Topic: Bessie, my first rebuild: 78 CB750F3 (Back on the road 2016-05-12)

[D.WHO]

Nice build! And a good write up to go with it! 
 If you don't mind me asking, how much did it cost to refurbish the head?

[wohali]

Thanks!

Gord Bush charged me right around $500 CAD for the following:

• Broken stud removal and helicoil
• Crankcase tear repair with TIG aluminum weld and touch-up with epoxy
• Two mounting holes for sprocket cover rebuilt from scratch and helicoiled
• Cylinder head valve guide installation and seat recutting
• Cylinder head complete blasting & cleaning and lower mating surface resurfacing

I think it was a very good deal, given the attention to detail and Gord's history of working on (and racing!) Hondas since the '70s. I didn't feel the need to get an itemized bill, but I'd guess that the work to the crankcase was about $300 and the cylinder head was about $200.

[wohali]

Interesting work today:

I was having a problem where the seat wouldn't lock at the second (tighter) setting. I tried to torque down the lock pin on the seat pan tighter...and in the process, sheared off one of the mounting bolts. Couple of hours later with an M6 bolt with the head cut off, some 1/16" 6013 rod, the arc welder set at DC 45A, and some water/wet rags, I had a new bolt...but the problem remained.

Turns out the fix was that the adjuster nut on the locking pin was too low. Near as I can tell, it'd always been too low, and the threads were in terrible shape. Removing the pin, cleaning up the threads, and making the pin slightly longer (pulling the nuts one turn up) locked the seat perfectly. I've always had to "slam" the seat closed to get it to latch - no more!

I also realized that the top bridge on the fork "triple tree" is the wrong one for a '78F3; it's missing the holes to mount the instrument cluster. The PO was using an older cluster and some 630 master chain links to mount it to the ignition holes. This lead to all sorts of problems, not the least of which was that the ignition lock itself was buried on the fork, and the key had to be cut down on one side to actually turn.

Instead, I took a small bar of 1/8" aluminum and cut a new backing plate. It attaches at the ignition holes, and the instrument cluster and idiot lights attach to it. The ignition is still a bit low in the idiot light cluster - about 1" below the top - but the key still fits and turns without too much trouble, even to the fork lock position. I had to swap out the rubber bungs that hold the instrument cluster in place with some extras I had for the rear fender. And the plain aluminum colour doesn't even bother me, though eventually I'd like to get the proper fork bridge for this model.

I also got most of the chrome bits back on, all of the turn signals & rear lights & both fenders, speedo/tach cables, headlight bucket, handlebars and the left controls. I rechecked all torque values, except for the rear axle, which is awaiting the chain to be master linked before final adjustment. I've temporarily popped the old side covers back on, as I want to ride her ASAP! Also realized I'd put the front sprocket on backwards, but unfortunately not before scratching off a bit of paint behind it with the (misaligned) chain... :/

Tomorrow (a holiday for us Canadians): final wiring in the headlight bucket, remaining controls and cables, a relay or two to save the headlight switch and cut out the headlight during starting (per Hondaman's suggestions), and some engine testing/carb syncing. Oh, and a call to Z1 to get the front master cylinder rebuild kit and a new 630 chain O ring split link.  Am hoping they'll let me ride by and pick it up...I'm impatient!

Pictures online tomorrow.

[wohali]

Picture time! More at these two new galleries:

• Final paint & reassembly
• Exhasut rebuild

Seat stud re-welding:


Aluminum instrument backing plate:


New wiring harness sheathing:


All dressed up and nowhere to go:


Next up: Visiting Z1 Enterprises tomorrow to get front master cylinder rebuild kit, new control cables, and take in a concert (woo, Weird Al Yancovic!) Also need a new master clip link; must wait for Parts Canada to get me one in.

Back in the garage wrenching Wednesday night.

[tweakin]

Awesome and congrats.  It's great to see another F brought back to life.

[CafeDawg]

Great build thread I've been reading through it and your photo tips.  This will be an excellent resource for me since I'm just getting into my own F3.  Thanks for all the useful info, let us know how she runs and rides.
Respect!
C

[D.WHO]

Very cool! I might have to send the head on mine to him, we'll see when I start digging! 
I can't wait to get started on my build, and reading around this forum doesn't help the itch!  I'm thinking about buying a second engine to work on while I ride the piss out of the one that's in it, because I can't have the bike out of commission for more than a week or so. Need it for transportation. 
  Oh, and glad to see another W.AL.Y fan! 

[wannabridin]

looking good! 

one piece of advice if it's not too late though.  on your wiring harness, have you considered running some wire mesh instead of that plastic loom??  the mesh looks better personally, and allows the harness to be tighter, especially if you put some sections of larger heat shrink tube around the whole harness in certain areas, especially where leads come off.  just my $.02, but i thought it would be worth a gander for ya!  here's what i'm talking about in case you're not certain:

this:  http://www.cabletiesandmore.com/BraidedSleeving.php

[brandEn]

Looks good! Getting the electrics to work without blowin fuses feels good doesn't it? Looks like that SV next to Bessie needs to be taken out for a spin. Looking a bit neglected with all the dust from shop work on it.

[wohali]

Braided sleeving: Looks nice. I think it may have to wait until the summer's over to go on, though PLus they have a Canuckistani web store!

Fuses: Only blew the main fuse once, and it was totally my fault for assuming "everything black in the headlight bucket is wired together." A little bit of time with the wiring diagram and it is sorted.

Brakes are finally bled, master chain clip went on, and a few other minor odds and ends tonight. I have confirmed I have the wrong sprocket cover, so while the correct one is on order I've put a few extra washers inbetween the cover and the crankcase to keep the 630 O-ring chain away from it. (It's already got a big gouge through it from where this was previously done as well.) It definitely was the older 530-sized sprocket cover.

Things still to do: Tune carbs, time engine, run the engine in (should I push it hard or run it gently for the first 50-100 miles? There seems to be conflicting advice...), change the oil again, and probably swap out the rear shock springs, though the stock ones are marginally OK (Picked up some progressive 90/140 springs from Z1 while I was there). Then, repaint the tank and the new side covers.

OK, sleep - will ride/sync carbs first thing in the AM, and post pictures in the PM.

[Tintop]

Regarding break-in.  The important thing is to vary the rpm's, don't go for a highway ride at a constant rpm.  Also you should limit the rpm;s to about 5/6K.  The object is to seat the rings, and bearings.

Looking great.

[wohali]

Need help.

She wasn't starting right, so I re-static-timed her (she was firing after TDC on 1-4 at the very least).

Now she'll start more easily, but it is still hard -- and once she starts, she is burning a lot of oil. In 10 minutes of testing I think I went through at least a litre of oil. Lots of smoke out of the exhaust; at first I didn't recognize it as oil smoke. The Rotella T smells a lot different burning than the other oil I used to use.

I pulled the plugs and they are oily and black, so definitely fouled.

What are some common problems that cause that much oil burning? I really don't want to have to pull everything off but I don't see much alternative. My greatest fear is ring problems...I don't have the right adapter for the compression kit I have, and I can't seem to find a 14-12 adapter anywhere. A new compression tester is quite expensive tho

Also the new CycleX oil gauge is leaking oil out from the centre allen key screw, if anyone knows how to get it to stop that lemme know.

I'm really unhappy and depressed; I'm not ashamed to admit I just cried a bit either. SO much work, and just to have this happen!

[Flying J]

Thats rough. I feel for you, i have been there on different projects and it is discouraging. There are compression testers at harbor freight for pretty cheap  but im not sure you have them up there.

[wohali]

Yeah, no Harbor Freight here. Canadian Tire has the full kit for a lot of money.

I read about using an old spark plug to make one here: http://www.dansmc.com/compression_test.htm

[GammaFlat]

I guess compression would give you clues but might not be the "tell all" in terms of oil usage.  I'll wait for others to contribute but a fresh rebuild will tend to burn oil.  What you got going on sounds excessive I guess.  It sounds like you did not bend a ring which is a "likely-ish" on rebuilds.  I've heard of folks bending an oil ring upon installation of the piston and not learning about it until all the oil consumption.  Yours does not sound like that if all of your rings are "oil-fouling"... unless you bent them all - doubtful. 

I'm sure things will work out (as I gulp with wide eyes as I'm about to finish up a fresh rebuild soon myself).  I have the same feeling now that I had when I was forced to split my cases with no idea where my "mystery noise" was coming from.  Now I'm hoping and praying my engine will be "correct" when all together.  I guess if there wasn't so much angst and mystery involved, it wouldn't be as much fun in the end.  The good news is that no matter what's wrong, folks here will help you get through it. 

How does shipping work out from the US to and from Canada for equipment loans (like a compression tester)?  Are there any duties or goofy complications? 

I did make an adapter for a compression tester with a spark plug.  I believe a 1/2" air hose male connector screwed into the "porcelain removed.. cleaned out" spark plug.  I had to use a few wraps of teflon tape but it worked. 

[wohali]

Ended up buying a compression tester with the right adapter from the local store. Here's hoping I can return it eventually Or I can sell the one without the adapter and write it off.

I wasn't able to easily get the hose+adapter into cyls 1 and 3 so I just tested 2 and 4 so far. 4 was around 40psi, 2 around 60psi. I then "followed the instructions" and put 15ml (1 tbsp) of oil into 4. Compression jumped up to 90psi. The instructions suggest that this means the rings are not sealing, and I can understand why, if the oil is effectively sealing the gap in the rings temporarily with a fluid barrier.

I guess I'm going back in But not today. Today is the day to drown my sorrows.

[wohali]

OK, I went back out and re-tested the cylinders. This time, rather than hand-turning over the engine with the nut on the points, or even with the kickstarter, I used the electric starter. I let it go for 5 compression cycles and then took a reading.

1: 150
2: 135
3: 142
4: 180 (had 10-15mL of oil in it)

I then decided to add oil to #1 and re-test it: it got up to 180 psi as well.

This lead to some quick calculation. The usual volume of the cylinder is 736/4 = 184cc. The compression ratio is listed as 9.0:1 in the manual, meaning at TDC during the compression cycle the volume should be 184/9 = 20.4cc. The manual also suggests the compression rating should be 185psi +/- 15. The compression gauge hose is about 3/16" in diameter, and end-to-end (including the gauge) is about 22.5". A cylinder of diameter 3/16" and length 22.5" has a volume of very nearly 10cc. Therefore, with the gauge attached, the compression is from 194 down to 30.4cc, or a ratio of only 6.38:1.

So we know for sure that the readings with the gauge attached will be lower. We also know that adding ~10cc of oil to the chamber roughly makes up for the loss of volume in the gauge, however adding the oil may also mask any leakage at the rings.

All in all, the numbers (not hand-cranked, but electric started to test) look good. In general the increase in the values looked like this:

Cycle 1: ~30psi
Cycle 2: ~60psi
Cycle 3: ~90psi
Cycle 4: ~105-115psi
Cycle 5: Final number

When adding oil to the cylinder, the sequence looked like:

Cycle 1: ~70-90psi
Cycle 2: ~120psi
Cycle 3: ~150psi
Cycle 4: Final number
Cycle 5: Same as 4

So I'm still not sure what's up. I figure I will next double-check the tappet clearance (make sure valves aren't being held open), and try running it again, this time with the adjust screws on the carbs turned out another 1/2 turn. I'll try running it at a higher RPM, around 4k, for a few minutes, and then again at a lower RPM. I'll also double check that all 4 cylinders are firing. If I'm still getting a lot of oil being burned off, I'll have to try and isolate where it's coming from...

Suggestions still welcome. I'm over the grief and frustration into problem-solving mode, but I really don't know what to do next.

[GammaFlat]

I guess I'm going back in But not today. Today is the day to drown my sorrows.

OK, I went back out and re-tested the cylinders.

I completely understand why you couldn't leave it sit today .  How could you leave it (out of your thoughts anyway)?  I guess drowning sorrows works too.. but obviously, you weren't convinced it was coming apart... you had to know more.    Good luck!  I hope it works out without yanking the engine. 

Here's what I'd do on the valve lash at a minimum: intakes at .003" exhausts at .004" (per thoughts of HondaMan in the FAQ).  The actual compression numbers mean less than the difference between the cylinders.  The rubber hose, for example, can "give up" psi which would give you a false reading but consistent across cylinders. 

[wohali]

Yeah, I'd done the valves at 0.003 / 0.004 previously, but I wanted to double check them. Maybe later?

Now I'm considering heading back out and doing a simple leakdown test with the compressor and my ears.

I'm also wondering if perhaps the breather hoses were clogged and perhaps pressure above the head was pushing oil back down? SO many theories.

Whether I go back out tonight or not I think I'll take lunch time tomorrow to put the head cover back on, plugs back in, check the wires, roll it outside and try running it again. I want to see if she's burning more or less smoke at higher RPM (~4k) vs. lower rpm (~2k, since I can't get her to idle lower...still haven't synced the carbs, not going to until the oil problem is solved).

If she's still burning oil that heavily, the only thing left is to suspect the rings or the valve seals...and boy howdy I don't want to have to deal with either

[wohali]

OK, I tried a "poor woman's" leak down test. I set my compressor at 50psi, rigged up an adapter, put the head cover back on, dialed the engine to T1-4, put her in high gear, stomped on the rear brake and connected the compressor to the plug hole on #1 (and then #4 in a second test). In each case, I could feel air coming out of the breather cover hole. If I put my thumb on the hole, then let go after about 10 seconds, I'd estimate the pressure would build up to around 5psi. After 20s of plugging the hole, I'd hear a little gurgling inside the engine, presumably due to oil working its way around various passages.

My question is: is this just because the brand new rings haven't set themselves yet? (The engine's only run about 10-20 minutes since rebuilding.) Or should I be pulling the cylinders and looking at the rings right away?

If I don't hear any suggestions, I'm planning on rolling her outside at lunch tomorrow and trying to run her at 1k, 3k and 5k for a bit, and compare the smoke output (if there is some now).

[grcamna2]

Hi,
     When you did the top end rebuild on your CB750 and replaced the piston rings,
etc. what procedures did you use to prepare the cylinders for the fresh rings ?

[wohali]

Hi! Good question. I very lightly honed the cylinders, checked clearances with the piston in the cylinder and feeler gauges, gapped each ring to within Honda's documented tolerances (1" down pushed in with the correct piston) and reinstalled.

[scottly]

If I don't hear any suggestions, I'm planning on rolling her outside at lunch tomorrow and trying to run her at 1k, 3k and 5k for a bit, and compare the smoke output (if there is some now).

That's what I would do, or better yet, ride it to load the motor. If you do chose to run the bike stationary, be sure to have a fan blowing on the motor.

[UK Pete]

Hi Wohali, thats not nice to have these sort of issues after a full rebuild, but there is hope, my F2 which i recently built also smoked quite a lot for about the first hour of running, also it was dripping loads of water from the exhaust down pipe to end can joint, for  a while i was really down hearted , but after taking it out for a 10 mile run came back, and no smoke or oil burning since
Hope you get some good luck, but dont despair these old bikes always seem to have teething problems after rebuilding
BTW are your valve guide seals new and installed correctly?
Pete

[wohali]

OK - today I had a chance to refill the oil, put Hondaman's ignition back in the circuit, wheel her outside and adjust the timing dynamically. She was very close but needed a little tweak (was slightly retarded). A small rotation and another check with the strobe and she's spot on, maybe 1 degree off, max.

A plug for the Hondaman Ignition: after adding it in, she started on the first push of the starter. No teasing required.

After about 10 minutes of running the engine and testing it, she doesn't seem to have dropped the oil level in the tank, though the level is a bit higher than I would like right now (even with the oil temp about 80F, ambient is 70F).

She's still blowing blue smoke at a steady pace, increasing in volume with more throttle applied. However upon first startup, there was no oil at all - it took about 30-60s before blue smoke started coming out.

I'm also getting a little smoking from the manifold, but this is my own fault: it smells like burnt paint. I used a heat resistant primer and middle coat, but I risked applying a silver top coat that wasn't heat resistant. And surprise! Guess I know how that work out now  My one place to skimp, I couldn't see ceramic coating a header in this condition for more than it'd cost to get a brand new header.

Ran out of time due to work running over, so tomorrow I'll rider her around the neighborhood at reasonable speed and low RPMs and see what happens. I'm hoping that 10-100 miles of riding will sort her out, even if I go through a quart or two of oil. If she's still burning oil after that, guess I'll pull the cylinders.

One last thing: she decided to start running a bit rough towards the end of the test. I'm going to assume this is due to oil in the cylinders, since the smoke didn't decrease with time. I'll be sure to take a mobile phone with me while on these test runs

More tomorrow. Feeling a bit more upbeat.