Author Topic: Slow jets, + Different floats ok or no go?  (Read 1210 times)

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Offline nixon

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Slow jets, + Different floats ok or no go?
« on: March 12, 2017, 05:57:10 PM »
I got a used set of  K4 round top for my auto..its now got 110 main but i forgot to check slow.

 It did have 130 main prev- used on big bore engine i think, so maybe slow bigger than 40.

what problems would too large a slow jet be? it seems to idle ok..but stutters quite a lot at stead throttle. under acceleration feels ok

The bike has 25k miles, no engine work except k4 cam, breadbox filter, more open exhaust

Also noticed the 2 inner floats are metal, outter plastic, is that ok?  Was about to buy kits, with or without bowls, happy to pay the $ if may fix issue!

« Last Edit: March 12, 2017, 06:00:35 PM by nixon »
cb750a 77, cbr900rr 93 with auto clutch

Riding tip " turn in late, feeling great.  Turn in early,  feeling squirrely "

Offline drumstyx

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Re: Slow jets, + Different floats ok or no go?
« Reply #1 on: March 12, 2017, 06:06:07 PM »
Floats shouldn't be a problem, but you'll have to measure the fuel level rather than float height, since at least 2 of them are the 'wrong' ones. You should do that anyway though of course.

Offline nixon

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Re: Slow jets, + Different floats ok or no go?
« Reply #2 on: March 13, 2017, 12:41:45 AM »
appreciate the input..will need to investigate what that means..not sure how to do either.. if setting float height is easier with 4 the same..ill just get ne ones.

i have minimal experience with carbs, if thats not obvious hehe


cb750a 77, cbr900rr 93 with auto clutch

Riding tip " turn in late, feeling great.  Turn in early,  feeling squirrely "

Offline flybox1

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Re: Slow jets, + Different floats ok or no go?
« Reply #3 on: March 13, 2017, 06:35:15 AM »
Measuring the fuel level =  Clear tube test.

http://forums.sohc4.net/index.php?topic=149299.0

'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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Offline evanphi

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Re: Slow jets, + Different floats ok or no go?
« Reply #4 on: March 13, 2017, 07:01:15 AM »
He's got roundtops so they won't look like that photo.

Here ya go:

The bottom of the meniscus sits right at 3mm for all the carbs. I measured them all off the same carb so they're as equal as they're ever gonna get! They all had to come up about 2mm.




Pro tip: If you want to raise the float height without removing the float (and losing your needle) each time, you can reach in there and give the tang a pinch (to lower it) with some long-nose needle pliers. If you need to lower your fuel level, raise the tang up with a flat screwdriver. The hose for mine is made with an old drain plug that I cut the head off, and jammed onto a piece of 1/8" fuel line.


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Offline evinrude7

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Re: Slow jets, + Different floats ok or no go?
« Reply #5 on: March 13, 2017, 07:04:16 AM »
i imagine that you have to keep the petcock open when doing the clear tube test, correct?  the amount of fuel that fills the clear tube would essentially lower the amount in the bowl if the petcock was closed.
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Offline nixon

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Re: Slow jets, + Different floats ok or no go?
« Reply #6 on: March 14, 2017, 01:49:16 AM »
thanks so much! makes more sense now..
cb750a 77, cbr900rr 93 with auto clutch

Riding tip " turn in late, feeling great.  Turn in early,  feeling squirrely "

Offline drumstyx

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Re: Slow jets, + Different floats ok or no go?
« Reply #7 on: March 14, 2017, 06:53:23 AM »
i imagine that you have to keep the petcock open when doing the clear tube test, correct?  the amount of fuel that fills the clear tube would essentially lower the amount in the bowl if the petcock was closed.

Correct. Also don't make the column of fuel shorter once its extended -- you'll be feeding the fuel back into the bowl making the level high.

Offline jonda500

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Re: Slow jets, + Different floats ok or no go?
« Reply #8 on: March 14, 2017, 02:45:21 PM »
i imagine that you have to keep the petcock open when doing the clear tube test, correct?  the amount of fuel that fills the clear tube would essentially lower the amount in the bowl if the petcock was closed.

Correct. Also don't make the column of fuel shorter once its extended -- you'll be feeding the fuel back into the bowl making the level high.
+1 this is vital if you want an accurate reading - tape or tie the clear tube securely to the side of the float bowl before turning the fuel on
John
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