Carb Jetting

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  #1  
Old 03-09-2012, 10:33 PM
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Default Carb Jetting

OK, 351 & pumper carb, I think I am pretty close on the main jet (130)..... but I am getting poor mileage. My pilot adg is about 1-1.5 out I think. I did a ATV trail with a healthy bunch of throttle twisting & only got 37.5 mpgallon. But this was not a difficult ride.

I was thinking of going to a vehicle smog test garage and have them put it on the machine..... would I get any usefull info out of this or does someone have a better idea.

The bike it running pretty good, but getting a definitive setting short of pulling the engine & finding a dyno is difficult.

351, 33 pumper, 3300 ft elev, stock everything else.
 
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Old 03-11-2012, 11:45 PM
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Did a little more research, seems like a wide band sensor & display may get some good info to see where the jetting is. I think I'll check into some of the local mech shops to see if they have one available.
I am thinking trying to get to A:F of about 14.7:1 under load.
Anyone ever use this?
 
  #3  
Old 03-12-2012, 12:04 PM
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I have a dynojet wide band that I use for my 10r. Welding a bung in the exhaust is generally the most difficult issue in order to place the sensor. That should be included with every exhaust now adays in my opinion.
 
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Old 03-12-2012, 12:28 PM
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You can run on a dyno and leave the motor in the bike and most of the places also graph your afr for tuning.
 
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Old 03-12-2012, 12:32 PM
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Originally Posted by linkin5
You can run on a dyno and leave the motor in the bike and most of the places also graph your afr for tuning.

that is true and about the same cost as a smog test

edit: I need to drive 4 hrs for the nearest dyno around here.
 
  #6  
Old 03-13-2012, 03:28 AM
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I ordered a wide band O2 sensor today.... interesting story to follow at the end of the month when I get back home.
 
  #7  
Old 03-30-2012, 03:06 AM
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OK, got the (Fuel to Air Ratio) wide range sensor installed and headed out to the biggest hill around I-17 south from camp verde. It took a while for the sensor to burn in as I was reading initially around 19-20. After burn in it went down to 13 WOT @ about 70mph-ish. Way to rich. MJ 135 (I thought I had a 130 in it, but not. Boys remember to write these things down as they are important).
Changed MJ to 125 and hit the road again, only I didn't go back to the big hill, the gauge will settle in pretty fast so picked a shorter hills around the house.... reading went to 16.5 ish on WOT in acceloration. The engine was stumbling a little on WOT. It pulled from idle very crisply though and at part throttle at normal speeds the reading were in the 13-15 range.
Therefore, I beleive 130 will be very close. I think I'll take the bike up to 7500ft elev and see how it goes next week though before I do anything, I am thinking of taking it to CO in August, so I may just live with it till then.

Putting the bike away I found the part in the picture... anyone know what it is? It is suppose to snap together around a cable/hose/wire? and then it may be a grommet? It may be off my bmw 650, if it is.. now I am worried.

The bike was dead when I tried to start it, had to bump start it. I removed the battery and topped off the water in it. I think I put too much in as after I started it, water was leaking out of it as it was boiling over. Oh well, it was really dry from the heat around here.
 
Attached Thumbnails Carb Jetting-part.jpg   Carb Jetting-install.jpg  

Last edited by durielk; 03-30-2012 at 03:13 AM.
  #8  
Old 03-30-2012, 04:31 AM
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  #9  
Old 03-30-2012, 11:02 PM
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jhoffy, I see the part you are holding up, but not very clear. The part I have when you get it hooked together has a smooth exterior cylinder shape like it is a grommet for a cable that passes through it, then it goes in a hole.
That is near the rear of the bike, where I was messing with it, but where does that thing you are holding up go?
 
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