smart carbs

M

madmax

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To make a long story short...97 mm 600, does not run right(irregular idle, plug fouling, for some reason runs better with fuel selector in the oxy position. What has been fixed...topend overhaul, carbs checked-everything within specs. Local Yamaha is stumped...I am tired of fighting this problem...any ideas? Would getting new solenoids forthe carbs help or is it the control box...just my ideas.
 

Is there no one out there who knows Smart carbs????

:? Getting info on these is hard to find. Sorry I can't be much help. I have 98 with smart carbs and it has worked perfectly since new. I have fooled around with the carbs but never the electronics. My dealer told me if I ever had problems, you could always disconnect all the sensors and run the machine that way. It might eliminate some of the guesses.
 
Thanks for the post...my 97 ran great till one day it started throwing fits...I have 98 too...might try swapping some parts like starting with pug wires and working my way back through the system ot see whats wrong. Do you ever use the fuel switch? Since the sled started giving me trouble it seems to run better on 'oxy', before i had problems I could never tell the difference. I always thought the smart carbs were a good system...till now.
 
had a similar problem in my 97 600 mm .found that belt dust was getting in to the carb and plugging the ports that lead to the solenoids.this also happened to my buddies 600 mm.never tried the oxy switch to see if it made difference.
 
Have a buddy with the same problem. One ride it was great and the next day it sucked back a tank of gas in less then 75kms. Always gurggling and loading up on its self.
Carbs have been off and cleaned # of times. Told the same thing by dealer to just jet down to regular carb jetting. But if the bad sensor ever kicks in and statrs working she'd melt down.
This was all last season. We dont have any snow yet to take it out and see what its like. If you guys find which sensor thats causing this pass it on.

Thanks, Culvert
 
Thanks:

Thanks for the info, was considering trying to just disable the system and go from there. I am not happy as after having the carbs cleaned twice I find a dead bug in venting orifice on one carb...but that might be a fresh bug from this seasons storage. I was going to take the solenoids out and see iff they were actually able to operate, but the srews are pretty well frozen in the carbs. I did change all the two black boxes and coil from another mm600, but no diff. I don't know why you can't jet it manually and leave the solenoids disconnected?? After having it apart myself and working on it there seemed to be a difference in the way the air moves through the carbs if you blow through the vent tubes. One side almost all air goes out the fuel supply line, the other seems to be more restricted and some air comes out the pilot jet, so there must be something plugged inside. No snow so I can't get excited about taking it apart again.
 
Thanks:

Thanks for the info, was considering trying to just disable the system and go from there. I am not happy as after having the carbs cleaned twice I find a dead bug in venting orifice on one carb...but that might be a fresh bug from this seasons storage. I was going to take the solenoids out and see iff they were actually able to operate, but the srews are pretty well frozen in the carbs. I did change all the two black boxes and coil from another mm600, but no diff. I don't know why you can't jet it manually and leave the solenoids disconnected?? After having it apart myself and working on it there seemed to be a difference in the way the air moves through the carbs if you blow through the vent tubes. One side almost all air goes out the fuel supply line, the other seems to be more restricted and some air comes out the pilot jet, so there must be something plugged inside. No snow so I can't get excited about taking it apart again.
 
Just wanted to add ,if you remove the vent line you will find an air jet this ties into the upper fuel solenoid circuit.Should also be included in the carb
cleaning.A little more info for the smart carb puzzle.
 
a cure I found for keeping the belt dust out of the carbs is covering the drain holes in the bottom of the air box.
there are four (4) small sholes in the bottom of the air box and they suck in alot of crud from there.
made a big diff in how long I could go between cleanings once I covered them over with some high speed tape.
 
I have these smart stupid carbs on my 600 twin mm. The first mod I did was to get these off. I put carbs on off a 95 600 and it works fine now. Keep in mind that our yamaha engineers are not stupid and if these were so great they would be still using them. Thank the good lord there not but thats no excuse for blocking off a transfer port with a reed cage since 1997 on our tripples.
 
Latest update

Just in case anyone is listening I may have solved my smart carb problem. Not sure what the problem was....finally disassembled the carbs as far as possible and found nothing wrong...except that the slides were not opening the same amount on each side, so I synchronized them as best as I could without using guages and guess what it works! Or atleast it seems to be better the 1/2 mile I drove it ...no snow to really test it. Yamaha service manager said to use a drill bit to get the slides set...they were at least two sizes off synch to start with. Would the carb that was operating "slower" cause that cylinder to run lean or rich?? I reason that it would be rich beacuse the smart carb controls the mix the fuel flow for both cylinders. Food for thought??
 
Just a note about my smart carbs. I totally disassembled my carbs, and once again I could find nothing wrong. Tested everything twice....double checked the air passages...there is a small nozzle on the back side of the carb throat, and a screw that looks like an air screw but it is not an air screw. Anyway I think that passage may become blocked. Good news is that yesterday the carbs worked good even in 40 degree weather. So I really don't know more than I did before except that its working now. Too bad its probably the end of the season. Also for what its worth I think that adding the thinner gaskets to increase compression is a good idea. A little more performance in my opinion. Happy seldding!!!
 
smart carb

ok no more issue with my sled now,,,,I remove the carb yesterday and they were full of belt dust so I done a good clean up and now the sled run like new.

Pat :nos:
 


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