11-06-2006, 05:30 PM #1
Yamaha Tech - Pistonwash old GP Tuning.
I have just got some Pro series 2''Tau Ceti F/A's to go on my 98 GP1200. I found an old post of Pistonwash's on Riva in 2002 regarding retuning the Low/high adjusters for F/A's.
This is what I understand,
Open low speed screws around 1 1/2 turns from OME settings
Open High speed screws around 1/2 turn from OME settings (will differ)
Tune low speed screws frist so the transition is smooth during throttle response then tune High speed screws.
Just two points I need to know is,
1/ When setting the transition between low and high should I be turning them in or out and by what increments, 1/8 at a time?
2/ High speed tuning, what am I looking for, drop in rpm's or just bogging or sluggish, missing maybe, and the same again, am I turning the screws out or in?
Just need to know which direction I should start adjusting the low and high screws in or out.
Others will know but Pistonwash knows his stuff on tuning these machines, will take all advice and guidance.
11-06-2006, 10:09 PM #2
11-06-2006, 10:13 PM #3
Thanks Addicted for the link, looks like I have got some more reading to do...
11-06-2006, 10:14 PM #4
- Join Date
- Dec 2005
- Beaufort, SC
Provided everything is jetted correctly, here's how I went about it: start with both adjusters 2 full turns out. Crank the ski up in the water and get it up to operating temp. With it still in the water, strapped to the trailer, adjust the low speed screws in 1/8 turn increments until you get the highest idle speed (you really need an aftermarket tach). Once you've established that, do a low speed plug chop to make sure you're not too lean. If all is well, work on your high speed screws, turning in 1/8 increments until you reach your peak RPM. The leaner you go, the higher your RPM's will get, until you get too lean. You are on the verge of getting too lean when your RPM's peak, then start to fall off (another reason to get a real tach). Then do your high speed plug chop.
Becareful, it doesn't take much to stick a piston......or three. If you are unsure at any time what you're doing, stop and take it to someone who does; it'll be alot cheaper and less aggervation in the long run. If you can't remember how many turns you are out, don't be afraid to screw it all the way in and back out again. Be safe, not sorry.
Mukuni has a good carb tuning guide that you can down load for free and do a search on these forums for more info. There is plenty more good stuff out there to read.
11-06-2006, 10:32 PM #5
Yes it is stock jetting I am running now. Im goinging to sound dumb here, whats a plug chop? is that pulling the plug and reading the burn/colour of the plug?
I think I will invest in a good tech as I don't really like the tiny tach, it is the engines life we are talking about isn't it.
What you have outlined all makes sense, thanks for that.
11-07-2006, 05:35 AM #6
Found out what plug chop is! Been reading GroupK's carb tuning papers. I would off done some runs and killing the motor and checking the plugs on the water. Putting new plugs in is a good point they make about getting a better reading of what's happaning.
Very interesting reading...
11-07-2006, 06:16 AM #7
11-07-2006, 07:32 AM #8
Yes RX951 what a wealth of information on his site, hate to think how many hours of work he and his team have done in testing over the years and to share so much with us all.
Bottom line is I think I will get a better tacho before I start playing around with tuning.
11-07-2006, 08:41 AM #9
Its an invaluable tool and instrument !
Jerry sells the Pet-2100 in his store. Don't forget to use the coupon code [green hulk] for a discount !
Also, not only is Harry's site very informative, we have World Class Tuners on this site too !!
11-08-2006, 08:57 PM #10
Pistonrash is a kook!! And does'nt know diddly about....wait. I know a little about alot of things.
Thanks for the kudos Kiwi, I still love those 65u's down in my heart. I almost wish I had one right now.
Did anyone cite extremeteam's racing site? I am not sure what the web addy is anymore, it's got some great stuff on it too.
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