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2000 XR200R Jetting?

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I will not have a place to try some jetting out before my next H/S race. Right now the bike is running very good and clean-the jetting it real close to spot on. Gas now days makes it hard to read plugs.

I have a stock XR200R that I use a UNI filter and right now a differant insert in the exhust (not the atv 250r one) but bigger I.D. than the stock one. My jetting right now is 112 main jet and 40 slow jet.

I have a FMF Power Core 4 laying round and was thinking of installing it, what do you think I should go one richer on my main jet??

I forgot I also have the snorkle on top of the air box removed also. And when I change the baffle on the stock muffler to the one I found out in the shop that has a bigger I.D hole that made a real big differance in low end pull.

Tom

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I've run similar jetting but found the #40 pilot and 112 main combo too rich, maybe your float is set a bit low.

Bottom end throttle response and power is very dependent on back pressure which is why you like the insert with a larger ID.

I ran a 38 pilot, 4th needle clip, and 110 main on stockers. Then just a 112 main with an aftermarket exhaust. On my Powroll build I changed the needle clip to the center groove.

I've run a variety of muffler setups over the years and haven't needed major jet changes, sometimes only one size richer.

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UMMmmm-well I live on the upper coast of Texas and almost at sea leval, and all of the H/S I'm racing are less than 500" above sea leval. And my plug sure looks clean and does not show to be rich. In fact my plug the electrode, the gap is facing the right side of the motor and on the intake side it is clean and just off white color and the exhust side as a tan brown color with just a hint of black on it- but I ran all the gas from the carb and used the choke to get all the fuel form the carb. But that is really what my plug looks like ever time I look at it. It seems to run real good right now with the set up I'm running. I have not had the carb back off cents I set it up it ran so well and clean. The only troubles I've has is if I drop it is getting it fired off again, seems to flood when I drop the bike.

Tom

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Forgot to add I have the clip in the middle. Chuck you said your running in the 4th- witch way 4th up or down?? What I'm trying to saw you raised the neddle right??

Tom

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4th groove from the top for richer.

Plug checks are good and they can also tell you things about ignition advance and mixtures other than full throttle but it takes a lot of time. So I have my shortcuts which may not apply to other bikes:

Besides the classic slide valve carb sections of main, needle, slide cut away, and pilot Keihin augmented the pilot circuit with two discharge ports; one with a mixture screw that responds mostly to vacuum for idle, and one under the slide that responds mostly to air flow to help transition from the pilot circuit. Both are fed by the pilot jet. To confuse thing a bit more my observation is the port under the slide is more important for starting than the mixture screw because of the low vacuum at kickstarting speeds.

I like my little Rs on the rich side for easier cold starting and warmup. Might be a legacy from the early Rs and the twin carb versions. I like the bike to start cold with one or two kicks using full choke, more than that and the pilot is too small or the port is obstructed. Immediately after firing I need to go to half choke, and if I hold the idle speed up a bit I can go to no choke in a few seconds. After initial warm up the choke is not needed for any starts even after sitting for an hour, if the choke is needed something is wrong with the carb.

When warm and trail riding the transition off closed throttle should be smooth, if it is jerky then one or more of the jetting circuits is too rich. I'm so borderline rich on a stock engine with the needle one clip rich that if I go up one size on the main the transition from closed throttle becomes jerky, and the engine tends to flameout.

The carbs seem to easily flood, make sure the vent hoses go down. Flooded engines can be hard to restart, I use full throttle until it fires and don't let the Rs fall too much until the engine quits blubbering.

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