Tachs for tuning

[tor*p*do]

What is the purpose of a Tach anyway?
Some people on here repeat "get a tach" over and over
but I see no benefit other than racing and top speed.
I read this much mentioned thread: http://www.x-h2o.com/threads/39846
and did not find it helpful.
It is full of statements like "tune with the tach for peak RPM"
but no info on how to do so.
Idling, full throttle, tune which screw, in or out, etc.?

I followed the instructions and ended 50 kilometers down the lake and WTH???

 

[QuickMick]

What is the purpose of a Tach anyway?
Some people on here repeat "get a tach" over and over
but I see no benefit other than racing and top speed.
I read this much mentioned thread: http://www.x-h2o.com/threads/39846
and did not find it helpful.
It is full of statements like "tune with the tach for peak RPM"
but no info on how to do so.
Idling, full throttle, tune which screw, in or out, etc.?

I followed the instructions and ended 50 kilometers down the lake and WTH???

Really?

 

[tor*p*do]

Really?

No, I was beingt sarcastic, my ski won't go 50 kilometers
to test the start response as specified in that thread

Too bad someone cannot put together a guide
for tach tuning that is easy to follow

 

[QuickMick]

another worthless post on your way to 16 THOUSAND. It is "actually" a mower and equipment tach

I have one on my generator and my blender thank you very much!!

 

[Mark44]

O

No, I was beingt sarcastic, my ski won't go 50 kilometers
to test the start response as specified in that thread

Too bad someone cannot put together a guide
for tach tuning that is easy to follow

I find Randy's techniques very helpful and it is a very easy way to tune and gets motors dead on IMO. I see a lot of people with big HP. motors and have never gotten the potential out of them because they don't want to spend a couple bucks on the proper tach. They don't get full potential and shorten the life span of the big money motors.

Mark44

 

[tor*p*do]

I find Randy's techniques very helpful and it is a very easy way to tune and gets motors dead on IMO. Mark44

Great, and that is why you always beat the "get a tach" drum
His technique may be great, but I do not find Randy's guidance very helpful

 

[Mark44]

First think you may need to know is 1 MPH = 1.609344 km/h

This should help.

Mark44

 

[SQUARE JOEL!!!]

What is the purpose of a Tach anyway?
Some people on here repeat "get a tach" over and over
but I see no benefit other than racing and top speed.
I read this much mentioned thread: http://www.x-h2o.com/threads/39846
and did not find it helpful.
It is full of statements like "tune with the tach for peak RPM"
but no info on how to do so.
Idling, full throttle, tune which screw, in or out, etc.?

I followed the instructions and ended 50 kilometers down the lake and WTH???

Randy's write up is about as cut and dry as it gets....with all the info needed.

Tune to peak RPM means you are tuning for the highest RPM reading shown on the tach.....thats max RPM at full throttle. You will need to turn the HS screw in and out, from the 1 turn setting, to see if there are positive changes. Tuning takes some time to be done correctly.

What specific questions do you have? Just saying you didn't find it helpful doesn't allow others to help you out. If you are really confused call Randy! He is a good guy and I'm sure wouldn't mind clearing up any questions you might have.

 

[tor*p*do]

First think you may need to know is 1 MPH = 1.609344 km/h This should help. Mark44

Well that is meaningless Mark, since no where in that post does he even mention mph or km/h

 

[tor*p*do]

Randy's write up is about as cut and dry as it gets....with all the info needed.

Tune to peak RPM means you are tuning for the highest RPM reading shown on the tach.....thats max RPM at full throttle. You will need to turn the HS screw in and out, from the 1 turn setting, to see if there are positive changes. Tuning takes some time to be done correctly.

What specific questions do you have? Just saying you didn't find it helpful doesn't allow others to help you out. If you are really confused call Randy! He is a good guy and I'm sure wouldn't mind clearing up any questions you might have.

This helps a lot, thanx Joel.
I understand the rest of the procedure, but it starts,

Start with the screws set at 1 turn out, and tune with the tachometer for peak Rpm, then stop there and count the number of turns on the high speed screws. Write this down on a piece of paper.. Then turn the high speed screws in all the way and open them to 1/4 turn open. (Now you will be testing starts only, so no more big high rpm trips around the course). You are only turning in the high speeds to allow you to easily tune the low speeds.

and it was not clear to me if he was setting the idle to peak rpm or top speed to peak rpm and what he was tuning, hi or lo speed screws.
Thanks for clearing that up!

 

[Matt_E]

and it was not clear to me if he was setting the idle to peak rpm or top speed to peak rpm and what he was tuning, hi or lo speed screws.

You might want to look at the Mikuni SBN Owner's manual here. This explains in detail the tuning procedure and the order in which the five different variables in an SBN should be tuned.
A properly tuned SBN will have the idle mixture screw adjusted to peak RPM (at idle) and the high speed mixture screw set to max RPM.

 

[tor*p*do]

I am familiar with the Mikuni manual, thanks Matt
That is why I was confused by the "start" section in the Watcon post.
Obviously if you are tuning the idle first per Mikuni
it would be at the start of the process.
Hence my confusion of tuning for peak RPM in the Watcon post
and not knowing if that meant idle or full throttle

 

[Big Kahuna]

This helps a lot, thanx Joel.
I understand the rest of the procedure, but it starts,

Start with the screws set at 1 turn out, and tune with the tachometer for peak Rpm, then stop there and count the number of turns on the high speed screws. Write this down on a piece of paper.. Then turn the high speed screws in all the way and open them to 1/4 turn open. (Now you will be testing starts only, so no more big high rpm trips around the course). You are only turning in the high speeds to allow you to easily tune the low speeds.

and it was not clear to me if he was setting the idle to peak rpm or top speed to peak rpm and what he was tuning, hi or lo speed screws.
Thanks for clearing that up!

Peak RPM is just that, Peak. That is the RPM's that you will find at wide open throttle. That is the only place you can acheave "Peak RPM".

Setting your motor up based off this will help you tune your high speed circuit of your carbs. Doing the plug chop and looking at your color just gets you in the ball park.

 

[waxhead]

These are not cars people that revs up as the car speeds up
When you grab the throttle the engine flares up in rpm and then the ski catches up.
If your engine is tuned to get to its top rpm then its also right in the midrange it takes hp to get to that top rpm under load
Every one that wants bottom end really wants good midrange with awesome throttle response

Setting your top rpm is important on a free ride boat as well to get it to pull cleanly through the mid

 

[kevbo]

Tachometers are very beneficial for long WOT tuning where they can save a piston. They are an absolute must for pump tuning and general testing. The pump tuning aspect is most important for freestyle where the correct pump load has a lot to do with thrust and response. Freestyle standups with big carbs are best tuned by sound and feel because the setting for best response will be too rich for best top speed.

 

[waxhead]

I use my low speed jet to get the throttle response

 

[Matt_E]

Freestyle standups with big carbs are best tuned by sound and feel because the setting for best response will be too rich for best top speed.

Is that a general rule? Because mine's the opposite. :clown:

 

[jetpilot08]

Freestyle standups with big carbs are best tuned by sound and feel because the setting for best response will be too rich for best top speed.

What do you consider a big carb?

 

[kevbo]

How close to peak the high speed can be depends on how rich the pilot/pop-off is to begin with and how you work the throttle. Throttle blippers need to run richer pilot/pop-off than riders that are slower on the trigger. They (blippers) need to be fourcycling around 1/4 throttle but can tune the high speed closer to peak or even lean of peak. A very clean part throttle will tend to be lazy and require a high speed setting richer of peak. I run my low end clean and tune the top screw for response. This gives me best overall range and keeps pistons from melting when chasing big boats across the lake.

 

[joesuperjet]

Nothing beats a good tac that has a super fast refresh rate. It makes it sooooo much easier to tune. I prob. could tune in a ski just as well on a slower tach, but it might not be spot on, and it would take longer for sure. If you want the best - you pay for it.

You gotta pay to play boys. :smoker:


JAM