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Discussion Starter #1
1997 XLT 600. I keep breaking the carb needle on the clutch side cylinder. No bad vibration from clutch (just rebuilt).I think its carb related. Anyone that I talked to has never heard of this problem. Help please!
 

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i've had this happen on a couple of customer's machines over the years. take a look at the needles that you've broke. do any of them have a wear mark on one side or the other? if so, then the needle is riding on one side of the needle jet. it would be a good idea to pull the needle jet out as well to inspect it. look thru the jet to see if it's oblonged from the needle. if so, replace it. another thing to do is take the top off the carb, and take the slide off the cable. leave the needle in and with your fingers, move the slide up and down in the carb. if you feel any resistance other than from the friction of the slide, then something's up. where exactly is the needle breaking off?
there's not really much that can go wrong inside these things. look for any obvious things such as bent or misaligned items in the carb. if it was me, i would replace the needle and needle jet. you could also switch the carbs around and see if the problem moves, or if it stays on that cylinder. keep us informed to what you find. if ya need more info, please ask. -Polaris Doc
 

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Discussion Starter #3
No wear marks on needle I only got 75 miles in before it broke again. The slide moves freely, any wear marks on slide are identical with other two. It breaks off flush with underside of slide. I will inspect needle jet. Waiting on parts. I am going to switch carb placement and maybe slide placement. Problem is when it breaks engine bogs until you hit powerband then broken needle raises and then jams causing throttle to stick. Risking engine damage if needle gets sucked into motor.
 

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Yes, you have a potentially serious problem on your hands. Try rocking the slide in the carb by hand with the needle on back and forth. Something has to be moving more than it should be to cause it to snap the needle. Cant hurt anything by trying to switch the carbs and slides/needles around. All the parts inside should be the same, but double check just in case someone has a different setup in there.
Another thing to check is if the needle jet has rotated in the carb. Its held in place from rotating by a locating pin near the main jet. If the pin has worked its way out, it can cause the needle jet to spin in place. The open side of the needle jet should face towards the engine. If it's not, its probably due to that. This is one thing that can cause the needles to break. However, this will cause symptoms of not opening up on top end and bogging out. Switch some stuff around, inspect the parts, and let us know what you find. -Polaris Doc
 

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Discussion Starter #5
I think I found problem. The main jet has wear marks on the inside of the bigger dia. hole. So when the needle passes thru when throttle is closing the point of the needle hits the shoulder. A brand new needle has a sharper point thus causing quicker failure. All needles have wear right at spot where needle protrudes from slide. I think if I replace all needles and main jets should solve any problems at least for the next 4000 miles.
 

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Discussion Starter #7
Well I changed the needles and main jets but I still think there is a problem. When I move the slide (with needle in but not connected to throttle cable) by hand up and down. The last 1/8" of travel down to idle stop the needle lifts. It's catching on the main jet. But only when side pressure on the slide is toward intake, which would probably be the case when engine is running. So I changed the position of the e-clip on the needle lower.(this would raise needle about 1/8") This would change mixture richer on midrange correct? The original setting on the needle is the middle groove. Other than having poorer mileage is there any other concerns? This is not a fix but I think the needles are less likely to break. The needle jet is on back order, but it doesn't look worn at all. I was going to change it for peace of mind.
Thanks for input so far Polaris Doc.
 

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Discussion Starter #8
You called It polaris doc the slide was rocking side to side 1/8 at bottom on all three carbs. I found new (used) ones for $125 can. Upon comparison they measured the same but were not worn at bottom of slide throat. The new slides have a bright chrome finish were the old slides have a dull satin finish which could have contributed to premature wear.I think anyone with 34 mikunis should inspect their carbs. as I had to do an engine rebuild do to shrapnel in 1 cylinder (the needle did not get sucked in).
Anyway I'm up and running again, waiting for next year!
 

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Just out of curiosity, how far are your carbs opening at wide open throttle? How far above the bore of the carb is the bottom, leading edge of the slide?
 

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my bro had the exact same problems with his XLT. He was constantly breaking needles. He even found one needle piece in his pipe!
The problem is your carbs are worn out. Plain and simple. There's just too much wear and too much slack in the slide assembly. New carbs was the only thing that stopped the needle breakage in my bros XLT.
 
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