to balance them, Any suggestions for a digital tacho, pref cheap, that would help me set it up. I was thinking of an optical tacho running of a mark on the cam belt. suggestions?? Anyone spotted one particularly good or even best avoided. Nik

TBH a tacho is not that useful for setting O/B carbs.................

First set the mixture screws to the setting specified in the handbook (usually between 1.5 to 2.5 turns anticlock) then run the engine and set the mixture on the 1st carb for max idle RPM by ear .......... then set that carb slightly richer by a quarter turn (2 stroke) or a 1/8 of a turn on a 4 strike.

Do the same for the remaining carbs and then using an airflow meter balance out the carbs so they are all flowing the same amount of air. Another way is once the first carb is set then measure the airflow and set all the other carbs to the same airflow.

Once finished use a tacho to set the idle ..............

You need to set them a tad rich if you are running on muffs .......... once in the water they will be fine.

Using the tacho method of max rpm at idle to set the mixture will result in the engine running very lean ........... a symptom will be stalling as you put it into gear.
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Old 06 October 2018, 06:15   #7
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+1 for gpsguru's method. You don't need to fork out for an air flow meter though, use a piece of small diameter plastic tube, one end in your ear and the other at the mouth of the carb - stethoscope. Be sure to place the tube end at a similar position at the mouth of each carb, you are listening for the same hiss from each one. Sounds a bit Micky mouse but it works well.
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Old 08 October 2018, 05:10   #8
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Don't forget to reset the position of the butterflies first as well.
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Old 08 October 2018, 07:57   #9
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this might help its a good site for other stuff to
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