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Author Topic: Cb550 with Cb560 camshaft - runs richer?  (Read 203 times)

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Offline titan joe

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Cb550 with Cb560 camshaft - runs richer?
« on: October 08, 2019, 10:58:02 pm »
My bike always seems to need leaning out every time I mess with it.

I found a parts motor of the CB650 type with a good camshaft. My original 550 camshaft had two intake lobes that were ground down by sideways rockers. It's been running great for the whole past year after I got everything dialed in. The plugs looked awesome. On a 40 degree day I could start it up and walk away after less than 30 seconds and the bike would idle on it's own. The state of tune was great.

I swapped in my 650 cam and adjusted my points and it's been like starting over again. I wish I hadn't messed with the points, but It took a while to get them set correctly again. My cam sprocket holes are slightly elongated so I can get my cam lined up perfectly with the crank.  Getting the timing set to a little advanced helps out the bottom-end power a ton, but it generally rich. Interstate cruise is way too rich, but the bike now wants to idle a little rich. I was expecting after a cam shaft swap to it running lean. I need to go down with my main jet it looks like, but I can't figure out why the idle wants to be rich. Before my fuel mixture looked dead on. There was no soot on the plugs, no white stuff and no black stuff. I probably only had 500 miles on these plugs, but I had done lots of mixed driving.

When I first got this bike up and running I had to lean it out a bunch and I'm running an air box without a lid.

My modifications are mild: I'm running no cylinder base gasket for more squish, I've smoothed the ports as hondaman suggested and knifed the valve guide bosses. I'm also running an aftermarket exhaust with a custom straight through fiberglass packed muffler. And I had to lean it out to get that dialed. Now it looks like I need to go down a few more sizes for the jets.

Does any of that make sense?

I'm using a wideband O2 sensor for detecting my AFR.

Online Scott S

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Re: Cb550 with Cb560 camshaft - runs richer?
« Reply #1 on: October 09, 2019, 03:21:13 am »
 Dirty air filter?

 And you made no mention of mixture screw settings. Or, for that matter, jet sizes or clip position.
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Offline maxheadflow

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Re: Cb550 with Cb560 camshaft - runs richer?
« Reply #2 on: October 09, 2019, 07:36:56 am »
Give the motor what it wants, not what you think it needs.

Online Jerry Rxman Griffin aka MuthaF'er

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Re: Cb550 with Cb560 camshaft - runs richer?
« Reply #3 on: October 09, 2019, 08:47:48 am »
IF you have the wideband sensor you have a great tool to tell you where you are with your jetting. I would suggest one size change at a time. 
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline titan joe

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Re: Cb550 with Cb560 camshaft - runs richer?
« Reply #4 on: October 10, 2019, 08:06:15 pm »
Making sure the air filter is nice and clean is a simple thing I've overlooked.

The jets I'm running are actually a set I got from 4 into 1, soldered up and drilled to a smaller size. When I did that, it was excellent. I also lowered the needle a notch. I can't remember what I figured the jet size ended up being, it went down from the original jets, which I think were 98's.

Time to get the soldering stuff out again. I was just hoping for more jet because of more air and that means more power. I want to recondition the old points and reinstall them since these new points disappoint. They've been working, but the 2-3 point set is a little snaggle-jawed. The timing light shows the timing to bounce around every other ignition event.

I'll follow the advice and give it what it wants.

Also on my list is another carb sync, since I found a loose boot clamp and signs of the minor back fire I've been noticing. It's been getting better, but I feel like it's still not to where I had it with a bad camshaft.

Offline scottly

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Re: Cb550 with Cb560 camshaft - runs richer?
« Reply #5 on: October 10, 2019, 08:14:41 pm »
Making sure the air filter is nice and clean is a simple thing I've overlooked.

The jets I'm running are actually a set I got from 4 into 1, soldered up and drilled to a smaller size. When I did that, it was excellent. I also lowered the needle a notch. I can't remember what I figured the jet size ended up being, it went down from the original jets, which I think were 98's.

Time to get the soldering stuff out again. I was just hoping for more jet because of more air and that means more power.
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Online Scott S

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Re: Cb550 with Cb560 camshaft - runs richer?
« Reply #6 on: October 11, 2019, 02:56:11 am »
 Jets are cheap, why in the world are you soldering them up? And do you have various sizes of jet drills? How do you know what size they are when you're done?
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Offline BomberMann650

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Re: Cb550 with Cb560 camshaft - runs richer?
« Reply #7 on: October 11, 2019, 10:51:20 pm »
Don't have that that trouble with my bike.

Similar mods, less dramatic porting.  105/42 jetting with 022a needles clipped in center.  Think it's somewhere around 2.5-3 turns out on the ad screw.

How's the carb sync? 
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Online Tracksnblades1

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Re: Cb550 with Cb560 camshaft - runs richer?
« Reply #8 on: October 12, 2019, 05:26:20 am »
Making sure the air filter is nice and clean is a simple thing I've overlooked.

The jets I'm running are actually a set I got from 4 into 1, soldered up and drilled to a smaller size. When I did that, it was excellent. I also lowered the needle a notch. I can't remember what I figured the jet size ended up being, it went down from the original jets, which I think were 98's.

Time to get the soldering stuff out again. I was just hoping for more jet because of more air and that means more power.

STOP. Move away from the motorcycle. ::)

How are you mantaining enough precision in the drilling process to achieve 4 jets that flow equally?
« Last Edit: October 12, 2019, 05:29:20 am by Tracksnblades1 »
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Offline HondaMan

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Re: Cb550 with Cb560 camshaft - runs richer?
« Reply #9 on: October 12, 2019, 10:02:34 am »
You're just fooling yourself if you are drilling your own jets....I've been building precision automation machinery for almost 40 years and I know it cannot be done by hand from that experience (despite what 1970s dragrace articles might say...).

First thing: advancing the spark timing on the 550 intake system WILL cause rich running. Retarding the timing advance RATE (i/e/ stiffer springs, like cutting off a half-turn or full turn from one or both advancer springs) will help it immensely: just ask Mooshie about Dash for the most recent proof of this (which I did for her). Then set your full advance to hit those full-advance marks.

Second thing: go to JetsRus.com and get some genuine Keihin jets in size 98. The increased (and earlier) cam timing of the 650 cam needs less jet than the 550 did, as the 550 had a short intake duration cam.
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