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 TK carb Main jet, needle spacing change

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goldenhtr
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PostSubject: TK carb Main jet, needle spacing change   Tue Jun 22, 2010 10:08 pm

Thanks to Centerline for this.


Pictorial TK carb Main jet, needle spacing change

DISCLAIMER: The following thread is for entertainment purposes only. Don't attempt this at home. If you do, it is at your own risk. My Yamaha TW200 is a model year 2006 North America spec machine. It runs with stock sprockets. I am using a DirectHits spark enhancer. The exhaust system has already been modified with an FMF Power Core IV muffler. The airbox is as yet unmodified. Due to the less restrictive exhaust system, I chose to re-jet the carburetor with a 130 jet, versus the OEM 126 jet. Thanks to Babaganoush and his thread http://tw200forum.com/forums/18477/ShowPost.aspx for the technical knowhow. Thanks to Monkeystone69 for this..... I found shims that will work nicely for raising the needle on the Teikei carbs. They are available from an industrial supply house called McMaster/Carr. They can be found at www.mcmaster.com. The shims I purchased were part #99040A300. They are available in packs of 25 washers. You can order them in varying thicknesses from .001" to .016". I ordered mine in a .010" thickness. The washers are made from 18-8 stainless steel. They are .125" I.D and .187" O.D. I paid $7.81 plus shipping for the pack of 25 washers. They fit nicely with no binding. And thanks to the "discussioners" in the thread. This deals with taking off the carb, shimming the jet needle and changing the main jet on my 2006 TW200 with a TK carb. It is probably similar to other model years, but I have no other TW experience, and actually less than 600 miles experience on the one I have. Perhaps I will post photos later of the beginning process, taking the carb off. Didn't have my camera with me at the time, so will walk/talk thru the beginning. 1. Turn off fuel petcock. 1 1/2. Remove the left side trim panel under forward side of seat. Three attach fittings. The top forward fitting is a friction bayonet one, on the lower edge of panel are two philip head screws. 2. remove fuel line to carb. (It is on TIGHT) 3. On right side of carb, loosen the locknuts on the throttle cables (2cables), remove the cables from their captive guides, then remove the cable ends from the carb throttle actuator. You will get them off, just a little bit of cable wrestling. 4. From the left side, with a philips head screwdriver, loosen the metal clamp that secures the carb to the airbox snorkel on the aft side then loosen the clamp that secures the carb to the cylinder head intake manifold at the front.. 5. Wrestle the carburetor out of the rubber boots whose securing fittings you have just loosened. Figure out the correct orientation to get the carb out of the left side of the bike, take the two drain lines along with the carb. The picture below is the top of the carb. The silvery metal lazy W fitting is where you wrestled the throttle cables free. We are going to open the top of the carb by removing the two screws, one of which has already been removed.


Okay, the vacuum chamber cover has been removed and we are looking down into the piston valve where the jet needle lives...underneath that big ass spring, the vacuum chamber spring. The outside circumference of the piston valve is a soft pliable silicon-like material, the inner portion a hard plastic.




Now, take the big vacuum chamber spring out and put it where you can find it again.
You are looking down into the piston valve assembly and onto the top of the jet needle holder



Gently grasp the outer edge of the piston valve and pull it straight up out of the carburetor. The jet needle can be seen protruding beneath the piston valve.
You are doing good. Place a finger under the exposed tip of the jet needle and push it up so that you can grab the white plastic jet needle holder. There is a small spring under the jet needle holder between the holder and the needle. Don't lose the small spring as you lift the white plastic holder clear of the jet needle. You will remove the jet needle white plastic holder, the small spring and the jet needle itself. They are all in the next photo.



Now the piston valve has been placed back into the carb, but the needle holder, spring and the needle are out. Put the holder and the small spring where they will not be lost. If you drop the little spring back into the piston valve recess, it will wedge itself in tight. (Don't ask me how I know this.)


It has been discussed elsewhere in other threads that raising the jet needle will be very helpful when also changing the main jet. Gathering the info from the guys who have gone there before, I chose to raise the jet needle by .05" Take the needle and slide the white nylon spacer off. Place 5 of the .01" stainless steel washer/spacers onto the needle and slide the white plastic spacer back onto the jet needle.



Place the small spring back on the needle, place the needle jet holder over the small spring and needle, and put the needle assembly back into the piston valve. It is easier if you have about 3 hands.


Replace the piston valve assembly back into the carburetor. Watch the flexible circumference of the soft piston valve outer edge.


Flush into the carb all the way around. It fits flush into the recess.



That's all the time for now. To be continued later today.....
However a little teaser....
Road the beast this morning for about 20 minutes.
Y-E-S. Freaking just added 50cc to the beast!!!! A really worthwhile improvement. It is a noticeable to the seat-of-the-pants, butt dyno. The beast is putting out some real improvement in power, throughout the briefly tested operating range. But that is the result of the needle position change and a new main jet. Stay tuned...pun intended.

So get the top all buttoned back together.


Turn the carb over and look underneath...removing the 4 philips head screws. The throttle stop screw assembly and its bracket will flop around out of the way, not to worry.



When you remove the bottom of the carb, the float bowl the needle jet and holder are actually filling the tapped hole for them. In the photo, the main jet holder has been removed and the main jet which was screwed into the top of the holder has been removed.
I actually did not drill out the idle mixture cap until I had put the carb back together, to keep debris out.
On the carb bowl mating surface can be seen residue from the carburetor bowl gasket. It needs to be scraped off and a new gasket put on. I got in too much of a hurry and did not replace it. Don't make the same mistake. When I order the gasket to fix my mistake, I will post the part number. The carb does not seal well now and after sitting overnight, the area around the old gasket is damp with fuel.


Here we go, the main jet, just sitting on the corner of the carb for comparison. I don't know who makes it, but the local Yamaha shop had a box of them. The thread fits perfectly the threads of the TK main jet holder.


Another view of the original and replacement jet. It would be helpful when you visit your shop to buy a new jet, that you take old jet with you.


Okay, screw the new main jet into the main jet holder and screw the main jet holder back into the carburetor.


Put a NEW GASKET on, put the float bowl back together. It was after this step that I drilled out the cap on the idle mixture screw.


Wrestle the carburetor back into its home. Pretty tight fit, but it goes back in from the left side. The airbox snorkel is just a whole lot of entertainment, trying to get it around the intake tract of the carburetor, have fun. Then you need to tighten up the circular clamp fastener around the snorkel. That is some fun too!
The fitting into the cylinder is pretty, as is tightening its clamp. Replace the fuel line from the fuel tank, and reroute the two drain hoses that go down underneath.
Reattach the throttle cables over on the right side. But note that in the pictures, the placement of the unattached cables is incorrect. The cable on the top should be on the bottom. Get em in the correct spots then tighten them in.
Replace the left side cover.


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PostSubject: Re: TK carb Main jet, needle spacing change   Wed Jun 23, 2010 7:31 pm

VERY NICE. SOMEONE SPENT LOTS OF TIME TO PROVIDE US THIS INFORMATION. THANKS!!! Gerry

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