Topic: 72 CB500 Restomod - *Update* Sold!

[Scramps]

Tested a couple more hypotheses this evening. Verified that my crummy old exhaust isn’t clogged up, so that’s good news. Also did some stroboscopic timing, which is what is recommended for the Pamco. Got it firing just right, but #3 still doesn’t want to do right.

I decided that I was finally ready to take the bike down the road and back, either way.

There’s a gas station about 2 miles from my house, I rode down to it and came back.

The bike seemed like it was running decently enough. I didn’t really call on it, but it seemed maybe a little underpowered. Shifts great! Front suspension is pretty soft, bounced me around a good bit. Brakes work just fine. Most critically though, nothing fell off. So that’s a win in my book.

Pulled back into the garage, #3 exhaust pipe is cool enough to wrap my hand around it.

I think I’m going to have to pull the head back off and get it checked out by someone who knows what they’re doing.

Confession time:
I didn’t lap my valves during my engine rebuild. I just cleaned all the carbon deposits out, verified that the ports looked serviceable, cleaned the thing up and slapped it back on there. I didn’t have access to a valve spring tool that would fit, or else I would have pulled it all apart and really cleaned it all up and replaced the valve stem seals. I still have new ones on my workbench.

But anyway,


Good night everybody

[seanbarney41]

If you have 150psi compression there is no problem with the valves

[RAFster122s]

Before you go pulling the head you should adjust the valves if you haven't done so by the book and then your compression test will tell you if you have #3 as a problem. You need three things to have combustion:   compression , fuel and spark.
Compression test can tell you if you have compression , naturally with 150 psi compression, you are good because they are all even.

Then you will check for spark pulling the plug wire and putting another new plug on the lead and hold it to the cylinder or a bare metal area while cranking...you should see the spark at the plug and as it jumps to the frame or a bolt on the motor. Lower light will let you see this easier than a bright sunny afternoon...

Then there is fuel. If after running if it doesn,'t have a wet plug with gas  then you have a carb problem... Because it should be drawing fuel even if it is not firing.

It feels down on power because it is running on 3 cylinders rather than four!
Otherwise you would not be able to touch pipe 3 without a burn...unless you were very fast and light with the touch.

FWIW, YMMV
David

[Scramps]

Not sure what else I can do in regards to the carbs. I pulled them again when I started trying to diagnose this issue. I read a thread from last year about a dead #3 cylinder that ended up being a loose jet in the bowl, so I wanted to make doubly sure that wasn't my problem first. While I had them off, I pulled all the bowls, checked all the jets, float heights were all level (22mm), no clogged passages, no debris, no stuck float valves, etc. I went back out a little earlier to confirm that there is gas in the bowl for #3, and there is.

As for the valve timing, I checked it Monday evening. Using the old shop manual as reference, everything checked out.

Cal mentioned a while back that a weak battery would cause weak spark. The battery being the only variable I can't rule out, I'm inclined to think (read: hope) that that's the problem.

I'll have to wait until I'm not quite so strapped and purchase a good one.

[RAFster122s]

Got a set of booster cables and car battery? Have you charged you MC battery? The car battery can be used in parallel with you MC battery (car not on) and if your MC starts firing on all four you could have a battery issue.

The coil should be showing inconsistent behavior where #2 and #3 are intermittently firing either #2 or 3. That apparently is not the case. I don't think you would consistently be seeing #3 misfiring or not firing and #2 always firing if the coil was bad as it would depend upon which began firing for the decay in voltage to only affect one cylinder and always the same. But, I guess it could. Swapping your coils and seeing if the problem switches to cylinder #1 or 4 then you have a coil problem.

With the compression you have you certainly should not see a lack of fuel in cylinder #3. So,if after running you do not find a wet plug on #3 then it is baffling how you can have fuel level in the bowl consistent with the other 3 fuel bowls and not have a wet plug as cylinder vacuum is going to be drawing fuel into the cylinder.

Is my logic on this deduction flawed? If others think so, please say so...
I would like to learn as I am sure Scramps would.as well.

[flatlander]

Oh yeah, I keep forgetting to show you guys my cool shirt that I found at Old Navy, believe it or not

LOL look what i wear today. bought this a few years ago, apparently then the routes were not scenic yet.

[Scramps]

That’s pretty cool, I like that super simple sketch style stuff. Did that shirt come from old navy also?

Historically, when I’ve pulled the plugs, #3 has been wet and clean. I’ve gotten this result with a couple of different plugs. It is not outside the realm of possibility that the 2 that I’ve tried were both dead, so that will be another easy one to check.

As for the clear tube fuel level method, I’ve seen some pictures of people doing it, but never really dug into how it’s done. Do you just pull your bowl drain plugs and jam the tube in there? Or do you need to get some special adapters?

[Scramps]

On the left, #1, on the right, #2



On the left, #4, and on the right, #3.



I believe I have found the cause of my problem

[Scramps]

Looking at the float needle valve, there does not appear to be anything impeding its movement. Air can flow pretty easily through the fuel line, through the t-splitter, and into the bowl. Seems like if the thing were sticking, it would stick in the open position.

Am I missing something?

[Robbo]

I would swap the float and float needle  between 3 to 4 and see if the problem moves to 4 or stays in 3.

You will narrow it down further.


Sent from my iPhone using Tapatalk

[flatlander]

That’s pretty cool, I like that super simple sketch style stuff. Did that shirt come from old navy also?

i bought it a few years ago, memory fades... could have been old navy.

[Scramps]

When I removed the drain plug to put the vacuum plug in, some fuel did come out of #3, but not as much as the others.

Air can pass through no problem without the float and needle in place, but once you put them back, air cannot pass through, in the upside down position

[spuds]

Hey Scramps,

Just spent some time reading through the thread.    The bike is coming along nicely----and (not pretending for a minute to have a ton of experience here) I for sure echo other's comments about taking your time with stuff, not allowing yourself to get too frustrated.   This activity of taking some old mechanical thing and making it function and look decent again (for me and I judge many of us) is a hobby----right?   Supposed to be therapeutic.   I've enjoyed hearing the joy in your voice when those small victories happened.   

On the carb not getting gas thing---any maybe someone else stated this suggestion in a different manner(?), but check to make sure the floats are not sticking in the upward position when the bowl is attached.   That was causing me some grief on my T500 build a couple of years back.   Turned out that the float was sitting a little crooked, and the bowl going on would lift the float, thereby making the carb think if was full of fuel.

Looking forward to seeing the finished product, and hearing the resulting happiness in your voice.

 

   

[Scramps]

Firstly, thank you spuds, that’s very kind. I’m glad that you’re getting some joy from my story.

Second, I need to take a moment to acknowledge that the last thing that I posted was pretty dumb. Of course the air couldn’t flow through in the upside down position, that’s what it’s supposed to do, dummy.

Anyway, carry on.

[Scramps]

Are these carburetors plumbed in such a way that 2 & 4 will fill before 1 & 3?

I also noticed that on the petcock, one of the brass fittings for the fuel lines is slightly longer than the other one. Are they intended to be hooked up in a certain way?

My tank is still harboring some rust flecks and other debris. It has partially clogged my fuel valve, so I’m going to prepare to do a very thorough cleaning of the tank. You know, to the best of my ability.

Any special tricks I should know about that will make cleaning easier and/or more effective?

[RAFster122s]

Chain or screws to break up any rust in the tank...shake shake shake

Electrolysis is a good method or getting rid of the rust.
If your rust is bad you may need to consider lining with Caswells after cleaning all the rust out.
You gotta get rid of the rust or it will dog you constantly until you take care of it...

[Scramps]

Sorry, I should clarify; the interior surfaces of the tank are not rusty, there’s just some loose granular stuff in there that’s clogging my fuel valve.

I rinsed the tank out a bunch when I did the evaporust treatment, but there’s clearly more stuff in there. Is there a trick to making the rinsing more effective? There’s a lot of corners and crevices for that junk to hide in

[Scramps]

That’s what I’m talking about, thank you cal

[Scramps]

Did some rinsing on the tank earlier, and so many tiny rust flecks came out. It was kind of upsetting. I got a flashlight and looked down in there as best I could, and saw that the top of the tunnel on the inside had rusted up quite a bit since the last time I cleaned it.

I'm starting to consider lining the tank. Caswell seems to be pretty good quality stuff. What would you fine folks suggest?

[Scramps]

2.25 gallons of evaporust in the tank today, turning it over periodically

[Scramps]

Rust treatment complete. Rinsed, degreased, rinsed rinsed rinsed then dried. Sloshed coating of MMO to stave off flash rust. Heading to Lowe’s for some ZEP after dinner

[Scramps]

Oh! Well heck yeah then!

I’ve got a few more parts coming in tomorrow, once those are installed and ready, I should be able to eke out a little bit of riding time before the cold weather hits.

New AGM battery
Front brake light switch
Fiberglass wrapped muffler inserts
Air filter

I also picked up a couple of inline fuel filters, and I’ve ordered some new small analog clocks from cognito moto.

I pulled off my 4-2 exhaust this evening, cleaned it up to the best of my ability and knocked out the end caps to make way for the muffler inserts. Then i shot it with some 2000* high heat black paint.

It’s not 100% ideal, but short of dropping several hundred dollars on a new exhaust system, this is probably about the best I can do for now.

The last piece of the puzzle is that clutch push rod. I’ve got the tool steel, I’ve cut it and done the shaping, now I just need to heat treat it. I have Zero experience with hardening steel, so I’m going to pay a local gunsmith to do it.

I plan to postpone repainting the tank until winter. Barring the unforeseen, I should be riding this thing next week!

[Gurp]

Heck yeah! I would be paying the smithy too pal.

[Scramps]

Got my gas cap hardware sorted out. I had to buy a bunch of these screws and nylon locknuts, minimum quantity was 25 pieces, so if anybody wants some of these I can fix you up

[RAFster122s]

If that is black oxide you are going to want to keep it well oiled or it will rust very easily. A swab of grease coating the fastener completely before assembly might keep it from rusting.