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Discussion Starter #1
Going to have to provide some background first so you all have an opportunity to weigh in.
Picked up 2 sleds. Both 2000 XCSP's with 3,500 and 4,000 miles. A 500 that needed minor work and maintenance to get going and a 600 that had a bad PTO crank bearing from a leaking oil tank grommet.(run dry) Got 'em cheap for the grand sons to tag along on trips to the cabin. 500usd for both. 500 is running great. Now for the 600. Pulled the motor apart. Replaced all 3 outside bearings (in reality the inner PTO was the only really bad one) because I was there and it was easy to do all 3. Everything on top end was super clean. Great looking cylinders and pistons. Reassembled all with SPI gasket set, crankseals, etc and the newer oem metal base gaskets. New gas (50% 100LL avgas and 50% 91 octane, 10% ethanol because that's all we can get in commiefornia, I add a little startron for good measure and ves to 100 to 1). Fired her up with no issues on full enrich. Dropped to 1/2 enrich, doesn't really want to idle yet so dropped the enrich and she speeds up a bit and startys to backfire through carbs. Thought great, missed something while cleaning carbs. Pulled and cleaned again, including pilots, again. Same deal. Ok, lean backfire vacuum leak? Did the spray of starting fluid around PTO seal, carb flanges, case halves and cylinder bases, where possible, no change. Pulled carbs and y pipe and plugged and used hand pump to pump up through impulse line. Holds air for 5 min with no leaks. Checked crank phase, just in case, it was perfect. Checked timing. (I had put it back to where it was) Timing was at 24 degrees at around 3,500 with TPS unplugged. Compression is at 118-120. Rebuilt fuel pump. Tried coil off the 500. Even tried the CDI off the 500. Nothing seems to make any difference. Jets are what the factory calls for. It'll run pretty good enriched and even rev to 8k+ at wot for a quick test but no idle and backfiring through carbs un-enriched (is that a word?). It's an ugly idle un-enriched until it dies. I did notice the idle linkage screw was screwed all the way in when I got the sled, which may or may not be an indication of previous idle problems?
Where to now? I'm sort of at my wits end here... Thanks in advance for any help. I really don't want to put this sled in storage until it's running right and then have to deal with it in the fall.
 

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On a 00 600 ves the fuel screws should be about 2 1/4 - 2 1/2 turns out from Lightly seated. If anyone turned them in till they bottomed out hard the carb is junk. The sled will run too lean and backfire through the carb. These carbs also have 1.0 fixed pilot air jets, no air screws.
 

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Discussion Starter #3
On a 00 600 ves the fuel screws should be about 2 1/4 - 2 1/2 turns out from Lightly seated. If anyone turned them in till they bottomed out hard the carb is junk. The sled will run too lean and backfire through the carb. These carbs also have 1.0 fixed pilot air jets, no air screws.
Thanks, I started at 2, went 2 1/2 and finally went to like 4. No change. Needles looked good but not sure about the seats. If they were cranked in at some point, that would damage the seats? Should I try the rack off the 500, with the proper jets? Same carbs? Yes, I noticed these little ves motors run pilot air jets, not air mix screws like the 800 ves.
 

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Should of made a big difference turning those air screws. Suspect something else isn't right, or those carbs are bad. Fuel needles if bottomed too hard will bend the tips, or break-off in the carb body...be sure you have at least a good clean 45 pilot jet installed to. I would try those 500 carbs with all the correct 600 jetting specs. At least it'd eliminate the carbs if not the issue.
On another note, these 00 600 motors are very cold blooded and will cough and fart till fully warmed up. Idle speed should be around 1500 rpm.
 

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Discussion Starter #5
Thank You. That will give me another way to eliminate another possibility. I will be back with results... Tomorrow?
 

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Was going to suggest trying the 500 carbs too, should be pretty much identical and with similar jetting IIRC.

as for the 600 carbs not reacting to fuel screw adjustment, either it could be a broken off tip , or clogged-up passageways to the pilots.
If the latter, I've found the best way to clear it out is to use an ultrasonic cleaner
 
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The 600 has a different slide cutaway iirc. Otherwise they are same except for jetting specs. I had an 01 500 that did the same thing until it was warm. Never did figure it out. Ran great otherwise.
 
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