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Old 04-24-2015, 11:28 AM   #1
mortimer OP
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Question KTM LC4 Petcock Question

Has anyone found a good replacement for the KTM LC4 petcock that does not cost $50+?

I have been able to replace the o-ring in my 2000 SXC400 petcock to make it stop dripping, but it still bleeds fuel into the bowl and out the overflow. I have inspected the needle and seat and they look great, no visible signs of damage. I use and oversized tank and this only happens when the tank is more than half full; i.e. more fuel pressure against the needle and seat. I have also adjusted the float so that is parallel to the bottom of the of the BST40 (per the great instructions posted here).

I see these Yamaha petcocks on eBay and I am wondering if they will fit. The seal looks identical to the KTM one. Can't easily locate the Yamaha petcock dimensions anywhere.

http://www.ebay.com/itm/2-pack-Fuel-...2844a1&vxp=mtr

Anyone have any luck with cheaper replacement petcocks or advice on how to make mine seal against the pressure from the oversized tank? Thanks.
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Old 04-24-2015, 11:39 AM   #2
clapped_r6
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a new petcock won't stop fuel pressure in the way you're describing. your needle and/or seat is likely the culprit. it's an on / off valve, not a regulator in any way. (the petcock)

i personally turn my valve off when not riding for any length of time. recheck your float valve. they can "look" good and still not "be" good
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Old 04-24-2015, 12:19 PM   #3
mortimer OP
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Quote:
Originally Posted by clapped_r6 View Post
i personally turn my valve off when not riding for any length of time. recheck your float valve. they can "look" good and still not "be" good
Thanks for response, I should have explained differently:

Setting the tank on a workbench with the petcock off and a full tank of fuel, it slowly drips from the fuel line connection point.

I turn my petcock off whenever I leave the bike for overnight or longer; i.e. yesterday replaced petcock o-ring, then closed petcock, this morning I see drips from the bowl overflow under the bike. It did this before the o-ring change too, just weeped a little fuel at the petcock before. This description of the problem may indicate two probs: petcock and worn needle/seat - but no fuel leaks from overflow when the bike is funning.

mortimer screwed with this post 04-24-2015 at 12:27 PM
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Old 04-24-2015, 12:34 PM   #4
NevBlu
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Tip on float needle

Quote:
Originally Posted by mortimer View Post
Has anyone found a good replacement for the KTM LC4 petcock that does not cost $50+? Anyone have any ... advice ...
Petcock. Stay with the original manufacturer for the petcock even with the cost; quality is more important than price in my opinion. Photo is from LC4 with 4.7 gallon tank 34 mm center to center hole spacing. On second thought, if you want to use a Yamaha part, go ahead since it's your MC.

Carb. The float needle (the special rubber tip near the float pivot) is likely worn even though it appears OK, but it is not. It seems pricey too, but compared to a fire hazard and nuisance of dripping gasoline, doing it right is my suggestion.

Good luck.
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Old 04-24-2015, 10:56 PM   #5
bmwktmbill
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Petcock is an incorrect term for the needle and seat in the carb. There is an O-ring above the brass seat sealing it to the carb body, if it leaks fuel will run out the overflow even if the needle seat and float are working correctly and the float is adjusted properly.

bill
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Old 04-25-2015, 08:10 AM   #6
NevBlu
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Petcock

Petcock

I would not normally reply but this is right where I am at with installing the petcock back on today. Sourcing a replacement could occur through a Mikuni suppler rather than directly from KTM. Good luck.

No doubt the length of the internal screens will be different on different sized tanks, but here is a Mikuni petcock from 4.7 gallon tank on a 2001 LC4 640 E.

For those interested the normal ON position draws fuel 5" up from the bottom. Reserve position draws fuel from only 1" up from the bottom. 33 mm c-c spacing on the holes.
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Old Yesterday, 04:17 PM   #7
mortimer OP
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Quote:
Originally Posted by bmwktmbill View Post
Petcock is an incorrect term for the needle and seat in the carb. There is an O-ring above the brass seat sealing it to the carb body, if it leaks fuel will run out the overflow even if the needle seat and float are working correctly and the float is adjusted properly.
Yep, been speaking about the two distinct parts. I've replaced the seat o-ring thanks to following Laramie LC4's a-w-e-s-o-m-e guide: http://www.advrider.com/forums/showthread.php?t=347184 Needle and seat must be worn out...

Quote:
Originally Posted by NevBlu View Post
Petcock

I would not normally reply but this is right where I am at with installing the petcock back on today. Sourcing a replacement could occur through a Mikuni suppler rather than directly from KTM. Good luck.
NevBlu: Great idea, will search for a petcock from Mikuni supplier see if I can save a few $$.

Have you ever taken the petcock completely apart? I am guess yes from seeing your highly detailed LC4 rebuild. There is a (blue colored) nylon (guessing) cone that diverts the fuel or seals it off that seats against the petcock housing. There could also be rubber bits inside that have turned to dust and since disappeared that I am missing... This seal (nylon to aluminum) seems to be bad on mine. Ever have any luck disassembling and cleaning? I am gonna give it a shot before I break down for a new one.

This is a picture from an older spare petcock:

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Old Yesterday, 05:13 PM   #8
tkent02
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I wouldn't have a problem using a petcock for a Japanese bike. They have been making petcocks for a long time that still work just fine. Easy and cheap to rebuild too if it ever needs it.

The ones you linked might be cheap Chinese crap. Pakistani crap? Bangladeshi crap? Hard to tell from the pictures.
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Old Today, 12:24 AM   #9
bmwktmbill
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Quote:
Originally Posted by mortimer View Post
Yep, been speaking about the two distinct parts. I've replaced the seat o-ring thanks to following Laramie LC4's a-w-e-s-o-m-e guide: http://www.advrider.com/forums/showthread.php?t=347184 Needle and seat must be worn out...



NevBlu: Great idea, will search for a petcock from Mikuni supplier see if I can save a few $$.

Have you ever taken the petcock completely apart? I am guess yes from seeing your highly detailed LC4 rebuild. There is a (blue colored) nylon (guessing) cone that diverts the fuel or seals it off that seats against the petcock housing. There could also be rubber bits inside that have turned to dust and since disappeared that I am missing... This seal (nylon to aluminum) seems to be bad on mine. Ever have any luck disassembling and cleaning? I am gonna give it a shot before I break down for a new one.

This is a picture from an older spare petcock:

I've had mine apart several times. Cleaned the bore with a Scotch brite pad.

For a new one you might try Sudco, they deal in Mikuni parts.

http://www.sudco.com/

bill
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'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing

The faster it goes the faster it breaks.
And high performance=high maintenance.
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