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Discussion Starter · #1 ·
need some info
i bought a 2000 t-cat and the middle piston lean and the other ones are perfect... carbs are clean with 390 main jets...anyone have any idea what can make that middle piston running lean?

i checked the intake flanges and the guy cut the rubber (duno why??)
 

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Do you mean he cut the "stuffers" off the manifolds? If so, probably had V-Force reeds on it at one time.
 

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Are you positive all 3 mains are 390's ? Also check that the E clips on the needles are all set in the same position.
Did you verify that there were no air leaks when the machine was a normal operating temprature, some
leaks will not appear until every thing has expanded with the heat and come up to normal temp.
If you still have a lean condition with everything verified, you can drop the clip 1 notch on that needle. If that creates
to rich of a condition than you can put the clip back to the previous location and add a .020 shim under the clip as it
sits in the slide.
 

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My money is on an air leak.
 

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I'd go up one main jet soze on the middle to see if that gets the piston wash and plug back in line with the others. First thing to do is verify there are no air leaks, like said above, but I'd go the main jet instead of the needle because the main jet covers all throttle positions. It is not unreasonable to have staggered jetting on a multi-pipe engine, and the centre cylinder may need extra cooling if it it picking up too much heat from the cylinders on either side.
 

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Discussion Starter · #6 ·
ya all the 3 main jets are 390 i tryed playing with the needle and did the same....
the only thing I dint try is changing the main in the middle carb....
is theyre a way to check if its an air leak like u said???
i got 3 new flange coming
 

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I have done a lot of big bores that end up this ,I have also seen a lot of these stock big triple engines that run lean on the center cylinder also,
bump the pilot and main 1 size and lower the clip on the needle one groove.
It should equal out everything to be the same.

your cut intake boots are cut as it use to have V Force reeds in it.
 

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If the 2 end cylinders look good leave them alone, yes upjet just the center with a pilot, clip and mainjet one size larger.
Mike
 

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Discussion Starter · #10 ·
i put a 2 size higher main jet (410) and still doing the same
the plug is like whitish grey and theres a somekinda greyish grease on it

my buddy's thinking maybe head gasket blown and theres antifreeze going in there just a bit could it be it???
 

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A greyish greasyness on the plugs usually always indicate head gasket failure and coolant to leak. Does your sled use any coolant? Have you done any compression tests on the cylinders?...you will quickly find out if you do have a bad gasket if you fail compression.
 

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You better take that head off and check things out. You'll be able to get a good look at the cylinder wall and hopefully there will not be any damage to the cylinder, or rings. Make sure you drain down the coolant before removing the head so as not to dump coolant into the engine. Get some new o-rings and see how much better it works.
 
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