Author Topic: 73 CB500 Boston Cafe (Read 8470 times)

lajos · « **on:** May 26, 2015, 08:53:47 PM »

Hello-

My name is Lajos and I live in Boston. I've picked up a 73 CB500 two weeks ago for my first bike build project. The frame is in pretty good shape and it came with an extra 550 motor that (from the outside) looked decent. More on that in a bit.

It's not a complete bike, so this won't be a restoration to original condition...

Here's a pic of the bike "new":

lajos · « **Reply #1 on:** May 26, 2015, 08:57:11 PM »

This past weekend with the help of my son we stripped most everything off the bike, pulled of the 500 motor and found broken off valve heads in two cylinders. No wonder that engine wasn't turning over.

My son was very eager to help, he now can identify 10 vs 12 mm nuts by sight and got pretty good with the impact driver

lajos · « **Reply #2 on:** May 26, 2015, 09:03:12 PM »

I also took apart the 550 engine. This is where things turned a bit disappointing. After cleaning up the cylinders and trying to hone them, the rust was deeper than expected. The valve seats also showed some major pitting.

So I ordered a 600cc big bore kit from Japan (got here in 2 business days, that's faster than shipping something to the next state over) and found a cylinder head on ebay that looked much better (that one is still in the mail).

Tomorrow I'm driving the jugs to the machine shop. Hope the rust pits are not more than 1.5mm.

knowsnothing · « **Reply #3 on:** May 27, 2015, 06:23:12 AM »

Hey Lajos,

Welcome aboard. It looks like you are off to a good start. Just so you know, there are a decent amount of us in and around Boston. There is a lot of knowledge and experience to be had. We try our best get together once a month for beers and motorcycle talk. If you are interested, head over to http://www.nehondaguys.info/forums/ and sign up. Good luck with the project.

lajos · « **Reply #4 on:** May 27, 2015, 01:02:23 PM »

Thanks for the NE Honda forum link I'll sign up!

I dropped off the cylinders at the machine shop, they almost had a heart attack when they saw the +3 pistons. Then I almost had a heart attack when they told me about the extra cost for such a big bore and that they have to send it out to another shop where they have a smaller machine.

More woes followed when I received my ebay carb purchase. The carb looks awesome from the outside, but I opened up the float covers and found the dreaded white dust with a lot of pitting. Maybe I shouldn't be buying carbs off ebay.

The pic is after I sprayed it with some wd40 to loosen up pins (that are still stuck). Is this at all salvageable?

Scott S · « **Reply #5 on:** May 27, 2015, 02:31:05 PM »

Carbs don't look too bad. Spray with PB Blaster and let it work for a couple of days. Maybe use a torch to heat cycle the posts/pins a couple of times and then try a small punch. Don't have to get them too hot....just enough to break the bond.

SOHC4 Cafe Racer Fan · « **Reply #6 on:** May 27, 2015, 02:41:48 PM »

If you need parts or a professional to rebuild your carbs, contact member harisuluv (James). He can restore your carburetors to optimal condition.

I'm not sure how much your machining shop wants to charge for the 600 cruzinimage piston kit, but you should shop around. The BEST person in your area for machine work is member Mike Rieck MRieck. He does The ulitimate port and polish job on CB heads. He can also bore your cylinders.

knowsnothing · « **Reply #7 on:** May 27, 2015, 04:03:41 PM »

Quote from: CB750 Cafe Racer Fan on May 27, 2015, 02:41:48 PM

The BEST person in your area for machine work is member Mike Rieck MRieck. He does The ulitimate port and polish job on CB heads. He can also bore your cylinders.

And lucky for us he is local to the Boston area

lajos · « **Reply #8 on:** May 27, 2015, 06:01:37 PM »

Thanks for the suggestions, I'll soak the carbs, hopefully I can get things loose in them. Actually the throttle valves are not stuck, the issues are with the float area as I suppose gas was left in there.

I got quotes for between $200-400 to do the boring, actually I talked to a guy called Mike, not sure if it's the same Mike though

For the valve job and resurfacing the head $150.

While those things are in the works I have to plastigage the crankshaft and I want to strip the paint off the crank case and repaint it. The transmission parts looked nice, so hopefully there it will just be cleaning and reassembling.

lajos · « **Reply #9 on:** May 28, 2015, 12:49:10 PM »

I was up 11-0 on the rusted cylinder studs, then this:

MickB · « **Reply #10 on:** May 28, 2015, 04:24:52 PM »

Get some heat (propane torch) and apply around the base of the stud, get some vice grips on the stud and make sure the block is held tight and it'll then start to move and you'll get it out. It might take a bit but you'll get it out
I had similar and it worked for me.

lajos · « **Reply #11 on:** May 28, 2015, 06:06:34 PM »

Thanks for the suggestion. I heated the stud with a torch a couple times and added more pb blaster. Then I welded on a nut, impact wrenched it and sheared another piece of stud off. So now I have a shorter stud. Damn. Will soak with the blaster for a couple days.

I'll try with the vice grip next time.

calj737 · « **Reply #12 on:** May 29, 2015, 04:56:25 AM »

Weld a nut on it again. Then, heat the stud to cherry red. Then whack the stud with a dead blow to shock it loose. Add PB Blaster while stud is hot. Don't use an impact to extract it. Slightly tighten the stud first, then turn loose. Use a wrench by hand to control the torque. If it won't crack loose, re-heat it again.

SOHC4 Cafe Racer Fan · « **Reply #13 on:** May 29, 2015, 07:56:27 AM »

Quote from: calj737 on May 29, 2015, 04:56:25 AM

Weld a nut on it again. Then, heat the stud to cherry red. Then whack the stud with a dead blow to shock it loose. Add PB Blaster while stud is hot. Don't use an impact to extract it. Slightly tighten the stud first, then turn loose. Use a wrench by hand to control the torque. If it won't crack loose, re-heat it again.

Cal, is ther any advantage/disadvantage to using a stud removal tool versus the double nut?

calj737 · « **Reply #14 on:** May 29, 2015, 08:06:28 AM »

I always prefer a stud removal tool as it grabs the shank never the surface of the deck. Then there's less longitudinal torque applied to the bolt/stud. His is so short now, that a welded nut is about the same thing.

Given how stubborn this last one is, even a stud puller might have sheared it. Whacking it while super hot should dislodge the stuck threads allowing it to be turned out.

MickB · « **Reply #15 on:** May 29, 2015, 04:47:48 PM »

For what it's worth this is what we did and I had 3 or 4 stuck studs, I took it to Ivan the ace mechanic. First he made sure the engine case was securely locked into place. This is what he used.

And he heated the base of the stud (it was nearly glowing red) and the area close to the stud and then with the vice grips (about an inch from the base of the stud - wear heat proof gloves) it slowly started to move, a bit more heat and it came away without damage to the engine case.

It took a while to get it to move, while he heated it up I was putting constant (a lot) pressure on the vice grips and then it slowly started to move.

We tried the double nut on the thread but only twisted the stud while it was red hot. It needed to be close to the case to the case to counteract the stud twisting out of shape.

lajos · « **Reply #16 on:** May 30, 2015, 04:32:34 AM »

I went through another couple welded on nuts, heated the stud to red hot a bunch of times, heated the block with a heat gun, still stuck. Used up a whole bunch of pb blaster and also something called liquid wrench.

Right now I have a washer welded to the stud, then a nut to the washer. That's how the night ended. Now it's soaking.

Restoration Fan · « **Reply #17 on:** May 30, 2015, 04:56:32 AM »

A little late now but if you had welded the nut just a tiny bit closer to the deck, it might have helped. Instead of using a wrench to turn it, see if you can square up the nut enough to use a deep set socket instead and let the socket go down to where it's literally almost touching the top of the head. Then, when you're applying pressure, try to make sure that you keep the ratchet directly above the shaft of the bolt so that there's not much left/right flex in the stud. You want rotational pressure directly down the shaft if possible.

calj737 · « **Reply #18 on:** May 30, 2015, 05:12:04 AM »

I said it before, while the stud is cherry red, use a dead blow and whack the stud. Then, before you try to loosen it, turn it tighter just a smidge, then try to turn it loose. the action of whacking and tightening, will dislodge the corrosion and free the threads.

lajos · « **Reply #19 on:** May 30, 2015, 05:33:49 AM »

Thanks for your advice, that's what I was going by it yesterday.

This is the routine:
- heat up block around stud with electric heat gun
- heat up stud to red with propane torch (not propane actually the yellow can whatever that is)
- whack down on the stud with a hammer a couple times
- add pb blaster even though it evaporates almost immediately
- put wrench on
- try tightening the stud
- try loosening the stud
- as it cools I add more blaster

Repeated this cycle about 10 times. Caused two smaller fires (left paper towels too close). So far it didn't move in or out. Maybe I need more heat?

calj737 · « **Reply #20 on:** May 30, 2015, 05:58:09 AM »

Forget the electric heat gun and stick with gas. Just keep pouring the heat to the stud/block connection. It will come loose. Keep spraying the PB to the joint as well as soon as the heat is removed. And hold the block while you turn the stud. If its withstanding your efforts so far, more heat. Rest, more heat, whack a few times. More heat. It will come loose.

I had to BBQ some rusted pistons for over 4 hours after 6 months of soaking to get them loose. Finally, with much effort and patience, they came out.

lajos · « **Reply #21 on:** May 30, 2015, 06:58:59 AM »

Those cylinder fire pits look awesome

My kids have a bunch of activities today so probably won't have time to get back to until tomorrow, but I'll torch that sucker to 11.

I also see the point of welding the nut lower to apply more rotational torque. If these shear off again, I will weld them closer to the surface (I've been trying to keep it as high as possible so I don't break the stud too close to the case). Wish I had a tig welder not just the flux core.

Can I apply heat to the crank case in that area with the torch? I don't know how far I can heat it up before things start warping.

calj737 · « **Reply #22 on:** May 30, 2015, 12:47:05 PM »

You can heat the case without warping. Understand, the more you weld to that stud, the more you de-temper it, the weaker it becomes. You've got probably this last shot at it, so take your time. Heat, soak, whack, heat, soak, whack.

MickB · « **Reply #23 on:** May 30, 2015, 04:30:44 PM »

Lajos do what Cal said, but we only used a torch right at the base of the stud on the case

lajos · « **Reply #24 on:** May 30, 2015, 08:22:20 PM »

Spent another two hours on the stud.

Heated the base and the case around it with torch, blasted it, whacked it, tried tighten/loosen with wrench, repeated 6 or 7 times, sheared off the nut again so now I have about ~1/2" left. Also tried a can of liquid nitrogen on it somewhere inbetween. Tried vise grip after nut broke off.

Is it time to take it to a machine shop? Or should I weld another washer/nut combo to it?

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Author Topic: 73 CB500 Boston Cafe (Read 8470 times)