Topic: Time to rebuild the top end?

[vigiltln]

This will be long and I am new to this forum.  If I am posting in the wrong place, please forgive me.  Picked up a 1971 500 a few month ago.  I have no experience with motorcycles, but could not pass up the $200 price tag.
Had been sitting in a garage, covered by a blanket since, at least, 1990.  Motor and frame numbers match for 1971.  Tank was full of crud.  Carbs lacquered with slides stuck.  No oil, clutch cover loose, front brake locked.  Motor was not seized and turned over easily (perhaps too easily). So, I started reading this forum, downloaded every manual I could and read, read and read some more.  Stock air box with new filter.  Four into two (or is it correct to say two into one?) exhaust.  14,000 and some change on the odometer.

So I:
Sent the carbs off to be rebuilt.
Tank to a radiator shop (had to red coat the tank, as the rust was almost through the sides of the tank).  Rebuilt the front brake and cylinder.
Cleaned front forks with new oil and seals.
New air filter for stock airbox.
Reassembled clutch and new clutch cable.  Would shift through all gears.

Got the carbs back and put them on.  New plugs. It started on the second try (no choke needed) and sounded great!  Put the tank on and on the road for a few easy miles.  Next day it started ok but would not idle smoothly.  On acceleration, would not idle down properly.  Pulled the new plugs and they were black, but not oily.  So I:

Got new points and condensers and installed them.  Points plate snug, with no wiggle room.
Borrowed a timing light and timed it.
Adjusted the valves (have now adjusted them three times, just to be sure).
Adjusted the cam chain.
Tested coil continuity (real weakness of mine is with the multitester--I know how to test continuity, just not sure of the proper setting on the meter).  Primary on coil 1-4 5.1@200. 2-3 5.2@200.  Secondary on 1-4 is where I am not sure of the proper setting.  Could not get a set reading on either coil.  Ranged from 11.9-19.2@200K, to 12-19@2000K on coil 1-4.  2-3 from 13.4-16.6@200K, to 13-16 @2000K.
Caps tested 7.46, 8.22, 8.18 and 8.33, 1-4.
Battery 12.4v.
Double plug at coils (black wire) 11.45v.

No real improvement.  So with it appearing to run rich, tried to see if the carb insulators might be leaking.  Tested with carb cleaner and the rpms stayed the same.  Broke down and bought a compression tester (INNOVA brand from O'Reillys).  I know an auto compression tester will result in lower compression numbers.  Put in new plugs, started it up and warmed up the engine.  Sounded great with new plugs!

Pulled all the plugs (after just 10 minutes or so the new plugs on 2-4 were black with 1 grey) and cylinder 1 was 90, 2-89, 3-89 and the really bad news, 4-72.  Checked it twice.  Used the starter for the test.  Squirted some oil down 4 and it then tested 90, so may be a valve problem.  Either way, it appears I need to rebuild the top end--valves, rings and check all specs for anything else that may need to be replaced/repaired.  Am I on the right track?   

[vigiltln]

Ok, sorry about errors in my previous post.  I did not do the compression test with the throttle wide open.  Ever read your own post and thought you should have known better?  Anyway, I just got in from the shop after a warm engine, throttle and choke open compression test. 1-140, 2-135, 3-140 and 4-145.  On the previous test (with warm engine open choke but closed throttle, 4 was over 10 low.  Don't know why it is now the highest.  With this new compression test, still in need of top end work?  New plugs are black, so it seems to be rich.  Thoughts?

[scottly]

  New plugs are black, so it seems to be rich.  Thoughts?

Sounds rich. Don't worry about rebuilding the top end, based on the last compression test. You have a carburetor problem.

[bamabiker]

Second the rich carb diagnosis.  I'm not sure about 500's but my 550 will not cold start with no choke.

[HondaMan]

With the carb manifold castings, where they bolt to the head: unbolt them and replace the O-rings. They are very likely leaking, from being too stiff and from age: the shelf life of those neoprene O-rings is 5 years at room temperature, 3 years at engine head temps. I find these to be leaking a bit on every [virgin] 500 and 550 that comes here, these days. The O-ring is the same size as the valve cap's O-ring. When these leak, the carbs 'think' they are running at a lower throttle setting, which is very rich (12:1 at idle speeds), and will foul the plugs quickly.

With the carbs:
Pull out the emulsifier tubes (they are above the main jets, a little tricky to get out) and make sure the holes in them are not blocked with tiny bits of crud. This will make it run real rich. If your tank was coated, it is likely that some loose debris could have found its way into these. Ditto with the even tinier holes in the pilot jets.

Also, make sure of your air screw settings, and that the screws are sealing ell, if your carbs have the tiny O-rings on the air screws (so do, some don't - the ones that do have O-ring grooves around them for some real small O-rings, right on the screw(s)). If those air screws are even 1/4 turn too far out from the stock setting, it takes about 10 minutes to darken the plugs.

Be sure you are using D7EA or X22ES-U sparkplugs. Don't use D8EA heatrange, too cold for the 500.

[Stev-o]

Third the rich carb, but you knew that. Do you know how to adjust?

[MCRider]

  New plugs are black, so it seems to be rich.  Thoughts?

Sounds rich. Don't worry about rebuilding the top end, based on the last compression test. You have a carburetor problem.

Yeah, at 140+/- you're good to go. Likely to get a little better as you get some time on it.

Do the carb thingies, not my forte.

[vigiltln]

Steve-o, I will do some more reading on carb adjustment.  Think I have a good idea from reading prior posts, but I have not been a carb man in the past, as I was usually the guy to hold the light, get the wrenches, etc.  Still, you absorb a bit anyway.  Do you recommend a thread?

HondaMan, new carb insulators and carb manifold o-rings on the way. Will put them on when they get here.  Using NGK D7EA plugs, gapped to specs.  Screw setting one turn out from soft seat and that is spec, I understand.  Will check carbs when new insulators arrive.  Sure could have some loose debris from the tank coating.  New petcock installed and tried to have inline filters on it, but while messing with it I know I ran it without the filters a time or two.  If the carbs are gunned, I did it, as the rebuild was done right, I know.

Thanks for all the replys.  This is a fun project.  I will post results as I make progress.

[scottly]

Any loose debris in the tank could possibly have gotten lodged in between the float needle and the seat, which could cause the mixture to be excessively rich. Do a search for the "clear tube method" for checking the fuel levels inside the float bowls.

[dave500]

drop a fuel bowl and have a look at the numbers on the jets.

a vacuum sync wouldnt go astray.

[vigiltln]

Just pulled the carbs to get ready for the new carb insulators and o- rings.  Dropped bowls and have 100 mains and 38 slows.  Spec is 40 slows.  Should I change them?  How do I get the emulsifier tube out to clean?  Probably need to check the notch for the needle.  Thank

[thehammer]

if the compression increases when you put oil in the combustion chamber, it indicates the compression is leaking  past the piston rings. if there is standing oil in the combustion chamber, however, the decrease in volume will result in a decrease in compression, thus indicating nothing at all. blow the oil out of the hole with compressed air and try the compression test again.

when the compression stays the same after oiling the piston rings as before, that indicates a compression leak in the top end.

[Brantley]

Think of the impedance selections on your meter as "up to". 200 for anything "up to" 200 ohms, 2k for "up to" 2000 ohms, etc. Going high (like measuring your secondary on 2meg [2000K]) rounds off the numbers after the decimal. Try trimming 1/4-1/2" off the ends of your wires to expose shiny copper and use the 20K setting, if your meter has it, and hold real still. The numbers should level out. Your primary numbers look good. You want to see somewhere between 13K-15K on the secondary. The way most manuals use the word "continuity" concerning coils is contextually confusing. Continuity is LACK of resistance.

[vigiltln]

Brantly, thanks.  Do not have enough length to trim as suggested.  Update--40 slows installed.  38s were clear, no clogs or dirt.  New carb insulators installed and new orings on manifold intake.  Did not drop emulsifier tubes.  Will reinstall, put in new plugs, turn air screw to 1 1/8 out for a leaner mix and see where I am.  Thanks for everyone's help.  Will update soon.

[stockscreamer]

Do old 500's have the same spark plug caps as 750's? If so they should test out at 5k Ohm.  Only asking cause yours tested from 7k-8k..

[vigiltln]

Stockscreamer, I also think the caps are supposed to test at 5k Ohm, with replacement required at(?) 9.5k Ohm?

[HondaMan]

Do old 500's have the same spark plug caps as 750's? If so they should test out at 5k Ohm.  Only asking cause yours tested from 7k-8k..

The OEM caps were 7500 ohms, considered 'burned out' at 8500 ohms. The post-1975 caps were 10,000 ohms. We can't get the 7500 versions today, 5k is as close as it gets.

[vigiltln]

So, if not needed now, will need new caps soon, right?

Update--after new carb insulators, orings (they were hard and brittle), air screw at 1 1/8 out, 40 idle jets exchanged for 38s, started goog, ran good.  Went for 15-20 miles max at 60mph.  Ran pretty good, but stalled at stop.  Pulled plugs and they were black.  Still rich.  So I guess the next step is to pull carbs, drop emulsifier tubes and check that all is clear.  Maybe lower the needle a notch?  Or should I do a carb sync and check the results?