Author Topic: CB750 K1 project (Read 60414 times)

Dunk · « **Reply #150 on:** March 23, 2014, 02:51:53 PM »

Yes, I will hone the bores and line sand the mating surface to ensure all is well. New rings on order too. What is the recommended orientation for the ring gaps on these?

Got the first intake port mostly done. Aluminum cuts a lot easier than cast iron that I'm used to, which is nice, but I have to be careful not to go crazy with it and the tighter access with smaller intake port and valve access is more awkward then big block heads. Hopefully it turns out well. I'm noticing a lot of inconsistency from port to port as it came from the factory.

Terry in Australia · « **Reply #151 on:** March 23, 2014, 11:48:55 PM »

Yep, the aluminum heads ports are easy to grind, I don't use a burr, I just use the cones and rolls to clean up the casting defects and once it's nice and smooth, well, that's good enough for me.

Re: ring gap orientation, I think the manual says to set the compression ring gaps at 8 o'clock and 4 o'clock (with the exhaust valve cutout on the piston at the 6 o'clock position) but the rings will move as the engine is running anyway, so don't worry too much, as long as the gaps aren't lined up, you'll be fine. Cheers, Terry.

Dunk · « **Reply #152 on:** March 29, 2014, 07:01:09 PM »

I think my ports are good. Chambers look like the sharp edges and some shrouding may have already been done either by a PO or this bike was early enough they still did some of this at the factory. At least looks that way when comparing to Hondaman's book. May or may not do any work on these. Been sick as a dog the past week and just starting to feel better. Ordered new exhaust valves and some other misc bits. Two of the valves had some light dimpling on the stem so I don't want to chance that accelerating. Dropped my dial indicator and must have bent the shaft... Irritating, but that's what I get for trying to get anything done while I'm sick.Still waiting on gaskets and so forth, probably clean up the pistons next. and I should just be waiting on parts to reassemble the top end.

Still have to polish the alternator cover and sprocket cover. Bike itself needs a few things done though I've forgot what they are and I haven't uncovered it in a week or two to make a mental note. Hopefully it'll all come together soon now that the weather is slowly warming up.

Dunk · « **Reply #153 on:** April 05, 2014, 05:21:28 PM »

Jugs are honed, brushed all holes, cleaned, etc... Head has new valve guides still have to cut seats and lap valves.

Pistons cleaned, new rings sized and on pistons. #2 is ready to go on but pin had some minor galling so waiting on a new one in the mail.

Getting there.

Dunk · « **Reply #154 on:** April 11, 2014, 06:32:15 PM »

What's the deal with the little white insulators/rubbers between the fins? I believe they were only on the earlier bikes and not on the later. Purpose to mitigate some of the noise/ringing/rattle/resonation/vibration? I removed mine and they are very hard as with any rubber part so would need new to replace. Seem expensive or difficult to get. Any reasonably priced source? Worthwhile to replace or just forget them?

Dunk · « **Reply #155 on:** April 11, 2014, 08:32:03 PM »

Also did some light deshrouding of intake valve and sanded chambers by hand to polish out some of the marks from original machining. It's getting warm, don't want to spend time to CC chambers so didn't go nuts with it. I may yet, but we'll see. Hoping to have the top end back together by next weekend... Which means engine would be more or less ready to install. That part won't be fun but hopefully I can recruit some assistance.

Dunk · « **Reply #156 on:** April 14, 2014, 07:08:24 PM »

More progress...

Air box before:

Air box after washing with soapy water, break clean, then rubbing down thrice with Meguiars Ultimate Black.

So far I'm pleased with the look. Much better. It says not oily, but it has been a couple hours and it is oily after wiping down with clean dry cloth a few times as per instructions. Fingerprints show unless you wipe them down after handling. Felt almost sticky after applying, like it sorta melted the plastic a bit and soaked oils in. Just observations. I'm pleased with the result. Box has a few scratches and scuffs, I'd imagine those would take sanding to fix. Good enough for my goals.

Also completely disassembled and repainted the brackets black. Internal gasket was a little pain to get back in as it was swollen. Cleaned well and used a few dabs of adhesive to keep it in place.

Clutch had plenty of meat left and looked good so I just cleaned, oiled, and reinstalled with new springs. I did drill extra holes in the basket and chamfer as per the tips here. I believe 8 holes evenly spaced and offset from existing holes. Clutch dragged slightly when hot, as they typically do, hopefully this will help.

To do pile:

Bike itself is pretty much ready for an engine and good to go. Odds and ends to do still but getting there.

Dunk · « **Reply #157 on:** April 21, 2014, 09:31:08 PM »

Looks more like an engine now...

Bench is more clear than it has been in a long time.

Tired... Shower, sleep.

Dunk · « **Reply #158 on:** April 23, 2014, 07:49:37 PM »

Got all these cleaned up, little oddball size orings for under cam towers should be here by the weekend.

Still need to polish alternator cover and repaint the black part. Need to pull the pan and do oil pump orings. And paint the engine, which will be no fun but whatever... Almost there.

Terry in Australia · « **Reply #159 on:** April 26, 2014, 04:51:50 PM »

Looking good mate, excellent work. Cheers, Terry.

Dunk · « **Reply #160 on:** April 27, 2014, 05:34:34 PM »

Finished the top end. Took some extra time to drill the cam towers for extra rocker shaft lubrication.

Cam timing looks good to me but just to confirm... I initially installed the cam sprocket one tooth over and the cam mark was more to the right. This is almost dead on slightly left I suppose. I think it's alright.

Replaced the countershaft oiler oring. Was definitely flattened.

As far as the engine I believe all that's left is replace oil pump orings, side cover seals and so forth and paint. Masking will suck. I'm thinking of taping up all the covers and installing them then paint that way. Any preferred paint. Probably do either Duplicolor or VHT depending on what's on the shelf tomorrow and what is available in an aluminum color.

Still need to polish the left side covers. Just about there. Starting to dread putting the engine in, I've looked at the various tricks here but doesn't look fun no matter which way you slice it. Probably gonna be a solo affair. Kind of wish I did the engine first and started with that in a bare frame.

Terry in Australia · « **Reply #161 on:** April 27, 2014, 06:20:48 PM »

Yeah mate, make sure you wear heavy gloves when you install the engine, it's easy to pinch a finger or rip some skin off your knuckles in the process. I'm building a 750 for another member here but I'm gonna lay the bare frame over the engine to try to save the fresh powdercoat.

I prefer Duplicolor epoxy engine enamel to VHT, it covers very well and the color is close to OEM, and I've had some issues with VHT not being very fuel resistant in the past.

Make sure you use an etch primer first though, or the paint may not stick too good. Do you have an old set of engine covers that you can throw on the engine before you paint? I do that, then just dump them in some thinner afterwards to remove the paint, and that saves me a lot of masking. Enjoy! Cheers, Terry.

Dunk · « **Reply #162 on:** April 27, 2014, 07:02:12 PM »

No spare covers unless I tear down the engine from the K1 I dropped years ago. Not gonna do that as that needs to stay compact for the time being. Probably just tape the ones for this engine up well and hope for the best. Kind of wish I didn't sell my first bike, a K2 I sold for $100 after I threw the chain through the case.... Young and dumb stretching maintenance and kapow! Of course I bought the bike for $100 so it was whatever at the time, but we live and learn.

Got the oil pump off and tore down. Some scoring but doesn't seem terrible, given the replacement pump choices of none and not available. Thought I was being smart had the orings and seal on hand months ago and... The three dowels are missing between the pump and lower case. Was gonna say screw it and run without 'em but with my luck an oring will pinch in and cause a catastrophic loss of oil pressure. Parts are ordered and should be here by the end of the week.

Someone has been in this bike and done some odd things. This, half the pistons backwards, apparently dropped the head, etc... Wonder if it was the dude I bought it from who lived on top of a mountain I had to drive up a rutted out dirt road to get to and go stuck and pulled out by a tractor after I broke my transfer case. It was an adventure for sure!

Dunk · « **Reply #163 on:** April 28, 2014, 08:14:22 PM »

Any tricks to getting the oil pump shaft seal out of the center main body of the pump? I got it out, though slightly divoted the center section just below it. Doesn't affect the shaft and won't affect seal after I put the new one in but if if I was just a hair rougher it may not have been as nice. Tried various picks, tiny flatheads, etc. along with heat and penetrant and just tore up the seal but couldn't grip the outer metal part. Honda sure loves to press parts in without leaving any lip or easy way to remove them.

Since I'm waiting on dowels and so forth I ordered two oil pumps off ebay on the chance either is in better condition. The larger rotor in mine is worse which I understand is the return and less critical, but still it's a bit rough. The smaller one is better but took some damage. Outside of pump looks to have been scrubbed with a stiff steel brush and inside looks like it had some metal through it. Never noticed any oiling issues, but never had a gauge on it either.

I'll wait 'till the new pumps come in and pick the best of them to reseal and install. Also stripped some remaining paint off the lower cases and cleaned, more or less ready to paint when the pan goes back on. Don't feel like I accomplished much tonight, but I didn't really spend much time on it. Getting anxious to ride, sick of waiting on parts.

mwvachon · « **Reply #164 on:** April 29, 2014, 06:52:49 PM »

Cadunkle - I know what you mean about putting the engine in. This is why I always plan on dropping the bare frame over the engine (meaning the engine and frame finish must be done first). I fought tooth & nail to pull the motor out of my current K1 project when tearing it down - and even with two people, it was difficult. One trick I read about was using a ton of old magazines. Protect the frame as much as you can with duct tape & what ever, and then pile up magazines under & beside the frame so that the engine will be very close to the right height. I've never tried it, but seems easier than trying to muscle the thing in - especially if you're working solo...

Dunk · « **Reply #165 on:** May 01, 2014, 06:51:56 PM »

I think when I install it I'll try the pipe straps and jackstands method. Maybe I can scrounge up another pair of hands but I remember pulling the engine out of the bare from on its side was even a little tight. Thought about grinding the top of the motor mount for clearance but I hate to have the frame not be correct.

Got an oil pump in the mail today... Not sure if I'm pleased or not. I think the one I got today is marginally better. Still looks like it swallowed some dirty oil or metal bits. All rotor clearances on the pump that came out of the engine are .003" Spec is .0138" limit (really? type? That sounds insanely loose) The new pump varies .0025" - .003" and rotors don't have staining like there was water in it though there are a couple spots that look like soft metal (bearing material or aluminum) were pressed into the rotor without chewwing it up.

Pump from my engine:

New pump, supposedly from a '74

The bodies are both pretty decent. The '74 pump has a fairly deep scratch on the back of the smaller pressure side of the body but is smoother on each cap. The pump that came off the engine also has a fairly deep scratch in the same area but less deep, though there are more scratches on each cover. Not sure but I'd say maybe the pump body that came off the engine is marginally better and the rotors off the '74 pump are marginally better.

I don't know they both look like crap to me. If this were a Ford engine like I usually build I wouldn't run either of these pumps. Of course even with the pump looking so rough it didn't seem to have any oiling issues from what I can tell of riding it or having the top end apart. Only lack of lubrication looking thing I replaced was #2 piston pin, it had some very minor galling so I threw a new pin in it. Of course that's not pressure fed so I'd imagine the cam bearings or rockers would show problems from poor oil pressure of lack of volume.

Thoughts?? Would you guys run either of these pumps? I do have a pump coming from a '78 (K or F? don't know, I assume they're the same). Maybe that one will be better. I hate to run a questionable pump given how critical it is, but the newest pump I can get is 36 years and who knows how many miles old. Doubt anything being parted out on ebay is gonna be a low miles barn find with religiously changed oil. What to do?

edwardmorris · « **Reply #166 on:** May 02, 2014, 09:42:20 AM »

Perhaps this will help you out a bit, I just tore mine down too, and Hondaman was kind enough to shed some light on the matter

http://forums.sohc4.net/index.php?topic=126735.msg1538228#msg1538228

I was concerned about the rotors but the real thing to look into are the covers. There is also a good write up from Mark/Hondaman about how you can determine if you need the lips milled using plastigage, I'll dig around for it and share if you'd like.I tracked down a new screen for my pump and grabbed the two extras that the dealership out in UT had, both my extras were sold almost immediately. If you need one, try calling around a few dealerships or boat shops, Honda is still making these are they are used in their boat engines.

Terry in Australia · « **Reply #167 on:** May 02, 2014, 05:51:21 PM »

I hate to admit it, but I very rarely even bother to disasemble a pump on a CB750, I give it a flush with some degreaser, then submerge it in oil, and spin the gear, and if it's pumping OK, I just install it.

I've been doing this for the last 30 years or so, and haven't had a failure yet, so maybe I'm just lucky. I always install oil pressure gauges on my CB750's though, which is cheap insurance. Cheers, Terry.

rtbmrgl · « **Reply #168 on:** May 02, 2014, 09:29:27 PM »

I'm subscribed, nice project.

Dunk · « **Reply #169 on:** May 03, 2014, 12:43:23 PM »

Thanks for the additional pump info. Side of gears and covers are all fairly scratched on the those though not crazy. Jackpot today, the second pump I got off eBay arrived and it looks good to me. Pressure side clearances are a little looser than the other two coming in at .004" and the larger scavenge side clearances are .003"-.004"... But, compared to the others the rotors and caps are beautiful! Scavenge side took some junk but very minor comparatively speaking but pressure side looks great. This pump supposedly came from a '78 and my first observations were that it is clean on the outside and the oil in it was relatively clean. I'm guessing it came from a higher miles bike that actually had the oil changed.

Anyhow, this pump is good enough for me. I'll finish cleaning it up, replace the orings and seal and throw it in. Wish I had a new stopper but I guess Elan has been busy with his wife and newborn and hasn't got to making these available again. At least that's serviceable in the frame.

Dunk · « **Reply #170 on:** May 03, 2014, 12:46:25 PM »

Also one observation I haven't seen noted in any of the oil pump threads I've read here is the early pumps like what came out of the K1 the oil pump shaft is supported only at one end and through the middle of the pump body. The later pumps are supported in the far end cover too with the little recessed area the shaft can ride on. Not sure how much lateral load the shaft gets going through a narrow rotor but the extra support can't hurt.

Dunk · « **Reply #171 on:** May 08, 2014, 07:26:40 PM »

Oil pump is in.

Engine is painted and curing as best I can with what I have available. Monitoring temps and trying to keep it fairly low and even. A few small spots bubbled up on the cases, probably from not cleaning well enough. The top end looks fine but that was all blasted and more thoroughly cleaned. I'll touch up as best I can.

Testing alternator to get ready for reinstalling that. Spec is .2 ohms... I have two stators, one measures .5 ohms, the other .6 ohms. The .5 ohms came out of the bike and is closer to spec, never had any issues with charging. I think I'll put new bullet connectors on and use that one. Will replace the rough semi-melted looking ones on the small engine harness too. Not sure if there's an acceptable limit on stator resistance, but if it's a problem I suppose it's easy enough to change if need be. I'd imagine this is another part NLA and as long as it charges to some extent I'd rather not have another oil pump fiasco. I may end up getting that lighter rotor higher output setup from the dude in NH anyhow.

Getting very close to putting this in the frame!

Just a few odds and ends, adjust valves, install covers and whatnot and then get creative with straps to slide it in. Not sure if I want to hang it from overhead or support on jack stands. I'll figure something out. Frame will get padding on it and hopefully between that and attempting to cure the engine paint I won't have to touch anything up.

rtbmrgl · « **Reply #172 on:** May 08, 2014, 08:35:22 PM »

Quote from: cadunkle on May 08, 2014, 07:26:40 PM

Engine is painted and curing as best I can with what I have available. Monitoring temps and trying to keep it fairly low and even. A few small spots bubbled up on the cases, probably from not cleaning well enough. The top end looks fine but that was all blasted and more thoroughly cleaned. I'll touch up as best I can.

What paint did you use?

Dunk · « **Reply #173 on:** May 09, 2014, 05:38:14 AM »

Quote from: rtbmrgl on May 08, 2014, 08:35:22 PM

What paint did you use?

Duplicolor DE1615 Aluminum over Duplicolor engine primer. There was also a 1650 aluminum and I couldn't determine the difference, from a quick search here it looked like 1615 was more commonly used. Might be true, might not be. The paint went on more "runny" and I had to be more careful with it than when using Duplicolor Gloss Black or Ford Blue engine paint. This was more of a pain to paint than a typical cast iron engine block where the paint goes on smooth and easy, sticks well, and quickly dries tough as a rock.

rtbmrgl · « **Reply #174 on:** May 09, 2014, 10:00:20 AM »

Quote from: cadunkle on May 09, 2014, 05:38:14 AM

Quote from: rtbmrgl on May 08, 2014, 08:35:22 PM
What paint did you use?

Duplicolor DE1615 Aluminum over Duplicolor engine primer. There was also a 1650 aluminum and I couldn't determine the difference, from a quick search here it looked like 1615 was more commonly used. Might be true, might not be. The paint went on more "runny" and I had to be more careful with it than when using Duplicolor Gloss Black or Ford Blue engine paint. This was more of a pain to paint than a typical cast iron engine block where the paint goes on smooth and easy, sticks well, and quickly dries tough as a rock.

I used the same but also topped with there high heat clear. Ive noticed on my 750 the cyld head has turned slightly yellow, but on my 500 it didn't yellow. I thought it was from running to lean, but the 750 is running on the rich side.
Nice project looking forward to see it completed.

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Author Topic: CB750 K1 project (Read 60414 times)