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Discussion Starter · #1 ·
I took the 800cc top end off from my zrt and put a 900cc top end on it. This sled has flat slide carbs and cat never sold a 900cc tripple with flats so I am wondering if anyone has an idea where to start with the jetting? I looked up a 800zrt and a 1000 tcat on brown's and the tcat has smaller main jets !!!!! ???????? How can this be? I think the 800 had 340's or 350's and the 1000 has 310's ?? The sled seems a little boggy and not snappy so I am looking for anyone who has done this swap b4 that can shed some light on where I should start ????

thanx
 

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The 2004 ZR 900 has flatslides and uses a 430 main jet , shouldn't matter too much if its a twin or a tripple as each carb is only supplying one cylinder.
 

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Discussion Starter · #3 ·
Originally posted by F7SNOPRO01@Sep 10 2005, 01:40 PM
The 2004 ZR 900 has flatslides and uses a 430 main  jet , shouldn't matter too much if its a twin or a tripple as each carb is only supplying one cylinder.
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Yes true, however the ZR900 is a twin so it has 2 roughly 450cc cylinders where as the zrt is a 900cc triple so it has 3 roughly 300cc cylinders. 450cc cylinders will need much more fuel then 300cc ones. I would imagine anyways... That is why I am hoping someone who has done this mod b4 will see this n respond.
 

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sorry I had assumed you used 3 cylinders off a zr 900 on a zrt 800 lower end,
if its around 300 cc's the 02 zr600 used 330 mains in a flatslide carb which should be close 135 starter jet and 40 pilot. but this is by looking up parts online not from 1st hand experience
 

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i would run 1000cc flat side specs to start. take a look at flat side 800 vs 1000 specs. the 800 ended up being changed by AC after first year on flats. was too rich. MJ tuning will be easy. the idle circuitry and NJ circuitry will be the issue. ideally EGT gauges would be nice to use. i would consider running dial a jet. i ran DAJ and found it enrichened by NJ area of throttle too much and could not enlean enough. here again the MJ was easy. modded zrt 600. ended up replacing the NJ. dropping the needle one notch helped but i did not want to drop it another so went to NJ replacement and enleaned the pilot i i can remember. i think that was done from 1996 to 1997 year anyway.
 

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Did you check the piston to head clearance? If my memory is correct the crankshaft stroke on all 1998 and latter T-cats and ZRT 800's was reduced .4 mm because Artic Cat changed the rod bearings to a larger size and at the same time changed the stroke. The slight reduction in stroke could be causing a small loss in compression and more importantly an increase in squich clearance. The squich clearance should be around .070 if you have a very large squich clearance you will have to mill the heads to reduce the clearance. As far as jetting is concerned I would start with the ZRT 800 spec's and work towards the T-cat spec's if you still have the air shelf in the carbs. If you pulled the air shelf I would go up to at least 400 main jets and read your plugs.
 

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:smiley-faces7:

Hi All

I have a similar setup on my 1999 ZRT ( Different Flatslides than 2000. 99 have only fuel screw adj,2000 have air & fuel screw).I can speak for a bullet proof ,slightly rich ( IE SAFE) setup.
I have 360 mains and stock pilots . Stock air box.3 deg timing key.Trail port on cyl's. 800 heads cut to 900 spec and shaved 10 thou.( sleeper).
It is a rocket. I can trounce stock 1000 Tcats on the ice.
On long runs I catch the new twins (up to 800 cc ) The 900's are sharp all along
The twins usually get me off the line as they come out quicker.I reel em in though.
This sled can be held WFO if you have the run to do it on.I ran 3 miles on the railbed sideby side with a buds RX1 WFO before I got my clutching dialed in ( was only turning 7800 rpm at wide open ) .No burndown issues.
 

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Originally posted by ext@Sep 23 2005, 08:45 AM
:smiley-faces7:

Hi All

I have a similar setup on my 1999 ZRT ( Different Flatslides than 2000. 99 have only fuel screw adj,2000 have air & fuel screw).I can speak for a bullet proof ,slightly rich ( IE SAFE) setup.
I have 360 mains and stock pilots . Stock air box.3 deg timing key.Trail port on cyl's. 800 heads cut to 900 spec and shaved 10 thou.( sleeper).
It is  a rocket. I can trounce stock 1000 Tcats on the ice.
On long runs I catch the new twins (up to 800 cc ) The 900's are sharp all along
The twins usually get me off the line as they come out quicker.I reel em in though.
This sled can be held WFO if you have the run to do it on.I ran 3 miles on the railbed sideby side with a buds RX1 WFO before I got my clutching dialed in ( was only turning 7800 rpm at wide open ) .No burndown issues.
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I have my 900 set up similar. Good advice!
 
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