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Old 07-09-2012, 09:48 AM   #16
turd polisher
Joined: Jan 2011
Location: Midcoast, Maine
Oddometer: 1,652
I found out, as it seems are, that you can't do the changes alacarte. I tried the 5dp7 needle in the stock NJ and it sure doesn't work. Likewise, you can't use the 169 po without drilling out the air jet, or as I did tapping the carb body for thread in air jets, 2.0mm.
I wouldn't bring her home to Mama, but Mama ain't home tonight.
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Old 07-09-2012, 06:39 PM   #17
caryder OP
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Joined: Nov 2007
Location: Phoenix
Oddometer: 217
Jets and other stuff

Right. I bought the needles initially based on Economy Cycle info without knowing the whole story.

The carb mod has to work together but the crossover stands on its own, which is why I want to try the crossover before I do anything else.

All my new parts shipped today so I should have more information next weekend. I'm also modifying my beat up set of expansion chambers with O2 bungs so I can see what's going on with wideband sensors. I'm also going to try to remove the dents in the chambers.

I'll probably foul an O2 sensor in a relatively short time but they are only $35. The idea isn't to dial in the jetting (although I could) but more to see what's going on with the AFR when the bike bogs at 5K and I add throttle. I don't think too many people put O2 sensors on two strokes but maybe someone else already knows the answer.

I also intend to purchase a dyna ignition from Vintage Smoke and EGT sensors from Economy or HVC but both were out of stock of the EGT sensors. I guess the supplier stopped carrying the sensors.
2012 Honda NC700X
2006 Gas Gas 300 Pro
2003 Kawasaki KDX220R
1976 Yamaha RD400C
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Old 07-14-2012, 04:28 PM   #18
caryder OP
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Location: Phoenix
Oddometer: 217
Well, first step was installing the new manifolds with the crossover tube. Not one other change. First kick start (like normal). The motor Idle speed was about 800 RPM higher (around 2K). Reduced the idle, let the motor warm, backed the pilot air screw a half turn (2 turns out), adjusted the idle down to around 1.2k and went for a ride. Complete difference in how it runs from 2k to 6k at part throttle. Still responds well at full throttle but maybe a little softer. It started raining so I returned home after just a couple of minutes in the lower gears. Need more time on the bike, but my immediate assessment is the crossover tube has a similar effect as leaning out the low and mid range fuel circuits except the same good throttle response still seems to be there. Then from 4.5k to 6k all the rich blubbering is gone, but no surging or bucking and it makes a really smooth transition into the power band past 6k without the abrupt hit. I think this gives me a good baseline to work from.

2012 Honda NC700X
2006 Gas Gas 300 Pro
2003 Kawasaki KDX220R
1976 Yamaha RD400C

caryder screwed with this post 07-14-2012 at 04:37 PM
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Old 08-27-2013, 12:06 PM   #19
Joined: Apr 2007
Location: Ohio
Oddometer: 15
I can only think of three things to, but could be more... :-)

The porting could be part of the reason. Pro-flow used to put a number on the cylinders usually on the flats facing the inside center-line of the two cylinders. If you have that number PM and I can probably get you specs and a possible cure "if the porting is causing your issues"

Have you looked at your pilot jetting any. 30-32 maybe, are you getting any off throttle lean conditions?

Lastly, with the moto carrera pipes you can custom make flange lengths (longer or shorter) that will affect mid range a little and also when the pipes sign on.

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Old 08-27-2013, 01:16 PM   #20
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Joined: Jan 2012
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Originally Posted by caryder View Post
Ordered $170 worth of jets and crossover kit from Economy Cycle. We'll see where that gets me. I'm going to try the crossover kit by itself before I drill holes in my carbs but I'm pretty certain the Dave F. mod will be the biggest improvement. Seems Dave has lung cancer and is going through chemo.


For $100 + shipping you could have got 2 x 32mm OKO flatslides, which are very easy to jet, and would have likely have cured your problems if they are carb related.
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Old 08-27-2013, 08:31 PM   #21
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Joined: Aug 2013
Location: Rocklin, CA
Oddometer: 100
Cool! Here's my 76: (was mine anyway...)

Ya, I know.... 77 bodywork. The original was painted with a brush by the previous owner.

I was lucky enough to have a Yamaha two stroke race mechanic living in my neighborhood.
'07 FZ1 (commuter)
'08 R6 (track)
'02 KTM 200EXC (trails)
'03 XR650L (ADV?)
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