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Discussion Starter #1
OK, I need some help from the carb gurus on this board.

Background: I bought a non-starter in Feb from a guy who apparently parked the bike in late '07 after a fall and had not ridden it since. Expecting carburetor nastiness, I removed the carbs and, not surprisingly, there was a lot of green gunk on everything. I went through all the points in the carb sticky in this section, scrapping and shrubbing as best I could. I used carb cleaner liberally on the metal bits and hit every orifice I could find with compressed air.

After an unsuccessful attempt at just running with just cleaning the jets and other bits, I bought new main and pilot jets (152.5 mains, 17.5 pilot) and installed them yesterday. Went for a ride and low throttle/rpm performance was good; not stumbling or backfiring now. Got on the highway and the bike topped out at less than 90mph. I checked the letters on the tail of the bike and it is a 650 and not a 250. :rolleyes:

I was in too big a hurry yesterday to sync the carbs before the test run, so I did that last night. Way out of sync, so I evened them up and put everything back together and hit the hay thinking I'd solved the problem.

Well, not so. Took the bike out for another spin this afternoon and while it is running much smoother at all rpms, there is no pull past about half throttle. On the highway, with the throttle pinned, I topped out a 80mph, even worse than before the sync! :angry1:

I checked the throttle cable adjustment before reinstalling everything and it is opening the throttle to the stop.

The bike is hard to start cold, stalls and dies at first, but after warmed up she purrs at idle.

Before all this carb work fun, I pulled the plugs and they looked fine but I replaced them anyway.

Have not checked compression, but it pulls strong under half throttle, so I don't think that is the problem. Other: Stock gearing. K&N filter. Micron exhaust with mid-pipe (headers looks stock, not sure though.) Previous owner jetted, looks like Factory Pro needle?

So, two things I can think of:
1) I haven't gotten all the green varnish out of all the fuel passage ways. I suppose the only way to get this is to tear it down again and soak the body in carb cleaner. I really want to avoid this if possible.
2) Throttle position sensor bad? I tried to check the resistance when I had the carb apart, but I'm not sure I understood how to read it. I don't suspect this because I can rev the engine in neutral all the way up to the redline.

So, fuel starvation sounds like the most likely scenario.

In and around town, the bike is fine. But this is to be my track tool, so top speed of 80-90mph and no response past half throttle is unacceptable.
 

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that main is way to big for that filter if not desnorkeled. you could just be running REALLY rich (?maybe).

to run 150+ mains you would need to have a full exhaust and desnorkeled filter from what I have read. i have an uncut k/n and full yosh and I am running 142.5.
 

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with those big main jets it might be getting loaded up with too much fuel..

Is there a stock exhaust?? with just a K&N those jets are probly too much..

TPS...??? Only on FI?? correct??

Carbs are coming off agian, whether you like it or not.
 

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Discussion Starter #4
Micron exhaust.
Good point on the filter. It didn't even occur to me that I might need to desnorkle the K&N.
With the stock jets, I had the same problem of no power about 5-6k rpm. Could that have been a lean condition + unsynced carbs and now I've gone too far the other way and am running rich? How can one tell?

How far in to cut? Don't want to destroy my filter.
 

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Discussion Starter #6
Are you getting good spark on both cylinders? Sounds like you may be running on one.
No, definitely running on both cylinders. Very smooth, no vibration and it sounds pleasingly like my Ducati. :)

She pulls strong up to half throttle. Not in any danger of spontaneous wheelies, but plenty of get up and go for a 650.
 

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DO NOT CUT THAT!!

compare that to a stock filter and you will see why... Anyone have a pic??

On second thought... no no no that thing is garbage you should send it to me and go get a new one..

Im guessing the micron is a slip on... so you should be really close with the jetting, maybe still too rich...uhh try going down 2 sizes on the main jet(147.5)and shimming the needle.. it should be a lil lean at the top RPMs at WOT..
 

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just a couple ?? i thought of
what elevation are you at?
what do you have your fuel screw set at?
 

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Discussion Starter #9
what elevation are you at?
what do you have your fuel screw set at?
Michigan, so a couple 100 ft above.
2.5 turns out from seated.
Clip on the needle was on the 2nd notch down, I believe. Didn't make a note.
 

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Discussion Starter #10
DO NOT CUT THAT!!

compare that to a stock filter and you will see why... Anyone have a pic??

On second thought... no no no that thing is garbage you should send it to me and go get a new one..

Im guessing the micron is a slip on... so you should be really close with the jetting, maybe still too rich...uhh try going down 2 sizes on the main jet(147.5)and shimming the needle.. it should be a lil lean at the top RPMs at WOT..
Roger, I'll keep the jigsaw clear of the K&N...
I don't know what the stock mid-pipe looks like, but the material is different from the headers, which I why I think they are aftermarket.
So, maybe I should exchange the extra 152.5 mains and 17.5 pilot I ordered by accident for a set of 142.5 and 147.5 mains to experiment with?
 

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I would check if there is a good flow of fuel from the tank to the carbs. Carefully pull the hose off where it goes to the carbs and check for a good flow, with motor running. The TPS wouldn't cause that problem and your K&N filter comes already desnorkled.
 

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Discussion Starter #12
Clip on the needle was on the 2nd notch down, I believe. Didn't make a note.
Correction, just pulled the diaphragm off the back cylinder. 3rd slot up from the tip.
 

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elevation not an issue

the stock needle has no notches so that it is not stock... 2nd notch down out of how many? As you move the clip down(towards point) it pulls the needle out of the jet more and allows more fuel sooner, so 2nd notch down probly right.

2.5 turns out is about right, a lil more is ok but not any more than 2.75 out. Do you know how to check if it is set correctly?? it is done while riding.
i took a tiny flatblade screwdriver bit and grinded it down a lil so that it would fit in the hole for the fuel screw, then i could make adjustments 'easily' when pulled over. i would just have to cram my hand into a really hot part of the motor and turn the screwdriver bit with my fingers, i said 'easy'...

i think the mains are just too big.


also has this been done... http://www.svrider.com/tips/retard.htm i assume it probly has because of the other mods already done. it wont effect the issue you are currently having but you should check it out..
 

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Discussion Starter #14
I would check if there is a good flow of fuel from the tank to the carbs. Carefully pull the hose off where it goes to the carbs and check for a good flow, with motor running. The TPS wouldn't cause that problem and your K&N filter comes already desnorkled.
I blasted compressed air through the fuel lines early in the process and so don't think I have any clogs. I drained the floats Friday prior to pulling the carbs out and go a decent amount of fuel out of each bowl, but I didn't measure carefully to see if one was low. I skipped over the part in the manual about checking the fuel level in the bowls. I don't get that at all.

I replaced the float needle and body and made sure the filter was clear.
I also pulled the petcock off and the filter was OK.
 

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you could try moving the clip up on the needle... that might plug the jet just enough to lean it out a lil.

also could be what marc said above about the flow from the gas tank.
 

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