Topic: 1978 Honda CB550K: Project *Education* Now W/ Video

[OneWheelDrive]

Thanks all!  I'm kinda an "all or nothin" kinda guy.  Plus my wifey works nights so I've got quite a bit of guilt free wrenchin' time on my hands.

The last few days have been interesting to say the least.  On Sunday it was 80 degrees and beautifully sunny here in San Diego(anyone catch the Charger's game?) so I figured I would get out on the 101 and cruise around.  I put about 25 miles on the bike and was able to get to know her a bit better.  There were definitely some issues I'm keeping track of and troubleshooting.  Between the intermittent issues, there were bursts of pure riding bliss as I powered up through the gears and got a taste for what these machines are capable of.  I was careful to avoid traffic and busy intersections as I still don't have turn signals  .

First eccentricity she has is tranny wise.  Occasionally when sitting at a stop light in neutral, the light will turn green and I'll press down into 1st and it just won't wanna go.  With a little rock back and forth (stressful with a line of cars behind you, especially the first time) and a click up, then down, she'll drop into first and be good to go. 

As I mentioned in my last post, there are definitely some carb issues.  My 2 and 4 cylinders are running much colder, as judged by a thermocoupler at the header.  After running for 1/2 hour or so I was only up to about 120 F on the cool pipes and 280 F or so on the 1 and 3 pipes.  Since they are not run by common coils I'm assuming it's an air/fuel issue not a fire issue.  So tonight I'm going to break them down again and make sure the jets are clear.  While I'm in there I'm going to measure the float heights and likely move the needle jet clip to the stock position (2nd from the bottom, right?).  The weird thing though is that it smells a bit like it's running rich, so wouldn't that be an air flow issue not a fuel delivery issue? 

I preemptively ordered a new UNI air filter, don't know why I put it off.  I know, I know, that ratty foam P.O.S is probably causing some major breathing problems.  I also noticed there are a few cracks in the rubber boots between the airbox and carb throats.  Could this be pulling more air into the hot running cylinders and air-starving the cool cylinders?  Any easy way to seal these up?  Could I use a coating of flexible epoxy on the inside or something? 

I also still need to vacuum sync the carbs, but there's no use in doing that until all 4 are running equally well. 

I did static time the Dyna S with a turn signal light, and only made a small adjustment to the 2/3 plate.  Weird thing when I was doing it though... I timed the 1/4, then rotated the crank, and when it hit the 2/3 mark, I got an insanely loud exhaust backfire that scared the $h*t outta me  *BANG*.  I'm guessing I cranked it hard enough to cause the cylinder to pull fuel into the compression chamber, but why the detonation out of the exhaust?  I thought that only happened with the timing 180 degrees off?  Maybe the exhaust valve was stuck open?

When should a dynamic timing adjustment be done?  Before or after the vacuum carb sync?

Also on order are some reinforced fuel lines and crimps.  I'm using crappy rubber lines that when they get warm seem to become flexible enough to develop kinks and leak a bit from the nipples. 

The PO butchered the stock turn signals, wires ripped out of the housings.  I've never been a fan of the stock ones anyway.  I've done a few searches for aftermarket signals, but it looks like every thread is discussing what a nightmare they are.  Anyone had good luck with simple plug and play signals?  I don't need fancy LED's or anything, just something that will be functional and not horrendously ugly like the stockers. 

Also, still haven't diagnosed my kill switch not working.  Anyone with the procedure to see why the bike stays running in any switch position?

I'd like her to be running like a dream before year's end, and I feel like I'm getting close!

I know this was an exceedingly long post, and I don't expect most readers to have made it this far, but if you did and you have suggestions for any or all issues, it would be much appreciated!!

[OneWheelDrive]

Bueller?

[Greggo]

First eccentricity she has is tranny wise.  Occasionally when sitting at a stop light in neutral, the light will turn green and I'll press down into 1st and it just won't wanna go.  With a little rock back and forth (stressful with a line of cars behind you, especially the first time) and a click up, then down, she'll drop into first and be good to go. 

I have the exact same problem with my '71 CB500-4...She doesn't like to go into first when stopped.  So, I drop it into first as I'm just rolling up to the stop-works like a charm every time.  Otherwise I have to roll it back n forth to get it in.  I think the problem is caused by worn shift forks...If you go into the FAQ or the Tricks & Tips section (don't remember which) there is a post named "Secrets of the CB500 transmission revealed" or something similar.  A great read for anyone with a 500.

[fantino]

I bet your shift forks are starting to look a lil' like this:



Pretty much the case with every 500 transmission with some miles on it, and it will result in hard shifting like you're experiencing. The only solutions are to a) repair your shift forks and undercut your transmission (best solution, but most $$$) b) find a good or NOS set of shift forks and ride them until they also burn through (very hard to find part now) c) live with quirky shifting.

Fast By Gast in NY charged me ~$75 to hard-weld my middle shift fork back to spec and clean up the other two (the middle one is usually the worst). They brought it from what you see above, to this:



Just something to keep in mind if you plan on splitting the cases in the future. I also had them undercut my transmission, which was spendy, but should solve the problem permanently.

Next time you take it out for a spin, do a plug chop so you can better diagnose what's happening in your cooler cylinders :-)

[fastbroshi]

How much did they charge for the undercut?  Don't see prices on their site, just a blurb telling me to call for prices.  Also, where's your pics?

1WD, Did you adjust your clutch during all this?  Maybe that's worth a look.

[Really?]

If I am at a light, I am in 1st with the clutch in.  Rare for me to be in neutral at a light.

Spray some carb cleaner around the cracks in the carb boots and around where they connect.  A change in RPM will give you an idea of a leak.  Those leaks will jack you up, lol.

[Stev-o]

If I am at a light, I am in 1st with the clutch in.  Rare for me to be in neutral at a light.

+1. Only time I go to neutral is when I plan to get off the bike. My 550 can sometimes be tricky to get to neutral too.

[OneWheelDrive]

Thanks for all the suggestions y'all.  The tranny is performing pretty well, and I can totally live with keeping it in first at a light.  I have to assume my shift forks look like yours Fantino, but for the cost of teardown/repair, I think I'd rather swap the motor again.  I had adjusted the clutch, and it has a good cm or two of play before engaging. 

I sealed the one crack in the carb boot with some gorilla glue and seran wrap (removed after curing).  That stuff is magic.  It goes on like a gel, fills cracks, then expands and forms a flexible seal.  We'll see if it holds under heat.

So when I bought the spare motor, it had a set of 750 carbs attached that were in great shape.  Since I was pulling off the 550 carbs to tear them down again anyway, I figured I'd plug the 750 set on there and see if they performed better.  I pulled the bowls and adjusted the floats to spec and they had 105 mains jets in there, so I'm guessing that they were tuned to the 500 motor they were on.

Gave them fuel, gave the motor fire, and she started right up!  All 4 headers got hot pretty simultaneously and although it still has some sync issues at very low RPM, at higher engine speeds it ran awesome.  It's VERY sensitive to throttle and/or idle adjust screw at very low RPMs so a fine tune is definitely necessary. 

A plug chop confirmed that it's running a bit rich in the mid RPM range, so maybe I will raise the needle clip (drop the needle) one notch to back off the fuel flow.  I'm also now considering pods as the PO said that was how it was set up previously.

There is a weird inlet screw/port on the downstream side of the carbs that I've never seen before.  In this picture I found it looks like it should be a screw/plug but my carbs have a hollow screw in this hole.  When the motor was running a constant push and pull of air was puffing out of this port.  Should I find the correct plug to stop this air leakage into the manifold?

[Greggo]

Is it just that #1 carb with that type of screw, or do all your carbs have that type?  Perhaps this is just conjecture, but it they're all the same, I'd just leave 'em.  You said she runs beautifully, right?  All the carbs I've ever worked on have air inlet screws in one place or another, but I don't claim to be an expert on your particular set, which BTW you should mention the specific carb model if you haven't already.  It's stamped somewhere on the bodies.

Keep up the good work!
Gregg

[OneWheelDrive]

The air inlet screw are on all 4 carbs but three of them have rubber caps on them (they don't look like they seal anything, they're cracked).  I suppose if it's even on all 4 carbs it shouldn't matter.

I looked closely at the carb body and wasn't able to find a number.  I'll take some pics tonight and try to find the number.

[Really?]

If those are the 750 carbs and you have one of those screws on each one (two on the left side and two on the right side), that is how you sync them.  There are tubes that will screw into them (5mm i think).  Then the vacuum lines slide on those.

The carbs on the ole lady's 750 started with 105's and were the stock size for that year.  I think I jetted her to 115's but they could be 110s.  Did that for the 4-1 I put on them.

[OneWheelDrive]

That would make sense that they are there for carb syncing, but why put a hollow screw in there?? Also, the intake manifold also has the standard sync port spot as well.  Was this just a redundancy?

[OneWheelDrive]

By the way I previously though, "I don't need to stinkin' front fender", that was until I went through a pretty wide swath of water at about 30 mph and got a face full of muddy sprinkler water off the front wheel.  The one I've got is pretty beat up, but I guess I'll have to make it work.

[Greggo]

Okay after a li'l research, I've determined that those screws used for syncing should be replaced by a solid screw after the job's done.  Try replacing them, and see how she runs.

[odiewan]

Hey, your picture links are broken. Can you repost? I'd like to see the pictures. I think I am having similar issue on my 750 K3

I bet your shift forks are starting to look a lil' like this:



Pretty much the case with every 500 transmission with some miles on it, and it will result in hard shifting like you're experiencing. The only solutions are to a) repair your shift forks and undercut your transmission (best solution, but most $$$) b) find a good or NOS set of shift forks and ride them until they also burn through (very hard to find part now) c) live with quirky shifting.

Fast By Gast in NY charged me ~$75 to hard-weld my middle shift fork back to spec and clean up the other two (the middle one is usually the worst). They brought it from what you see above, to this:



Just something to keep in mind if you plan on splitting the cases in the future. I also had them undercut my transmission, which was spendy, but should solve the problem permanently.

Next time you take it out for a spin, do a plug chop so you can better diagnose what's happening in your cooler cylinders :-)

[OneWheelDrive]

I can see the photos 

[OneWheelDrive]

So after riding around for a bit yesterday, I've concluded that the 750 carbs are not well suited for this motor.  The low RPR range is so sensitive that it's very difficult to take off in first without slipping the clutch considerably.  Also, the idle adjust is VERY sensitive making it hard to dial in the idle.  I'm going to re-clean the 550 carbs and put them back on the bike before (hopefully) a vacuum tune.

I also think I may have found another transmission issue.  At the top end of the RPM range, like above 9k, it feels like the clutch is letting go of the power.  Like a smooth acceleration to 9k, then the motor runs away and power doesn't transfer to the wheel.  Feels like at 9k I pulled the clutch lever.  Could this be clutch plate wear?

[Greggo]

So after riding around for a bit yesterday, I've concluded that the 750 carbs are not well suited for this motor.  The low RPR range is so sensitive that it's very difficult to take off in first without slipping the clutch considerably.  Also, the idle adjust is VERY sensitive making it hard to dial in the idle.  I'm going to re-clean the 550 carbs and put them back on the bike before (hopefully) a vacuum tune.

I also think I may have found another transmission issue.  At the top end of the RPM range, like above 9k, it feels like the clutch is letting go of the power.  Like a smooth acceleration to 9k, then the motor runs away and power doesn't transfer to the wheel.  Feels like at 9k I pulled the clutch lever.  Could this be clutch plate wear?

If you're accelerating at WOT, be aware that your analog tachometer can't keep up with actual engine speed...so if you're jammin', and you see nine grand on the tach, you might just be at ten or eleven grand...BE CAREFUL

[OneWheelDrive]

Valid point.  I'm going more off of the sound of the motor and feel of the acceleration, but blowing up the motor would not be bueno.

[OneWheelDrive]

Got her running pretty good with a carb and timing tune thanks to Odiewan!

The problem is still int he very low RPM idle.  The vacuum tuner fluctuated greatly at low RPM so I had to sync at about 2500.  Any way to avoid this without dampers on the lines?

*CLICK ME*

CLICK ME ^^

[Really?]

You have to have the dampers in the lines to stop or slow the needle bounce on the gauges.

[fastbroshi]

Wow your muffler is actually intact; those are pretty hard to find.  Not to nitpick but the baffle has probably seen better days.   Cool that you got her up and running so fast.

[tweakin]

Looks good man and sounds pretty smooth.

[Zaipai]

I found this pretty informative.. He sets his carbs at 1500 to 2000 rpm... However it does not help with the bouncing gauges, however I believe some where on youtube.com there is a video that explains how to deal with that. I just did not have it bookmarked.

.: Scott :.

[wick]

yo- san diego-----sweet-- im just` sync`n my carbs  also-- cb750k2-  836kit.....never ending project////////

-- see you on the 101.. or water-front;//////////    im in mira` mesa........