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Discussion in 'Old's Cool' started by tom c, Aug 14, 2019.
Hey, Tom, it might be worth checking the #3 exhaust for a possible restriction.
Have you checked the exhaust for that cylinder to see if there are any restrictions? If the exhaust is more restrictive than the others it would also run rich. I found that the stock jets are too lean, I went up on the main to a 105 and lowered the needle, up 1 click to position #3 and it screams. It is a 74 with stock carbs.
I will! Reminds me of when I was working on @goosecreek 's CT90.... Fully blocked exhaust!
I took pipes #3 & 4 off and there seems to be no difference in restriction at least as far as my "blow through it like it was a tuba" test.....
Use the shop vac.
When I last reported on this thread I had still not solved the mystery of cylinder #3 fouling:
I thought I had found the cause when I found problems with the spark plug cap resistances. After replacing the ignition coils, cables and caps, the situation was no better. Consistent fouling of the plug in cylinder #3.....
Check the compression again: no change - all readings within 10%
Switch out the jets between carb #3 and #4: no effect
Switch out the spark plug wires between cylinder #2 and #3: No effect
Re balanced the carbs: no effect
Hotter plug in cylinder #3: no effect
Check and adjustment of float bowl fuel levels using the tube method: no effect
Air mixture screw of carb 3 turned out to lean out the mixture: no effect
Not sure what else to do now, so I read through Hondaman's CB750 book again, paying particular attention to the carb section that includes a story about how plug fouling can be the result of a blockage in the air passage between the carb inlet and the emulsifier tube.
I took the carb rack off the bike - again - and rechecked all the air and fuel passages in carb 3, paying particular attention the that air passage to the emulsifier tube, circled in yellow in the photo below:
I sprayed carb cleaner into the hole and it all shot right back at me - straight into my eye! Ugh.....
Sure enough, it was clogged in carb #3 and unobstructed in the other 3 carbs. So I corrected that situation and buttoned everything up yet again (I am getting really good at removal and installation of the carb bank!).
Went to start her up - no juice in the battery.... (I had left the ignition on) Sigh.
...oh wait, this bike has a kick starter! She starts right up on the first kick and sounds great!
I put on my gear and took her for a short ride and the bike has never felt so powerful! I'd been running on less than 4 cylinders for all the time I've owned the bike - it felt like a million bucks! Back home I put her back up on the lift and pulled the #3 plug, which was clean and happy!
Time for a Manhattan!
That's awesome, Tom.
After some minor jetting tweaks suggested on the SOHC/4 forum and replacing the stock D7ES plugs with one heat range colder plugs, I took the 550 out yesterday in an attempt to grab the DelMar tag. The tweaks were not successful so I aborted the TOR and headed home to untweak the carbs. As soon as I put it up on the lift I noticed that the left side cover was (again) missing.... dammit. I found it a couple of miles away on the side of the road. Fortunately the damage was minimal
the badge broke off and has not yet been put back on other than that the damage is the nicks towards the front of the cover.
I don't want that to happen again so I drilled a small slot into the top of each side cover that I can use to loosely zip tie each side cover to the frame:
Carbs were reset to factory specs and the original plugs put back in, I went for another ride - the engine felt much better, pulling on all 4 cylinders again. I pulled the plugs this morning to take a look see and was pleased to see four happy plugs:
Maybe I'll go grab that tag today......
Well I did go grab the Delmar Tag yesterday:
...this guy's driveway is a friggin runway! Interesting.
Anyway, as soon as I switched to the reserve tank the bike ran like crap, I limped along for 5 miles or so until I filled the tank up, after which she ran great again. I ended up having to clean out the middle hole on the bottom of the tank where the petcock goes:
I had not gotten all the paint residue out of it before mounting the petcock, so when the petcock was switched over to reserve there was very little clearance betweeen the tube and the hole so fuel was in short supply when on reserve. I cleaned it up and reinstalled the petcock so now things are good again.
Beautiful, Tom. Quite the trial and error on this one but it is coming together nicely!
Safety glasses. I have done the same thing.
I fitted the painted side boxes to her today. I like them!
@goosecreek says he needs to repaint the boxes more in style with the tank. Who am I to argue? :)
She looks pretty good without the boxes:
Beautiful bike. Are the stripes on the tank painted or a decal? I need to repaint my 74 and the PO painted it all 1 color. I have seen some as decals and some are painted. Did you also replace the chrome trim on the tank or just clean it up? If you replaced it where did you get it from?
Those are decal stripes purchased from reproductiondecals.com - the decals are for the black, white and gold stripe only - the large black area is painted.
The tank trim was purchased from Amazon - NASU Chrome Trim Molding for Honda Fuel/Gas Tank CB500 CB550
Thanks for the info, did you clear coat over the decals on the tank?
I did years ago.
...of course. My painter is a professional!
When I first put the luggage rack and top box it looked kind of funny hanging way off the back of the bike:
It hung way off the back , well beyond the light. I think it must have been designed for a later model of the CB550.
The original mounting hole for the rack that goes into the shock mounting hole is clearly wrong for this bike. I decided to chop off the end that mounts to the shock mount.
Then I used a strap to connect what was left to the shock mount - as you can see above.
This allowed me to use the other hard mounting point to connect the rack to where the turn signal and grab bar mount is:
This resulted in the rack sitting much farther back on the bike:
Looks good so far. How 'bout with the top box?
I like it!
I've not yet attached the box, but so far so good.