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I bought an 89 a couple weeks ago. The previous owner stated in his ad "freshly restored quad" which was the biggest BS statement ever. Some paint here and there doesn't count (I knew before I bought it though).
1. My first concern is the motor. This thing refuses to idle. When it's cold it will idle without a problem but after I've ridden it for a while it will die down and stall every time. The idle screw is as far as it can go as well. What's the deal here? Is this related to my next problem?
2. The motor is running really rich. I even dropped the mixture down to 36-38: 1 from 32 and it did absolutely nothing. I had the carb apart and the main jet is a 170. Is this the stock size? Do I need to adjust the needle to help out with the idle? The motor is also easily "loaded up" if I'm not on it hard. The previous owner claims a new topend but I'm suspicious.
I've got more to ask of other owners which will come in time. I'm in the process of rebuilding it so I'll be back with more questions.
The first thing I would check would be to see if your power valve is operating properly. Look through the sight glass on the clutch side of the engine to make sure. You'll have to rev it up a little before it does open up though, appx. 5000 RPM I think. That will cause it to load up and lose power if it is not operating properly. It will also seem to run rich and get a lot of buildup in the exhaust. Also, make sure you have fresh gas, a clean carb, and do a compression test.
Check and see what size jets are in the carb also. I wouldn't recommend cutting back on too much premix just because it seems to be running rich.
I'll check the powervalve when I get the chance. I only cut back the mixture as a quick attempt at a fix. I was going to ride it and it was becoming unbearable. If the motor blew I wouldn't have been disappointed, going to be torn apart soon anyway...
You are experiencing a common problem with these machines. The needle and needle jet wears out on those 34mm Mikuni's and cause a rich running condition that is impossible to eliminate without replacing them. I went through this with my wife's 91 last year. Also when you go to a higher premix number you are making it richer becaue there is less oil and more gas in the same space. Drop the pilot and/or turn out the air mixture scew and see if you can get it acceptable. The quad would be a dog on the bottom end in comparison if the powervalve was stuck open.Bubba
The needle jet is the brass tube that fits in the middle if the carb assembly. The needle comes out the bottom of the slide and slides in and out of the needle jet. Well, after many years of riding it wears them down enough that is messes with the calibration. Remember that they measure jets in 1000th's, and 5/1000 is about the thickness of a sheet of notebook paper. The parts man at Suzuki was telling me it was a common problem when I went to oder the pieces. Anytime anything wears down on a carb it definitely changes how they respond and feed fuel.Bubba
Umm 1st of all are u talkin about a 250 quadracer,or a quadzilla?@nd if it is a quadzilla which i have one the main jet should be #350. Up to #420 depending on the elevation.2nd the problem wit ur quad not ideling even if u adjusted ur carb,try adjusting ur throttle cable(out), 3rd u should stick wit 32:1 to be on the safe side.
Bubba297 is correct. Your method of adjusting the fuel-air mixture by changing the fuel-oil mixture is backwards. To lean out the fuel-air mixture you should have gone from say 32:1 to 20:1. However, this only makes a very small difference in "jetting" and will probably result in numerous problems associated with an oil-rich mixture (spent plugs, smoke, messy pipe/silencer, gummed-up exhaust valve, poor ignition, etc.).
Check your carb slide for wear. Take it out and inspect the area where the idle screw contacts it. On my 500, the slide wore away in that spot to the point that the idle screw would not hold up the slide far enough anymore (even when it was screwed in all the way). I replaced the slide and the problem went away. Since then I have replaced the entire carb which you may want to consider also. A new slide is over $40. If you also have to buy a new needle, needle jet, main jet, pilot jet, etc. you will have a sizeable investment. In the end you will still have a stock performing carb rather than a newer, better one.
It is not a good idea to try to adjust the idle with the throttle cable adjustment. That adjustment is only meant to adjust the cable freeplay. If you try to use it to hold up the slide, the slide will not return to exactly the same position time after time and will require frequent adjustment.