Topic: CB500 dies after 10 mintues (another one!)

[zanorak]

Hello all..

1972 CB500 here, runs great until 10 minutes in and then dies rather quickly. Feels and smells hot at this point, can be restarted with choke all the way on and throttle wide open. No power afterwards, dies within a mile. Waiting helps - but it's 30 or 40 minutes not 3 or 4 as some say here.

Bike:
14k miles, previously maintained by someone who didn't really do everything right. Not sure if it was the previous or the guy who he bought it from. I get the feeling he didn't run it long before buying a newer bike.

4 into 1 pipes that sound GOOOOOOOD
Pod air filters that fit like crap
Stock carbs that haven't been cleaned or adjusted - but the seafoam is doing its thing
-two carbs will overflow after shutdown if tap isn't closed before parking
-adjustments unsure because I really haven't wanted to tear them down yet
-replaced fuel lines yesterday because the old ones rotted off
-jetting appears stock (#100?) because I have to run with choke or it will bog over 4k when hot

Starts reliably, if a bit hard (as in a few seconds of cranking)
Proper D7AE plugs
Original plug boots/wires
Original coils
All 4 pipes get hot
Carbs probably synched poorly by previous, but run ok before the problem
Cleaned the tank vent with wire and with carb cleaner/air
All other electricals appear ok - new battery
Has oil, fuel is new and has seafoam in it

I've read all the other similar posts I can find and I was wondering if I missed anything. I tried popping the cap and no sucking sound after it died. I cleaned out the petcock and the screen looked very clean already, seems to flow uniformly though not a gusher. (maybe this is standard) I can't see any obvious crap in the tank, and I cleaned out the petcock passages with carb cleaner and a wire. New fuel lines yesterday and put an inline filter in. (the second one wouldn't fit - so I'm going to remove the first until I can find smaller ones)

Plugs look wet and oily, but I did crank it a bunch after the shutdown. Usually kind of dark, but powdery.

Thoughts? I got this puppy for very little money, so I'm trying to get a bit of use out of it before throwing down $100 on carb rebuild kits. I was just going to pop in new jets (#106? and maybe take the pilot jets up to 52?) and put gas through until the carbs got freed up. So far it's worked but this is not good.... I want it to be reliable so I can get the miles in. Was going to spring for new tires as my big investment to this thing.

Any and all suggestions/questions welcome! My local honda shop is not very helpful btw... good people but they just kind of look at you like you have two heads when you come in with a list of parts and start asking.

Thanks in advance! Gotta say I love the 500 so far, get lots of compliments, and lots of attention. More than if I had a newer bike I'd say! Smiley

[Gordon]

I'll ask the same thing I always ask others with a similar problem. 

Does the bike have a known good battery that holds a charge?


Also, just running seafoam through the tank won't help the carbs if any of the jets or emulsion tubes are completely clogged.  It has to be able to flow through to clean. 

[zanorak]

Thanks for the reply Gordon.
Yes, new battery - cranks well and takes a charge. All cells are evenly filled.
Emulsion tubes could be gummy, but it runs so darn well right up to the 10 - 15 minute mark that I'm not feeling the carbs are the issue. That's academic anyway since I'm going to have to open them up and re-jet them. I'll do the cleaning ritual as a matter of course. Looks like I won't be able to put it off. :/

I've been reading more about petcock problems - and I'm thinking that the previous owner may have reinstalled the petcock incorrectly. I'll drain the tank again and see if that's the culprit! I re-checked and it's not filling the inline filter all the way - more of a trickle coming through.

I get the feeling that these carbs were cleaned in 07 when the last guy bought the bike. Otherwise they'd be totally slagged up. He did leave gas in them for a year or so - maybe 2 - but barring foreign matter in the float bowls I can't see them being THAT bad....

Thanks again!

[Hush]

Never ever ever trust (1) your previous owners workmanship (2) your carbs!
I'd say Gordon was on the money with his suggestion on cleaning them out, seafoam might help flow but emulsion tubes and float valves require individual attention.
The fact that the bike starts up for you is really good, it means the tuning and electrics are probably OK, carbs will be your culprit.

[Scott S]

 Pod filters + carbs that haven't been cleaned, adjusted or synched (at least properly) + looks and feels hot, makes me think you're running lean and on the verge of overheating it and locking it up.

[zanorak]

She certainly got hot! I'll tear down the carbs this weekend if possible. Thanks for the replies!
I'll see if I can post pics too...

[zanorak]

Got the tank torn down and sure enough - lots of rust particles. I'm guessing that the float bowls are full of it by now. It must have been stirred up by use after years of neglect... reminds me of a date I went on once - but that's another forum.

Anyway - I need to clean out the worst of the tank. I was going to use hot water and simple green for this. Maybe soak overnight? What say you gurus? I don't have the time or the battery charger for electrolysis. I'll go look for some phosphoric acid and maybe POR sealer tomorrow - but in the mean time I've torn the carbs off the bike. I wanted to avoid it but whatever.

Question: How do I get the clips off of the throttle linkage without ruining them? I don't want to screw these up...
If you have a link to a thread I'd love it! Pics are gold.

Carbs were obviously messed with. Have been beat on with what looks like a waffle faced framing hammer. (Tapped on?) The choke and throttle linkages don't line up so that throws the whole synch thing out the window right off.

Please excuse the cellphone pics!

[zanorak]

Flange number

[zanorak]

Back

[zanorak]

Front

(Whew - now I'm getting a headache from teh gas fumes... )

I've put a box around the area I need help with. Anybody know what to call these clips? I've searched for clips, throttle linkage, separate carbs, etc... no dice.

If I can get them apart I can soak the carb bodies too and do this right.

[Spanner 1]

MR.Z...... see your first post?.... see the Q's your asking?..... go to the FAQ section and read, read, read... info = power!

[zanorak]

Gotcha Spanner - just spent the last 4 hours doing just that. Running in and out to the garage. I'm sure I'm not the first to do it... My current question isn't really covered in the FAQ.

I was hoping somebody who knew would chime in and say something like "just put a screwdriver there and it pops off..."

Thanks for the read though! I'll keep digging.

[Spanner 1]

Wait-up!, you've got loads of Q's in your post... can you condense it to one ( at time )?

[Spanner 1]

The first 4 hours should be spent just looking-over your 'new' bike... best spent in a folding chair with a beer in the cup holder and thinking how best to get it working over the next few days/weeks..... or get a sportbike 'ready to go'... and enjoy.... SOHCS are not for everyone, be warned !!

[zanorak]

lol spanner!
I know all too well about the buy a classic/ride or drive a classic paradox!
Lucky I enjoy this kind of thing.

The first 4 hours were spent fooling with it - and THEN the brewskis came out!

I know I put a lot up there on the first post, but that's just my nature.

That being said, more info for the experts is always better than less in my experience. In the most recent case - the "spring clip" I was afraid of breaking was actually rubber. I'm just being cautious. Can you blame me? Every part I've tried to get for this thing so far has been a 4 or 5 day "we can order it for you" part. The honda dealer sure isn't into classics I guess.

So - got one of the carbs off and it IS jetted at stock settings. No surprise there. Tomorrow I'll get the right size jets and clean these puppies out if anything works the way it should. The o rings and jets appear to be recent, so this was probably done in the last couple years so I'll just be getting the little bits of rust out of the passages and installing some inline filters. BOOYAH! I love it when a plan comes together. A soak will do these carbs good I'm thinking.

Also - something not prominently covered on the forum - the pieces of hose connecting the carbs (assuming it's vacuum) were cracked. I'm sure this led to wandering conditions between the two pairs. This is enough of a reason for all this trouble I think.

So thanks again! I know I'm acting like an eager puppy but you gotta love this thing. I'm actually doing this instead of being at the bar with my friends... my values must be skewed. HAHA!

Here's a pic of the inside of the carb - kind of grungy but not awful...

[Spanner 1]

Still haven't seen a question!?.... we've all seen pics of carbs before, Zan, no need to post....... very hard to impress with carb inside pics here, much better to ask specific Q's.... we will help longer than you will listen..!!!!

[scottly]

Hello all..


Plugs look wet and oily, but I did crank it a bunch after the shutdown. Usually kind of dark, but powdery.

Thoughts?

Fouled plugs. Why? We don't know!

[zanorak]

You're right.. gotta remember it's almost 2am here so I'm kind of wandering. Ok, specific questions:

Given the intake/exhaust that I have is my jet choice appropriate? (going for the 106 range main, 42 pilot) Should I err on the rich side rather than the lean side?

Would the stock jetting and the lean condition be sufficient to cause this problem? Is this a product of too much time at part throttle or too much time above 5k rpm?

Thanks for sticking with me guys. Appreciate it. I don't want to trash this bike, so I'm trying here. 

[scottly]

Not trying to trash you; we just need more information. Fouled plugs are caused by a rich condition, not lean. Too early to make jetting recommendations! Hang in there; we can work this out over time...

[zanorak]

Thanks Scottly. I think the wet plugs are from running it on choke. As I said above, it's got free flowing intake/exhaust so I'm pretty certain it's lean. Afer it quit I did my best to keep it running while I got it to a safe spot. Today I bought #42 pilot jets - maybe then I can run it without the choke and do a plug chop? Hoping...

Totally cleaned the #4 carb today and the needle was set on the second groove from the top, looks to me marked #026.