Topic: Marissa's 1972 CB500

[754]

Is your rear brake arm upside down ?

[DaveBarbier]

Is your rear brake atm upside down ?

Hmm, it doesn’t look like it but that would mean the brake would operate off a “push” instead of a “pull”. I assume you’re talking about the 90° lever inside of the frame that the brake arm links to. I think normally it aims up but since it’s welded to the splined shaft I don’t see how it could be installed the other way.   

[MauiK3]

When I did my K3 750 I wanted to avoid future corrosion here on Maui so I made some changes. I used a hex head engine bolt set made from stainless. It was very nice going together and being able to use a torque wrench on them. They look great too. I know, not stock. My bike is "stockish". For some of the small fasteners such as the chain guard I bought stainless hex head bolts and polished the heads.
No corrosion!! Most of that was pretty ugly when I took it apart and I struggled with plating just as you have. I think I never quite got the control I needed to make it come out right.
It will be great to see yours completed. I know for projects like that there is really never an end but at some point you'll call it done, at least for the time being. Then you get your shot at bike of the month.

[Marissa]

For some reason, I can't post on mobile sometimes so I lost what I wrote, but I got it to idle on it's own a bit for today.

A few things:

That T fitting I rigged up earlier? Epic fail; leaking gas out everywhere, oddly though mainly when it's on reserve. My hardware store doesn't have anything like it so if anyone has one to sell please let me know. PayPal ready and shipping is to 06437. It sort of looks like the piece is a brass fitting that is zinc plated? but my metals class is over so I can't test out soldering to it.

What hardware do people use to keep the hose snug on the fittings? I think OE was just wire clamps? Or maybe nothing at all?

Another oil leak appeared, this one from the left side cam cover. Think I just need to hammer it flush to the valve cover a bit more and it should be good. It doesn't seat as well as the right side so I'm sure I just need to make it snug.

The oil pump leak seems to have disappeared for now. Though I guess I can't totally tell after gas was pouring over it from the carbs (thank god the cases are powder coated lol. Hoping the paint on my carbs is strong too, but I think my boyfriend did a good job with paint so we'll see.) Gonna get new hardware for it this weekend just to be safe.

My boyfriend borrowed my new carb synching kit, didn't even get to use it before him and he just so happened to snag it on the week I get it running, so that I should get back next week  haha. I noticed that in the 2-3 minutes of idle time (Ironically got it to idle after gas poured out of the thing and was hoping to drain it out by running it) the bike held a good idle, however it sped up on it's own? And the idle got quite fast (no tach hooked up so I don't know RPMs but I could tell by sound) so I went to slowly take off the choke, it held for about 10 seconds, then died off. Is this just something to get used to?

[Marissa]

It will be great to see yours completed. I know for projects like that there is really never an end but at some point you'll call it done, at least for the time being. Then you get your shot at bike of the month.

Haha, someday it is a goal to be nominated for BOTM. Lots of great builds on here and I would be honored to be amongst them!

[Marissa]

Idk why these photos off my iPhone never attach like a normal jpg.

[seanbarney41]

I think I got those fuel t's for ya...those are some parts you really can't mess around with anything less than the real thing. 

These are from a rack of 022a's that were offered for free to me so just double check they are what you need and pm and we will get them headed your way.

[DaveBarbier]

I don’t use any hose clamps. If you use OEM size 5.5mm hose you don’t really need anything. You can get little spring clamps, but really if it fits tight there’s not much pulling force on it so it doesn’t really matter.

Behind that cam cover (I’ll call it the rocker shaft cover) there’s three places it could leak from. The two rocker shaft holes and the valve cover screw that’s in there. Tightening down the rocker shaft cover won’t do much to help the leak either way. Those o-rings that are on the dowels go into a bore. If they’re in at all then putting them deeper into the hole won’t make it a better seal. Did you replace those o-rings? The valve cover screw has two copper crush washers under it. One under the head of the screw and one under the little L bracket. Did you replace them? If not, you can try and anneal them and see if that works.

For the oil pump, honestly the JIS screws do just fine. You don’t need to buy new hardware to get more torque out of it. If it leaks, replace the o-rings. I’d hate to see a post that says you sheared off a screw or stripped out the threads in the case. Remember, there isn’t a cork gasket between it which might benefit from more “squish”. There’s metal to metal contact with an o-ring inside. If the metal of the oil pump is contacting the other metal of the case, tightening it more is just stretching the fasteners.

The racing idle could be out of sync carbs, but it could be an air leak too. Other things could cause that like poorly routed throttle cables too. BUT as the motor heats up the idle is going to increase just due to a more efficient burn. Was it increasing really fast or was it a slow increase?

Good posts lately, you’re getting close!!!

[Marissa]

I think I got those fuel t's for ya...those are some parts you really can't mess around with anything less than the real thing. 

These are from a rack of 022a's that were offered for free to me so just double check they are what you need and pm and we will get them headed your way.

I think I actually have 627Bs, but I could take them apart and give you the sizing of the T fitting to see if they interchange!

[Marissa]

I don’t use any hose clamps. If you use OEM size 5.5mm hose you don’t really need anything. You can get little spring clamps, but really if it fits tight there’s not much pulling force on it so it doesn’t really matter.

Behind that cam cover (I’ll call it the rocker shaft cover) there’s three places it could leak from. The two rocker shaft holes and the valve cover screw that’s in there. Tightening down the rocker shaft cover won’t do much to help the leak either way. Those o-rings that are on the dowels go into a bore. If they’re in at all then putting them deeper into the hole won’t make it a better seal. Did you replace those o-rings? The valve cover screw has two copper crush washers under it. One under the head of the screw and one under the little L bracket. Did you replace them? If not, you can try and anneal them and see if that works.

For the oil pump, honestly the JIS screws do just fine. You don’t need to buy new hardware to get more torque out of it. If it leaks, replace the o-rings. I’d hate to see a post that says you sheared off a screw or stripped out the threads in the case. Remember, there isn’t a cork gasket between it which might benefit from more “squish”. There’s metal to metal contact with an o-ring inside. If the metal of the oil pump is contacting the other metal of the case, tightening it more is just stretching the fasteners.

The racing idle could be out of sync carbs, but it could be an air leak too. Other things could cause that like poorly routed throttle cables too. BUT as the motor heats up the idle is going to increase just do to a more efficient burn. Was it increasing really fast or was it a slow increase?

Good posts lately, you’re getting close!!!

Thanks Dave! I’ll have to check what type of washers I used now that you brought it up. I think some of my stainless hardware kit went there and potentially may be using stainless washers that aren’t crushing and sealing.

[seanbarney41]

I think I got those fuel t's for ya...those are some parts you really can't mess around with anything less than the real thing. 

These are from a rack of 022a's that were offered for free to me so just double check they are what you need and pm and we will get them headed your way.

I think I actually have 627Bs, but I could take them apart and give you the sizing of the T fitting to see if they interchange!

or just check Honda parts fiche

[Marissa]

16191 300 004, doesn't say sizing or anything

[754]

300  is a 750 part  so there should be a few around..

[Marissa]

Oil pump leak fixed, cam leak fixed.

Got it idling for 2-3 minutes, again, for it to seemingly run out of gas. Here's what's going on:

Put fuel valve on ON, sit for 2 minutes to let the fuel fill up. Turn it over, sounds good but not starting. Open throttle all the way, turn it over again, pretty much start right up.

However, on ON, it seems to suck up all the fuel and eventually die out.

Reserve however, seems to work instantly. The problem is, it will start to pour out fuel.

*ALL 4 FLOATS WERE ADJUSTED TO 22MM*

After we had it idle for 2-3 minutes, I looked at the exhaust pipes. 1 & 2 were getting appropriately hot, 3 & 4 were only a tad warm.

Out of curiosity, I swapped the fuel lines to the two fittings on the fuel valve. When I did this, I then found that 3 & 4 were getting warm.

I'm pondering if my fuel valve is just out of wack and dirty? It was one of the first things I rebuilt and I'm thinking of just buying a new one, potentially looking for a new one with a single fitting and then just running a Y fitting that will feed into both lines instead.

This weekend, I will pull the plugs and see what they look like. I have extras just in case.

Side note: when it doesn't start up and the fuel valve is on ON, we heard it backfire and smoke come out of some of the carbs. Is that a sign that it's flooding?

[754]

Sounds plugged in petcock or tee.
 Is it dual outlet petcock ? Put 2 pieces of hose to a catch can and observe flow.

[Marissa]

Sounds plugged in petcock or tee.
 Is it dual outlet petcock ? Put 2 pieces of hose to a catch can and observe flow.

Yep, this confirmed it! I have the whole petcock assembly taken apart and all metal pieces in the ultrasonic. I feel like inherently they will never be equal, as the second fitting seems to feed off of the first, and has to travel through 2 90 degree angles.

Some yucky stuff.







You can see in this photo that there's only one way for fuel to flow into the fittings, and the one that is seemingly clogged is the fitting that gets fuel last.

My concoction of ultrasonic magic.



From earlier:

[calj737]

Pine Sol is very acidic to aluminum and will turn it grey promptly, with little ability to return things to a shine without huge efforts.

[DaveBarbier]

So the green circle hole feeds the right barb, right? Well it looks like there’s supposed to be a hole on the left side circled in red. Is that the case?

[DaveBarbier]

After cleaning the petcock, I’d make sure the jets are not clogged from some debris working it’s way down the line.

[754]

A picture back a few shows the drain lines, one has sediment in it. Just drop the bowls and make sure they are clean.
 Sometimes one outlet will flow less, and when you block or pinch off that one the other will start flowing faster.
In this case though the one appears to be plugged up somewhere. 
 You are getting close.

[wolf550]

im using the 627B's on my 500/550 the T fitting measured 11.21mm where the o rings attach to. its the same measurement as my set of 022A's T fittings. i'd get those from seanbarney41

[seanbarney41]

Yup, o rings are same part number from honda.  These carbs are the same castings

[Marissa]

I actually found a T fitting local to me and picked it up Saturday thanks to Justin, he's here on the forums. Thanks again!

Cleaning the fuel valve ended up being a waste of time. I was cleaning the brass pick up tube with a nylon plastic bristle and instantly it developed cracks and fell apart. I can't get solder to stick to it either. So a new OEM one is on the way.





Blurry image Dave but there is only one opening for the fuel to go through.

Also decided to order new float bowl gaskets, and I found reproduction floats and pins which I also ordered. One of my floats has some foam missing (not sure how?), two of the floats have broken brass pieces, etc. At this point I want to eliminate all points that could lead to fuel issues. I realized some of the floats have better range of motion than others because some of the pins are chewed up, wondering if that could cause the floats to "catch" at certain angles and prohibit it from stopping the flow of gas.

Weather is getting nice out and I'm antsy for these parts to arrive now that I'm out of this semester.

[Gurp]

Rough pins can def cause them to "bind" had it happen a few times myself. And the ole backyard mech throwing a nail in instead of the pin.

[Godffery]

Cleaning the fuel valve ended up being a waste of time. I was cleaning the brass pick up tube with a nylon plastic bristle and instantly it developed cracks and fell apart. I can't get solder to stick to it either. So a new OEM one is on the way.

That cracked pickup tube can be replaced.
Mount the petcock in a soft jaw / padded vice, take note of the measurements of the tube OD and height, grab the tube at the bottom, wiggle around till it snaps off at the bottom, get a new (slightly larger) brass tube at local hardware / craft store, Using a slightly under sized drill bit, drill out remains of old tube (being careful to go just deep enough to remove only the old bits of the tube) now you should have a fresh hole that is a tiny bit tighter then the OD of the new tube, (you want a press fit of the tub into the newly drilled hole) for getting the new tube cut at the proper length, measure the depth of the drilled hole, and ad that extra amount of length to the measurement for the desired total height of the tube, using a standard plumbing pipe cutter will give the tube a tapered end, this will help with starting the pressed fit, then get a nail that fits easily into the top end of the tube, this will protect it while you drive the tube in the rest of the way, now set the newly restored petcock on the bench, take some pix, post them on your build thread, sit back and revel in the glory of the moment!