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Post by jimthejet on Apr 23, 2005 3:20:39 GMT -5
Here is a way to shim your Jet Needle without modifying (or struggling with) your stock Jet Needle Holder (called Plate Set, Valve in microfiche) or whatever the nylon retainer for it is. Just go to Home Depot (or any Home Improvement store or lumber yard or hardware store) and look in the miscellaneous hardware boxes (slide-out trays) for nylon washers. Two #8s are what you need to replace it, probably packaged in 4, for less than a $. You then need to modify one of the washers in the same pattern as the feet(?) on the stock Holder. You can use a Dremel Tool, woodburning tool, or a knife or whatever. The nylon is soft, so it doesn't take long. You need to mark 3 notches, 120 degrees apart (use the bottom of the stock Holder as a pattern), and then remove material. This allows it to seat on top of the Needle and wedge against the 3 locators in the slide. You will also want some washers to use as shims and to replace the spring from the Jet Needle Holder. For the shims, you can try to find flat washers that will fit in the .250 i.d. recess in the bottom of the slide, or you can use a (1) #4 split lock washer bent flat. They are .030" thick (.75mm). You need one that will seat in the recess, preferably in stainless. The zinc-plated steel ones will eventually corrode, but you may not have your scooter for as long as that takes. For any additional shims and spacers as required, you can use #4 flat washers in brass, stainless or even nylon (Home Depot has them all). They are .280 o.d., so they won't fit the recess. You must use them under the head on the Jet Needle, stacked as high as necessary, but with a < .250 o.d. washer at the bottom (pointed end of Needle) of the stack, see photos. You will need to make up the additional height of the Jet Neelde Holder base, less the shims you've used under the Needle, to keep the Needle from possibly rising or sticking. The other #8 Nylon Washer becomes the seat of the Diphragm Spring, holding all the washers, etc. in the slide. This is not easy to explain, but, hopefully the pictures will do it. I find it is quite a fast method in shimming, and beats trying to make shims or modify the Holder.
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Post by abe on Apr 23, 2005 8:20:39 GMT -5
You need to make your pics smaller. I can't even read your info.
Sorry man
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Post by chanito on Apr 23, 2005 16:03:44 GMT -5
Interesting alternative, turning the washer to lock it in place looks like a challenge though. The washers my home depot had were way too thick, following a ruckass sugestion i finded the perfect ones at Radio Shack
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Post by jimthejet on Apr 23, 2005 21:37:08 GMT -5
I'll resize the photos when I figure out how to do it and make it stick, as they had already been reduced when I posted them.
Chanito, the washer with the 3 notches doesn't need to be turned or twisted. It is a "press" fit, in that it wedges on the locators. The thickness of the various washers at Home Depot was anywhere from .020" (.5mm) on the brass and some of the nylon, to .030" (.75mm) on the stainless and other nylons.
The modified nylon ones used as the locking device and the spring seat are .060" (1.5mm), but are not used as shims.
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Post by KiwiMetII on Apr 30, 2005 12:24:33 GMT -5
whats the point of needle shimming? how does it work/what does it do?
-I have a metI carb spring, an 85main carb jet and a battlescooter CDI installed already....
will needle shimming help?
YES I have a metroII.. same diff to your ruckases... kinda
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Post by chanito on Apr 30, 2005 12:47:46 GMT -5
When you start modifying your air intake, you have a lot more air rushing into the engine when you accel, so the motor goes lean and boggs down, by shimming the needle you raise it, allowing more gas so your engine accelerate smoothtly.
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Post by KiwiMetII on Apr 30, 2005 14:36:43 GMT -5
yeah.... my airbox (the same stock one on the ruckas I think) has been opened up to (the small intake tube was cut out so that the intake is as wide as the external intake, and I cut open the once false vents on the intake pipe). so is shimming the needle a fine adjuistment compared to jetting?
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SuperJ
n00b Ruckster
Posts: 28
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Post by SuperJ on Apr 30, 2005 22:32:28 GMT -5
yeah.... my airbox (the same stock one on the ruckas I think) has been opened up to (the small intake tube was cut out so that the intake is as wide as the external intake, and I cut open the once false vents on the intake pipe). so is shimming the needle a fine adjuistment compared to jetting? In order to figure out what you need to do to the carb you need to know what changes you actually made to the airflow. With a Ruckus/Metro opening up the airbox obviously increases the airflow but it has a larger effect at lower RPMs. Once you open up your airbox your Ruckus will likely be running extremely lean off the line and through the midrange and kinda lean on the top end. Because the change is not equal 'across the board' you can't simply change the main jet to get things running perfectly again. Merely increasing the main jet size would result say a 10% fuel increase across the board which means you now might be running properly at high RPMs but still stuttering at lower ones (cuz the top end only needs a bit more fuel to run correctly but the lower RPMs need a lot more fuel). If you then try a bigger jet still...say a 25% increase you might now be running properly off the line and throught the midrange but you're now too rich up top. A lot of people, myself including, intially just kept increasing the jet size until it ran nice off the line (cuz stuttering off the line is much more noticable than your Ruckus dying off 1-2mph sooner) and then noticed that this mod really helped the Ruckus rip off the line but wasn't any faster or even a bit slower on the top end. The solution is to first find what main jet gives you the best air/fuel mixture on the top end and then worry about shimming the carb. The correct main jet is likely which ever one gives you the highest top speed but in the case of a tie go with the bigger one cuz rich is safer than lean. Also remember that temperature does play a role since the density of air changes so don't adjust your stallion on the hottest day of the summer. It is important to understand how the carb works so you can make sure you're adjusting the right thing. If you think of your carb as a garden hose then the main jet size would be the diameter of the hose. The shim would be how far open you've got the tap cranked when you flick the hose on and the diaphram spring would be controlling how fast you opened the rest of the tap. If you increase the hose size (main jet) you're basically going to get a linear increase in flow across the board regardless of how far open the tap is cuz a 2" hose will flow more water at 25% capacity than a 1" hose that's also at 25% capacity. If you open the tap farther (shim) before turning the hose on (assuming you're playing with the master water valve in your house or something) then you're going to start out with more flow and continue to flow higher until the tap is fully open at which point the flow is entirely determined by the hose size. The last major adjustment discussed here is the diaphram spring which controls the rate at which the tap opens. A stiff or long spring will offer more resistance to opening so it would be like opening the tap slower. On the other hand, if you want to reach max flow sooner you'd want a shorter or lighter spring. In the case of the airbox mod you'll want to find the correct main jet size and then shim the needle until you've got enough fuel flowing at lower RPM's. It isn't necessary to adjust the diaphram spring unless you really know what you're doing and really want it to run perfect. On the average Ruckus that has had the airbox opened significantly I'd say the average main jet size is .80-.85mm and should be shimmed 1-2mm. You could try cutting down the spring a bit too but it really isn't necessary.
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Post by chanito on May 1, 2005 6:10:50 GMT -5
;D ;D, I agree with 99% of that post, the only difference is about the importance of the spring, and its need to be adjusted, the thruth is that if we adjust our spring right we would not need to shim the needle, the problem is that working in that spring is super tricky, we would need to find a softer shorter springs, since that is easier said than done, our only alternative is to shorthen the one we have, now spring behaivior laws tell us that if you shorthen a spring you increase its hardness, so just shorthen the stock one is only part of the solution , anyway back to topic, fluid laws tells us that if we accel a fluid it has to overcame inertia so it flows slowlly, but once its inertia is overcome it flows faster, thats the reason we use a spring along with gravity (the weight of the piston holding the needle), when you accel an engine air flows in much faster than gas, vacuum from the engine is feed to a chamber on top of the needle making the needle go up very fast, so fast that the inertia will make it keep going up compresing the spring, allowing more gas to flow to compensate for the extra air rushing in, then the spring would push the needle down to its right place, stopping the temporary rich condition, and every thing would be hanky-dory. Now the fun part is that if you cut a spring too short, that temporary rich might be too rich fouling up your plug and killing your engine (not fun), so spring tampering is a hard thing to do, you need to have a couple of extra springs in case you go too far, just gab a new one and start again, lots of trial and error will go into getting a satisfactory spring lenght, so untill someone does the work of guinea pig, the shim is a way easier alternative, i hope i did not bore you to death by now, happy scooting
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SuperJ
n00b Ruckster
Posts: 28
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Post by SuperJ on May 1, 2005 9:07:47 GMT -5
Thanks for the correction/update Chanito. I (DandyDan) wrote it under my brothers account as I was on his computer and he was already logged in.
Have you tried messing with your spring yet Chanito? I'm finally home from a Co-op job in Ottawa so next time I'm at my local dealer I'll order a spare spring and then mess around. I've got to get in there anyways cuz I'm a bit rich since I have it jetted for the pretty cold Ottawa winters (average low maybe 20F or -10 to -15C)
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