1987 yamaha exciter flat slide carb help

S

skidooer1

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Dec 21, 2012
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Location
iowa
Ok, I recently put a set of flat slides from a 1994 vmax 600 that I have setup exactly as a 1993 sx. The machine runs great on the top. However at 1/2 and under it has a bog .If I set the air screw to 1.5 turns like it should it always has a bog from not getting enough fuel. If Turn the pilot air screw in to say 3/4 turns total it runs almost perfect. At the moment I have 55 pilot jets in it. Tried the 52.5 pilots at first and it was obviously worse. Although I see people that run 47.5 pilots and 50s at my elevation with no troubles. My clutches needed an overhaul as the belt deflection was out of whack and it was engaging at 2500 rpms, and after it's at 4200( I used a silver orange comet spring) still no difference at all. Could this be a fuel pump issue or do I really need bigger pilot jets? Kinda has me stumped without spending money on parts. Thanks in advance for any help .
 
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Not a fuel pump issue. Either run the fuel screw at 3/4 of a turn or bump the pilot up one size. Even though the SX has the same engine as your machine, there are some differences between the two. Get your clutches in tip top shape before you start tuning carbs. Bad clutching will sometimes disguise itself as a carb issue. What clutches are you running?
 
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Comet 102c and the original secondary. Clutches work good now and shift out/ back shift very well. I figured it wasn't a fuel pump issue as the choke being flipped on made it run perfect when it started to bog. Fuel pump seems to pump fuel well when it's disconnected from the carbs. Just seems strange that folks get away with running a much smaller pilot jet and I keep moving up in size to get it to run correctly.
 
SX700triple said:
Not a fuel pump issue. Either run the fuel screw at 3/4 of a turn or bump the pilot up one size. Even though the SX has the same engine as your machine, there are some differences between the two. Get your clutches in tip top shape before you start tuning carbs. Bad clutching will sometimes disguise itself as a carb issue. What clutches are you running?
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X2 seen the clutch prob making carbs not work right.
 
Clutches have both been rebuilt and they seem to work great. Before I rebuilt them the primary was engaging at 2500 rpms, now it's engaging at 4200... Gonna order some larger pilot jets and see if it goes away.
 
Well I have it narrowed down to the needle and jet needle. the carbs im using have the 2.5 cutaway however I noticed the exciter sx needle is a lot longer. so I swapped back in the needle and jet needle from the vmax and now its really rich.so my guess is a needle that's in between the two size wise should work. anyone have a chart for the needle jets for this carb?
 
dont the vmax 500 carbs have the same slide cutaway as sx? cant remember as i switched from 600 carbs to sx ones,if so you can find em on ebay cheap,im also using sx intakes,a little shorter,
 
im thinking the actual slide must be longer on the 3.0 vs the 2.5 of the vmax 600?.. as the needle is nearly a 3/8 of an inch longer on the 9el02(stock 93 sx). it is literally poking through the main jet with the clip at the bottom of the needle when its at idle position. ive tried a 52.5,55,57.5, and 60 pilot with my air screw at a half turn to get it to run.. neither pilot jet made any difference. which is why I tried throwing the vmax600 jet needle and needle jet back in.. glad I did cause I now know its in the needle circuit for sure. thinking a different set of carbs will be in order unless some one can verify that the 2.5 and 3.0 carbs are indeed a different length.
 
while the 570 motors are the same bore and stroke there is nothing the same about the sx verses the regular 570 number one intakes on the sx are shorter porting head and exhaust is way different and ignition with a longer intake track you can have lower suction signal that is why you are seeing drastic changes with a needle change plus there is a big difference in a 2.5 to 3.0 slide the slide plays a huge roll on the bottom end up to about 3/4 throttle and a flat slide has a stronger signal than a round slide making tuning more precise plus every motor is different just because some one else is running it does not me you can run it ...been there many times you must tune to your motor ....
 
any details on the big difference on the 2.5 vs the 3.0? other then the cutaway? has to be a length difference?
 
anyone? found some 3.0 slides from a 500. now I know they are a tm36 but just need to know if they will fit in the tm38 body without issues.
 
I know its not a big help to your carb issue, but id switch your Comet out for a Yamaha clutch. After years of driving sleds Ive always found Yamahas run better with oem clucthes (even when tuning)
 
Im interested in your findings with the 3.0 slides. Im kind of having tuning issues on some cable style TM's on my Exciter. If the comet is in good shape and tuned well, they will run pretty good, cheap to rebuild and cheap tuning parts. However the service life isnt so great. A54's with a purple spring worked good on my set up. If you have a known tuning that works with your set up, by all means use the Yamaha clutch. You will get a ton more miles out of a yami clutch vs a Comet. The down side is that the tuning and service parts are stupid expensive.
 
Throttle Junkie35 said:
Im interested in your findings with the 3.0 slides. Im kind of having tuning issues on some cable style TM's on my Exciter. If the comet is in good shape and tuned well, they will run pretty good, cheap to rebuild and cheap tuning parts. However the service life isnt so great. A54's with a purple spring worked good on my set up. If you have a known tuning that works with your set up, by all means use the Yamaha clutch. You will get a ton more miles out of a yami clutch vs a Comet. The down side is that the tuning and service parts are stupid expensive.
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Nearly ready to give up and it is consuming too much time. I have tried 55,57.5,60 pilot jets with not luck. switched to the exciter sx carb boots which did seal the carbs up a lot better. but still have that slight bog. Sunday will be the last day I mess with it.
 
I have vmax 600 carbs on my exciter, also tried the slides from vmax 500 just recently. It went like crap, had to run with the choke on just to get it running. I hace the complete set up from exciter sx on my pair. It works fine with that, moved the clip down 1 and have the mixture screws set at 1,5.

This place can be a good place for you that have exciters, lots of great info in there:

https://www.facebook.com/groups/377732505654647/
 
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