carb tuning?

cougar1985

cougar1985

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Joined
Jan 26, 2006
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290
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67
Location
sault ste marie ontario
were does the mid speed come in in mph. i had problems running too rich at approx 30 mph.took the sled in and got it synced. the mech said the clip was on the 3rd pos. he moved to the second. ran better for a while now its starting to run rich again.am i barking up the wrong tree or should i move needle to the top position?air screw is at 1 1/4 and seems to do best there.could it be a reed problem or that equalizer on the carbs or ??? i ishould add it seems to get worse the longer i ride. if i hammer the gas it runs great.
 
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was driving me nuts so i took the carbs apart a found a pilot jet partially plugged.i dont know about anybody else but the sled runs much better with bre8,s than 9,s. ive been keeping a close watch on the plugs and the color is perfect so far. im going out tomorrow and will keep a close eye on the plugs as ive backed the air screw to 1 3/4 out as it was running a little too rich.
 
cougar1985 said:
was driving me nuts so i took the carbs apart a found a pilot jet partially plugged.i dont know about anybody else but the sled runs much better with bre8,s than 9,s. ive been keeping a close watch on the plugs and the color is perfect so far. im going out tomorrow and will keep a close eye on the plugs as ive backed the air screw to 1 3/4 out as it was running a little too rich.
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Be carefull running 8's you could over heat in maginal condtions
 
thanks will do, im not above stopping at least once during a trip after adjusting to check plug color. it just seems to run so much better with the 8,s for some reason. i suppose every sled has its own little quirks. actully im going to go for a ride in a few minutes and will check and adjust under real world conditions which as you know are differnt than shop cond.
 
cougar1985 said:
thanks will do, im not above stopping at least once during a trip after adjusting to check plug color. it just seems to run so much better with the 8,s for some reason. i suppose every sled has its own little quirks. actully im going to go for a ride in a few minutes and will check and adjust under real world conditions which as you know are differnt than shop cond.
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Be carefull.... :2strokes:
 
i seem to have more problems than i thought. only 1 cylinder will work. i do have spark but i wonder if its enough or if the coil is packing it in? is it possible for 1 side of coil to go weak.!? im going to pull the carbs again and check the left side again ,will also check the reeds on that side. it use to be that it took 1 hour or so to start running odd but today i didnt make it off the truck. the left side plug was reletavily cool compared to the right and i tryed several with no improvement.
 
nix that running great . argggggh. :o| took the sled out today and it ran like crap. same symptoms. seemed like the left cylinder was loading up big time.well to make a long story short , believe it or not the choke cable was improperly routed and was pulling out just a hair,but enough to make a mess out of the system.boy do i fell stupid!no wonder it was running superrich.next time i buy a used sled i guess i better check it over a lot more carefully. owe well live and learn. :yam: :die:
 
also, those carbs dont have air screws, just fuel screws. Opening them up gives it more fuel.
 
im reading the factory manual as i type. low speed tuning can be done by adjusting the air screw.1 1/8 from lightly seated.turning out leans mixture. ok whats happening is the sled will load up at about 25-40 mph. is this concidered low speed? yes the jets are proper for this elevation.when i had the carbs synced the mech said that the needle clip was on the number 3 position.and should be on 2 . was changed. he said if the sled starts to act up again i might have to go to the number 1 position.any thoughts on this??? at high speed no problem but a lot of the running around here is through very windinng trails were 25-40 is more normal.that sounds more like a mid range problem to me, right?? could worn needle and seat do this? sled has 3800 miles on it. other than this really annoying problem the sled goes like a rocket and so far the plugs are a nice tan color. p.s. how about weak reeds???
 
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cougar1985 said:
im reading the factory manual as i type. low speed tuning can be done by adjusting the air screw.1 1/8 from lightly seated.turning out leans mixture. ok whats happening is the sled will load up at about 25-40 mph. is this concidered low speed? yes the jets are proper for this elevation.when i had the carbs synced the mech said that the needle clip was on the number 3 position.and should be on 2 . was changed. he said if the sled starts to act up again i might have to go to the number 1 position.any thoughts on this??? at high speed no problem but a lot of the running around here is through very windinng trails were 25-40 is more normal.that sounds more like a mid range problem to me, right?? could worn needle and seat do this? sled has 3800 miles on it. other than this really annoying problem the sled goes like a rocket and so far the plugs are a nice tan color. p.s. how about weak reeds???
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Yes my manual calls it an "Air screw" too.
 
well im wondering if i should go to the number1 position on the clip or could the annoying mid range[30 mph] stuttering or bogging be a case of weak reeds. also if i put in a set of carbon-tek reeds do i have to do jetting . :die: :yrules: will the new reeds basicully help in smoother throttle response and perf???
 
checked the compression the other day with a friends gauge . both cyl. said 100 psi!!!. i didnt think his gauge was very good as the sled has tons of power so i borrowed another better gauge and got 140, 140.. thats better[lol]. i also put in some carbon-tech reeds this week and they sure make the sled more responsive to throttle[crisper]. no wheres in the yamaha factory manual can i find what the compression should be but i would think 140 is very good.
 
yes, the old vmax twins have air screws not fuel screws, thats why they are in the rear bell of the carb, behind the slide. fuel screws are before the slide.

Remember, a warmer engine is a richer mixture engine, so take that into account with temps your riding in and the amount of low speed riding your doing to heat up the engine more.

I would set up the carbs to the factory specs and then tune from that base line. But if your riding in significantly warmer temps, your gonna need to lean it down some.


your compression sounds fine, it has alot to do with the guage you use as to the amount shown on the guage, you have to use a thread length adapter to be accurate and some guages are better then others. But all you really need to know is if they are even and anything over 100lbs no matter what guage, tells you the engine is in decent working order.

When reeds go bad it will run like crap at low speeds, very rich, dull sounding and will be quite noticeable, will be like a plug is fouled.
 
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