Topic: Phaedrus CB750K2 - The Project Continues

[seanbarney41]

I use a Kerker with the quietest baffle available (think it was known as street baffle)  on a stock CB750F0.  It works great and is very quiet, just barely more noise than a OEM Honda system.  Fantastic pipe!  If you ask me, hands down best 4 into 1 ever made to fit a cb750, and I have tried many different ones.  At about 85mph in fifth everything goes dead smooth and you can hear the whole intake go resonant and everything is working so perfectly airflow in and exhaust gas out and the bike is just singing.

[grcamna2]

I installed a new Kerker on the silver/blue 77' Kaw. Z1-R which I owned in 1981' and tried it w/o the baffle(the neighbors complained)  re-installed it and rode from Ma. to Fl.,enjoyed the system quite a bit.

[CBJoe]

I use a Kerker with the quietest baffle available (think it was known as street baffle)  on a stock CB750F0.  It works great and is very quiet, just barely more noise than a OEM Honda system.  Fantastic pipe!  If you ask me, hands down best 4 into 1 ever made to fit a cb750, and I have tried many different ones.  At about 85mph in fifth everything goes dead smooth and you can hear the whole intake go resonant and everything is working so perfectly airflow in and exhaust gas out and the bike is just singing.

I think the street baffle is the extra one I have which I have not used before. It came with my 836 when I bought it from Art (sparty) back in 2015'ish.  I don't remember the comp baffle being as painful as the 4-2s that were on phaedrus. 

Curious to see what it sounds like on Phaedrus...I believe it has a 910 in in it now with Mikuni 29 Smoothbores.  Here's my 836 w/ RS34 Rattle slides and the same exhaust...poor thing has been down for a long time waiting for me to get my $hit together

Going to shop tomorrow to replace some brake lines on a friends car...if I have time I'll get it started up and see.

[MRieck]

Medium Comp baffle works well in the Kerker

[Jerry Rxman Griffin aka MuthaF'er]

The street baffle is moderately quiet. Small diameter hole. The comp baffle is not obnoxious, sounds really nice under throttle and is noticeably larger dimeter hole.

[CBJoe]

Nice to hear from you Mike/Jerry....been a minute. I hope you both are doing well.  Hopefully I'll be around on the forums more as I'm getting back into my bike projects now that the Jeep and firebird are all daily driver capable though never done 

I got the exhaust all installed and did some test idling....I'll keep the competition baffle in there for now.

I am having some issues with it surging a bit at idle, and it doesn't want to idle much below 1000rpm.  But the bike has never really been broken in.  I think on its current motor setup it only has maybe 60 miles and a single dyno run.  There was so much back and forth motor work over the last 4 years its hard to remember all the things Ron had going on.

Probably time to take a step back and double check all the ignition timing, plugs, and carbs.  We have a set of 29mm Smoothbores on there now and I'll be honest I dont remember any of the jetting or needle settings.  Currently it also does not have any connections to hook a balancer up to.  So I think that's gonna be next on the list as time allows.

I have the RS34s from my other bike...but Ron was all about the smoothbores...so I'd like to get it running good with them if possible.  I have zero experience with them at this point.

Joe

[CBJoe]

Just was fishing around on rons old thread....I'm dropping this info here for future reference

Pulled the needles, which were all set on the middle notch of five. Lowered them 1 notch each, to get a little more lean in the middle. Raised the main jet 1 size from 125 to to 127.50, to richen the top end.

So I'm guessing they are 127.5 Mains and Needles at 2 notches from Bottom.

[denward17]

If he lowered them 1 notch to get leaner, he actually lowered the needle and raised the clip, so it would be in the 2nd notch from top?

[CBJoe]

If he lowered them 1 notch to get leaner, he actually lowered the needle and raised the clip, so it would be in the 2nd notch from top?

I think its all foggy    ...I'll plan to pull the carbs to go through them and verify bench sync and all the settings. It was years ago that we did this and I cant remember any of it 

[Stev-o]

I use a Kerker with the quietest baffle available...

I had a K5 with a Kerker, was not too loud, I really liked it.  Not sure which baffle...

[CBJoe]

I started it up with the Kerker and comp baffle, and it sounded good.  We'll see how it is at speed.

Checking the points and timing last night...first was confused because I couldn't get voltage at coils with static timing light...then realized it had HondaMans transistor ignition on it.  I got that bypassed and was really struggling for some reason getting 1-4 to light up at the "F" Mark.  Seemed the best I could get was at the T. 

I followed what I think is correct procedure for setting points gap.  I first put to the T for 1-4...then rotate crank appx. 90* clockwise and set gap to .012" - .015"....repeat for 3-4.  But I cannot seem to get the light to trigger at the "F"....even rotating the plate I couldn't seem to get it to fire before the "T".  Ran out of time so will go back to it next I'm at the shop.

I will admit that every bike I've ever had either came with electronic ignition, or already had a Dyna 2000 or something on it    so maybe its an ID10T error...

Joe

[CBJoe]

I got the points gap and static timing all checked and adjusted.  It seemed like if I adjusted the 1-4 points gap at the tight side of spec, I didn't have enough adjustment on the plate to static time to F.  I had to adjust the 1-4 gap to .016" and then its triggering spot on with the Fire Mark.

Prior static timing for 1-4 was hitting at TDC...I adjusted to "F" for both 1-4 and 2-3.  Still isn't idling very well, surging a bit and almost seems like a misfire. I think next step I'm going to pull the Smoothbores and go through them again.  It sat for quite a few years, so maybe there's something funky with the idle circuit.

Joe

[RAFster122s]

What clearance are you running on the valves. What idle speed? Sometimes running clearances at the tightness specified with today’s fuels can lead to idle issues.  Sometimes a little looser makes them run much smoother. Confused by what you are saying about the timing values… this is isrunning you aren’t seeing it fire at F even with full advance rpm range?

[CBJoe]

Valves were lashed to .004/.005 (in/ex) recently

I should clarify...when I checked the static timing the other day, it was incorrect and instead of triggering up at the "F" it was trigger at the "T" for TDC.  So timing was retarded.  Tonight I corrected this and verified points gap and set and verified static timing.  So ignition timing should be ok as far as I can tell.
 
Does not want to idle smooth below appx. 1100 RPM...And even there it is a fairly rough idle.  I seem to remember it idling much better a few years ago when we got it going.  But to be honest its been a long time since then.

I thought target Idle RPM was 1000...but maybe I'm trying to Idle too low for this setup?

Joe

[CBJoe]

Well crap...after reading this I think I should be happy with 1400-1500rpm

http://forums.sohc4.net/index.php?topic=131821.0

Bike has 915 with cx-7 cam.  I'll adjust and recheck next I drive down to shop. 

Sent from my Pixel 6 using Tapatalk

[CBJoe]

Let warm up and tuned idle to 1500RPM.  Ever since I first started helping Ron out years ago and heard phaedrus running, i thought the top end valve train chatter was very noticeable.  He never seemed concerned. 

To be honest...my only other CB750 had RS34 Rattleslides...so you couldnt hear anything over their rattle clack! 

[grcamna2]

Let warm up and tuned idle to 1500RPM.  Ever since I first started helping Ron out years ago and heard phaedrus running, i thought the top end valve train chatter was very noticeable.  He never seemed concerned. 

To be honest...my only other CB750 had RS34 Rattleslides...so you couldnt hear anything over their rattle clack! 

Phaedrus is a 'hungry wolf' and needs some good runs 

[CBJoe]

Lol....can do.  Weather is cooling down now. 

[newday777]

That isn't too bad of ticking, especially if it's got a cam added to it. A little loose valve setting is better especially once it warms up out on the road.

[CBJoe]

Thanks...makes me feel better.  gonna finish a nut and bolt check and add exhaust hanger next week and will put some miles on it.