Topic: Honda CB500 getting it running

[Liquid]

Hey guys,

First of all let me introduce myself. Im a 22 year old student (read: cheap basterd) from the Netherlands. I have been reading the forums for a while now seeing how I had the cb500 in my possession for a couple of months but no time to really work on it. I got it from one of my dads friends as my first project. He had it sitting in the garage for over 10 years in a semi-assembled state, when i went to pick it up he handed me half a motorcycle and some cardboard boxes.

The last couple of weeks, I had some time to put in some work and have made serious progress. The bike was missing some parts and not everything was in working order, especially the engine was a mess, even though it looked good most of the bolts and studs were broken off and seeing how I want to get it on the road for daily traffic asap I figured the easiest thing was to buy a donor bike.

I painted the frame with some black (hammerrite) paint, cleaned all the parts, cleaned the surface rust from the chrome and started putting it back together. Along the way I have picked up a lot of inspiration for some cool mods (looking at a lot of very nice and tricked out bikes on here), so now I have a spare engine + carbs that I will rebuild over the winter prob tikkle it a little bit with a 650cam and overbore 555cc kit, as well as doing a dual front brake mod seeing how I have a complete spare front end, prob some work on the fenders, the lights especially blinkers and I want to make a custom exhaust... 1 muffler each side

For now I want to get the bike running though, so I put in the rusty rims and grimy looking engine + carbs (which I did clean out). I have not opened up the engine, however I did adjust the valves (out and in to 0.08mm as suggested by hondamans faq) and smoothed out the intake runners. I also fitted an electronic ignition (some german make). Yesterday I fired it up for the first time, which took me a min because I forgot to open up the petcock. After the gasoline was in the floatbowls it started up right away but its not running very well. Idle and till around 4k is fine but higher causes problems.

There are several problems which I still need to figure out, first of all carb adjustment...

The carbs I have are Keihin (649A) which are fitted with airscrews (1.2 K), stationary jets (40) and mains (100) jets ( i bought those, since 78 were fitted which were to small because 100 was noted as standard) and floats adjusted to 22mm. After starting it up it would very difficult rev up above 5.5k, so I figured it might be due to, too big main jets but 100 was listed as standard. After doing some searching on the forum I noticed that some dutch bikes had an ''snorkle'' on the airbox restricting airflow to the carbs and the carbs were fitted with 78 jets. My bike does have this snorkle, so now im trying to figure out what would be best... remove the snorkle and mod it to a US model intake (does somene have a pic of this??) or are the carbs diff from the US carbs which would force me using smaller main jets?
The rest of the bike setup is: standard airbox (with snorkle), standard keihin carbs, smoothed intake runners and a 4-1 exhaust with an unidentified muffler (see pics).

The second problem I have run into is the coils... even though the engine runs (rough) when I touch the nr.1 and 4 coil wires or caps, you can feel the spark leaking over to my hand and engine. I have tried fittting 2 different pairs of coils, but they both have it ... so i was thinking it could be due to my main harness, which wouldnt make any sense to me ... after a closer inspection I figured its just bad luck and putting on some new coil wires wouldnt hurt. All my caps have the right resistance when measured etc. After reading a how-to on the forum I still really cant figure out how to remove the old wires, so can someone enlighten me with a bit more in depth guide?

Lastly some weird engine noises, but I will not bug you guys with those yet, because I read that most noise is caused by unsynced carbs... something I havent gotten around to yet. I figured its best to first find out which main jets to use etc... before I start the syncing. Does someone have a nice tutorial on how to adjust carbs and how to do it in the right order.

So without further re due I shall post some pics... nothing great because it was raining out side and the shed is pretty small. I will take her out monday/tuesday and take some more pics. Hopefully I can soon post the happy news that the engine is running fine and I can get down to my other mods.

The bike from the back (with a way to large registration plate):


The muffler (yes, I know I need to polish it just sanded the rust off for now):


drivers POV:


The snorkle:


Grimy engine + carbs:


My donor cb500 and moms ride:

[TwoTired]

We did not get the 649A carbs here in the states.  Our, 500's got the the 627A or B carbs.  The US carbs have the #100 mains.  And, no snorkle or air restrictor on the air filter.
If you use the snorkle you will have to use the 78 mains with the 649A carbs.  In previous discussions with Deltatider, it seems there were more differences with the carbs that just the mains.  I think he said something about an air jet being blocked too.  I've not seen the 649A carbs in person, but, all the other carbs for the 500/550 I have seen.  At the carb inlet there are two air jets on the 627 carb one feed the pilot or slow jet emulsion tubes and the other feeds the  Main throttle vavle emulsion tubes.  I believe Deltarider said his 649 carbs did not have the main throttle valve air jet.  It would also be interesting to find out if the Jet needle size and taper were different between 627 and 649 as well as the emulsion tube bleeds holes size and shape.
Just to get it running the cheapest way, you are probably better off putting the #78 mains back in the bike ad run with the snorkle.  However, if you can obtain 627 carbs easily, then remove the snorkle and use those.  I would expect a performance improvement based on physics principles.  But, I have not tried it due to lack of 649 and snorkle components here in the US.

About your spark "leakage".  You could try cleaning off all the high voltage components with alcohol.  Dirt, grime and other contaminants are conductive and can aid leakage.
Also, touching the leads gives and alternate path for the spark voltage that would not be there if you weren't touching it.  So, you may not have a real problem.  Run the bike in the dark with lighting off.  If you are truly losing spark, you'll see the arcs in the dark.

You could check the head pipes to see if they are of even temps.  Cooler ones indicate and issue with firing.  Could be spark plugs, spark, or plugged idle jets if you find cool head pipes. (assuming compression is correct)

Cheers,

[Liquid]

thanks for the quick response twotired!

Well seeing how I got the other carbs already disassembled we could do a quick comparison test I guess... Ill make some pics of the carbs for comparison. I wanna see if theres any difference... if so ill stick with the 78 jets and prob upgrade over the winter to diff carbs all together.

As far as the coils go, Ill go clean them after dinner and see if the sparks will still leak in the dark.

Ill report back asap

[Liquid]

So I cleaned the coils and wires and checked if I saw any sparks in the dark, which I didn't so I guess thats a good thing. Still felt some leaking on 1 and 4 on touch, but I guess I shouldn't worry about it for now.

Also made a pic of the carbs... Hopefully someone can enlighten me with some info, I see 2 inlets the brass one at the bottom and a small hole in the sides... no idea if thats diff from what it should be though. It is fitted with a slide 103 k2.5, airscrew k1.2 and a needle was numbered 272304, forgot to check the emulsion tubes, but I can do that if necessary.

Tomorrow or tuesday, ill pull the carbs or fiddle with the snorkle according to the comments on here. As well as doing a compression test and carb sync, hopefully that will get rid of the ''lil midget running around inside my engine with a mallet'' noise.

[TwoTired]

Good pic of your carbs.
It does look like you need some choke butterfly adjustments as they are in different positions.

The lower brass jet should be for feeding the main emulsion tube.  If you squirt fluid in there, it should come out the main jet holes.  The 627B orifice for the air jet is #150, or 1.50mm.

Since you have the slides out, you should also push out the emulsion tubes for cleaning/inspection.  Be gentle, as the place you push on is the needle jet orifice that really shouldn't be altered.

The other hole off to the side is the slow air jet.  That hole should feed air to the slow jet, the Idle air bleed screw, and of course the hole feeding into the carb bore.

Your jet needle number appears to be the same as used on the 627B carbs I have.

Cheers,

[pdxPope]

+1 what TT says.

The coils and wires are a one piece affair and don't really come apart. Some people have had success cutting the old wires out and replacing them, but I don't recommend it.
Just get yourself some new electrical components. Coils, wires, plugs, caps, points & rotor. It's cheap insurance, and also eliminates (most) ignition variables during the troubleshooting phase.

The Midget with a Mallet (nice!) is probably loose cam chain. Does it go away when you rev the motor?

-JP

[Hush]

These bikes have 3 noise makers,
Clutch rattle (get used to it they all do it and my mechanic says its normal )
Cam chain slop, adjust at least twice once the motor has been running a bit.
Carb synch (sounds like clutch rattle) bench synch, even I can do that then get it done by a bike mechanic later when you want it spot on.
You will need to find an old timer mechanic, any mechanic younger than the bike will be totally lost.

                         Enjoy and welcome...........Hush

[Liquid]

thanks for the quick heads up guys... I tried running the bike today with the snorkle removed to see if it would run better with some extra breath, there was some improvement but that was to be expected i guess seeing how the jets are way to big. I decided that i will just pull the carbs for now, re clean and put in the 78# jets. Hopefully I will get around to this in the next couple of days.
The ''midget'' noise could very well be the cam chain although i did adjust it. It comes from the base of the cylinders, sounds like its coming from behind the ignition cover. I keep getting more paranoid the more I listen to it so ill drain the oil again and check the oil pan, see if I can see anything floating down there. I also ordered a morgan carbtune which will probably come in tomorrow, hopefully I can reduce the noise that way as well.
As far as ignition goes ill see if I can do some more cleaning up of the wire harness connections and re screw the spark plug caps after cutting some cable of to see if that improves it some more.
Ill report with more happy news soon... thanks again guys

[TwoTired]

How many miles on the bike?  I've not seen it, but BrianJ claims that the primary chain can loosen with wear and erode into the case metal.  Extreme wear can cut into an oil galley.
There is no chain tensioner on the primary chain.
Carb imbalance can make the crankshaft change speeds causing alternating slack and tension on the primary chain and all the meshing gears in the transmission.  Then you can get gear clack as it makes contact with alternate tooth faces.  The noise usually changes pitch when you pull in the clutch.  A good carb sync can take a lot of the noise away, so all the cylinders are firing with the same impulse strength.

Cheers,

[Hush]

Oh yeah and one other chain noise I forgot about, drive chain to back wheel!
I managed to cock up the alignment of my side cover so badly that the drive chain was smashing against the casing when I rode the bike, scares the bejezzaz outa ya I'll tell ya.

[pdxPope]

Re: your Midget with a Mallet-

It comes from the base of the cylinders, sounds like its coming from behind the ignition cover.

Could be your points plate or mech. advance unit is loose (although I've not heard of that happening.) Or possibly the points cover itself. There should be a rubber O-ring between the cover and the engine case it screws to. If that's missing it could cause the cover to rattle.

Does the noise change with engine RPM?

-JP

[Liquid]

After another careful inspection I lost faith in my cleaning skills and decided to give my carbs another clean. Took off the rack cleaned it all out. Then when I assembled it back together and tried to vacuum sync when I noticed what was wrong, the 4th carb slide was almost closed, so it was just barely running on that cylinder. Now its all synced it runs a lot better and only a bit of clutch rattle remains, which doesn't bother me. Also as pope suggested there was no rubber ring behind the ignition cover, which caused some noise, all fixed now.

After that little victory I decided to work on the stopping power, so I drove down to the hardware store bought some bolts followed the brake faq (awesome info and pic), bolted up a spare disk to the front hub. Fitted perfectly after grinding of the speedo backplate. Even if it doesn't stop any better, its still worth it for the looks! Just need to get some new lines and clean out the calipers. Also noticed the post in the general forums about removing the push cable. Figured I should give it a try and the gas handle is a lot smoother now, def a good tip.

I also messed around with another back end a little bit, tried to mock it up and see what it looked like. Dunno what to think of it, but my brother said it looked good. Got it off an old 50cc bike that was standing around the back of the shed. Perhaps I will post a pic of it soonish...

Thanks for all the info guys ill report back soon and hopefully get it outside for a nice pic.

Edit: btw. I ended up installing 85# jets

[pdxPope]

Glad to hear you were able to get things sorted.

-JP

[Liquid]

Ok, so I got a little work done again. I decided im going to persue the cafe'ish look and that the paintscheme will have to be black and some chrome. Seeing how I was working on the front brakes I decided to actually take the whole frontend of again repaint it straight away. So I got the calipers cleaned up, which turned out to need a rebuild badly... the pistons were covered with little holes caused by corrosion, which cant be a good thing. Took off the front forks, disks, top of the tree, the hand control and the gauges... grinded off all the old paint and sanded them down a little bit.

I wanna see if I can pull off a decent paint job with a can on these parts, but after doing some reading up im completely lost in the woods. There is a million options to choose from and seeing how I want the paint to stay on after im done, I think im in need of some advise. Most people seem to suggest using an etching primer and then 2k paint. I can get the etching primer, but I dont know if I can get the 2k in a spraycan, I know I can get some clear 2k in a can though. What exactly makes etching primer superior over other primers? If I use a primer then filler and some regular black automotive paint (acrylic) and top if of with the 2k clear will that be sturdy enough to take a beating?

[Deltarider]

It is fitted with a slide 103 k2.5, airscrew k1.2 and a needle was numbered 272304

These are correct for the 649A carbs. I have experimented with #100 jets (removed snorkle) and found no positive effects. My experiences were confirmed by German 500riders.
We still dont know if 649 and 627 carbs differ only in jetting. Maybe the venturis are different too. What I do know is that France, USA, UK amongst others had #100 main jets and models for Germany, Holland, Switzerland amongst others (Italy?) had #78 main jets. Surprisingly performance proofed equally good. Some have pointed at different qualities in gasoline between the various countries in those years. Could be, but there is little left of that difference I'm afraid.

The other hole off to the side is the slow air jet.  That hole should feed air to the slow jet, the Idle air bleed screw, and of course the hole feeding into the carb bore

I think he [Deltarider] said something about an air jet being blocked too.

At the time I was referring to the blocked hole you see on the other side opposite the one that feeds air to the slow jet. But..., when I think again, it's probably there for manufacturing reasons.

It does look like you need some choke butterfly adjustments as they are in different positions.

This is interesting. Decades ago I did exactly what TT suggests and adjusted the butterfly chokes on my carbs. But... when I look at the picture of your carbs I start to doubt, as your butterfly chokes are positioned exactly as I found them on mine. Is this merely a coincidence or did Honda position them like this for some reason we don't know? Has the asymmetric shape of the plenum anything to do with it?

[Liquid]

Thanks for the heads up Delta. Cant comment on the butterfly chokes except for the fact that they are exactly identical to the ones on my other rack, so I reckon this is as intended by Honda. For now I decided to not further fiddle around with the carbs, since it runs very smooth now.

I did get some other stuff done after my last post, which I will posts some pics of perhaps tomorrow or the day after. I started polishing the dashboard, hand controls and I almost finished up polishing the front fork legs. All by hand, so its taking a lot of time. I also ended spraying my brake calipers black and they turned out decent. I used spray cans from a brand called motip, used a primerfiller, high gloss black spray paint and topped it off with a coat of clear. The Clear was hard to get it right and on the first parts the clear got on a bit to thick and caused some drips, they're hard to spot so I am not gonna sand them down.

Im really getting the bug and Ill prob spray the tank and cut the fenders, whence I am done polishing and putting the front end back on.

[Liquid]

I made some pics today of a couple of items that I have polished. Used a lot of diff grid sandpaper ranging from 240 up to 3000 then finished it off with an alu polishing compound called ''belgom'' will prob try some ''never dull'' I have laying around to see if the shine gets any better. The pics dont really do the polishing justice but its an impression of what it looks like. Ill update over the weekend when I get the frontend back on hopefully.

[gene03079]

nice work on the polish.

[Hush]

Very nice work on the polish