Topic: 1978 CB750A Turbo Build

[BenelliSEI]

My comment got buried in the original post. Those head nuts only 1/2 engaged look dicy to me. Why not eliminate the washer and get full bite?

[LiveeviL81]

Thoughts?
Kaleb

  I've always liked that color.  I've used it on several engines I've painted.  Depending on how much you want to do, it would look really nice if you removed one screw at a time from the covers and cleaned the head and re-inserted it, move on to the next one, and so on.  An hour or two of cleaning parts like those and the valve covers and maybe the Honda on the alternator cover would really make it pop.
[/quote]

I purchased a kit for converting all of the cover bolts with JIS screws to hex head stainless, It looks great! Though it makes me want to do that with the case half bolts as well, or at least polishing their heads. But I worry about untorquing some of the important bolts, even if its one at a time. My big worry is this paint has not seemed to be very good at adhering so far, granted it hasn't been baked yet, but some of the bolts have had their paint flake, and a few small scratches have appeared. I even had some paint removed when using painter tape!

Kaleb

[LiveeviL81]

Was able to get the engine fully assembled and painted this last weekend. Left the ARP Bolts and Nuts stay torqued for a week before loosening and retorquing them. I noticed that some of them have a lot less thread engagement than others, All studs were torqued to 15ftlbs and the nuts were torqued to 22ftlbs. Running a Cometic Head gasket and normal base gasket. I am using the original steel washers with the ARP nuts, and notices the APR nuts are taller. I think it'll be okay, but it was a little worrying.

Kaleb

Why not take out the washer? It serves not purpose and you’ll have full engagement.

I had thought the washers were used so the steel nut wouldn't "bite" into the aluminum casting when torquing the head down, since the stock nuts and the ARP nuts both had the same diameter flange.

[MRieck]

Was able to get the engine fully assembled and painted this last weekend. Left the ARP Bolts and Nuts stay torqued for a week before loosening and retorquing them. I noticed that some of them have a lot less thread engagement than others, All studs were torqued to 15ftlbs and the nuts were torqued to 22ftlbs. Running a Cometic Head gasket and normal base gasket. I am using the original steel washers with the ARP nuts, and notices the APR nuts are taller. I think it'll be okay, but it was a little worrying.

Kaleb

Why not take out the washer? It serves not purpose and you’ll have full engagement.

I had thought the washers were used so the steel nut wouldn't "bite" into the aluminum casting when torquing the head down, since the stock nuts and the ARP nuts both had the same diameter flange.

I'd eliminate the cylinder stud washers too....you want to grab as much thread as possible especially with the puny 8mm head studs. Lube the threads and bottom of the nut with light engine oil

[newday777]

 My big worry is this paint has not seemed to be very good at adhering so far, granted it hasn't been baked yet, but some of the bolts have had their paint flake, and a few small scratches have appeared. I even had some paint removed when using painter tape!

Kaleb

Kaleb
Did you wash the motor, then sand the old paint, then wash again, final step is to wipe down well with denatured alcohol and let dry before painting?

[LiveeviL81]

 My big worry is this paint has not seemed to be very good at adhering so far, granted it hasn't been baked yet, but some of the bolts have had their paint flake, and a few small scratches have appeared. I even had some paint removed when using painter tape!

Kaleb

Kaleb
Did you wash the motor, then sand the old paint, then wash again, final step is to wipe down well with denatured alcohol and let dry before painting?

I had the motor media blasted, cleaned with brakeclean and rags until no more dirt appears, then after assembly before painting I again used brake clean and a rag to wipe down.

[LiveeviL81]

Was able to get the engine fully assembled and painted this last weekend. Left the ARP Bolts and Nuts stay torqued for a week before loosening and retorquing them. I noticed that some of them have a lot less thread engagement than others, All studs were torqued to 15ftlbs and the nuts were torqued to 22ftlbs. Running a Cometic Head gasket and normal base gasket. I am using the original steel washers with the ARP nuts, and notices the APR nuts are taller. I think it'll be okay, but it was a little worrying.

Kaleb

Why not take out the washer? It serves not purpose and you’ll have full engagement.

I had thought the washers were used so the steel nut wouldn't "bite" into the aluminum casting when torquing the head down, since the stock nuts and the ARP nuts both had the same diameter flange.

I'd eliminate the cylinder stud washers too....you want to grab as much thread as possible especially with the puny 8mm head studs. Lube the threads and bottom of the nut with light engine oil

I appreciate your guy's insight. The engine was actually installed in the frame last night... I know the Hondamatic's are able to have the valve cover removed in frame, but I wonder if I can take all of the valvetrain out enough to get to those head nuts in order to remove the washers, or if I'll have to get some buddies to help remove the engine as well... Shoot you guys got me worried.

[BenelliSEI]

Those nuts already have a flat on the btm. face. Take out those washers.

[LiveeviL81]

Ended up taking the top end apart and helicoiling the cam tower threads while it was all apart as well. Scratched the paint a bit getting the valve cover out, but totally possible to do the entire top end in frame. Only real issue was torqueing the cam sprocket bolts with the torque wrench. Took the washers off and covered the threads with oil, tightened to torque spec, then checked again a day later. Got the whole engine back together so now I'll be focusing on getting the exhaust, turbo, and intake mounted up along with the wiring and plumbing for fuel.

I purchased a larger petcock and flange, converting to a Harley 22mm with a 5/16" petcock ID. Found out the stock petcock flange was brazed, so I will also try to TIG braze the fuel tank when I put the Harley bung on it. Any tips for cleaning out light surface rust and draining the tank? I had a ton of issues trying to get all the old gas out where no matter how I shook it, something still sloshed.

I also got ahold of some reverse comstar wheels from a buddy at work, and I was happy to find out they are easy swaps. Bolted right up!

If I push hard, I should have first start this weekend.

[LiveeviL81]

Busy weekend! Didn't make first start, mainly due to the pulled out exhaust stud I wrote about in another thread. Ended up getting a lot of other things done that I was pushing off till "After first start". Fresh rubbers are getting put on the reverse comstar wheels, brazed in the larger petcock bung to use 22mm Harley petcocks with 5/16" I.D. Got the new exhaust stud in, and manifold and preturbo pipe installed.

Thinking about painting my turbine housing for the turbo with some "2000F" paint I have, it has some flash rust on it from sitting, and I think it would look pretty good!

Kaleb

[LiveeviL81]

Is there a good method for priming the oil pump on the CB750A's? Since its a different oil pump system I tried to follow the documentation before assembly, but it made a mess! Was thinking about using a syringe to push oil up in the oil filter area to try to put a "head" on the pump.

[LiveeviL81]

First Start!
Was able to get first start Sunday Night, she popped right off with a little coaxing from the accelerator pump and choke. I am surprised it runs as well as it does with no tuning on the carb yet since the big bore. Plan to install the Lambda Sensor here after a few more minutes of idling and reving to clean out the assembly lube from the cylinders. Everything sounds good to me, a little excess cam chain noise at idle, but I followed a method of HondaMan by releasing the tensioner hold bolt while Cyl 4 Intake Rocker was starting to head down, light pressure in the back to make sure it adjusted, then tightened back up. Will probably need to do it again as the brand new cam chain stretches a bit.

https://www.youtube.com/watch?v=H97wL0DKJIc

Now to the bad part. You can see some oil leak out of the torque converter case cap, tried to RTV it last night and see if I could get a drive in but its still leaking. So I'll wait for the gasket to come in. I also idled it for a few minutes today and saw another leak I'm asssuming from the rubber grommet for the 3 stator wires, So I'll be digging in there as well to RTV.

I also was not able to get the engine to provide torque to the wheel in 1st gear, revving up wouldn't spin the rear wheel anymore than the bike in neutral on the stand. 2nd gear seems to work fine, I did a bit of brake torquing, but didn't want to drive it with the leak on the torque converter cap. Going to double check oil level since the troubleshooting manual says it could be low line pressure in 1. Really hoping no major engine removal issue.

I have attached the a photo of my shifting mechanism, which lets me correctly shift through all the gears, and the kickstand return works as well, but maybe I missed something obvious. More photos to come if the oil level isn't low and I need to open that cover.

Thanks!
Kaleb

[LiveeviL81]

Ended up having to pull the engine from the frame, which sucked seeing all my work go back on the shelves. Engine paint didn't get too badly scratched on the way out though. Took the time with the engine out to try to fabricate my own engine stand/rotisserie. Sadly I didn't realize engine stands are canted back about 5 degrees and doesn't allow the two bore axis to be aligned and rotate the engine. Made mounts to hold the engine upside down for me, but I won't be able to rotate it. Planning to cut some sections out and align the bores in the future for other projects.

Figured out pretty quickly the issue with the engine after splitting the case-halves. The bearing race/oil feed piece for the low clutch rotated in the case and blocked the oil feed to the low clutch. Easy fix, but I am surprised it happened since I can feel the pin and hole align so hopefully that doesn't happen again. Time to clean all the RTV and get ready put the engine back together.

Found another issue. The main oil gallery feed from the filter through the case halves seems to have cracked on the o-ring seal, and while I was seeing 60+psi oil pressure in the main gallery when the engine was running, it worries me enough to try to fix it before putting the case halves back together. Currently discussing in the main SOHC forum about solutions but I think I've settled on attempting to weld it back up with the engine still assembled, and seal it off with some RTV/Hondabond along the steel insert and monitor oil gallery pressure more often in the future.