Author Topic: I think I've confused myself (carbs)  (Read 2809 times)

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Offline Lostboy Steve

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Re: I think I've confused myself (carbs)
« Reply #25 on: July 27, 2012, 07:32:12 AM »
Rule #1: if the bike burns oil, fix that first. Otherwise, the uneven compression between the cylinders will defy all attempts to make a smooth-pulling engine.

Rule #2: Millions of miles with the stock pilot jets can't be wrong. Leave those stock. You can adjust the air screw to accommodate 40% change richer (out 1/2 turn from stock setting) or leaner (1/2 turn in from stock setting). If you need to go further than this with a stock cam, see rule #1.

Rule #3: The clips on the needles adjust the mixture about 1% of the mainjet per notch, richer or leaner. Moving the needle upward makes it richer. Open velocity stacks will usually require a richer mainjet (about 5%) and the idle air screw be turned outward about 1/8 to 1/4 turn from stock settings. Be sure to provide dead air to those stacks above 30 MPH, as the turbulence of the air around your legs will strongly affect the airflow into the outer 2 carbs, causing them to act strangely. In other words, build a still-air box around the openings of those stacks for best results.

Or, just use the stock airbox, which does all this for you...

 ;)

+1... and honestly my bike feels way more powerful and smooth throughout the rpm range with the stock airbox.
1968 Honda Z50
1977 Honda CB550K
2018 Indian Scout

Offline Really?

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Re: I think I've confused myself (carbs)
« Reply #26 on: July 27, 2012, 08:15:20 AM »

HM:
#1: It burns oil, but I've wet and dry compression tested and all the cylinders are within 10% of each other. I know I should be fixing it, but I'm saving up for a full rebuild (being unemployed sucks).



So it's basically the carbs themselves that don't like the turbulent air? Switching to different carbs, say CR29s or RS34s would remedy that? (Obviously going with a more aggressive cam or big bore to go with that)

The red areas do not compute Dimitri!.   ???
I don't have a motorcycle, sold it ('85 Yamaha Venture Royale).  Haven't had a CB750 for over 40 years.

The Wife's Bike - 750K5
The Kid's Bike - 750K3

Offline lucky

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Re: I think I've confused myself (carbs)
« Reply #27 on: July 27, 2012, 02:03:54 PM »
NO NO NO!  Your all wrong!  All you need is a big bore kit.  It will solve all your problems.  More displacement, 10.5 to 1 compression, It will solve ALL your problems!


OK not really, but I'm dying to  hear how one works (big bore kit) and I can't afford to get one so next best thing is talk someone else into it  (BMFG)

Then after that comes the cams.....LOL.lol

Offline cgswss

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Re: I think I've confused myself (carbs)
« Reply #28 on: July 27, 2012, 02:10:09 PM »
Same people that have the big bore kit have a couple of high performance cams for the 550, I don't know why they couldn't do the same thing only starting with the 650 cam