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What am I on!? (Jets - CV carbs)

  • Thread starter Thread starter Macmatic
  • Start date Start date
M

Macmatic

Guest
At mid throttle (1/3?) cruising at 60mph or so in 5th I feel a little surging, not bad but some. I raised the needles one notch from middle notch and it seemed to help some but its still there. Should I drop the e-clip to the lowest notch or try a half turn out on the air screws? Out is richer I think?

Going to buy the bolt now...
/\/\ac
 
I doubt that 1/3 throttle is 60 mph in top gear. More like 1/5 throttle.
But you have the right idea. You should test the jet needles at a solid 1/3 throttle. Use tape and mark your throttle housing and grip. Do what the plugs/performance say. Always "chop" the bike off.
If you're raising the needles I assume you've made intake/exhaust changes.
If you have pods or removed the airbox lid or modified the box, remove the two floatbowl vent lines to avoid fuel starvation.
Be sure carbs are synched well to get accurate reads and as a basic part of jetting.
Don't forget to oil the pods if they require it.
Yes, turning the mixture screw out richens the mixture. This will have the most effect at closed/nearly closed throttle position, though there's some overlap effect with the jet needle at lower speeds/smaller throttle openings.
 
KEITH KRAUSE said:
I doubt that 1/3 throttle is 60 mph in top gear. More like 1/5 throttle.
But you have the right idea. You should test the jet needles at a solid 1/3 throttle. Use tape and mark your throttle housing and grip. Do what the plugs/performance say. Always "chop" the bike off.
If you're raising the needles I assume you've made intake/exhaust changes.
If you have pods or removed the airbox lid or modified the box, remove the two floatbowl vent lines to avoid fuel starvation.
Be sure carbs are synched well to get accurate reads and as a basic part of jetting.
Don't forget to oil the pods if they require it.
Yes, turning the mixture screw out richens the mixture. This will have the most effect at closed/nearly closed throttle position, though there's some overlap effect with the jet needle at lower speeds/smaller throttle openings.
Click to expand...


My intake is stock other than a foam air filter insert and the exhaust is... half stock. I've got the stock header going into two Hayabusa mid pipes and canisters. I bench balanced and then used a carbtune II to synch the carbs once I had it running.
Right now the air jets are about 3 turns out. I had them at 2.5 turn but tried another .5 turn yesterday. It made no difference I could see other than maybe making it more likely to stall when cold so I'm going back to 2.5 turns out. I came to 2.5 turns by the "highest idle" method and once balanced I set my idle to about 1100rpm.

Will it do any harm to remove the vent lines even if the intake is more or less stock? If I accelerate to say...70mph, pause and then quickly go up to 80mph (all in 5th) its smooth but if I cruise at 70mph and then go to accelerate up to 80 it feels sluggish/not the same.

The bike is very rideable now, in fact I rode it to Atlanta this past week from New York. 8O I'd put on 600 or so miles in NYS and snow was coming...so I strapped on the bags and headed south. It was a nice trip, no problemsand I now know she starts fine in 26F weather.

/\/\ac
 
Low Speed: The pilot screw, slow jet, control the air-fuel mixture from Idle to 1/4 throttle

Mid-Range: The jet needle/needle jet control the air-fuel mixture from 1/4 to 3/4 throttle

High-Speed: The main jet controls the air-fuel mixture from 1/2 to full throttle

Make sure that none of your jets or air bleeds are pluged and your jet needle is not gumed up. check your float leve If its too low your bike will run lean so try adjusting your float level up. synchronize your
carburetors



the pilot screws are only for idle to 1/4 throttle
raise the needle another notch or shim witch ever applys
 
With a stock airbox except for a foam filter, removing the vent lines shouldn't change anything. Just be sure they're clear/not kinked. But if you like, try removing them?
Be sure the foam filter is oiled with filter oil.
Sounds like the mixture screws (not air jets) were adjusted correctly.
I always check ignition timing/advance action with a gun too.
Be sure this "lean condition" isn't related to fuel flow. Gas cap vent and petcock must be operating right. If you put the petcock to prime and plug the vacuum line, does anything change?
Fuel flow can be slowed by a dirty float valve screen or sticking float valve too. Only takes one carb to cause your problem.
I have no idea how your exhaust mod will effect the jetting.
If you believe the carbs are clean/synched/no intake leaks and float levels are correct, then you can focus on the jetting. If the 1/3 throttle test shows lean plugs, raise the jet needles. I'm assuming you have a jet kit and may have initially set your needles at the jet kit recommended base settings? I've found the needle base settings to be lean almost always.
As always, if all the basics are done first, test and do what the plugs say.
 
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