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Discussion Starter · #1 ·
Well as some of you know I bought another YFZ other day, an 07 model all stock. I had a slightly modded 07 a year ago for a short while and it was impressive, the stock one....not so much. Anyhow a little history. I rejetted to 168/45/35 leak jet, GYTR needle on 3rd clip and 2 out on the AF screw, zip tie mod, pulled spark arrestor and airbox lid. NICE improvement. Then did the cam mod. I think that was one of the best bangs for the buck....FREE. Well I knew I needed a new airfilter so was gona buy a UNI and be done. Well that turned into a FCI with UNI filter and a Monster Big Core full exhaust. Also rejetted main to a 170 but left the rest alone. Just got them put on a little bit ago and Im impressed. This thing is a BEAST! What I use to have to do in second gear now you can leave it in third and let it get lower in the RPM range and use the shear torque. I cant say enough about it. On straights/dirt roads you just bang through the gears and before you know your clicking up trying to find 6th....lol!

I wasnt too impressed with the FCI transition ring....poor fit but put it on with JB weld and let it dry then took a Dremel and blended it properly. FCI was a little tight but got it on no problem. Monster pipe went without incident. As stated I did up the main to a 170 and left everything else alone. I just got the standard head pipe from Monster and in just a 30 minutes ride time its changing color....I figured it would but do you guys think Im jetted up enough? It doesnt pop on decel, cranks right, good response, etc. Any help on that is appreciated.
 

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As u know, i installed the dasa shorty, and fci should be here nxt week. Fooling with Fatboy on that one! Any who, while running the fmf set up, jetting was pretty good with 165/45. After putting on the dasa, i could tell i was lean. I then up'd the main to a 170 and thought i was set until I hit the hwy. for a top speed run. It was skipping just a little pinned wot in 5th. Starving for fuel some. I need to throw a 172 or 175 at it. If it seems fine, try opening it up and see if skips any. If not, ur more than likely good. Of course you know to read the plug n such for reassurance.
 

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Discussion Starter · #3 ·
It seems strong all the way up but ill take it out for a high speed tomorrow and check the plug. I hope its good...im tired of messin with it...lol. Did you get the cam mod done bud?
 

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It seems strong all the way up but ill take it out for a high speed tomorrow and check the plug. I hope its good...im tired of messin with it...lol. Did you get the cam mod done bud?
Still dragging my feet on that one. Waiting for fci, then I'll go for it; is my latest excuse lol.
 

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Discussion Starter · #5 ·
Lol. You need to get with the program! Well didnt have time to check plug today. Did some horse trading for a 86 Toyota 4Runner for a beater/hunting rig and the red paint had to go...shes now camo!

Anyway took the bike for a ride right before dusk and the header was glowing fire red. Yes Ive heard of this before. I do have a slight bobble every now and then during accell so I wonder if I might be a little lean. Most of the time it stumbles on take off....zip tie might have broke too though.

Goin to pick up a 05 Honda 250ex for my boy tomorrow so Ill mess with it more when We get back.
 

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Discussion Starter · #6 ·
Allright guys I put a 172 main in it after observing the head pipe look like lava and it seemed to run great till I got to some woods creek riding and got it pretty hot from hard running. Ive got 15 acres here at my place with a creek that runs through it. Several times I was trying to ease around and it had a slow speed stumble at times and when I got to several parts where I needed to carry the front end over BIG ruts it would stall out and leave me hanging over the bars....NOT fun! I pulled the plug and it looks tannish to me with carbon just making it to the bottom of the curve on the electrode. I thought my zip tie mod might have broke and checked it and its good. Dont get me wrong it runs like a raped ape in the throttle and right off of throttle but easing around it will miss occasionally. That doesnt bother me as much as going over the bars thinking your fixin to have 50 horses at your thumb.....any ideas? Just for kicks. 172 main, 65 pilot, GYTR needle on 3rd clip, AF screw 2 out.
 

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Allright guys I put a 172 main in it after observing the head pipe look like lava and it seemed to run great till I got to some woods creek riding and got it pretty hot from hard running. Ive got 15 acres here at my place with a creek that runs through it. Several times I was trying to ease around and it had a slow speed stumble at times and when I got to several parts where I needed to carry the front end over BIG ruts it would stall out and leave me hanging over the bars....NOT fun! I pulled the plug and it looks tannish to me with carbon just making it to the bottom of the curve on the electrode. I thought my zip tie mod might have broke and checked it and its good. Dont get me wrong it runs like a raped ape in the throttle and right off of throttle but easing around it will miss occasionally. That doesnt bother me as much as going over the bars thinking your fixin to have 50 horses at your thumb.....any ideas? Just for kicks. 172 main, 65 pilot, GYTR needle on 3rd clip, AF screw 2 out.
I'm going to go out on a limb here and say your pilot is too rich. Shouldn't need much more than a 50 with that set-up, and that's max. A 45/48 is more likely closer...
 

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Discussion Starter · #8 ·
My bad, Im knee deep in a 30 pack. 45 pilot is whats in there....geesh
 

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Pipe will glow red regardless even if tuning is A-1. Thin walled header. But does it seem your troubles are coming from too much fuel, and not enough air now? If so, try the 170 main.
 

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Also where exactly do the problems start in reference to throttle position?
 

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Discussion Starter · #13 ·
Its off idle or right there about it. Here are the problem areas (all woods riding) rolling into a turn with speed in 2nd and roll into the throttle (not stab it) and it studders. This in turn slows it down enough that second is useless now and you gotta clutch/rev/drop to second. The other place is creek crossings where you want to float the front end across and roll into the throttle and it stumbles. I pulled the plug last night after running the 172 and it looked good to me. I might put the 170 back in here ina bit and see what happens.
 

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Try turning in the screw to 1.5 and see if that helps at all. If you get down to 1 turn out I would try a 42 again. You can always go the other way also.
 

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Discussion Starter · #16 ·
I would have never thought to go down on the pilot. They recommend a 45 for just a stock bike rejet. Not disagreeing just goes against everything ive read.
 

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Look at my jetting in my signature, this was done on a dyno. I never would have thought a 42 either.
 

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Discussion Starter · #18 ·
Tried turning fuel screw in to 1.5 and it ran like crap....WAY worse bog, didnt really want to crank either. Came back and swapped the 172 main out to 170, turned fuel back out to 2 and it runs way better. I still cant believe what a screamer this bike is from how it was stock. I cant see ever wanting anything more out of it. Its flat dangerous in the woods and creeks....lol!
 
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