Author Topic: Pin2Hot's 73 CB750 (Read 56305 times)

Pin2Hot · « **Reply #50 on:** November 13, 2016, 06:53:20 AM »

Quote from: Phoenix on November 13, 2016, 06:47:48 AM

To my tired old eyes, it looks like you left the two o rings out between the jugs and the engine case. Hope it's my eyesight.

They're there, if you look at post #41, second photo, you can see the orange o-rings sitting beneath the gasket. I haven't yet tightened anything down nor put any gasket sealer on the gasket between the jugs and case but I'll make sure those o-rings are still there when I do. Thanks!

calj737 · « **Reply #51 on:** November 13, 2016, 07:28:29 AM »

When you do torque the head, let the motor sit overnight. Release in reverse order all the nuts, re-torque in stages. This will finalize the compression of the gasket and stretch your studs giving you a final, correct torque value on the head.

Pin2Hot · « **Reply #52 on:** November 13, 2016, 09:05:20 AM »

Quote from: calj737 on November 13, 2016, 07:28:29 AM

When you do torque the head, let the motor sit overnight. Release in reverse order all the nuts, re-torque in stages. This will finalize the compression of the gasket and stretch your studs giving you a final, correct torque value on the head.

Excellent advice, I'll do exactly that.

Pin2Hot · « **Reply #53 on:** November 14, 2016, 06:15:53 AM »

Torqued and letting it rest overnight. It's very satisfying to see it so "complete" considering it had been sitting in various bins for literally the past 5 years.

Pin2Hot · « **Reply #54 on:** November 15, 2016, 07:00:55 AM »

I have an engine, fellas. Feels so good to see tons of empty parts bags littering my workbench. I was worried I'd have a tough time timing the engine but it was actually really straight forward. I guess I just had nightmares of valves crashing into pistons. Now it's time to finish polishing the covers and get this thing in the frame! Thanks for all the inspiration.

Pin2Hot · « **Reply #55 on:** November 21, 2016, 06:52:53 AM »

I hammered in some new bearing races from all-balls to get the front end put together and all of the sudden, I have something resembling an actual motorcycle.

I'll have to push the tapered bearing back off of the steering stem for paint but I wanted to start mocking up the bike to get the frame ready for modification. Here's a general idea of what I'm going for:

I'm also trying to decide on the headlight set up. I really dig the different sized headlights but may also go with a single light up front.

5 3/4" high beam and a 90mm low beam projector w/ LED halo

Single 5 3/4" high/low combo w/ LED halo

It's a lot of fun finally seeing this thing taking shape. The next major items are modifying the swingarm to fit and chopping off the back of the frame.

SOHC4 Cafe Racer Fan · « **Reply #56 on:** November 21, 2016, 11:20:37 AM »

I like the double light mock-up.

70CB750 · « **Reply #57 on:** November 22, 2016, 04:12:55 AM »

Making good progress

Pin2Hot · « **Reply #58 on:** November 29, 2016, 07:33:17 AM »

Edit - 6/21/17
This is not the best approach to this modification. See later posts (page 7) to see why. Heed the warning in calj737's post below, he's right.

I spent the past couple nights working on the swingarm. I'm using a 1980 DOHC swingarm to extend the rear end out a bit, mainly for looks. I was sure to capture all of my math to get this thing to fit so that it may help others in the future. I measured the swingarm gap in the frame using the stock arm to get an accurate measurement.

IMAGE DELETED

I measured the depth of the DOHC dust seal and bearing retainers to subtract that from the frame gap. That gave me the new overall width that the DOHC arm needed to be which was 228mm. I needed to chop off 11.7mm. of metal from the drum brake side of the DOHC swingarm. This side is obvious because it has the most meat on it. I used a zip tie to mark where I needed to cut and used an angle grinder to do the work.

IMAGE DELETED

I pushed in new greased up roller bearings as well as the retainers. Luckily the width of the new roller bearing and retainers were juuuust enough on the modified side to not have to machine out any more material in the swingarm.

IMAGE DELETED

So the one thing that's obviously missing here is the hardened spacer that I have yet to cut to size. I also haven't decided if I want to drill out the frame to accept the wider swingarm pivot or machine a spacer/shim so I can use the stock 73 pivot bolt with the hardened spacer. I think the latter is where I'm leaning.

~~As of now, I just slid the stock pivot bolt through the new swingarm to see how things turned out and I couldn't be happier.~~

IMAGE DELETED

IMAGE DELETED

calj737 · « **Reply #59 on:** November 29, 2016, 09:25:21 AM »

Not to sound patronizing, but did you center the arm or maintain the same offset plane for the sprocket between the stock arm and the DOHC arm? Simply reducing the overall width isn't the best approach as the stock wheel sometimes travel "off center" to the arm.

Pin2Hot · « **Reply #60 on:** November 29, 2016, 09:53:24 AM »

Chopping off the wider side brings the center of the arm more in line with the geometry of the stock arm. I believe there's still a slight offset but I can handle that by adjusting the spacers on the cush drive side. I'm probably making that sound easier than it truly is but with the success of other members on the board doing this particular mod, I think I'll be able to handle it.

Pin2Hot · « **Reply #61 on:** December 05, 2016, 08:23:08 AM »

A quick update with things going on behind the scenes. Along with the help of my brother, we've been working on the headlight mount at his shop. I'll post pics of it when we stop screwing it up.

I finally chopped the frame and got some chromoly tubing to replace what I cut. I'm looking in my area for some help here as I don't have the necessary skills/machines to bend up the tubing the way I want it. I'd considered using sand and a torch to bend the tube around a form but I think I'll consult a professional with this one.

Here's the shape I'm going for on the tail section of the bike. I'm going to attempt to 3D print that part in sections to mock up on the frame but this will be the first time I've printed something this complex in various parts. Should be exciting to see when/if it turns out.

SOHC4 Cafe Racer Fan · « **Reply #62 on:** December 05, 2016, 09:43:39 AM »

You might want to add a cross member to the hoop, since you cut out a lot of lateral bracing.

calj737 · « **Reply #63 on:** December 05, 2016, 09:46:07 AM »

It appears the hoop is bent both in the plan and elevation planes? If so, you want make a wooden bunk to mimic the final shape, then you can clamp and bend the tubing using the wooden plank as the form. Easier than it sounds and certainly seems to be within your skill set-

Pin2Hot · « **Reply #64 on:** December 12, 2016, 08:16:47 AM »

Cal, yeah it's bent in both planes. I'm working with a roll-cage guy in my area to see if this is possible, if not, I'll go your route. I have a feeling that his dies may not be able to do bends in both directions so close together but we'll see.

I was able to start working on the tank this weekend. It looks like the original owner either intentionally put two giant dents in the tank or it was a wild coincidence.

Having built myself a slide hammer a few months ago, I gave some dent pulling a try. I'm learning quite a bit through this process and I'm already having some success. I'm learning that finesse is the key and the working from the outside in works better than starting in the dead center of a dent.

I know there will be some body work / filling involved at the end of the day but I think I can make a lot of headway with this method. And please, correct me if I'm going about this in the wrong way!

Oh, and this little guy showed up too:

calj737 · « **Reply #65 on:** December 12, 2016, 09:00:55 AM »

Tack on numerous tags around the circumference, pull gently in a circular pattern, moving towards the center. Patience and finesse (as you've learned) is paramount. Once you get the metal moving, it will suddenly pop on you leaving you with a high spot (or several) to tap back down. Use a blunted punch, tap gently until you get it close.

I use Guide Coat to sand down and find high/low spots. Tap down the highs, fill the lows. These tanks are not as stiff as people believe and the metal moves easily once you get it to "understand your intentions

".

Some people might suggest using compressed air, but I dislike that approach completely. You are more apt to balloon the tank than solve this problem. Others have had success heating the the dented area, then applying ice/cold spray immediately to the metal. Cause the metal to expand then contract rapidly. Again, not a fan, but some make it work...

A last option is to use a 3/8 round stock. Bend a 90* tip in it, about 3-4" long. Put a heavy grip on the other end. Use the bent tip inserted into the tank to "push" the dents up. You'll need a bit of slow arc to it so the tip reaches the underside and the rod levers against the filler neck. Careful not to push the filler neck in while leveraging against it. That method works really well (Paintless Dent Removal approach). I've done heaps of tanks that way.

palepainter · « **Reply #66 on:** December 12, 2016, 09:18:44 AM »

I don't know. I kind of liked the dents on top of the tank. Could help the female riders.

Project is looking great!!!

Pin2Hot · « **Reply #67 on:** December 12, 2016, 11:20:13 AM »

Quote from: calj737 on December 12, 2016, 09:00:55 AM

These tanks are not as stiff as people believe and the metal moves easily once you get it to "understand your intentions ".

You aren't kidding! I was really surprised by how pliable the metal was when I hit it the first time. That's what made me learn very quickly that easy does it. It'll look into using Guide Coat when I get to that point. Thanks for the help.

SOHC4 Cafe Racer Fan · « **Reply #68 on:** December 12, 2016, 02:13:35 PM »

I agree about the compressed air method. It's a dice roll to ballooning the tank.

Pin2Hot · « **Reply #69 on:** December 27, 2016, 08:44:14 AM »

Made some progress removing more dents over the Christmas break, still a lot to do though.

I made an effort to be more methodical in my dent pulling and it's made a huge difference:

I burned a few holes on the right side but I'll fix those later.

The biggest achievement was pulling the massive gash out of the front left side of the tank, it almost completely came out!

I also picked up some paint....

Tank - Ford Grabber Blue

Frame - Toyota Cement Gray

calj737 · « **Reply #70 on:** December 27, 2016, 08:54:09 AM »

I'd wager the underside of that tank is probably pretty rusted up. Before you repaint, you might give thentire tank a solid soak and flush with some Vinegar or The Works toilet cleaner. Follow up with some Prep N Etch to apply a protective coating.

Pin2Hot · « **Reply #71 on:** December 27, 2016, 09:16:10 AM »

The whole tank is going to get media blasted, metal etch primed, primed and painted to ensure longevity. I'll seal the inside as well using either Red Kote or something similar.

SOHC4 Cafe Racer Fan · « **Reply #72 on:** December 27, 2016, 08:16:16 PM »

Quote from: Pin2Hot on December 27, 2016, 09:16:10 AM

The whole tank is going to get media blasted, metal etch primed, primed and painted to ensure longevity. I'll seal the inside as well using either Red Kote or something similar.

Good idea on sealing. Make sure you use something ethanol resistant like Caswell epoxy.

Pin2Hot · « **Reply #73 on:** January 17, 2017, 10:13:06 AM »

Hey everyone, I hope the new year is treating everyone well!

A LOT has been going on since I last posted ranging from the headlight, seat upholstery to modifying the gas tank.

I'm apprehensive about posting the progress on the gas tank because I have a feeling it might ruffle some feathers or I'll get some "YOU'RE CRAZY" comments. The plan is to relocate the oil tank INTO the gas tank using a double wall of sheet metal to prevent hot oil from coming into direct contact with a wall that touches gasoline. Mostly to prevent/minimize direct heating / pressurizing of the gas tank. I don't want to hang an oil tank on the back of the bike for pretty much aesthetic reasons only. I want a wide open empty space in the back.

Here's where I stand today:

Big hole:

Shaping patterns for the double wall:

First metal cut for the first wall:

There's still a lot of fitment to do but I'm also at a crossroads. Is welding these pieces in my only solution? I'm afraid of warping the tank out of recognition with this process. My TIG skills aren't the best but I might be able to handle this. I have a bunch of carbon fiber and epoxy laying around from my canoe racing days (yes that's a thing) and was wondering if laying up some carbon fiber and epoxy around the joints may not only hold the walls in place but also seal it up. What other options do I have other than welding?

calj737 · « **Reply #74 on:** January 17, 2017, 01:33:27 PM »

TIG or MIG. Don't rely on or trust an epoxy. You'll probably also want to line the fuel tank portion, and perhaps even the oil portion so that you're certain you have no leaks whatsoever.

It wouldn't be the end of the work if oil infiltrated your fuel, but it would be very detrimental for fuel to enter your oil.

If you do TIG that, I'd offer the following: use a gas pedal definitely. Use a #4 cup with a gas lens, 1/16" tungsten. And, use 0.040 308 stainless wire. It will weld beautifully and at much lower heat ranges to help prevent the distortion. Even so, I'd be 4-dipping and moving to another area to avoid warpage. Take your time and move far and frequently. And stop every few minutes for several minutes.

And that type of "mod" has been done before, so you're not crazy

Just crazy to undertake the welding work

News:

Author Topic: Pin2Hot's 73 CB750 (Read 56305 times)