Author Topic: 1972 CB500 - Rebuild Project (Read 31125 times)

Puffin · « **Reply #100 on:** August 11, 2015, 10:10:11 PM »

Cal you are correct... I am getting befuddled by piling up the issues and looking for an overall solution.

I was going to post a few more comments and photos after my last post but I got distracted by going to the pub.. I tend to find this happens a lot?

I can address a few of your questions quite quickly...

"It's hard to see from the pictures, but is the rear wheel assembled with the correct spacers? Does the rear wheel (rim) spin freely and without obstruction on the axle?"

This was my first assumption and I have checked and checked again and I can only conclude that everything along the rear axle is correct.. I will post some pics as a fresh set of eyes may pick up something I have missed. The rear wheel spins beautifully on the rear axle and there is no obstruction.

"For the front end, first thing I'd do is to release the tension on the triple trees and allow the forks to be adjusted. But, is the steering stem bent is my concern? This would show by rotating lock-to-lock and feeling for rough spots in the steering bearings, and leveling the underside of the lower and comparing it to the upper clamp."

I did release the tension in the front forks and this led to my next discovery... bent front fork tubes. (see Pictures below). No idea how i missed this? It's subtle... but they are bent without a doubt. Hopefully I can get these straightened? A bent steering stem or frame is still a real worry though.. particularly if I know I have bent forks, misaligned sprockets and a ding in the alternator engine case.

There is definitely no rough spots on the steering head bearings. I replaced the bearings with new All-Balls tapered bearings and they run real smooth. I double checked them and they are installed ok.

When I installed the tyres I tested the wheels for 'trueness' on a jig and I was happy at the time that they were good. I will double check again.

As suggested I will go back and check the sprocket alignments with the straight edge and follow your 3 steps below..

Your suggestion of setting up the string box is interesting and a method I've not heard of before... I'll give it a go.

Bootsey · « **Reply #101 on:** August 11, 2015, 11:29:21 PM »

That's a shame about the forks, but hopefully some new tubes will get everything back on the straight and narrow.

calj737 · « **Reply #102 on:** August 12, 2015, 04:14:23 AM »

You may be able to find someone who can straighten them. (I know it can be done locally, and have seen others write of it). The big concern will be marring the chrome. Complete disassembly will be required, and be incredibly careful that if they're straightened, they do not get any burrs in them where they pass thru the fork seals. That's a deal breaker! A very scrutinous inspection of their surface condition is a must. And perhaps a polish.

Puffin · « **Reply #103 on:** August 15, 2015, 10:48:39 PM »

So I have sent the feelers out to see if I can find some new, or decent second hand, fork tubes and I've also found a couple of places that advertise that they can do fork straightening. I need to give them a call this week.

Given that I can't really take any decent measurements around aligning the front and rear wheels till I get straight forks I'm a little stuck for now.... I may take the bike down to the frame shop and they will run a full alignment test using some fancy computer and a load of probes. This is about $250 for the test ($175 USD or 100 Quid UK) but to be honest it may be worth doing just for the piece of mind.

Couple of other things I have found that also point to frame issues are an uneven gap where the upper-front engine brackets sit ... see pictures below

Puffin · « **Reply #104 on:** August 15, 2015, 11:07:05 PM »

I took the front sprocket back off and noticed that the back side had been wearing much more than the front side which indicates my current problems were obviously in place before I took everything apart.

The front sprocket also had '17' and '750' stamped on it...

I know 17 teeth is correct for a CB500 front. But would a 17t CB750 sprocket and a 17t CB500 sprocket be interchangeable?

There was also quite a lot of play on the front sprocket... is that normal?

Puffin · « **Reply #105 on:** August 15, 2015, 11:27:44 PM »

Some pictures of my rear wheel and axle set up...

You can also see how that with the chain on, the sprocket retainer is being forced inwards towards the front of the bike and being forced outwards at the rear. With the chain off everything sits nice and straight.

calj737 · « **Reply #106 on:** August 16, 2015, 05:12:36 AM »

There really should be no play in the front sprocket once bolted down.
Some 750 drive sprockets have a "dish" to them that indicates orientation front-to-rear. I don't recall the 500 having that. This may be a source of your problems that the sprocket is too close to the motor, and case damage will occur.

The frame tube/engine mounting boss in front is concerning to me. When I install motors, I don't tighten any bolts down until all bolts are fully installed. This helps "center" the motor within the frame. I do tighten the 2 10mm bolts underneath the motor first, then work my way up to the front, then upper rear, and finally lower 12mm (the one that hangs the driver pegs). The rear hangar bolts have spacers that somewhat self correct the center, but the front mounting plates need to be installed, and these pull the front tubes and motor together.

Of course, all this is moot if your frame is actually bent

. I think it very wise to have it professionally inspected before you go further. With a repainted frame, visual evidence of it being bent is much harder to detect.

Regarding your rear sprocket and carrier, do you believe there's damage to them, or do you suspect the drive sprocket is causing the misalignment?

Meanwhile, you can do some checking yourself with the front forks off the bike. Using the string box I described earlier, also install a plumb bob from the steering head (remove the triple tree and steering stem). Suspend a bar across the head, string with bob dropped through. This will enable you to determine whether the neck is straight vertically, and use it as a centerline of the frame for measuring side-to-side distances.

Bike on center stand, and shimmed slightly to insure you have a true parallel sitting compared to the ground. Level the bike front to rear, and side-side with a level and shims.

Once level, a small level to test the exterior of the steering head for plumb, and begin finding the centerline of the bike and stringing to your outside lines with tape dimensions. A bit complicated in words, but it's a DIY technique until you get to the frame shop and deposit cost you a penny.

Puffin · « **Reply #107 on:** August 20, 2015, 12:58:18 AM »

Thanks for all the advice Cal,

Good news is that I managed to track down some new-old-stock fork tubes locally and they arrived this morning. I didn't realise before how much the bent tubes were affecting the performance of the front shocks... with the new tubes in the whole front end is so much smoother and it's made a massive difference.

They look so much better as well... no more dull and pitted chrome for me....

Puffin · « **Reply #108 on:** August 20, 2015, 01:15:53 AM »

This weekend I am going to set up all the string lines as per Cal's suggestions and test the frame. Now I know the front forks are straight i've taken a variable out the equation which is a step in the right direction

For now I've un-buttened all the engine bolts and I can already see that the frame-engine spacings in various locations has changed so something is definately wrong. I'll tighten them up in the order Cal suggested and see if this makes a difference.

In the meantime I did a quick test using a level

1) Level at rear of frame - Dead level
2) Level in middle of frame - Dead level
3) Level at top of triple clamp - Dead level
4) Level at base of triple clamp - Dead level

Result = Font wheel is pointing right

If I turn the wheel so that it is pointed dead ahead (visually) then the level at the triple clamps goes off level. The middle and rear of the bike frame remains dead level.

To me this simple test confirms that the frame is slightly twisted... this would account for the front end angle being off vertical and could also account for the sprocket misalignment if the engine is not sitting in a straight frame.

calj737 · « **Reply #109 on:** August 20, 2015, 04:26:36 AM »

Probably a bent steering stem, Puff. If the forks were that molested, the stem had to take a massive hit too. Probably a very good time to slide it out and inspect the upper top clamp, lower tree, and stem. Also, with levels at Zero, check for plumb of steering neck.

Puffin · « **Reply #110 on:** September 25, 2015, 08:46:30 PM »

So haven't posted for a while and progress has been a bit slow but I'm hoping to speed things up again now I have had my frame sorted. I'm supposed to be riding this bike round New Zealand in February and there is still a load of work to do before she is ready for such a trip.

Good news is that I found a guy a couple of hours away who straightens frames so I bunked off work for a day, popped the bike in my van and drove down to his workshop so he could take a look. He did a few tests and turned out the front end was twisted. $250 and half a day later he had it all straightened out and lined up again. He also straightened out my front wheel that had a bit of a bulge in the rim.

Happy that is sorted

Puffin · « **Reply #111 on:** September 25, 2015, 09:03:00 PM »

I also found out what is causing the issue with my rear sprocket...!

Here is my problem.... excessive play on the final drive flange...

Puffin · « **Reply #112 on:** September 25, 2015, 09:07:48 PM »

You can see from the pictures below that the internal 'bush' inside the drive flange is really badly worn. The grease grooves have almost completely worn away and you can see a lip that indicates how thick this bush used to be...

I have attached a picture of a new drive flange for comparison

Puffin · « **Reply #113 on:** September 25, 2015, 09:23:33 PM »

The question is how to deal with this?

Not sure if it's even possible to find new-old-stock although the Part# 42610-323-000 seems to be the same for the CB500's and all of the CB550's so that increases my chances.

I've sent the feelers out to see if I can find a low-mileage second hand part locally.

I guess the other option would be to see if a machine shop can insert a bush or a sleeve to bring it back up to the original thickness?

calj737 · « **Reply #114 on:** September 26, 2015, 04:31:58 AM »

I think Deltarider is dealing with this exact issue as well. Might cruise through and look at his recent (4 weeks ago) thread. I'll check my stash, I may have a spare lingering around.

Puffin · « **Reply #115 on:** September 26, 2015, 11:32:32 AM »

Thanks Cal... much appreciated.

Yes it was actually Deltariders post that led me to this point. Another win for the forum methinks...

Puffin · « **Reply #116 on:** September 30, 2015, 03:44:30 AM »

So I'm over in another part of town this afternoon and i'm heading back to my van when out of the corner of my eye I see a small sign pointing down an alleyway indicating a Motorcycle Breakers. Luckily I had my worn-out final Drive Flange in the back seat so I wander down fully expecting to walk back out the alleyway 2 minutes later with nothing lost but nothing gained.

Once there I was barely acknowledged by a rather short and incredibly grumpy old man who seemed nothing short of inconvenienced by the fact I'd come down to his place of business to potentially part with some money for something he made a living from selling. Anyway, when I asked whether he had a 1970's CB500 he was breaking he surprisingly replied with "... only the back wheel".

The brief glimmer of hope that I initially had was soon quashed when he appeared from round back holding a rear wheel assembly that looked like had been outside in a puddle for the last 30 years. Undeterred I asked for some tools to start taking the hub apart to examine the condition of the drive flange....

Despite acting like I'd asked him for a go on his teenage daughter, he eventually provided the necessary equipment and watched me for 20 minutes as I disassembled the rusted up and greasy pile of crap whilst trying not to get #$%* all over my best shirt and business attire.

When I finally got the drive flange off, and managed to convince him to part with an old rag to clean the part up, I found that somebody had already had the same problem as me but resolved the issue by machining a bronze bush that sat neatly inside the flange.

Eureka..!

"ll take this please" I said
"No.. it's the whole wheel for $120 or nothing" he said
"but I only need this and the rest of the wheel is junk" I say
"fine I'll throw it in the skip" he said
"..........?" I said
"Ï told you it's $120 for the whole lot" he said
"yeh... but now I've just taken it apart for you?" I say
silence
"I'll give you $40 for the lot" says I
silence
"fine... hold onto it for another 30 years" I say

Then he starts putting the whole thing back together

....after another 10 minutes of childish exchange I start to walk away and he calls me back and we agree on $75 for the whole wheel.

I ended up with working drive flange, plus a spare hub, rim, cush rubbers and bearing retainer... all of which I don't need.... and he got lucky and made $75.

To be honest I would have spent more than that at a machine shop plus the arse of driving around town for the next couple of weeks so I'm generally happy with the outcome. I had a number of breakers contact me to say they had spare flanges but they were all worn just like mine so I was running out of options.

Anyways... pictures below... all fits perfect and no more sprocket wobble...

Puffin · « **Reply #117 on:** September 30, 2015, 03:45:33 AM »

More pics.... Bit of a clean and a polish and I reckon it will come up real nice

Puffin · « **Reply #118 on:** October 05, 2015, 09:12:08 PM »

Now I've sorted those problems out I have a new found enthusiasm and I'm getting this thing back together at record speed...

Drive Flange came up almost as good as my original and the rear wheel is back together and working perfectly.

In the Honda Service manual it states that you should grease up all contact surfaces in the cush-drive.. something not mentioned in the Haynes and Clymer manuals. Makes sense given there are 0-rings and grease grooves in the hub and flange. I guess you don't want to over do it because there are holes into the Drum Brake side of the hub so you really want to avoid this seeping through onto your brake shoes.

Ended up treating myself to a new set of sprockets as well

Puffin · « **Reply #119 on:** October 05, 2015, 09:21:26 PM »

I've had these really classy front indicator lights for some time... I think I got them from 4into1.com about a year ago?

They have a really good quality, flat black metal shell and are really bright... what really like about them is that they match my headlight perfectly. I mounted them with a simple bracket.

Definitely digging the flat black and chrome look that's developing.

Puffin · « **Reply #120 on:** October 05, 2015, 09:34:09 PM »

I ended up taking my Carbs back off because I wasn't happy with the way I originally bench sync'd them. Since originally restoring them I have read up on it a lot more using the info in this Forum so I took the time to do it properly using a 3mm drill bit to balance the throttle slides whilst remembering to have the idle screw turned about half way so that I had plenty adjustment available on the idle screw when it comes to the final vacuum balancing.

I also took the time to fix the broken pin on the backing plate and eliminate the side-to-side movement along the bar that holds the throttle slide arms. This involved drilling out the broken pin and inserting a new pin. I tried a number of things but ended up using a ridged nail cut to about 11mm in length.

It's not Grade-A engineering but it works perfectly and to me perfect is good enough....

Puffin · « **Reply #121 on:** October 05, 2015, 09:47:15 PM »

My tank is currently getting painted so I thought I'd work on the Petcock and gas cap.

I did strip the tank and fill out the dents and I was prepared to paint it myself but you can't get the Spraymax type 2-part paint in rattle cans in this country so I was limited to a standard lacquer clear coat which would melt the second it got a whiff of fuel near it.

The bike deserves a quality finish so I dropped it off at a little place down from my work and he's gonna do a proper job for me..

I had this gas cap with a fuel gauge in it and it looks like a cool idea on the surface but the reality is a bit different.. for a start it's #$%* and doesn't actually work.. the weight of the float is not enough to pull the needle down to empty and it has this massive hole underneath which looks like it would let gas through every time you moved with a full tank. I spent a good couple of hours trying to make the thing work but in the end I stopped wasting my time.

Settled instead on a new classic, cool, Honda, period original gas cap....

Puffin · « **Reply #122 on:** October 05, 2015, 09:54:11 PM »

Got some new o-rings, fiber washers and a filter for the Petcock and gave it a good clean .

I'm sure you can get fibre washers from a hardware store but I couldn't find the dimensions so I just bought a couple from Honda for now and made a note of the dimensions for future refurbs... see picture for details.

Puffin · « **Reply #123 on:** October 05, 2015, 09:57:59 PM »

Once again that product detail is as follows...

Make sure you enunciate clearly when ordering over the phone....

SOHC4 Cafe Racer Fan · « **Reply #124 on:** October 05, 2015, 11:22:50 PM »

Quote from: Puffin on October 05, 2015, 09:47:15 PM

My tank is currently getting painted so I thought I'd work on the Petcock and gas cap.

I did strip the tank and fill out the dents and I was prepared to paint it myself but you can't get the Spraymax type 2-part paint in rattle cans in this country so I was limited to a standard lacquer clear coat which would melt the second it got a whiff of fuel near it.

The bike deserves a quality finish so I dropped it off at a little place down from my work and he's gonna do a proper job for me..

I had this gas cap with a fuel gauge in it and it looks like a cool idea on the surface but the reality is a bit different.. for a start it's #$%* and doesn't actually work.. the weight of the float is not enough to pull the needle down to empty and it has this massive hole underneath which looks like it would let gas through every time you moved with a full tank. I spent a good couple of hours trying to make the thing work but in the end I stopped wasting my time.

Settled instead on a new classic, cool, Honda, period original gas cap....

I have one that I tried as a novelty. The problem with mine is that the latch is a PITA to release.

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Author Topic: 1972 CB500 - Rebuild Project (Read 31125 times)