If you have a 686 and stock carbs. . .

Please answer the following:

0. Head port work by? (example: Craycraft)
1. Stage 1 cam or Stage 2 cam? (example stage 1)
2. Cam Type: (Webcam, Hotcam??)
3. Compression? (example 11:1)
4. Fuel? (example, pump 91 octane)
5. Pipe? (example - Yoshi full exhaust)
6. Air filter? (example - K&N - ProDesign)
7. Riding elevation (example 4000')
8. Pilot jets sizes (example 25/25)
9. Needle position (example bottom clip) / Stock needle or other?
10. Main jet sizes (175/180)
11. How does it run? (great on the top but real bad on the bottom / mid)
12. Any other carb mods?

(My answers are above. I've shown you mine now you show me yours! [img]i/expressions/face-icon-small-blush.gif[/img])

 

All I can say is call Bob! I can't get mine perfect either, I've tryed for ever. He has a cure for these.

 

have you tried raising the floats in the carbs, air fuel mixture screws? needles all the way out?

 

I will be putting the needles on the middle clip position this weekend.

The idle screws I had at 2-1/2 and 3 turns (if I remember correctly) I screwed them in about 3/4 of a turn each after it was running so poorly.

 

1: stage 2
2: Hot Cam
3: 12.5 approx.
4: was on VP 107
5: full POS...errr I mean FMF[img]i/expressions/face-icon-small-wink.gif[/img]
6: dual K&N clamp-ons w/velocity stacks attached
7: sea level
8: 27
9: third clip
10: 190/195
11: it ran good to a point then just quit pulling
12: none then

One of the biggest things you need to check is the float level. MANY of us that switched to race fuel and really started trying to tune the carbs had BAD float problems. There are other problems as well, but the only person to take care of that would who LOWBOWTIE said, Craycraft.

Just to add one to your list; 13: How many turns out on the fuel screws (2.5/2.75)

IMO your needle looks really high.

 

Before I gave up on the stock carbs and bought FCRs, I was running:

1) Stage 2
2) Hotcam
3) 12:1 JE (Craycraft spec)
4) VP C12 (112 motor octane) but VP Red (105 motor octane) may have run a little stronger now that I think about what I had going on with the stock carbs when I tested the VP Red.
5) Yoshi full comp
6) 14mins adapter K&N, no lid
7) Sea Level
8) 27.5/27.5, somewhere between 1.75 and 3 turns out depending on the float's attitude that day
9) 3rd groove, stock needles
10) 190/195
11) Ran like a raped ape on top, bottom would bog BAD when the needle valve would leak. When I raised the floats to get enough pressure on the needle valve to seal, I ran the bowl dry.
12) I worked with Bob Craycraft on part of his new mods but there weren't fixes yet for *all* the limitations of the stock carbs, I couldn't wait. The mods I performed may or may not be part of his final package and I respect his intellectual property rights for the R&D. Call him, if he's going public it's going to be right.

You should also ask if the head was ported and who did it, you could end up with a hell of a lot of information if everyone is honest.

 

Head port work is item "0"

If anyone has a web site and we get a bunch more responses we can post this somewhere for future reference. One of the guys on the DS forum did this and it was quite helpful.

 

--------‐-----‐----------------------------------
-686 with stock carbs
- Ported and polished head with 1mm larger intake and exhaust valves.
- stage 2 cam custom grind
- hotcam
- compression 13:1 CP Carrillo piston
- 110 octane
- FMF power bomb header with FMF muffler
- stock air box with UNI air filter, no lid
- Maryland 1000- 1200
- pilot jets 27.5
- main jets.. 182.5 left side/ 185 right
- needles are dyno jets.. e clip in very bottom slot with 1 nylon spacer and 2 needle adjusters per carb.
- runs good, no bogging through out power range low to full throttle.
- port matched intake boots.

Over all I'm pleased the way it runs and gos but stock carbs are a pain in a ***. I'm limited to full potential of new engine setup because of the factory carbs, needing true dual exhaust and air intake box.