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Anyone re-jet their Mikuni flatsides?

1299 Views 16 Replies 6 Participants Last post by  xc racer
Was thinking about re-jetting my 99 XC500.
I hear you get better performance and milage.
Anyone done this yet? Did it make a big dif?
What size jets? How hard to change?
Thanks

1999 XC500
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MIne have been rejetted. It is a 700 twin. It wan'ts to flood out all the time and we still have to figre out what the problem is.


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i'm going to mess with my sled's carbs too. same engine as you ebby69k- runs too rich for my taste. you might consider changing the needle position first- raising the e-clip a notch or so- to lean it out. remember to always keep a close eye on plug conditions when messing with jetting- and do it in small steps as not to harm anything.

When in doubt- Throttle out!

'99 XC SP 500
xc racer... I was was thinkingabout doingthat
too. I've done it on the round slide carbs before and it really helped. especially in warmer weather. I noticed your favorite websites in your profile are mustang ones.
Those are my regulary visited sites also.
I've got a 89 GT.

1999 XC500
Flatslides are very similar in pricipal to rounds Except the throttle cable is a little bit more of a pain to get back on. At what throttle position do you feel the sled is not crisp. All positions? try the mains and needle and air screw. Just midrange? try only the needle. just topend ?try only the mains.Good luck if you get it right you should feel a difference.
hey erick didnt know you were having troubles. If its flooding it really should only be the floats, the choke plunger settings,or inlet needle and seat. Did this problem just develope on it own or after some work on the sled?
Hotrod..... I feel the throttle response is decent throughout the range. In a tech article in snowtraxx they said it can be improved. I saw a reference to a past article
in a newer edition. Can't find the issue though. They said it was a great improvement
all around to downsize the main jets cause the factory over jets.

1999 XC500
sounds like we're the only ones around here with our heads on straight eh ebby69k? ;) how do you like your sled? as for the cars, i have a 94 stang, my brother has a 94 gt and a 73 coupe, and my dad has a fully restored 67 coupe. i'll get the pics up someday.

When in doubt- Throttle out!

'99 XC SP 500
Xcracer Where did that comment come from. Everyones just trying to help. Your 17 years old and Your head might be on straight right now, but with comments like that , I wonder how long it will remain like that. Not that you will care, but you will not receive another reply from me.....your BLACKLISTED
hotrod, i'm just playin around man. i'm not trying to offend anyone here. did you fail to notice the ;) at the end of that line? i said that because ebby69k and i have the same interests- polaris and ford. didn't mean to get you fired up man. and by the way, i'm not 17 and i already tried to give ebby69k some advice, being we have the same sled.

When in doubt- Throttle out!

'99 XC SP 500
I love my sled it's awesome. My wife wants it so I may get a new one next year. I really want the edge. She's got a 97 Indy 440 and
wants to upgrade. I need to get some pics
of my car too. It's real clean.Bought it this past spring from the original owner with 10000 miles. where ya from rc

1999 XC500
sweet, that gt must be clean. is it stock? i'd like the edge too, but $$ prohibits it since i'm in high school. i'm from south dakota- you?


When in doubt- Throttle out!

'99 XC SP 500
Hey xc check your private message inbox.

1999 XC500
There's gotta be someone out there that's messed with the flatsides.

1999 XC500
Ebby< I have rejetted My flatsides and Yes it made a Huge Difference, but this was on a Yamaha who are know for Jetting very fat to start with.Very simple change. Hope someone with your machine can give you some basine jet #,s .But they will have to know the temps your running and elevation.If your willing to spend some $ get the dail-a-jets.they will keep a constant jet no matter the conditions.


Vmaxyam
Yah, rejetted mine twice in a week. Talked to the shop where I bought the sled, they recommended going from the stock 430s to 410s. Then I put a power breather on and D&D recommended jetting up 2 sizes, so I had to go back to the 430s. Runs great!
It's a simple job especially if the carbs are rack mounted. Just had to pull the choke lever out of the cowl, didn't disconnect any cables from the carbs. Take the plug out of the bottom, unscrew the old ones and screw the new ones in. Bolt the carbs back on and let her rip!
I'd talk to your local shop for info on the correct size to go with, don't want to burn anything up.


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sorry i can't help you yet ebby69k. i really want to lean out my sled a bit, but it's impossible to do without snow to test it on.

When in doubt- Throttle out!

'99 XC SP 500
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