Topic: 1972 CB750 Four K2 -- Rebuilt to NEW OLD STOCK -- PIX ON PAGE 50

[edwardmorris]

Cleaned up some more hardware and sprockets along with the splash guard. The splash guard had so much rust on it I pretty much was going to throw it away. Before doing that, I thought I'd give evaporust a try and wow did that work! Took three nights of soaking but ALL of the rust is gone and pitting shows. I cleaned it up well with a wire wheel cup on a dremel shaft and it looks like its ready to go back on. How do the sprockets look? Reuse or replace?

[Kickstart]

Looking good... I think I'll try the same with my splash guard.  Are you clear-coating it with something?

Replace the sprockets.  Always a good idea to replace the sprockets and chain at the same time.

[edwardmorris]

Thanks Chris, any recommendations? I don't think I saw OEM ones at motogrid but I haven't checked DSS and such just yet. I know Hondaman/Mark mentions in his book that the OEM ones were made of a special material that worked well, have to do some digging on aftermarket ones..

[Kickstart]

Hmmm... yeah, as I recall it's not he material but the way the teeth were cut, and I don't believe they're available anywhere.

Also, I'm not sure when they stopped supplying them.  You may not have the original OEM "cut" anyway.  Try reaching out to Hondaman to see if he can shed some light on how to check.  If it's not the original cut then just get an aftermarket one.  If it's original, then maybe consider re-using it if the teeth don't look worn.

All that said, what are you riding plans for this bike.  If you're planning on doing some touring on it, you may just want to buy all new stuff and get yourself an O-ring chain.  Sure, you'll lose a couple hp at the wheel, but the convenience of not having to clean/oil the chain every 500 miles (especially if you're on a long trip) I think makes up for it.   If you are racing it, or just need to squeeze out every extra hp (which I totally understand) then ignore my comment on the o-ring.

 

[tweakin]

Ed, I am using this sprocket on the K.  http://www.amazon.com/gp/product/B004ZIXIKW/ref=oh_details_o03_s00_i01?ie=UTF8&psc=1  The photos are not what I got, it actually looks pretty close to stock as you can see in the picture.  It is a Sunstar stock replacement steel sprocket.



For the front I used
http://www.amazon.com/gp/product/B004ZIVPZM/ref=oh_details_o04_s00_i02?ie=UTF8&psc=1

with an o-ring chain.

[edwardmorris]

Thanks Chris, building this as a mundane daily rider so not too keen on saving HP fractions, all in favor of low/less frequent maintenance I looked back at Mark's book, the original Honda material, much like their crank bearings, was softer to allow grit to embed in it instead of hurting other parts, along with what you mentioned about the cuts.

Tige, thanks,  just looked at Yamiya and its the same brand they're selling too. How's it been working out for you? I might just get the Sunstar set with a low maintenance chain.

[Terry in Australia]

Ed, not wanting to start an oil or tire thread type argument, but don't get too fussed about using OEM sprockets, good quality sprockets (JT for example) are at least as good, but probably better than OEM.

A note about O ring or X ring chain maintenance too, the rings seal grease around the pins and inner rollers to stop them from seizing/wearing, but you still need to use a good quality chain lube to stop the plates and rollers from rusting/wearing.

If you ride in wet or dusty conditions, you need to keep them cleaned and lubed just as often as you do non-o ring chains. Cheers, Terry.  

[edwardmorris]

Thanks Terry for the chain clarification. Not too dusty around here but incredibly humid during the summer living between two lakes so rusting would be something I'll need to worry about. If O-ring chain is slightly less maintenance than one without, it makes sense to go with that for me. Also, I'll stop over thinking the sprockets, JT is the other brand I see listed abundantly but when I saw Yamiya selling Sunstars, I figured that's more close to OEM...

Still too bloody cold out here to do any kind of painting, desperately waiting to paint the engine cases and frame so I can start putting this thing back together. But there is plenty of little stuff left to deal with until then anyway so hoping to get more things squared away on my day off tomorrow.

[edwardmorris]

Had some time to clean up a few more parts, is this cam toast?

Side 1

[edwardmorris]

Side 2

The journals and lobes both look awful compared to the 41-a, can these be micro polished like the crank?

[Terry in Australia]

G'Day Ed, yep, that cam looks completely clagged. While you could possibly get it re-ground, that would increse the clearance betwixt the bearing surfaces, so it'd just rattle around in the cam towers. Get yourself a better one. Cheers, Terry.

[HondaMan]

That one looks like a good candidate for a reweld-regrind core, but with the kind of rust and chips I think I see, it would be pretty rough on your other parts. Those kinds of cams are good to keep around (or use) with Megacycle, sending it to them when you want, say, a nice 125-04 regrind (they are out of cores for the new ones, they say, which is their 125-00).

If you have one with smooth journals, it's a better candidate?

[HondaMan]

Thanks Terry for the chain clarification. Not too dusty around here but incredibly humid during the summer living between two lakes so rusting would be something I'll need to worry about. If O-ring chain is slightly less maintenance than one without, it makes sense to go with that for me. Also, I'll stop over thinking the sprockets, JT is the other brand I see listed abundantly but when I saw Yamiya selling Sunstars, I figured that's more close to OEM...

Still too bloody cold out here to do any kind of painting, desperately waiting to paint the engine cases and frame so I can start putting this thing back together. But there is plenty of little stuff left to deal with until then anyway so hoping to get more things squared away on my day off tomorrow.

You get a day off?

You lucky @#$@!....

[edwardmorris]

You get a day off?

You lucky @#$@!....

LOL not my choice, the wife has mandated no work on Sundays for a while now. Me, I prefer picking up every available shift I can, especially now that I have a big ticket item on the list, the yamiya body kit. A whole another debate running in my head with that, WHAT COLOR TO GO WITH? Don't like the candy gold, and that's the only correct K2 color they have.


As for the unfortunate cam situation, I paged Bill Benton and he's got one! I still have the Web-Cam 41-a that was in the  original wrong F head along with its HD springs and what nots but it doesn't seem like I can simply drop it in with stock everything else, will have to learn and do the whole degreeing shabang!

As always, thank you all, for keeping up with me so far, I'll do all I can to get it on the road asap.

[edwardmorris]

Not a whole lot going on, but managed to get round 1 of 500 grit sanding done on the fork legs and front hub. Fork legs had major atrocities, the hub only had minor gouging from over tightened spokes. Still need to clean up the grooves a little better. For the fork legs, I'm thinking about leaving the casting marks as is, because that's how they came out the factory. Not entirely done with them, but its a start.

[edwardmorris]

Hub and casting marks..

[BPellerine]

polishing and cleaning sure eats up the time and fingertips!bill

[edwardmorris]

polishing and cleaning sure eats up the time and fingertips!bill

Definitely, I'm dreading the Sunday I'll start with the valve train cover. There's never enough time to do more than a couple things anyway so most of my fingertips have survived thus far

Hoping to get the master cylinder torn down sometime before next Sunday, any tips on cleaning brake fluid deposits? Is Acetone interchangeable with lacquer thinner when cleaning parts?

[BPellerine]

just did the valve cover for my engine build and it took me 4 nights of sanding and polishing!bill

[edwardmorris]

OK, so taking a short break from sanding as I'm getting sick of it. Started to take the master cylinder and the upper hose assembly and got stuck pretty fast. From searching, watching a youtube vid, reading through Mark's book and the factory manual, the MC piston should come out once the boot, retaining ring for the boot and the circlip are out. I got all of this out, the only thing I didn't see come out was the 10.5mm washer that's in the parts fische. Instead, the pix below are what I see, something is blocking the piston from coming out. How to proceed?

[goldarrow]

Once both clips are out, just whack the cylinder out

[Terry in Australia]

To extrapolate on Goldy's post Ed, as I'm sure you'll be installing a rebuilt kit, you can poke a suitable drift/punch into the other end (brake hose end) and push/tap the whole piston assembly out.

You can try just pushing and releasing on the lever end of the piston assembly and hope that the internal spring pressure will pop it out, but my experience has been that you may need to tap the assembly out from the brake fluid hose end.

Just make sure that you don't go in sideways and score the cylinder with the drift. (unlikely, but anythings possible..........) While you have the piston out, make sure that the fluid hole and air bleed hole in the bottom of the reservoir are clear, this is the most common reason for the brakes not bleeding properly on re-assembly, and will save you a lot of time if you do it with the piston assembly removed.

I actually slightly enlarge the air bleeder hole with a jet drill, but just ensuring that the hole is clear by poking a stiff wire thru and looking into the cylinder to make sure the wire is all the way through will do. Cheers, Terry.    

[edwardmorris]

Thanks guys, its kinda hard to tell from the pictures, but what's making me nervous about just whacking it out of there is that it looks like there is another circlip without the eyes to pry it out. The piston moves pretty far up and down but won't budge past the point where the circlip is/was. Is it possible that it's gunked up so bad that? If so, then I'll try and get it out as suggested.

[goldarrow]

What you're seeing is the washer and it got rusted and stuck.  Just push it out from the other end like Terry mentioned

[edwardmorris]

Alright, I gave it a shot and it did break free. The washer is shaped like a c-clamp, not sure why, wouldn't this cause leaks?

I cleaned up the cylinder in hot soapy water and gently removed the corrosion at the entry point with a wire cup on dremel. Once clean, I noticed that there seems to be some kinda scratch on the inside where the opening of the C-shaped washer was. Is this thing toast?