Thread: My Weekend Tuning Nightmare
07-03-2012, 01:47 PM #1
My Weekend Tuning Nightmare
After going through my skis I finally got a chance to get them on the water.
Mistake #1 on ski #1- when first launching your ski, run it for a short period of time, pop the seat and check for anything out of the ordinary.
I however did not and somehow forgot to attach my main water supply line to the exhaust; on my fresh topend. Therefore flooding the hull, putting water down the carbs and into the crankcase. Somehow no water got into the cylinders. I removed the crankcase drain bolts and drained what I could. I'm sure I roasted some compression numbers off with overheating. The ski still starts no problem, runs good, and I'm hoping the excessive rich fuel fuel flow and high oil content helped.
SKI #1 - runs great now for some reason (amen to that), however when going WOT then engine sort of has to build up rpms, but it accelerates nicely. It won't just go full rpm how my other ski does. I've adjusted the high speed screws with no effect. All of the high speed screws are richer than stock settings. Stock is "1-1/8M | 1/4C | 7/8P" and mine are "1-3/8M l 1C l 1-1/8P". If i decrease the fuel flow to stock, the ski falls on its face/blubblers when giving it throttle. What explains this?
SKI #2 - This ski has great pickup and rpms, once you get it past the flat/blubber stage. The carb settings are just a tad richer than stock and it almost instantly dies when you give it throttle. You have to keep blipping the throttle until it finally builds rpms and will take off. This ski also starts and idles no problem. Also when in turns and going WOT the engine was extremely slow/bogging a couple times, then I changed the settings to what they are now.
I'm guessing on ski#2 that I need to richen up the high speeds just how I have ski #1. I sort of concluded that all the low speed adjuster does is to provide a steady idle speed and is pretty much fine at any setting as long as they're all the same (there was no difference for me between 7/8 open to 1 -1/4 open). From testing, the hi speed adjuster seems to effect the hole throttle range; i saw this with ski#1.
So my question is, Why are the high speed settings so far off from factory settings? And why is SKI #1 sluggish with the throttle?
When tuning what is the difference between falling on it face, and blubbering? I could not tell one from the other.
I should state the all fuel system upgrades are done, and each cylinder is firing individually by itself.
07-03-2012, 03:02 PM #2
I assumed you have gone thru this link (post #5):
Noob common mistake is always squeezing throttle to WOT when tuning.
Go 1/3 throttle or less to tune your low and tune it first. Once done with the low you can go WOT to tune your highs.
Just be sure don't go WOT crazy on your first tank till you have a chance checking your piston wash.
07-03-2012, 03:14 PM #3
07-03-2012, 07:21 PM #4
Blubbering = keeps running, barely, may die after a few seconds. Flat on its face = dead, immediately.
07-03-2012, 10:18 PM #5
They 1995 sl650std's
07-03-2012, 10:21 PM #6
For an example; when going from idle to half throttle, 3/4 throttle, WOT; the engine goes " chuga chugga chuggga dead", would be blubbering?
Where as falling flat would be " idle ,rpms decreasing, dead"
07-04-2012, 12:42 AM #7
Theoretically yes but haven't tried it though You could close the high by 1/2 turn if you want.
07-04-2012, 07:03 AM #8
Cut & pasted tips from WATCON.
Tuning Tips for Girls
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.
Now check the low speed screws and set them at 1 turn and do a practice start; To test the low speed setting pretend that you just jumped the start and you have to start with no holder. Hold the ski by yourself and hold as many Rpm as you can (don't blow it out first for testing) and then nail the throttle hard.... NO FARTHER THAN 50 FEET, as you are only testing the start response
If it blubbers like a schoolgirl trying to guzzle a quart of beer, then it's too rich on the low speed screws..
If it falls flat on the line (like someone punched you in the stomach).. It's too lean on the low speed screws.
When you like the acceleration off the line, stop there and count the number of turns on the low speed screws. Write this down on a piece of paper.. Then re-set your high speed screw where they show the best peak Rpm earlier and try both a start and a peak Rpm run...
It will probably "blubber" a little off the line... DO NOT turn in the low speed screws... Instead, go back out on the course and fine tune for peak Rpm again.. The blubbering off the line is caused by having too much fuel in the high speed circuit... Write down your new high speed setting on the piece of paper along with the best low speed setting that you found earlier, this will be your base-line carburetor settings.
If the high or low speed screws are open more than 11/4 turns, then you need to swap to the next bigger jet.
If the high or low speed screws are closed all the way, then you need to change to the next size smaller jet.
*** If no matter what you try, it still won’t leave the line without falling on its face "lean bog"... Then try the next size lower pop-off spring in the carbs... Don't be afraid to try #95 or even #80 gram springs..
07-04-2012, 07:54 PM #9
Thanks for the input guys.
One thing i'm a bit confused on is how tuning adustments should correlate on all 3 carbs. Should the low speeds be the exact same setting for all three carbs?
How do the high speed adjusters relate since they're factory specs can be vastly different from one another? Would you increase/decrease them all the same, or adjust them based on a percentage of the factory spec?
Trying to tune without a tach could be contributing to the problem.
07-04-2012, 08:36 PM #10
Increase or decrease from factory same amount for all 3.
Make adjustment individually when you have piston wash.
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