Topic: '71 cb500 with idling problems?...carb problems?

[vulture0027@gmail.com]

hello,

i have a 1971 honda cb500. (Up until recently) it hadn't been running for 8 or 9 months, but with the help of you guys on this forum i got it running....not running WELL, but never the less, it's running.
I'll give you the run down (as best i can... forgive me for the lack of lingo- i'm very much a novice when it comes to motorcycles)

I sent the bike to the shop around April of last year (2018). when i got the bike back, the mechanic said it was in "tip-top shape". it ran very well for about a month or so, and then it started losing power and eventually stopped running and wouldn't start. I noticed that there was a crack in one of the rubber carburetor boots- replaced that.  checked spark plugs... got spark, checked points- filed them with a point file... got spark, drained float bowls- reintroduced gas... got gas, checked gas tank petcock- carbs getting gas/ no kink in the gas lines, new battery, checked the brass tubes at the the bottom of the carbs to see if they vented (by blowing air into them with a surgical tube)...seemed fine. I knocked the bottom of the carb bowls to loosen the floats.....
After doing all of this, i finally got the bike to start.
It starts with the choke in the "on" position (up). It USED to start with the choke off (when a little pressure was applied to the throttle- this is how i would normally start the bike)...after i few seconds i turn the choke down a bit, and eventually turn the choke off (in the down position-after five to seven minutes).
runs rough. adjusted the idle screw to the point where the engine was running at 1000-1100+ rpm...took the bike for a spin around the block- little to no power. got it into second gear and had the throttle completely pinned back and still couldn't go over 30mph. rode it back home, put it in neutral...rpms shot up to 2500, lowered the idle adjustment screw, got it back down to 1000-1200. after a few minutes the rpm dropped to 900...800..then died. turned the screw again to turn up the rpm back to 1000-1100 and after a few minutes it shot back up to 2500rpm.. it was hard to keep the rpm consistant...

....any advice?

[dave500]

first up the ignition has to be looked at,its gotta be spot on before you #$%* around with anything else full stop!forget what the shop told you,ill bet they took your money ok?

[vulture0027@gmail.com]

what exactly should i be looking for (as far as the ignition goes?)

...made ZERO adjustments to the bike (other than the idle adjustment screw...which i was told that could be adjusted AND readjusted back and forth with NO damage to the bike)

[Deltarider]

first up the ignition has to be looked at,its gotta be spot on before you #$%* around with anything else full stop!

+1
5-7 minutes choke is far too long for an oldfashioned CB500. I myself open up the choke already after 5-8 seconds, so you may have fouled the sparkplugs. You need a raised idle for some minutes however. So verify if it runs on all four cylinders. You can touch (very quickly!) the headers to feel if they're all hot. Take plugs out to see what they look like. Try to remember what you've done after it ran OK. If bike has been inactive for a long period of time, verify the advancer works as it should. You need a strobe for that. Also check the spark does not jump (and so leak) between the HTleads or plugcaps and the engine. Best seen in the dark. Are plugcaps making good contact with the plugs?
Any arcing at the breakerpoints?

A bit of sparking is normal like shown in the vid at breakerpoint (2+3), the arcing at (1+4) however indicates a faulty condensor. Another cause could be that after you fitted breakerpoints and/or condensers, one of the forked terminals at the back of the breakerpoints is too close to the plate and so intermittently makes contact to ground. The 2+3 breakerpoints is more prone to this, because it's more in the vicinity of plate and crosshead screw than the 1+4 breakerpoints. Make sure the forked terminals do not touch the plate!

[vulture0027@gmail.com]

thanks deltarider,

didn't quite get through your list of "to-do's", but here's what's going so far...

- started the bike up
-header #1 and #3 were COLD after five minutes of run time...#2 and #4 left my hand the way i like my steaks ("blue rare")
-pulled spark plugs out- no soot on #1 and #3, minimal on #2 and #4.
-put spark plugs back into the spark plug wires, checked to make sure each spark plug was getting spark (by placing each spark plug against the engine block....ALL spark plugs had spark.
- i unloosened the carb drain screw on #3 and there was NO gas...didn't try to do the same to #1 because the drain screw has been partially stripped, so i didn't want to create another problem by stripping it for no good reason.
-no adjustments to ANYTHING where made to the bike (except for the idle adjustment screw)
- only took a point file to the points.
You (Deltarider) helped me last week to get my bike at least to the point where it ran, so thank you!

also: forgot to mention in my initial post...

-%50 of the time when i get the bike running, there is a sound that comes from the bike... it's like a weird slide whistle sound... sounds like a dwarf is in the engine blowing on the top of a soda pop bottle (ever-so briefly)
-last week you advised to me to put some "fuel cleaner".... i added an ounce of "seafoam" to the gas.

[bryanj]

Sounds like you need to bite the bullet and remove the carbs for a total clean and reset.