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Discussion Starter #1
Does anyone have 4 or 5 .010 spacers that I can purchase?
 

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JdubSC, Part number for McMaster-Carr is Z9750. They come in a quantity of 25 and cost about 7 bucks.

Wayne.
 

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Funny this came up today. I finished putting the carb back on my bike about 30 minutes ago and just came in from a test ride. I put in a new main (116), two 0.02 shims that I got today at Radio Shack and adjusted the pilot to 2 1/2 turns out. It definitely runs better at midrange and seems to run at least as well as before at low and high speeds. I lost that surging in the midrange that I've been putting up with since I got the bike last spring. I wish I'd taken the plunge sooner! The shims I picked up at Radio Shack were in an assortment package of small washers and one size was just under 0.02", so two measured about 0.038" or so. The package was $2.19. You might try there if you have one close by. I could put a couple in the mail if you'd like, but since I'm about 3000 miles away in Washington State, it might be easier to pick some up locally. PM me if you want a couple though. My bike is a 2000 with the older style carb so I'm assuming they'd fit the newer model carbs too.



Dave
 

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I just use flat washers from a hobby shop or hardware store. Cost a nickle. If I want one thinner, set it on the anvil part of a vice and whack it with a hammer. No problem customizing thickness.
 

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Discussion Starter #7
1 of the washers I have equals 1/2 a notch on a needle. Is this similar to the thickness of a .01 shim? I don't have a micrometer to measure the exact thickness..
 

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Hmmm? 1/2 the difference in clip grooves is twice as accurate as fuel quality. Itry one and see how you like it.
 

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Discussion Starter #9
Hmmm? 1/2 the difference in clip grooves is twice as accurate as fuel quality. Itry one and see how you like it.
"fuel quality"? Are you reffering to octane or ethanol levels. I use 87 octane with 0 ethanol. You confused me. Just to clarify, you think I should use 1 washer or 2 to start with?
 

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I started with a 128 main jet. That really helped top end, but was still a little lean in the middle. One washer almost took care of all the midrange lean surge, so I added another. Worked great.



The weather got cold so I switched to a 132.5 main, which was just a tad too rich--loss of a mph or 2 from top end. Midrange kind of bogged with 2 washers, so I took one out, and throttle response was restored.



In the spring I drilled the 128 halfway to make a 130. One washer still had a tiny bit of lean surge in the midrange, two had a tiny bit of bog. I laid them on an anvil and gave them a good whack with a hammer to thin them a bit. Perfect.



that's how I tune a carb.



What will work best for you? Try one. If it helps, add another. If that helps, add a third. If the second washer makes no difference, go back to one, or whack a pair with a hammer to reach a happy median.
 

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Discussion Starter #11
So you tune your carb 3x a year!? Is this what most people do or just you? Im not nearly as intuitive as you about surging and bogging. Looking to learn though... Im gonna shoot for a one-and-done, but im sure I wont be that lucky ^^)
 

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I do carb work when the butt dyno tells me something isn't right. That usually works out to somewhere between 12 times a day and once a decade.



When I was racing I often tuned the carb several times during practice and between each heat, which at a short track event might be 10-12 times a day, seeking perfection for the specific conditions for each heat.



For general trail and street riding I try to predict what state of tune will provide the best overall performance for the entire ride. I really shy away from roadside tinkering--it is too easy to drop or break a part and be stranded.



However, that is not always possible. If facing extreme changes in riding conditions it is sometimes beneficial to retune on the side of the road. This is especially true with significant changes in elevation. Your 12.5RWHP at sea level becomes a whopping 7.75RWHP at 14,000 feet. Altitude alone severely limits horsepower potential so it makes sense to make the effort to keep the tune close to ideal.



When I rode Pike's Peak I stayed near Buena Vista at 8000 feet elevation. I faced a nearly 60-mile ride at altitudes between 7500 and 9500 feet, conditions well within the range of the tune I did when reaching Buena Vista after riding from Texas. On the way to Pike's Peak I stopped in Cascade, found the post office parking lot a convenient place to retune the carb, spread a piece of clean white Tyvek under the bike so dropped parts would be easier to find, and fit the #122 main, removed the two flattened washers from under the needle, and closed the pilot screw a full turn. I started the bike, but throttle response off idle was dead, so I opened the pilot screw back up. Sure, the engine was running a bit lean at 7300 feet, but from Cascade the Pike's Peak Highway is pretty much steadily up. In just a few minutes the bike was running fine, and by the time I reached the summit Tdub was showing signs of a bit of lag when rolling on the throttle--a sign of too rich. Back at the base of the mountain, I restored the carb tune for the ride bike to Buena Vista, and all was well.



My experience is that a 5000 foot change in elevation warrants thinking about a jetting change. Whether to make the change before or during a day of riding depends on the period I'll be riding at the extremes. If I'm just riding over a pass, I might not make a change at all, and just live with the brief period of too rich right at the top of the pass. If I'm riding a straight shot up or down, then will be messing around at the extreme for most of the day, I'll usually make the change the night before and live with the lean operation first thing in the morning and on the way home. If the bike starts running poorly from altitude extremes, I will pull over and tinker, but only if I have to.
 

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Discussion Starter #13
Thanks Qwerty. I have a lot of respect for you and your opinions. All these things are good to know. Im a bit curious about the temperature differences and how that effects the carburation. Sometimes I wish you were my next-door neighbor
Anyways, Im excited to get to work tomorrow on tuning my carb right, and thanks for all the info!
 

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What matters is #O2 molecules each fuel molecule needs to oxidize completely to #O2 molecules. There are literally dozens of variables that affect that ratio for each particular circumstance. Most people shoot for acceptable performance all the time and let it go at that.



Generally, I run a bit richer than optimal. Better cold weather starting and throttle response in the winter and a cooling effect in the summer if I'm doing a lot of highway or tight, technical trails, or stop-and-go traffic. These days 99% of my riding is under 10 miles, in town, 30-45mph speed limit, no heavy traffic. I jet a little leaner for the summer to save gas because additional cooling isn't really needed.
 

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Got my TW in Dec 11, so I;m just now chasing down all these "mod" threads. For what it may be worth, our local "HobbyTown" (national franchise - one may be close to you) has #PHU8504 2.5mm Washer with a 0.125 hole that perfectly fits the needle. $1.39 for a pack of 6. Each washer is 0.020 thick.



Opinion and speculation starts here so take it for what you think it may be worth:



Reportedly, Australian TWs have needles with 5 clip positions, with the distance between each clip slot on those needles measuring 0.050. Suspect that is what we basing the often suggested 0.050.



Me, I'm running 3 x 0.020 and telling myself I've raised my needle at least one full clip position. Can't get excited about being +/- 0.010 from some purely speculative "starting value" for carb work. Proof is only what works with your bike for you based upon where you may be on the planet.
 

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Rather than start a new thread, thought I'd add to this posting. I am in need of spacers also. Have gone to my local hardware store with no luck. Also purchased the Radio Shack assortment, none of which fit. All of the spacers are just too wide, the jet needle with the washers that I have tried simply won't fit into the jet needle holder. Anyone out there have any spares lying around? Thanks.
 

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Rather than start a new thread, thought I'd add to this posting. I am in need of spacers also. Have gone to my local hardware store with no luck. Also purchased the Radio Shack assortment, none of which fit. All of the spacers are just too wide, the jet needle with the washers that I have tried simply won't fit into the jet needle holder. Anyone out there have any spares lying around? Thanks.




Try your local hobby shop. They have several sizes, so you can find the right diameter washers, cheap, and local. Think the ones that worked for me were marked 2mm?
 

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SFscooter, if you PM me your address, I can send off a few .013's and .002's that I got from McMaster Carr.



BuddyMc, I agree that +/- .010 will likely not make or break a needle setting. However if most folks are getting along with a .030 (or whatever really) and someone else suggests they have had great success with something very different, I am curious as to what it is that I am failing to understand...



I am marginal when it comes to playing with numbers, and am not very skilled at manipulating/reading precision measuring instruments. My hope is, should I dare to present information, and it is found to be incorrect, someone will be kind enough to steer me in the right direction. With luck, this re-direct will not require anyone to eat 'humble-pie' or be faced with derision.



Seems we have had a string of posts recently dealing with some 'mysterious' carb. hic-up. Since I have some extra time on my hands, I have been trying to help others as well as myself (I also have a hic-up). With this intent, I may question what I read if it seems to stray from what "I thought" represented the norm. Should something erroneous make it's way into the mix, with luck, it will never be elevated to the level of 'fact' thus sending one's head to spinning when they proceed with some well intentioned tutorial.



I don't want to be some 'Old fart' always seeming to wag my finger at someone else's ideas or opinions. It is always my hope to treat others with appreciation and respect. Should I fall short, please let me know.



2mm on my caliper seems to equal .08 which is approaching three times the suggested setting (.03). Perhaps you are shooting for "very rich".. Gerry
 
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