81 Excel III - Mikuni Carb Model / Mystery Spring

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Kato3man

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Jul 17, 2015
Messages
8
Location
Cincinnati, OH
Bought a 1981 Yamaha Excel III last summer that was stored in a barn with only 1100 miles on it.
Did the normal clean up and it started just fine. Now that we have snow my son wanted to ride it so we got it fired up and it bogged really bad.
We yanked the carb off - removed only basic internals like jets, float etc gave it a good cleaning by hand and then in a ultrasonic cleaner.
It came out looking almost new........changed fuel lines, put it back on and sled fired right up.
I got it tuned pretty good as far as idle and throttle response and thought we were all set

Here is where the question comes - when I went to clean up the bench I found this super small spring.
I have no idea where it came from - it must have fallen out when I turned the carb over.
Problem I'm having is finding what Model carb I even have to try and find info on where the spring goes.

Pretty sure it says Mikuni Kogyo and it looks exactly like pic attached.
Based on what I do find I'm thinking it's maybe from the float area / float needle that makes the float bounce.
Sled is running great - I don't want to take the carb back off until I know where it goes........if I even have to since its running so well.


81 Excel Mikuni.jpgIMG_1301.jpgIMG_1065.jpg


Any help on carb / spring info would be much appreciated !!!
Mike / Steve - Cincinnati, OH
 

Almost looks like a spring for needle and seat?? Go to Cycle Parts Nation and select Yamaha. Find ur year/model and look at carb parts breakdown
 
Sifton - for sure not the choke plunger spring - much smaller.
I didn't remove the needles just the jets and float by popping out the pin.
I'll try Cycle Parts Nation.........Thanks

Found the Part# for a new needle valve but not spring shown in parts bag with new or in diagram.
Update - this pick of parts in bag show a spring - but where in the world does it go.......??

Needle Valve.JPG
 
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Anybody have an idea on what model Mikuni this might be.....?

Son rode the crap out of it for 2 days and it ran great.
Mystery spring even needed.....?

IMG_1313.jpg
 
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I am by no means an expert, but it looks like the spring that went under the plastic plunger inside the needle and seat on my Exciter 300. The plunger was inside the needle and would contact the float, then the spring was there to allow the float to move if the terrain was rough and caused the fuel in the bowl to slosh around. I think it acts as a buffer so the floats don't get bent up and end up out of adjustment.
DS79
 
That spring is from your float needle. It goes around the skinny end of the small plastic piece that then goes back inside your float needle. The larger end of the plastic piece goes against your float lever. I'm not sure how critical it is, but I'd hold onto it until next time you have the carb apart and reinstall.
 
deerslayer1979 said:
I am by no means an expert, but it looks like the spring that went under the plastic plunger inside the needle and seat on my Exciter 300. The plunger was inside the needle and would contact the float, then the spring was there to allow the float to move if the terrain was rough and caused the fuel in the bowl to slosh around. I think it acts as a buffer so the floats don't get bent up and end up out of adjustment.
DS79
Click to expand...


This answer is correct.

Seat needle Buffer spring.

opsled
 
Thanks to all with info on where the spring goes !!!
Son put 42 miles on the sled last weekend and I'm sure he exercised it pretty well.

I'm going to keep the spring and info and put it back when I yank the carb to clean it next fall......maybe :)

*** Snow is about gone here in Cincinnati - going to be 58- 62 Fri, Sat and Sun
 
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