jetting on 98 t-cat

879 Views 9 Replies 3 Participants Last post by x3m, Jan 5, 2007

dynocat

Discussion Starter · Jan 2, 2007

for those who are own a 98 t-cat or did......how the stock jetting was?? too rich or too lean?? because i just put 1000 jugs on my other sled (zrt 800)....naturelly i"ll put the "Q4" neddle..but i was thinking to put 420 main rather 430??? what do you suggest???

thanks........ :beerchug:

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x3m

· #2 · Jan 3, 2007

It was too rich at top. I ride at +200 meters above sea-level and 410 is no problem, could go lower for hp if it was for race and 201 meters. But watch the mid around 7000 rpm's as this is the usual lean spot for the 1000.
And it also comes down to how you have adjusted the stroke for those cyl's. You have 0,4mm more stroke in the 800 and this may alter the port timing a little depending on what way you go when you put it all together. This combined with a other than stock 1000 pipes will also affect the need for fuel. They are a bit sensitive in the mid 7' rpm's if you go high in comp. Remember this if you're to mill the heads to compensate for the stroke.

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blackmax

· #3 · Jan 3, 2007

It was too rich at top. I ride at +200 meters above sea-level and 410 is no problem, could go lower for hp if it was for race and 201 meters. But watch the mid around 7000 rpm's as this is the usual lean spot for the 1000.
And it also comes down to how you have adjusted the stroke for those cyl's. You have 0,4mm more stroke in the 800 and this may alter the port timing a little depending on what way you go when you put it all together. This combined with a other than stock 1000 pipes will also affect the need for fuel. They are a bit sensitive in the mid 7' rpm's if you go high in comp. Remember this if you're to mill the heads to compensate for the stroke.[/b]

x3m... would it be possible to go Q8 and a lower main like 380 ish, wondering if that would help with the mid lean spot....

BM...

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x3m

· #4 · Jan 3, 2007

Blackmax wrote:

x3m... would it be possible to go Q8 and a lower main like 380 ish, wondering if that would help with the mid lean spot....[/b]

You mean to use the "main" as a restrictor for the needlejet!?

The main would be too small at WOT as in it would work as the same main with a smaller needlejet. I understand what you are getting at but it's hard to stretch the capacity of a jet (ex. make a 380 work as a 400 by oversizing the needlejet). And you would have big troubles in the mid as soon as the carb begins to run on the needle. -The engine would be drained in fuel.

Depending on tune you may fix this on a stock engine by just moving the needle clip. With stock here I mean that you haven't altered too much. Changing the needlejet you should have gone up in tune noticeable.
Just one size in needlejet makes a great difference.

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blackmax

· #5 · Jan 3, 2007

Blackmax wrote:
You mean to use the "main" as a restrictor for the needlejet!?

The main would be too small at WOT as in it would work as the same main with a smaller needlejet. I understand what you are getting at but it's hard to stretch the capacity of a jet (ex. make a 380 work as a 400 by oversizing the needlejet). And you would have big troubles in the mid as soon as the carb begins to run on the needle. -The engine would be drained in fuel.

Depending on tune you may fix this on a stock engine by just moving the needle clip. With stock here I mean that you haven't altered too much. Changing the needlejet you should have gone up in tune noticeable.
Just one size in needlejet makes a great difference.[/b]

I was just checkin browns, a stock 99 tcat runs a Q8 and a 390 main with a 3.5 slide... 98 ran a Q4 and a 430 main with a 3.5 slide... I just thought maybe cat tried to cure the hot spot with bigger needlejet and smaller main :dunno: I never knew anyone with a 99 to see what there jetting was....

BM...

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x3m

· #6 · Jan 3, 2007

I was just checkin browns, a stock 99 tcat runs a Q8 and a 390 main with a 3.5 slide... 98 ran a Q4 and a 430 main with a 3.5 slide... I just thought maybe cat tried to cure the hot spot with bigger needlejet and smaller main :dunno: I never knew anyone with a 99 to see what there jetting was....
BM...[/b]

Yes I know that the -99 used those needlejet's. But they also changed them to Q5's to fix a rich condition in the mid..
You will fix the lean spot with either moving the clip, or if you have made some mods, gone up to a Q5.

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blackmax

· #7 · Jan 3, 2007

Yes I know that the -99 used those needlejet's. But they also changed them to Q5's to fix a rich condition in the mid..
You will fix the lean spot with either moving the clip, or if you have made some mods, gone up to a Q5.[/b]

I didnt realize they dropped to Q5s... :div20:

BM...

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x3m

· #8 · Jan 4, 2007

BLACKMAX are you sure about those 390's??
At sea-level I don't see why they would have as the -99 were to deliver the same power as the -98!?
A guy I know came by with his -99 tuned, so I don't really know. But I found that the air-box robbed a lot of hp in the -99's so that would in that case explain why they had to go down that much. But on the other hand that air-box saw the light the first time feeding the ZRT 800...

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dynocat

Discussion Starter · #9 · Jan 5, 2007

thanks to awsering x3m........ :beerchug: since i have the cylinder in stock form!! i"ve put the stock jetting on it!! 430 with Q-4 i will see when gonna come the time to "tune it" but for now here in montreal and surrounding we have not snow yet!! worse rain for tomorow!! the grass comeback everywhere..... :banghead:

every big cat have had a lean spot...even my 95 had a lean spot around 7000!! bjankuski made a thread about this last years or so...cat have played a lot to try to cure this problem with the years...but generaly the problem have always been there at the end......

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x3m

· #10 · Jan 5, 2007

No problem dynocat I look forward to get feedback on that engine of yours.

x3m

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