Topic: Cb550 with Cb560 camshaft - runs richer?

[titan joe]

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.

[Scott S]

 Dirty air filter?

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

[maxheadflow]

Give the motor what it wants, not what you think it needs.

[Jerry Rxman Griffin aka MuthaF'er]

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. 

[titan joe]

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.

[scottly]

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.

[Scott S]

 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?

[BomberMann650]

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? 

[Tracksnblades1]

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?

[HondaMan]

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.

[titan joe]

Wow, quite a bit of hate for drilling jets one here.

Excellent information on timing advance correlating to richness and the 650 cam lending itself to more fueling. The original jets (I think they were 98's) were too large before, I think partly to the elevation and now from what I've learned the advanced timing. I cut the springs and watched for proper advance thanks to Hondaman's helpful article on here about tuning these bikes.

As far as equal flow in the jets, I got lazy and never got the right size genuine size since it was running so well. he spark plug's had very consistent coloring.

I did find an issue I thought I had checked pretty thoroughly for before. The number 2 carb boot was a little loose and was leaking. That explains an occasional backfire I would get near idle. After cinching that down it made a difference. But not completely. I'm not convinced that the boot is sealing perfectly. That will require another carb sync to get perfect again.

Thanks guys. Back to tuning.

[RAFster122s]

Treat the bike to new boots if you have not done so already. Do not buy aftermarket as they just do not last more than a couple years and some are reporting they are not even lasting a year. Genuine Honda boots are about $40 and some shipping.  South Sound Honda in Olympia Washington is probably the least expensive Honda dealer in the US and they are very reasonable on shipping. It usually takes a week or two for them to get the parts if not in stock on and order and then whatever it takes to ship to you. Expect at least 2-2.5 weeks.

Thanks for replying with what was done to start to or was done to fix the issues.


Stay away from most condensers out there, especially the Chinese.  Seems only the TEC brand at $23/ea. are any good. Dealer carries TEC brand and few online SOHC4 suppliers. TEC brand points are well made and many of the points even when stamped as made in Japan can be Daiichi brand. I have not heard of one case of the Chinese points being easy to time and some are impossible to time correctly.  Odds are your new 2/3 points are Chinese if you had to bend things on them to get them to time them close to correct. Very common problem lately...


Oh yeah, make sure you have some thread locker on the cam chain sprocket. Another member here didn’t and bolts must not have been torqued tight enough and the gear slipped causing valves on one cylinder to hammer piston until valve broke and it destroyed head’s combustion chamber. It was in a rebuild and the carnage was on a MRiech stage 2.5 ported head which was likely a big investment with new guides and valves (I think he went oversized on the valves). It was during first ride that the damage happened...  Mike (MRiech) does fabulous work on heads for the SOHC4 motors, he is a member here...

David

[BomberMann650]

Forgot to mention, there are a hotter set of plugs in my Honda.  So instead of the d7ea - the bike runs on d6ea (iirc it's down a number for higher heat plug)

So that's how I tuned in a cb650 cam with 105 mains.

[titan joe]

I never think of plug heat. I'll have to try going with a hotter one.

I'm sure these points are Chinese. I bought a points and condensers as a kit and the points died in a week or two. I went back to the 40 year old ones. I just need to get around to putting my old points back in. I need to quit doing other people's timing belts in my spare time and instead give attention to my bike.

Genuine boots it is. I'm always amazed how quick new rubber fails from China. I was going to try RTV, but I kinda hate that stuff. Under $50 is totally worth it.

I'll have to thread lock that cam sprocket too. If I didn't already. I can't remember.