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Discussion Starter #1
'05 TW. I managed to lose the small spring that sites on top of the carb needle and under the small white plastic cap. I wouldn't mind buying a carb rebuild kit to get a new spring but it isn't clear from the kit descriptions that this spring is included in any of them. Anyone know if the carb rebuild kits include this spring or know of any substitute? Reason I took carb off is the bike has an FMF power core and it runs really lean and hot at higher speeds. Spark plug grey, pops on decel. I drilled the main jet with a 1/16" drill which was the smallest drill bit I had and bought some washers to shim the needle a little - I couldn't find 2.5mm washers locally in stainless, only 3mm stainless and 2.5mm for zinc. Any opinion regarding using the 3mm washers which are only a little loose vs the 2.5mm zinc ones? I did order a 130 main jet but it won't come in until mid next week which is why I drilled the stock 126. I also removed the cap over the enriching (?) screw which was only 3/4 turn out and backed it to 2.5 turns out. Carb was pretty clean but I am soaking in Pinesol.
 

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Discussion Starter #5
Well, of course since I ordered a new spring I found the old one. It had dropped/popped a couple feet from where I was working onto a tangle of lashing straps. I must have spent a couple hours looking for it including each individual strap and surrounding garage floor without any luck until I ordered the new spring, one last go thru on the straps and there it was on the floor. No worries, I'm glad to be able to put the carb back together today.

I won't be surprised if the drilled out main jet doesn't work, there no concensus that I could find that says what orifice diameter is for each jet #. I have a #130 ordered if the drilled stock #126 jet doesn't work.

The pilot jet was almost completely clogged and I couldn't pass a small copper strand thru it. Pinesol made it nice and shiny but still clogged. I had some all metal safe rust remover and soaked it overnight - now there is a perfectly round looking tiny central orifice, maybe the rust remover helped or just more soaking.

Keeping my fingers crossed that this all works out.

before removing the carb I replaced a slipping clutch pack with EBC that included new clutch springs, great improvement and now the friction zone feels more like other motorcycles, not just the on/off that the worn clutch had.
 

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Glad you found the spring. Otherwise I was going to suggest a section of ball point pen return spring or simply a solid block of anything of the correct height. The compressible spring of the stock unit is simply to take up excess free play depending on how many shims one has, it was a cheaper option for Yamaha than having it’s jobbers mill grooves and supply cir clips for their supplied needles like those featured in the majority of other carburated motorcycles. Anything that fixes the needle in position so it does not ride up in the bakelite slider to the top of the white cap will work...glue, a piece of toothpick, piece of zip tie, tubing, a rock, a wad of plastic bag. Whatever works, no need to pay $15 shipping for a $2 spring. This is not rocket science, just a simple constant velocity carb.

Note: Without the spring the TW will often start up and run just fine until at some point opening the throttle will raise the needle and then without the return spring the needle may not re-set itself resulting in a suddenly seemingly inexplicable rich fuel mix as the needle remains hung up...the big spring pushes the bakelite piece down just fine, but need the little spring, or something similar, to keep the needle held down inside the bakelite.
 

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Discussion Starter #7
Good to know Fred, I was thinking of the pen spring, the ones I pulled from pens were larger but still seemed to fit the top of the needle and the plastic cap but I wasn't sure what the spring was there for - thanks for clearing this up, it'll likely help someone else down the road.

The bike starts and runs great low speed but boggs with higher throttle so I overdid things. I'm curious to see the diameter of the #130 jet that is coming and I take things step wise after replacing the jet instead of going all in. The carb base gasket wasn't that great so I coated it with a thin layer of permatex non-hardining gasket maker. No leaks but I'll have to pull it off again when I change the jet out, do you think it will be better to just replace the gasket next time?
 

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If readily available I would replace the float bowl’s gasket ( one side needs to face up, make sure yours is not up side down) if only to avoid the mess of re-newing the Permatex.

I misplaced this spring too the evening before I departed for Moab2016 when in my darkened garage I decided at last minute to add a shim based on a fellow forum member’s strong recogmendation. Missing spring darn near ruined a week long group ride.
I subsequently removed the shim in order to restore reasonably lean jetting for higher elevations.
 

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Discussion Starter #10
like2wiz check this Jet size chart out. 49ccScoot.Com : Printable Drill Bit Size Chart
I saw a chart like that but then also read that jet size wasn't always same as mm diameter in thousands. I used a 1/16" drill which would be a #158. That explains the bogging. For fun I might solder the jet and get some small dremel drills to redrill it smaller and see what happens since my #130 jet won't be delivered until mid week. I did remove the washer from the needle and turned the pilot screw to 1.5 turns instead of 2.5 (stock was at 3/4 turns out). Runs great at lower speeds but bogs down higher speed currently.
 

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Discussion Starter #11
The #130 jet came today so I popped it in, stock had been 126 which ran too lean and hot, maybe because of the FMF exhaust. Runs great now with no shim under the needle, the pilot screw is out 2 turns (stock was 3/4 turn). With the carb squared away, the FMF repacked and a new clutch pack it feels like a different bike than when I got it.
 

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Try a shim or two for fun. I thought mine ran good until I put two on. The midrange acellerates way better. My wife's bike had better throttle response with the same carb tuning as my bike. It turned out I didn't push the plastic spacer all the way down against the washers and stop. So I sanded down one more shim for two and Half shims on both bikes.
 

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Discussion Starter #13
Try a shim or two for fun. I thought mine ran good until I put two on. The midrange acellerates way better. My wife's bike had better throttle response with the same carb tuning as my bike. It turned out I didn't push the plastic spacer all the way down against the washers and stop. So I sanded down one more shim for two and Half shims on both bikes.
I'm going to ride it more including on the highway to get a better feel for it. I am thinking of a longish ride in a couple weeks and I don't want to make it overly rich because some riding would be at higher elevations but I might give the shimming a try just to see.

Do you have stock exhaust and main jet?

I have some UNI foam 1" air box plug/vents, I was thinking of putting a few in and covering them with gorilla tape, if too rich at elevation remove the tape and put back on at lower elevations if too lean. Anyone with experience with drilling the air box like this?
 

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My bikes were modified when I bought them running crappy due to the air box changes and DG pipes. Running way lean. They run ok up to 10,000 ft with the correct tune for sea level. I taped over the drilled holes in the air boxes. See my byline
 

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Discussion Starter #15
My bikes were modified when I bought them running crappy due to the air box changes and DG pipes. Running way lean. They run ok up to 10,000 ft with the correct tune for sea level. I taped over the drilled holes in the air boxes. See my byline
I need to start reading the bylines!

so it runs good to 10,000ft without removing tape from your drilled airbox?

I did some searching and found old mixed reviews for drilling the air box. The Admiral indicated it helped for his, pictures on his post no longer active.
 
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