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Carb tip – TT600RE – lean (flat) spot gone. Carb tip – TT600RE – lean (flat) spot gone.
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  #1  
Old 30 Jun 2009
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Carb tip – TT600RE – lean (flat) spot gone.
Hi all, a small teck tip..

The bike is a 2005 TT600RE.

It had a flat (lean) spot in the power band just before the second carburetor opened. Very annoying.

The solution turned out to be simple, I made the second carburetor open a little sooner.

I adjusted the screw (see pic) so that the gap (see the other pic) increased from 8.1mm to 9.1mm. This small adjustment was all it took, now the flat spot (lean spot) is not noticeable .





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Old 30 Jun 2009
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I fail to see how that can richen up the mixture.

Please tell me.

If its a tad lean in the middle area, you could/should raise the needle(s) a notch, og half a notch with shims.
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Old 1 Jul 2009
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the screw opens up the secondary throttle early allowing fuel from the secondary carb to enter the engine its probably just enough to get rid of the flat spot on your bike the ydis carb set up is designed to keep those flat spots from happening its a bit like variable valve timing the engine needs different volumes of fuel/air mixture through the rev range but its not a linear curve so the two part carb is a way around that problem.
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Old 1 Jul 2009
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But, it also opens up for more air, right? Dont know the TT, i have a XT but they seem pretty simular.

So unless the secondary carb is richer mixed, I cant see the logic, or atleast undestand it

But if it works, it works =)

Im nut trying to be "out there" with a whip, just trying to understand.

Which year is yours?
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Old 1 Jul 2009
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the xt and tt use the ydis carb, it will be slightly richer as the 2nd carb butterfly valve will only just be open but as the secondary carb is a cv carb the vacuum will have lifted the diaphram operated slide raising the needle slightly too thus giving a richer mixture

kinda irrelevant to me though as i have junked the yam carb and fitted a pair of 32mm mikuni's but i have done some head work and fitted a high comp 3mm oversize piston which is more than the ydis carb is designed to cope with
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Old 5 Jul 2009
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Dav Jens

The bike is a 2005 TT600RE. I am told it has the exact same engine as the 1990-1995 XT600E but with bigger carburetors.

I was not trying to richen up the mixture in the entire middle range. There was an annoying small “flat spot” or a small hesitation in the powerband just before the second carburetor opened (I think).

There is no great science behind this adjustment. It was just a test that worked out. I read some posts were an Australian guy talked about this adjustment (advancing the opening of the second carburetor) and decided to give it a try.
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Old 28 Aug 2009
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Quote:
Originally Posted by wolfzero View Post
the xt and tt use the ydis carb, it will be slightly richer as the 2nd carb butterfly valve will only just be open but as the secondary carb is a cv carb the vacuum will have lifted the diaphram operated slide raising the needle slightly too thus giving a richer mixture

kinda irrelevant to me though as i have junked the yam carb and fitted a pair of 32mm mikuni's but i have done some head work and fitted a high comp 3mm oversize piston which is more than the ydis carb is designed to cope with
Wolfy... any chance of some data & photo's for you 32mm carb replacement mod's please
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