02-11-2018, 04:47 PM | #1 |
Join Date: Oct 2017
Location: shelton, Washington
Posts: 167
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Difficult tuning. Hey dan!!
Grrrrr. I have a 200 cc witha vm26, 22.5 pilot, 110 main. Needle fourth notch. I cannot for the life of me get this tuned in! Compression is 180, valves set correctly. Nice blue spark. I start out one turn on the idle mix, and it just snaps and farts out the exhaust. No “snicking “back thru the carb. When i pull the choke, the idle steadies, but is way high.
In my experience when the choke is pulled on a warm engine, it should stumble because it has tto much fuel, too little air. Im 5 turns out on the mix, and shouldn’t be that far out. Nothing changes except easier starting. I have not history on this bike, nor does the previous owner. Could it have been kitted to a 250cc? I have a 25 and a 27 pilot, but all info points to 22.5 or 25. When i try the 25, same issues. Really frustrating Im guessing i have the idle in the middle. And it still wont start with a air filter.. Its so difficult to adj the mix while its running. I had to modify a extended mix screw so it wouldnt hit the starter. I cut a groove in it for a screwdriver, and have to use a flexible screwdriver to get at it. Ive tunned many bike carbs, mostly cv’s so im no newb What am I missing?
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2006 roketa 200cc 1971 Yamaha xs650 2x 1980 xs650, 1 is a café, other is a chopper/brat 1972 Honda xl250 2x early 90's Honda rf600 parts bikes more mc junk laying around. |
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02-11-2018, 06:54 PM | #2 | |
Join Date: Jun 2016
Location: akwesasne, NY-13655
Posts: 2,220
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Quote:
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02-11-2018, 06:59 PM | #3 |
Join Date: Oct 2017
Location: shelton, Washington
Posts: 167
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There are no vacuum leaks.
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2006 roketa 200cc 1971 Yamaha xs650 2x 1980 xs650, 1 is a café, other is a chopper/brat 1972 Honda xl250 2x early 90's Honda rf600 parts bikes more mc junk laying around. |
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02-11-2018, 09:40 PM | #4 |
Join Date: Jan 2018
Location: Forney Texas
Posts: 498
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When you pull the choke and it idles too high that means it's starving for fuel, at full choke it gets just enough to run. More than likely it's original jetting is close enough to run with room to see change from some adjustment. So it leads me to believe it may be a restricted jet or gummed up carb, possibly a vacuum leak.
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02-12-2018, 02:27 AM | #5 | |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
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Quote:
If you are confident that you have no vacuum leaks, then I would suggest jumping up to that 27.5 pilot just to see how it behaves. It seems like a drastic change, but considering it takes you past 3 turns out to even get a somewhat decent idle, a full step up might be what you need. One thing you weren't clear on is the throttle position at which these running issues happen. Idle? Just barely opening the throttle - like a light steady throttle while going at low speed? I am fairly sure you mentioned going through and cleaning the carb really well a couple of times, but if not then ARH's suggestions are definitely worth a look. The smallest piece of debris in the pilot circuit or idle mixture passage can cause all sorts of hell. Dialing in a carb can be a long tinkering process when you have no direct analog or other setup to start from. The CG250 should be close, but it may take a few changes. You might find that the pilot jet size and mixture settings are almost the same as the 250, Even though the 250 is larger, the extra 30cc's will also mean that there could be a slightly weaker intake signal through the same size carb on the 200 engine, thus needing a larger jet size to compensate for the lower "Draw" on the jets during an intake stroke. Also keep in mind that cooler weather will also mean the jets may need to be a tad richer as well than many of the setups you are looking at with the CG250 bikes - which are likely all figures from the warmer parts of the year. Just keep in mind these throttle ranges to help diagnose running issues with the setup. Idle mixture and up to 1/4 throttle is mainly affected by the pilot size 1/4 to 3/4 throttle is mainly affected by the needle position 3/4 to wide open is main jet size.
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02-13-2018, 08:56 PM | #6 |
Join Date: Oct 2017
Location: shelton, Washington
Posts: 167
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Found vacuum leak. This is one of thew ones. Ill get another on the way.
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2006 roketa 200cc 1971 Yamaha xs650 2x 1980 xs650, 1 is a café, other is a chopper/brat 1972 Honda xl250 2x early 90's Honda rf600 parts bikes more mc junk laying around. |
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02-13-2018, 10:23 PM | #7 |
Join Date: Dec 2015
Location: CO
Posts: 1,525
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Wow... big gash
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"Think as you like... but this self proclaimed Professor is always right" - Buckshot "You never know what someone is hiding beneath their smile..." - NinjaTom - R.I.P. |
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02-13-2018, 11:48 PM | #8 |
Join Date: Nov 2016
Location: robertsdale alabama usa
Posts: 1,007
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duct tape it for now and ride the piss out of it
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1991 harley heritage softail classic 2016 hawk kaw h1 400 tripple 13' long chopper in progress 2009 johnny pag bar hog 2004 hd electra glide ultra classic shriner edition 1997 harley davidson 1200 sportster 1972 harley davidson amf sx250 |
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02-14-2018, 10:23 AM | #9 |
Join Date: Jun 2016
Location: akwesasne, NY-13655
Posts: 2,220
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That's a good suggestion. That will let you get the carb more dialed in before the new intake gets here. I know that you already know not to overtighten the two mounting bolts for the carbs, and the two nuts used where the intake attaches to the head...ARH
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02-14-2018, 11:53 AM | #10 |
Join Date: Oct 2017
Location: shelton, Washington
Posts: 167
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Yep. Just snug with some smear of greaes on the orings
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2006 roketa 200cc 1971 Yamaha xs650 2x 1980 xs650, 1 is a café, other is a chopper/brat 1972 Honda xl250 2x early 90's Honda rf600 parts bikes more mc junk laying around. |
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02-14-2018, 12:05 PM | #11 |
Join Date: Jun 2016
Location: akwesasne, NY-13655
Posts: 2,220
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Good man, good man...ARH
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02-16-2018, 02:10 PM | #12 |
Join Date: Oct 2017
Location: shelton, Washington
Posts: 167
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I was able to salvage the first new one, the one with the stripped hole. Running much better, but 3&1/2 turns out and on the fifth notch. Cant find my 27.5.
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2006 roketa 200cc 1971 Yamaha xs650 2x 1980 xs650, 1 is a café, other is a chopper/brat 1972 Honda xl250 2x early 90's Honda rf600 parts bikes more mc junk laying around. |
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02-16-2018, 02:23 PM | #13 |
Join Date: Jun 2016
Location: akwesasne, NY-13655
Posts: 2,220
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I used to change pilot jets up until the idle mixture was at 1 and 1/2 turns out, and the bike ran good (but not "perfect") with the needle in the middle slot. then I went on to the main jet, then back to the needle to 'tweek' the 1/2 to 3/4 throttle response....ARH
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02-16-2018, 07:47 PM | #14 |
Join Date: Oct 2017
Location: shelton, Washington
Posts: 167
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Huh. I will try that when i find my 27.5 pilot.
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2006 roketa 200cc 1971 Yamaha xs650 2x 1980 xs650, 1 is a café, other is a chopper/brat 1972 Honda xl250 2x early 90's Honda rf600 parts bikes more mc junk laying around. |
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02-18-2018, 12:43 PM | #15 |
Join Date: Mar 2009
Location: Sardis, BC, Canada
Posts: 25,977
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A general rule of thumb is that if you need to back out the pilot mixture screw more than 2.5 turns, the slow jet is too small.
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Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer |
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