Topic: 1972 Honda CB 500

[honder]

Yeah, the cylinders measured up within spec so I decided to keep things standard. I did have to replace the pistons as the bike sat for sometime outside and acquired some corrosion on two of the piston heads as well as the underside of the cylinder head. Since getting the new pistons though, they have a bit more play in the cylinders than the old pistons do, they all measure up to the required diameters, but I would've thought that new pistons would fit as snugly as the old did?

I'm planning on dropping the head off at the shop in the coming weeks to have the valve seats recut. As far as I know this will be the first time the valve seats have been redone. Are the few thousands that the valve seat cutters will take off a concern as far as changing how far into the head the valves seat and a slight change in the geometry of when the rocker pushes down on the valve? I figure that slight of a change wouldn't amount to much, but thought I read somewhere that it was a point to consider.

[calj737]

Re-cutting valve seats is not going to create a piston/valve clearance issue. As for the slop in your piston/cylinder clearance, are the rings installed? Did you happen to check the rings for end gap before installing them onto your pistons, and into the bores?

[honder]

No, I haven't installed the piston rings yet. I just slid the pistons into the cylinders to double check the fit and found they were looser than the old pistons with the piston rings off on both. Everything measured up within limits so I figured it wasn't something to get too concerned about.
As for the valves, I wasn't so much concerned about the piston/valve clearance as the contact between the rockers and the valve stem, but I'm figuring that with only a few thousands of an inch difference between the where the valves would sit if I do recut the seats vs not, that it shouldn't pose much of a difference. 
 

[honder]

I did check the piston rings for end gap clearance as well and they both came in at tighter than .020 "'s

[honder]

Would anyone know how much clearance there is between the pistons at tdc and the valves when they are open?
I have the face of the cylinder head machined and am now wondering if there is a possibility too much was taken off and the clearance between the pistons and valves now taken down to something that'll allow contact to occur.

[calj737]

Best to install the piston, then measure it's distance to the top of the cylinder deck for accuracy. Stock, piston sits about  32 thousandths short

[honder]

Ok great, thanks Cal

[honder]

Tank Painted

[honder]

brake light installed

[honder]

Brake Light

[honder]

Carbs installed

[honder]

So it seems I have hit a wall. I had the carbs rebuilt and cleaned and jetted for pod filters and the mac 4 into 1 exhaust.
When I installed the carbs I could get the engine to idle with the throttle partially opened, but wouldn't continue running with  it closed even after a few minutes warming up. With the throttle opened, the engine would hunt, the rpm surging then falling back to the point where the engine would almost die. I suspected it was running lean, so I just upped the pilot jets one size
(from 40 to 42). I tried to start without the pod filters on with the bigger pilot jets and it ran well. Good throttle response, though the rpm would stick around 4000 even when the throttle was returned to idle (which I am guessing is indicating a lean running situation in the mid throttle range), with only the application of choke bringing it back down. I began installing the pod filters as the engine idled and it began to idle progressively worse with each pod installed, finally stopping altogether once the fourth pod was in place.
Anyone else ran into this situation or have any ideas as to where to start troubleshooting?

[calj737]

Vacuum leak, not likely jetting. You upped the mains, but where are your needles and screws set?

[firebane]

Geez seems to be a lot of us Cow Town folk on here.

[honder]

Ok, thanks Cal. I have some larger main jets coming, so I'll try those in there, but I'll also have a look for leaks and put a new set of seals and rubbers in.

[honder]

the idle screw is out 3/4 of a turn currently and the needle is on the 5th slot.

And yes, there seems to be lots of us Calgary folk here.

[calj737]

Don't jump to the assumption that larger jets will solve your problem. Yes, pods do want larger mains, but you first need to solve your hanging idle issue. Plug chops are well and truly the best method for tuning your carb settings short of a Dyno.

But first your baseline tune MUST be right. That means, timing, valves, and no vacuum leaks. Insure you've done a comprehensive 3,000 Tune-up, then go with a fresh set of plugs and an idle chop. If everything is right, proceed to a Wide Open Throttle chop. Then you'll make the fewest number of "beneficial" changes and be riding  like you stole it promptly and reliably. 

[honder]

So it looks like I have the idle sorted out. There were two things going on. I upped the pilot jets to 42 from 40 and after reinstalling the carbs back on the bike I decided to do a quick test run with no pod filters. Ran well, but was slow to return to idle from about 4000rpm on. As I installed the pod filters with the engine idling the idle became progressively lower to the point where the engine died with all four installed. I had them oiled and sitting in the garage where the temp is around 0, so I took a blowdryer to them to remove the excess oil, and that solved the idle issue, possibly in conjunction with the upped pilot jets.

Now that it will idle, I'll do some plug chops to see how the plugs are looking.

Since it has been idling reliably I have noticed a tapping noise that is more prominent on the left side of the engine than the right. I double checked the cam chain and the valve clearances and everything checks out there. I am at a loss for what is normal engine operating sounds and what is a sign of trouble as the bike hadn't ran for a number of years prior to me buying it, so I really have no baseline on which to draw any conclusions.
I'll put a link to a video with the engine noise when I get it uploaded

 

[calj737]

Touch a screw driver blade to different areas of the motor with it running, the handle gently pressed to your ear. Its called a "Mechanics Stethoscope". You'll be surprised at how effective it is. Once you isolate where the sound is coming from, determine what is causing it becomes easier.

But a ticking sound is very often an exhaust leak, especially at the header. If you removed the exhaust, new copper crush rings are required.

[honder]

Here is the 500 idling. I pressed a screwdriver against the engine in various spots and it seems like the tapping is more prominent near the #2 exhaust on the cylinder head cover. I have double checked the valve clearances and the cam chain tensioner as well as installing new exhaust crush gaskets. Clicking is still there however it may be a tad quieter than it was before. Anyone have a better idea of whether this is normal engine noise or perhaps something that should be looked at a tad closer?

[calj737]

Video is marked private. If you installed new copper gaskets, simply "snug" the exhaust nuts a tad tighter and see if the ticking goes away.

[honder]

Changed the setting on the video, should be open now. I have the exhaust bolts cinched down, but I'll try torquing them a bit more. 

[calj737]

Sounds like it could also be your carbs needing a vacuum synch (in addition to exhaust possibly). Have you done that yet?

[honder]

No, just bench synced as of yet by harisuluv. I've yet to vacuum sync, but I'll do that next and let you know what comes of it.

[honder]

Been busy the past while with work but have managed to get a few things done. I think I have narrowed down the tapping coming from the left side near the head to the rocker arm shafts. This an educated guess, though I watched a video of a guy with a 500 of the same vintage who replaced the two rocker arm shafts with the single rocker arm shaft that was used on the later model 550's and added a grub screw to hold it in place and prevent it from rotating around. I had spare rocker arms and shafts so I am going to try poly coating them to tighten up the clearances and provide a teflon buffer between the shafts and the cylinder head cover. I'll keep you all updated when they are installed.
I have been trying to wade my way through electrical stuff now. I have a new wiring harness from sparck moto that I have installed, and a regulator/rectifier from Ricks. I hooked everything according to the sparck moto and Ricks directions and have everything working though the battery isn't charging. (No increase in voltage measured at the battery as the rpm is increased) I've gone through the field coil and stator and measured the resistance and both are showing within spec. If I disconnect the white and green wires from the regulator to the field coil it shows voltage coming from the regulator, though as soon as the wires are reconnected, there is no voltage. Is this normal? I thought there may be a short in the field coil, so I tried a test on a spare field coil I have with the same results. I have also tried holding a wrench close to the generator cover with the power on with no noticeable magnetic field that I can see. Anyone have thoughts as to where to go from here?