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2000 YZ 125 half throttle sputter

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Hi! I have a 2000 yz125 that I've been riding for white a while thinking there was a slight sputter until I rode my friends 06 yz125 and realized how much it was affecting the power and performance of my bike. It idles great, and has great top end. It suffers a little in the bottom end, and has a terrible sputter at about half to 3/4 throttle and is impossible to maintain a speed there as it just sputters and makes like a "Bing bing bing" sound while trying to maintain a speed or decelerating.. this is only at about half to 3/4 throttle. Ive switched out multiple main Jets, adjusted the needle position, and adjusted the air screw. I took out the reeds (vforce 3) to inspect them and they seemed fine. This is when I realized someone had shave the flanges on the reed side of the intake manifold.. I realized they did this because the little flanges wouldn't have fit in the vforce reed cage. I am curious if someone can tell me if this will affect the performance of the bike. To me, it looks like the holes for the reed cage and the intake manifold don't align 100%. I'm thinking he bought the reeds for a different year bike. If someone can tell me why my bike is sputtering, and what the reedcage intake port is supposed to look like for a 2000 yz125, I would greatly appreciate it

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Can you afford to buy the correct reed assy? If so, that's what I would do, first. Fresh reeds, clean plug, get everything cleaned up, make sure there are no air leaks...see where I am at before next move...

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Can you afford to buy the correct reed assy? If so, that's what I would do, first. Fresh reeds, clean plug, get everything cleaned up, make sure there are no air leaks...see where I am at before next move...

Yes, I ordered a used oem reedcage and manifold from eBay.
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Inspect it carefully. Hold it up to a light. You shouldn't see any light through gaps at the ends of the petals. Hold it at a 45 deg angle too. Make sure you can't see light through gaps along the sides of the petals, either.

 

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After install of the factory reeds, switch everything back to factory carb settings or you may be in the same boat again or be running to lean depending on your settings and smoke the motor.

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After install of the factory reeds, switch everything back to factory carb settings or you may be in the same boat again or be running to lean depending on your settings and smoke the motor.

That was my plan.. I'm running an FMF SST pipe with a Powercore 2 silencer... You wouldn't be able to tell me how that would affect my air/fuel mixture, would you? (if it richens or leans it) just so I know where to go after I install the OEM reeds.

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From the tests I've read, (pipe shootout) the FMF SST pipe is particularly picky to tune for,

it's ideally meant to run with a specific SST silencer and, 

in most cases requires race fuel due to increased combustion temperatures.

 

Perhaps a problematic design for lesser experienced 2-stroke tuners as it seems

discontinued for late model ('05-current) YZ125's.

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Couple things to consider. If you are near sea level and running the stock premix ratio, then starting with stock jetting sounds safe. Need to lean out if you are at high altitude or are running less oil than stock premix ratio. Maybe, search some jetting threads for your bike...see what worked for others...

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From the tests I've read, (pipe shootout) the FMF SST pipe is particularly picky to tune for,
it's ideally meant to run with a specific SST silencer and, 
in most cases requires race fuel due to increased combustion temperatures.
 
Perhaps a problematic design for lesser experienced 2-stroke tuners as it seems
discontinued for late model ('05-current) YZ125's.

I have heard that about the SST pipe. I am thinking I might actually have the SST silencer as well.. I didn't know they ever made once, but when I bought the bike the guy told me it was all SST, and I just assumed he meant Powercore because it had no sticker, and I didn't think they made an SST silencer, but it looks too long to be a shorty.. but possibly too short to be a powercore. (Only 1 mounting tab) Anyway, I emailed Moto Tassinari about the Vforce 3 reeds and they told me that to make the reeds fit, you do have to cut off the plastic flanges from the intake manifold. So I'm going to assumed I have the correct year reeds. I will still be installing the OEM reedcage later today and will post my results. May have to order the stock exhaust.

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From the popularity of aftermarket pipes simply for their shiny bling,

it shouldn't be to hard to find a 'like-new' used OEM pipe for your bike.

 

I picked up a spare stock pipe & silencer for 60$ a while back,

the kid ran it for one ride and decided he wanted the bling of a shiny FMF pipe.

Doubt there were any real power improvements but the placebo effect must have given him 5 more horsepower.

 

Again from what I've read, the SST pipe has a particular stinger length and diameter which is tuned to run with it's specific SST silencer.

 

Edited by mlatour

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From the popularity of aftermarket pipes simply for their shiny bling,
it shouldn't be to hard to find a 'like-new' used OEM pipe for your bike.
 
I picked up a spare stock pipe & silencer for 60$ a while back,
the kid ran it for one ride and decided he wanted the bling of a shiny FMF pipe.
Doubt there were any real power improvements but the placebo effect must have given him 5 more horsepower.
 
Again from what I've read, the SST pipe has a particular stinger length and diameter which is tuned to run with it's specific SST silencer.
 

Nice, haha. Yeah, I figure I will be able to find a stock exhaust for pretty cheap..

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