Suggestion of carb for 1984 yz490

[1983_Enduro_YAMI]

G'day all,

I recently purchased an 84 yz490. When I was checking the bike over yesterday, I found out that the original owner has replaced the 40mm carb with an aftermarket 38mm mikuni back in the 80s. What should I do with this carb? If I stick with it what Jetting should I use in this 38mm? Or which carb should I get if I decided to replace it?   

[80-85 husky]

soooo if the po replaced the carb many moons ago ..why wouldn't it be jetted correctly now?

A 38 mm from 40 is a fairly common mod to tame the sudden rush that the big bores have.

[kim80y]

WR500 std jetting.They came with a 38mm
Cheers
Kim

[1983_Enduro_YAMI]

It goes really well with the 38mm (after you said that it takes away the sudden rush i kind of want to put the 40mm back on  i don't like taking the aggression away from the big bores...) This bike was raced by the previous owner in the 80s so there no much to do with the jetting but only minor adjustments.

[80-85 husky]

the 40's (in the husky 500's) generally cause hard starting, poor low end and unrideable (other than perfect loamy ideal ground) power. 38's are good for a couple of seconds a lap from what I can gather...

[1983_Enduro_YAMI]

So will the 38mm still do the job??

[80-85 husky]

unless your name is S Gall I rekon it should be fine.....if you find yourself wringing the throttle hard against the stops 3/4's the way down the main straight...yelling "cmon you pos!!!"  upgrade to the 40...

[1983_Enduro_YAMI]

I wish my name was S Gall  A new production-based factory 490 for me!!!