How do I know which Exciter needle is right?

bajardine

bajardine

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I have an '89 Exciter 570 with VM 38 carbs. I suspect that I don't have the correct jet needle in the carbs. In my absence my brother took my sled to a new riding area and couldn't get the sled to run right. He said some buddies tried to fix the jetting and played with the needles. I'm afraid they left the wrong needles in and I have no idea what was in it before. My brother has no idea what they did exactly. The sled hasn't run right since. How can I find out what is the correct needle for the carbs? I called my dealer and they only have a Yamaha part number. They couldn't tell me the Mikuni needle number. Is there another source I can turn to? Is there anyone out there that knows what needle they have in their Exciter?

Bruce
 
Mikuni carbs come from with 40 pilot jets, 166Q-0 needle jets, 6DH3 jet needle and 260 main jets. I am running this setup but have changed the main jet. And I am running my 88 Exciter at 12000 feet, that is at the parking lot and we go up from there. My air screw is 1.5 to 2 turns out. oh ya float hight is 17-19mm or .66-.74"
 
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Nightmanx1 - Did you mean to say this is how the Mikuni carbs come from the factory? The parts catalog lists a 320 main jet and 42.5 pilot jets as standard. I thought that this was how they were set up when they got to the dealer. From there the dealers would change the jetting to your riding requirements. Am I mistaken? Did you buy your Exciter new? Your sign says you ride a '87 which didn't even come from the factory with these carbs. They had butterfly carbs in them. The round slide carbs were an update for the '87s. Although your set up looks about right for your riding altitude I can't believe that those setting are stock. That is what I am trying to get at; what needles came in the VM 38 carbs standard. Can anyone else chime in on this?

Bruce
 
From my '88 and on EX 570 manual,

mikuni VM-38 carbs,(STOCK)

M/J- 320

P/J- 42.5

pilot outlet- 0.8

pilot air screws(turn out)- 5/8

power jet,
L/H-160
R/H-200

and some others if needed, hope this helps,,
 
Daman - Thanks for the response. I have the Clymer repair manual with all the settings you listed but there is nothing listed for jet needles. You don't by chance have anything on them do you? I think Olav Aaen has a book on tuning Mikuni carburetors. Does anyone have a copy? Does it list anything on needle selection?

Bruce
 
Ok yea i see it but no spec for it,

it has 5 spaced circlip grooves, i would try the middle first
then go from there..
 
Daman - Thanks for looking. I'm coming up empty handed too.

Nightmanx1 - I was asking Shane what altitude he is running at. But on your comment I appreciate it. It gives me a range to think about. I rebuilt my old Exciter last year and even before I did, the jetting was off. I also bought my son an Exciter last year that runs great. I compared all the settings in the two sleds and the only difference I could find was the needle. My sled bogs badly in the midrange but runs great if I can snap it straigt to full throttle. I thought the problem was a lean bog and that I needed to richen up the mixture. My son's sled had a 6DH7 and mine had a 6DH8. When I put the 6DH7 needle in my sled from my son's, it ran great. Both needles had the e-clip at the middle position. When I looked for needles online I found that the the one that ran best was a leaner needle, not richer. That's why I was confused. I didn't think that going one needle size richer would make the sled bog so badly. That was why I was wondering what came in the carb stock, if either of the two needles did at all.

Bruce
 
Looking up your sled on parts filch they only show one... needle
P/N,, and it's #239-14116-68-00

so i'm thinking that must be the right one,,dunno
 
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My dealer told me the same thing. It doesn't actually list the Mikuni part number though. I don't want to order more from the dealer and find out that they're the ones that don't run well in my sled. I was just hoping to find what Mikuni number was the Yamaha #239-14116-68-00.

Thanks Daman,

Bruce
 
1989 exciter float height

nightmanx1 said:
Mikuni carbs come from with 40 pilot jets, 166Q-0 needle jets, 6DH3 jet needle and 260 main jets. I am running this setup but have changed the main jet. And I am running my 88 Exciter at 12000 feet, that is at the parking lot and we go up from there. My air screw is 1.5 to 2 turns out. oh ya float hight is 17-19mm or .66-.74"
Click to expand...

How do you measure float height on the carbs? :o|
 
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