Author Topic: Keep telling yourself - a restored 750 K2 is an investment (Read 38586 times)

HondaMan · « **Reply #150 on:** February 04, 2009, 07:12:22 PM »

Ah, the long rusty rest got those top rings as soon as someone kicked it over. That intake valve may need to have a new seat cut, if it's burned, but check to see if it is bent. Those engines love to rev so much, that sometimes it's their undoing! the pistons kick the valves at about 11,500 in stock trim, can go to 13,000 RPM with the torsion bars set up one notch.

Those cam followers are the weak link in those engines. look for deep wear at the point where the cam pushes down and wipes on the face of the follower. Usually they wear rounded depressions into the followers, right there. Those look pretty good, but the reflections make it hard to tell.

If you have the right valve spring compressor, the cam cover doesn't have to come off to get the springs out. It can be a bugger to remove the cam cover-to-head gasket there, as it really cooks on!

the-chauffeur · « **Reply #151 on:** February 05, 2009, 10:04:34 AM »

Cool. I gotta say that I had the same first thought regarding the piston rings - dry barrels were the most obvious cause.

As far as removing the torsion bars is concerned, the manual says you need (all together now) a special tool, but looking closely-ish at the appalling quality photos of said tool, it looks to me as though an old socket with a chunk cut out of the side will do the same job. Is that right? Strikes me that as long as the tool can take the pressure off the retaining pin, it doesn't have to be all that special.

HondaMan · « **Reply #152 on:** February 05, 2009, 06:11:50 PM »

I just used pliers with masking tape on them to prevent scratches. You have to lift up a little on the pin area to release the friction, and wiggle them a bit, and as soon as you clear the pin, release the slack. It's easier than it sounds. Putting it back on is even easier. I think the preload is only around 18-25 lbs.

the-chauffeur · « **Reply #153 on:** February 08, 2009, 09:47:01 AM »

That's the torsion bars sorted. Right again - pliers were the way to go.

So now I've got the valves out, I'm left with this:

,

Any suggestions for cleaning that crap out? I thought about a drill mounted wire brush, but then realised that might be a little too abrasive.

And another thought just struck me - I'm expecting the over-bored barrels to turn up during the week, along with a full engine gasket kit. I'm assuming that because the pistons are oversized, I'll need to 'modify' the head gasket. Sharp knife maybe?

And whilst messing about in the garage, I thought I'd have a go at tidying up some of the frame welds before it goes away for shot blasting and powder coating - since buying the bike, I've been kinda disappointed with just how agricultural some of the welding work was. I only really worked on the most visible seams, and tried very hard to just clean them up (rather than knacker the structural integrity) with a deburring grinder, wire brush and wet 'n' dry. So in the space of an hour or so we went from this:

,

. . . to this . . . (apologies for the flash reflections)

,

Next up is to work out the paint colour scheme. Initially, I wanted to get the bike as close to showroom as possible, but there are a couple of things keeping me from going that way - the most important being that I'm really not keen on the colour schemes available for the K6 models. The other issue is that I can't find anyone who makes the decals for the K6/7 models (and frankly, they're pretty horrible when compared to the earlier models). And one other thing - the chrome headlight ears aren't in the most fantastic shape. The outers are fine, but the inners are showing some surface rust.

I want a classic, understated look, so I might have to settle for a hybrid - either candy gold or candy ruby red - with painted ears, headlight bucket and a black tank stripe (already on order). I was gonna keep an eye out for the right panels and badges for those colours (K2/3), but having looked at the fiche, I gather they were different on the earlier models, so I think that's an idea I'll abandon before I make a few expensive mistakes. What does occur to me is that if I'm getting the frame and a bunch of bits bead blasted, it it worth taking the ears along and getting them done too, so that painting prep will be that much easier.

Decisions, decisions.

HondaMan · « **Reply #154 on:** February 08, 2009, 07:50:02 PM »

For the chambers: put the valves back in before wire brushing out the chamber, or you'll damage the valve seats. They look like they are rusty, will probably need a light refacing. I'll bet the valves look wetted, too. A touch-grind should clean them right up. Scrape out the port's carbon with a small screwdriver.

The stock head gasket is good for up to 2mm overbore, so not to worry there.

Honda's welding didn't go automated until in the 1980s, on the Gold Wing first. Their spokesman, once asked by Cycle Magazine about the gloppy welds on their 1970 bikes, misunderstood the reporter: he asked, "Aren't your welds made by machine?" The Honda rep, fresh from Japan, said "Yes", not understanding at the time that in the U.S. this meant auto-feed welders: to him, the arc welder WAS a machine, as opposed to gas welding. That misconception went on for years. "Agricultural" is a great description!

the-chauffeur · « **Reply #155 on:** February 09, 2009, 05:45:46 PM »

Arc welding? Jesus, I hadn't realised the big H was still that primitive in the early '70's.

A couple more questions before I get going on cleaning up the head. Firstly, the rust that you can see is only light surface stuff - the photos make it look worse than it is. So what's this refacing business? Sounds expensive. Can I achieve the same kinda results using a very small fine wire brush on a Dremmel? It seems to lift the surface stuff off without buggering up the faces.

Secondly, the coked-up ports. Amongst other things, I've noticed that (under all of that coke and crap) the casting inside the exhaust ports is about as well finished as the welding on the frame. Assuming I use the Dremmel with mini grinding stones/wire brush bits instead of a small screwdriver (and go about the clean up process very carefully whilst avoiding the stem guides and seats), is there any point in trying to tidy/part polish the ports up inside - or am I just asking for trouble?

Just a thought. And yes, the valves themselves look pretty scruffy, to say the least. They're soaking in Redex for now.

HondaMan · « **Reply #156 on:** February 09, 2009, 06:08:37 PM »

Quote from: the-chauffeur on February 09, 2009, 05:45:46 PM

Arc welding? Jesus, I hadn't realised the big H was still that primitive in the early '70's.

A couple more questions before I get going on cleaning up the head. Firstly, the rust that you can see is only light surface stuff - the photos make it look worse than it is. So what's this refacing business? Sounds expensive. Can I achieve the same kinda results using a very small fine wire brush on a Dremmel? It seems to lift the surface stuff off without buggering up the faces.

Secondly, the coked-up ports. Amongst other things, I've noticed that (under all of that coke and crap) the casting inside the exhaust ports is about as well finished as the welding on the frame. Assuming I use the Dremmel with mini grinding stones/wire brush bits instead of a small screwdriver (and go about the clean up process very carefully whilst avoiding the stem guides and seats), is there any point in trying to tidy/part polish the ports up inside - or am I just asking for trouble?

Just a thought. And yes, the valves themselves look pretty scruffy, to say the least. They're soaking in Redex for now.

Those twins had pretty poor castings. The Four was the first bike that seemed to get significant attention in that area, probably because Honda was concerned about heat buildup on the new inline engine. The newer ports had smoother finishes and were consciously designed to NOT have step-in restrictions along the exit path. If you clean out the 450 head and look out the exhaust through the valve hole, you'll see 2 places where the port steps downward in diameter as it enters the pipe. This arrangement caused lots of carbon buildup and head heating on the exhaust side. It can be smoothed out, and sanded down with 80 grit emery paper, to a decent finish that will let the gases leave faster and not drop their carbon so badly. Some used to say they filled in the bigger step of the two with high-temp epoxies, like JB Weld High temp, with good results. I never tried that one, though.

A small (real small) flapper wheel in a Dremel or drill ought to do a nice finishing job in about an hour or so. I used to whittle a short piece of dowel and stick it into the guides to prevent inside damage during the grinding/sanding process.

the-chauffeur · « **Reply #157 on:** February 11, 2009, 02:17:19 PM »

Had a go at the ports with the Dremmel, and they cleaned up pretty well. Not machine quality brilliant, but shiny and straight enough for me. The +1mm barrels and pistons have been delivered - looks like the outers were blasted or chemically stripped at some point, 'cos they're good and clean. I think the next job on the engine front - other than removing the alternator assembly so I can sort out the starter clutch springs/screws - will be to paint the cases/barrels/head. I reckon that the cases will need a metal primer, but the other two almost certainly won't, simply because the finish on them is already much better than that on the cases.

In other news, I'm equally delighted and amazed that the 450 frame and bits have been bead-blasted and powdercoated - all within in the space of twelve hours. Mark the Spray is off on holiday tomorrow, and when I dropped the stuff in yesterday afternoon, he said it'd have to wait until he got back which suited me, 'cos I'm still waiting for all sorts of bearings 'n' bushes to arrive. Anyways, he called me up this morning and said that he'd managed to get it all done. And wow! does it look good. All of the mounting parts, battery tray, swingarm, toolbox, chainguard and so on look phenomenal - as does the frame. And I'm especially pleased with how the areas I tidied up look - probably the best thing I can say is that you can't tell what work I did or where it was. Still waiting for the bearings though. And I'll need to put in some time with the polishing toys. I wanted to keep the finish on the wheels as original as I could, but having taken the spokes off the back one, I can now see that the hub's quite scruffy. Given that they're pretty easy to shine up, I'll probably give that a go. I'll post some pictures in the next little while, along with . . .

. . . (hopefully) pictures of the completed 750. It's all pretty much back together, with the exception of a few finishing touches - for now at least. I haven't tried to start it yet, so I'm not getting too excited, but barring disasters, it won't be long now. Again, a few bits are still on the way here, including some decals and caution stickers, but nothing too crucial. Once they arrive I'll send them away with the tank and one of the side panels for lacquering/ding repairs and with any luck, it'll be back on the road.

Busy, busy, busy . . .

the-chauffeur · « **Reply #158 on:** February 13, 2009, 11:33:03 AM »

And the 750 lives again . . .

Balancing the carbs turned out to be a pig of a job, but now it's done the bike is about 98% there. Rear footpegs, chainguard, and tacho need to be finished/fitted. Beyond that, I think it's pretty much done for now. Other remaining jobs include getting a couple of very small dings on the neck of the tank patched up, and while that's being done I'll get the black tank stripes and warning stickers put on and lacquered over. Oh, and I need to get it MOT'd (assessed as being fit to ride on the road).

It's missing the rear sprocket protector (I assume that's what it's called - the round guard thingie that fits on the outside of the sprocket) and for the life of me I can't find one this side of the pond.

And the garage is tidy now, too. Well, sort of. I'll take some photos of the 450 stuff when the light outside is better.

Back to work.

HondaMan · « **Reply #159 on:** February 13, 2009, 07:39:29 PM »

What a beautiful job, chauf! I like those tires, too. Are they Metz or Avon, or ?.

the-chauffeur · « **Reply #160 on:** February 19, 2009, 11:39:59 AM »

Y'know, I have no idea what make those rubbers are. I'd go outside and have a look if the bike wasn't at the shop being certified fit for use on the road (it's passed, incidentally, but the guys there are just doing a couple of cosmetic bits and pieces before I collect).

Back to the 450 for a minute or two . . . took a couple of photos of the parts of the powdercoated frame that show the areas I tidied up - well, sort of; detail in black powdercoat isn't the easiest thing to capture in pictures:

Lower frame . . .

. . . neck . . .

. . . and ancillaries . . .

Mmmmmmm . . . shiny.

Unfortunately, reassembly has ground to a bit of a halt right now, 'cos I'm waiting on two fairly sizeable orders of spares including rims and spokes, bearings and bushes and nuts and bolts. I've resprayed the engine, which looks pretty good, but again, I'm waiting on some little odds and sods before I put it back together. I think I need to pick up a honing tool, too, 'cos there's a little surface rust on the faces of the barrels.

And talking of barrels, I've discovered - disappointingly - that one of the fins on the replacement barrels is broken. Not badly (about 1cm long and at the end of a row) and I think it'll be hidden by the exhaust, but it's a pity nonetheless.

Updates as they happen.

the-chauffeur · « **Reply #161 on:** February 20, 2009, 12:25:56 PM »

Nuts. I seem to have come unstuck with the oil passages on the 750. I picked it up from the shop earlier today and went for a little ride, and the oil light came on. And stayed on. And wouldn't go off again.

After deciding something very definitely wasn't right, I gingerly rode the bike home. I drained changed the oil filter, drained the oil from the sump and inspected the pump (cleaning the gauze as I went), and changed the oil. Started the bike up again and almost instantly the oil pressure light came on again. And wouldn't go off.

I guess my next move is to pull the pump apart. With everything else being clean, I'm struggling to think what else it could be.

Slow progress . . . I think . . .

mystic_1 · « **Reply #162 on:** February 20, 2009, 01:49:49 PM »

Do you have a gauge installed? That'll tell you if you have a real problem. Check the oil pressure sender first, it may have gone south on you.

mystic_1

the-chauffeur · « **Reply #163 on:** February 20, 2009, 04:26:01 PM »

Hey Mystic

Unfortunately, I don't have a gauge - I'm kinda reliant on the light/sensor in that respect. The light goes off periodically - like when there's no oil in the bike (go figure) - but since I've not had the pump apart yet, I thought it could do with disassembling.

So I pulled it off the bike and and cleaned/freed up the oil flow stopper (or at least I think I did); at any rate, the plunger seems to move more freely than before. The relief valve didn't seem to do much of anything really, but I cleaned that too.

I then broke open the main housing and had a good look at the inner and outer rotors. Although they're well within tolerance, there's some pitting on the edges/faces. Not catastrophic - and they're not scored or squared off - but I'm wondering how much pitting they can stand before they need to be replaced. When reassembled and lubricated, the pump rotates freely, and as far as I can gather, the individual rotors move in and around each other without any obvious restriction.

Just before I put the pump housing back on its base, I poured engine oil into the channels on the underside and rotated the drive wheel. Depending on direction, the pump either forced out the oil, or sucked it through, so I assume that's a good sign.

But I can't test it properly right now, 'cos it's just gone midnight, and I won't be popular with the locals . . .

Back soon

I gotta say the fact that you can't buy rotors as individual parts worries me a bit.

HondaMan · « **Reply #164 on:** February 20, 2009, 08:55:37 PM »

These oil pumps are very robust. Most of the ones I've seen have side pitting, yet still develop well over 60 PSI pressure.

Chances are, the switch is bad or the wire is grounding against the case, near the countersprocket on the left side of the engine where it snakes around this & that on its way to the white connector at the rear left side of the engine.

Try this: disconnect the wire from the switch and connect an ohmmeter to the engine case and the wire, see if you get a short to the engine case. With all the in & out you've had to do with this engine, and the number of times that left side case has been off by folks who don't know what to watch out for, I suspect a nicked wire there before I suppose anything is wrong with the oiling system.

That said, do make sure the oil hoses are properly connected: if they are reversed, then it will only pump about 3/4 of one quart of oil before it lowers the tank to the upper tube's level, then when that little bit gets scavenged back into the tank, it sends a little more out again.

If the hoses (especially the lower one) have a blockage, that could explain why you started out with bad bearing issues: interrmittent oil supply could potentially damage the bearing shells on the crankshaft.... $:-\$

But, what could be blocking the hose? Maybe a dead mouse? A big bug? A nasty neighbor who didn't like the previous owner?

the-chauffeur · « **Reply #165 on:** February 24, 2009, 02:27:15 PM »

Well, after overhauling the oil pump, checking the switch, electrics and hoses - and finding nothing untoward - it took a bit of head scratching and pacing back and forth before I finally figured out what the problem was. That, and looking at the engine from the front . . . turns out that the switch was working fine, as was the oil pump. And the oil was flowing through the hoses exactly as it should.

I'm not sure why it didn't dawn on me earlier that there might be something wrong with the engine oil pressure, but the (quite impressive) oil leak down the front of the engine between the crankcases and the cylinders told me just what I didn't want to know. Either the head gasket's failed and/or the genius who put the head back on didn't torque down the nuts on the studs properly.

Outstanding.

So for the nth time, the engine's gonna have to come out. Only this time, I'll be redoing the whole bit myself. Then I've only got me to blame when it all goes sideways . . . again.

On the upside, a while bunch of stuff arrived in the mail for the 450. Spent an hour or so polishing the rear hub and and respoking the rear rim this afternoon. Also picked up a honing tool to clean up the interiors of the overbored cylinders (and I guess I can also have a go at the 750 cylinders when the head's off). Next up, cleaning up the valves and putting the head back together.

HondaMan · « **Reply #166 on:** February 24, 2009, 08:02:51 PM »

Ouch. Maybe someone forgot the O-rings in there?

the-chauffeur · « **Reply #167 on:** February 25, 2009, 03:09:21 AM »

Guess there's only one way to find out . . .

. . . although I know they were all there when I put the engine back together the first time all those months ago. Hey, who knows. All I can tell you is it should take me a hell of a lot less time to work out than it's taken the boys at the shop to get it this far.

Schoolboy error.

HondaMan · « **Reply #168 on:** February 25, 2009, 05:49:37 AM »

With the 3 bikes and 4 engines I've got here, I'm getting pretty fast at them again, myself

andy750 · « **Reply #169 on:** February 26, 2009, 04:58:17 AM »

If its any consolation, same thing happened to me...small engine leak from same spot as you described...pulled the engine for the nth time and replaced cam tower pucks etc...and then buttoned it back up and re-installed...first test ride went well and it sounded healthy...however walking around to the front of the bike I noticed oil now streaming out the front...

....in my case it was I had somehow managed to not torque everything down correctly and the cam towers were not so tight...

good luck in getting it sorted!

cheers
Andy

the-chauffeur · « **Reply #170 on:** February 26, 2009, 12:34:27 PM »

Thanks for the support, chap.

It is a little consolation - if for no other reason than I now know I'm not alone. My guess is that I'll find the same thing as you (toque settings being off, that is). I get the feeling this is one of those jobs that needs to be done, left, checked, left and checked again over a period of a day or two - just to be sure. And I'm sure Loctite will be my friend . . .

Ho-with-a-capital-hum.

HondaMan · « **Reply #171 on:** February 26, 2009, 09:18:22 PM »

You shouldn't need the Loctite, but I do this: tighten to the 14.5 ft-lbs. Wait overnight, loosen each nut (in torquing order) 1/2 turn, then retorque.

the-chauffeur · « **Reply #172 on:** March 01, 2009, 03:04:09 PM »

It's elastic bands, Jim . . .

After a very frustrating day Friday (including several hours trying to remove an internal circlip with both eyelets broken off out of the 450 master cylinder), I pulled the 750 engine out of the frame yesterday and tore the top end down. Having pulled the cylinders off the crankcase, it was quite easy to see what the problem was - all of the large o-rings were there, but whereas three of them had located in their respective recesses and sat slightly proud (so they seal against the crankcase gasket), the fourth looked as though it had been poked into its recess by little fingers. There were two or three areas of 5mm or so around the circumference where the highest edge of the o-ring sat below the edge of the recess - clearly not providing any kind of meaningful seal.

Given that the o-rings came in an aftermarket gasket kit, I decided to pull all four and will replace them with Honda parts just to be sure, but obviously I want to avoid making the same mistake when I put the cylinders/head back on - so what's the best way to put the o-rings on? Should I locate them round the cylinder outers but not push them into the recesses and just let them seat themselves as the barrels are mated to the crankcase? Or do they need special help?

I'm pleased to report that everything else looked pretty much as it had after the first time I opened the engine up; all the pistons and valves looked fine (although a small piece of one of the piston rings broke off while we were fiddling with them, so another set of those will go on order, too). And the cylinder walls looked even better once I'd honed them. Shame I'll have to repaint parts of the engine again though - I cannot understand why the paint is so damn fragile, even after it's been heated up - although I gotta say I'm not having a hole lot of luck with spray paint of any description right now. I think next time(?) I'll get the cases blasted and stove enamelled.

HM - thanks for the tip on torquing the head down. If all goes well - and pending helpful hints from you folks - we'll have the engine back together this time next week. It's so much quicker and less frustrating knowing that I'm in control of its destiny.

As for the 450, I've pretty much finished rebuilding the head, and I honed the barrels on that, too. The bloody master cylinder was an absolute nightmare, but I think I rescued it - and temporarily losing a collet gave me a bit of a scare. The side cases have been painted (again, see comments above) and the next jobs will be fitting the pistons/cylinders, and then rebuilding the starter clutch thingie, which I understand have a nasty habit of lunching themselves.

And when I remember, I'll order some paint for the tank and panels. Quick straw poll on colours - http://www.spookytoms.com/CB750-PaintColors.html - suggestions? Bear in mind two things - the bike badges show it's a K5 or K6; and I've got a set of black tank stripes. I want to stay as original as possible, but as long as it's a Honda 450 colour, I don't think I'll go too far wrong. Right now, I'm kinda now leaning toward the gold, but I'm open to opinion.

Like the Duracell bunny . . . still going . . .

HondaMan · « **Reply #173 on:** March 01, 2009, 05:35:22 PM »

Those tube-like "O-ring" seals can get folded if the head has crud in its receiving hole, or if the head gasket lifts up from the cylinders while the head is being lowered. The gasket then can lift and tilt the rubber seal, probably making something like the mess you had.

Just try to keep an eye on the gasket as the head's being lowered, and it should go smoothly.

the-chauffeur · « **Reply #174 on:** March 08, 2009, 02:12:15 PM »

Thanks HM. Barrels are back on now, with new O-rings and the rest of the engine is back together, gapped and timed. Unfortunately, I managed to repeat one of the mistakes the garage made and cracked the clutch pressure plate, so it's not 100% yet - but it's very nearly there.

Back to the 450, I thought I'd got everything in the top of the engine right, pistons in and matched up, etc. But when I went to re-join the camchain, no matter what I tried I couldn't get the timing marks on the camshafts to line up with those on the casings. The back was about 1mm out; the front was at least 3mm out. I thought I'd carefully and correctly labelled everything I pulled out when I disassembled it, but I'm now starting to wonder whether I mixed up the valves (how hard can it be?).

So today's question . . . which are bigger - the inlet valves or the exhaust valves? I'm pretty sure the exhausts are the bigger of the two, which means that like the genius I am, I must've put them in back to front (oh, and I can't find any pictures in the manuals).

Shouldn't be long now . . .

News:

Author Topic: Keep telling yourself - a restored 750 K2 is an investment (Read 38586 times)