Topic: carb help, please

[traveler]

Carb help, please.

I initially tried to run my bike with the stock jetting with pods, and the 4-2 MAC mufflers on the stock headtubes.  As expected, it would only run with the choke on, and barely at that.  The pilot jets are 42, and the mains are 90's.

So, I went ahead, and installed some 115 main jets.  Good news!  She will run now just like she is suppossed to....until you hit 4,800 RPM, then she falls flat on her face!  It plain won't go!  To increase speed, you have to back off the throttle and wait for it to gather speed.

Once I got back to my garage, I started the bike up in neutral and revved it wide open and killed the engine by turning the key off.....I pulled the #1 plug, and she looks lean.....I also noticed that the headtubes looked a tad bit yellowed....

Now, I know that if the pipes blue, then it is rich.....and if the plugs are black, it is rich.  But, these plugs are showing lean, the pipe color shows lean, and she runs great until 4,800 RPM, so the question is....

Do I need to just step up the main jet a bit more or what?

Thanks in advance.

~Joe

[HondaMan]

Carb help, please.

I initially tried to run my bike with the stock jetting with pods, and the 4-2 MAC mufflers on the stock headtubes.  As expected, it would only run with the choke on, and barely at that.  The pilot jets are 42, and the mains are 90's.

So, I went ahead, and installed some 115 main jets.  Good news!  She will run now just like she is suppossed to....until you hit 4,800 RPM, then she falls flat on her face!  It plain won't go!  To increase speed, you have to back off the throttle and wait for it to gather speed.

Once I got back to my garage, I started the bike up in neutral and revved it wide open and killed the engine by turning the key off.....I pulled the #1 plug, and she looks lean.....I also noticed that the headtubes looked a tad bit yellowed....

Now, I know that if the pipes blue, then it is rich.....and if the plugs are black, it is rich.  But, these plugs are showing lean, the pipe color shows lean, and she runs great until 4,800 RPM, so the question is....

Do I need to just step up the main jet a bit more or what?

Thanks in advance.

~Joe

With results like this, I'd stop playing with the mainjets and such and look for vacuum leaks first. On the 550 in particular, the O-rings inside those castings where the manifolds bolt onto the heads are usually stiff and thin by now. Get new ones and install them, then re-evaluate the jetting situation.

Last summer, someone brought me a cafe 550 in exactly the same shape as yours, with identical equipment, all the way down to the 115 mainjets. After a tuneup, proper valve lash settings (inlets far too tight), cam chain adjustment, and new O-rings in those castings, we went to 100 mains and the bike hit 95 MPH at 6500 feet altitude, sitting upright on the bars. 

[scottly]

we went to 100 mains and the bike hit 95 MPH at 6500 feet altitude, sitting upright on the bars. 

Wasn't that rather uncomfortable, sitting upright on the bars??? 

[traveler]

Carb help, please.

I initially tried to run my bike with the stock jetting with pods, and the 4-2 MAC mufflers on the stock headtubes.  As expected, it would only run with the choke on, and barely at that.  The pilot jets are 42, and the mains are 90's.

So, I went ahead, and installed some 115 main jets.  Good news!  She will run now just like she is suppossed to....until you hit 4,800 RPM, then she falls flat on her face!  It plain won't go!  To increase speed, you have to back off the throttle and wait for it to gather speed.

Once I got back to my garage, I started the bike up in neutral and revved it wide open and killed the engine by turning the key off.....I pulled the #1 plug, and she looks lean.....I also noticed that the headtubes looked a tad bit yellowed....

Now, I know that if the pipes blue, then it is rich.....and if the plugs are black, it is rich.  But, these plugs are showing lean, the pipe color shows lean, and she runs great until 4,800 RPM, so the question is....

Do I need to just step up the main jet a bit more or what?

Thanks in advance.

~Joe

With results like this, I'd stop playing with the mainjets and such and look for vacuum leaks first. On the 550 in particular, the O-rings inside those castings where the manifolds bolt onto the heads are usually stiff and thin by now. Get new ones and install them, then re-evaluate the jetting situation.

Last summer, someone brought me a cafe 550 in exactly the same shape as yours, with identical equipment, all the way down to the 115 mainjets. After a tuneup, proper valve lash settings (inlets far too tight), cam chain adjustment, and new O-rings in those castings, we went to 100 mains and the bike hit 95 MPH at 6500 feet altitude, sitting upright on the bars. 

Cool.  Thanks!

~Joe

[Retro Rocket]

we went to 100 mains and the bike hit 95 MPH at 6500 feet altitude, sitting upright on the bars. 

Wasn't that rather uncomfortable, sitting upright on the bars??? 

I bet it looked pretty cool...

Mick

[traveler]

I just ordered the O-rings through Western Hills Honda.

Thanks again.....I'll get back with results from this.

~Joe

[scottly]

Nice looking bike there, traveler! Where is the tank from?

[Retro Rocket]

Nice looking bike there, traveler! Where is the tank from?

It is a very tidy looking ride isn't it....

Mick

[traveler]

My CR750 style tank and seat were hand beat and welded out of thin aluminum.  I paid extra to have him polish them out.  He is a true craftsman, and the stuff DOES cost major bucks, but if you want alloy instead of fiberglass, then you have to "pay to play" I guess....

www.roccitycafe.com

Sean is the owner and fabricator.  He does nice work!

~Joe

[traveler]

Well....installed the new intake O-Rings and with the 115's she REALLY rips until 5,000 RPM then hits the wall again......so, I put in some 125 mains, and it runs worse.  Also, If I rev the engine up when warm, the rev's won't drop to idle unless I turn the idle knob out and then turn it back in to get the idle back at 1,200 RPM.

So, it looks like it's back to 115 mains, and raise the needles one notch.

Any help or comments would be MORE than appreciated!

~Joe

[scottly]

Plug chop at 5k rpm please..
Edit: also check timing advance is working properly.
Vacuum leaks tend to rear their ugly heads at lower, rather than higher rpms.

[traveler]

How do I check if timing advance is working?

[scottly]

Quick and dirty test is to twist the point cam and make sure it rotates freely and returns on it's own. Scientific test is done with a timing light and tach.

[traveler]

Ok, thanks.....But according to the manual, advance starts at 1,150 RPM and full advance is at 2,500 RPM......everything is perfect until 5,000 RPM.

I'm going to drop the 115's back in, and do a plug chop at 5,000 RPM.

Thanks again,

~Joe

[bwaller]

A sticky advance may hold revs up though.

Try 117.5 mains, as I mentioned to you not sure why you'd need them, but one thing at a time.

When it "hit the wall" at whatever rpm, did you get an improvement pulling the choke?

[dave500]

maybe a little exhaust back pressure?5000 is nothing for these motors.i tried and tested to plug my exhaust outlet to what i use now,i never had your real lean out though,have you got a timing light?this must be done first before you chase fuel trouble.

[steam-powered man]

you may be in the transition where the needle clip placement still has an affect.

my 77cb550k w/pd46a carbs, pods and oem 4/4 "hit the wall" at about 6000rpms, i lowered the clip position and it now screams to 8000rpm (haven't dared to run my pride to redline, although she pulls to 85/90mph easily).  strong power everywhere, no popping on decel, etc.  here's my set-up, 0-2000ft el.

pd46a carbs
pods w/oem 4/4
mains -- 105
idle jets -- 42
clip position -- 4th down
a/s -- 2t
needle -- e2350f
floats -- 14.5mm
ngk 5ohm caps
relative compression, cold--150, 155, 160 and 150psi

[traveler]

Thanks, guys!

More to fiddle with.

~Joe

[traveler]

Today was a day of more fiddling, and I am kind of frustrated right now.

I went ahead, pulled the carbs, and fixed the float in the #1 carb.  I checked the float height, and they were all the same when I buttoned it up.  I also turned the fuel on and pushed up on the float and ensured the float needle was working, and I already know that the float is good becasue I floated it in water yesterday.  So, I went back to the 115 mains, put the pods back on and did a WOT plug chop.  #1 was a little rich, #'s 2 & 3 were pretty good, but a tad lean, and #4 was spot on.

I then pulled the pods, and installed the factory air box with the lower vent plugged with a bolt, and my air filter adapter still on, but with the filter off.  Took her for a short ride....bike just felt sluggish, and did a WOT plug chop....looked the same as with the pods for the msot part....#1 rich, the rest tan/beige, but when I pulled the air box there was wetness in each of the rubbers, so I know that was rich.  I then removed the metal air filter bracket I had made earlier on the airbox, and re-installed....tried to start the bike....she didn't wnat to run, pulled the choke....still didn't want to run....(must be WAY lean.....but then the battery went dead.

So...the battery is charging....and I don't know what the hell to do.  I feel like just getting rid of the bike right now.

I'm playing with the idea of using some paper and start blocking off the air inlet on the airbox until I am blocking off enough air flow to get her to run...and then I'll know how to build a mesh filter of some sort.

The carbs are PD46A model with 42 pilot, 115 main, and needles in stock position.  

i guess I'm just going to have to read some more and get motivated to do something new with it....as it stands right now, I'm kinda burned out.

~Joe

[Zaipai]

Well what plugs are you using? Have you tried different types? I put pods (with filters, not the cone type) on mine, with the Mac 4-1 and she pulls hard to at least 8k, I have not gone further, because I tend to baby her. I did manage to hit just over 70 in like a 1/4 mile or so. The odd thing is I never touched the jets or any thing else bike was warm and choke wide open. The only thing I did was bench sync them and that is it. That said, I really have no idea if how it runs is the way it should run, i just know I am happy with it. I also know I never want to hit 90+ mph with this bike..

So that begs the question, is it the carbs or some thing else? These bikes can run a tad lean or rich and still pull like they did when new, so I would not focus too hard on how rich or lean it is as long as it's close. However, things like coils, advance, plugs. condensers etc all play a role. Even new condensers can go bad, and all the things Handaman said, tho I am not saying that the condenser is the issue.

However I understand you are burnt out so try not to think about it and give your self a brake and come back with a fresh take on it and see how it goes then.. Sell it.. well if you must.. However it would be a shame cause that is one dandy bike you got there..

.: Scott :.

[TwoTired]

First, I'd want an explanation about why the plugs don't all have the same deposits.

Is compression equal?
Are the valves adjusted with equal gaps?
Is your camshaft worn unevenly?

If these check out, then its carbs.
Are they vacuum synced? 
If so, you need to find out what is different between the carbs that would explain cylinders not operating equally.

Cheers,

[traveler]

Well, I wish you were nearby, I'd pay you to straighten this darn thing out for me.

Since you're not, I'm going to go ahead and start going through EVERYTHING.  I'm going to check the valves, switch over to breakerless ignition, and go through the carbs, set them up just like "shoemaniii", as he has the same setup I have, and sync them.  nobody around here has a vacuum sync, so I will have to bench sync them and live with it.

At some point, I'm going to throw it on a trailer and drop it off with one of you guys to fix what I can't....but I will be there to watch and learn.  Honda man is right on the way to my GF's house in Colorado Springs, so that's easy....getting him to do the work...that is the HARD part!

~Joe

[Zaipai]

nobody around here has a vacuum sync, so I will have to bench sync them and live with it.

I have a set I can ship to ya, as long as when you are done you ship them back..

.: Scott :.

[traveler]

WOW!!

That is awful nice of you, Scott.

Sure, I'd borrow them.....I need to get everything set first, then use them.

Did you make them yourself?  I need to get a set to keep!

Did you see the GS550 I am looking at?  I posted about it.  I'm not sure it's worth it....I'd rather have a CB750 SOHC of course, but could turn it for a profit pretty easy.

Anyway, back to my carbs on the racer......any advice from anyone is appreciated!

~Joe