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

[BPellerine]

electric impact  works great!if you don't have one most garages do and would most likely remove it for you it works fast and easy.bill

[edwardmorris]

No luck on finding a shop to widen the grooves on SKF replacements. Worst case, I'll leave the old ones in, or shell out for yamiya ones. Haven't had time to get back to the rotor yet but thanks for the tips Ron and Bill. Been working like crazy and got some good news today, the first oversize pistons from yamiya are in Chicago, so should make it home any day now.

Any particular tips/advice for properly instructing the machinist?
As for blasting of the cases, should I ask that they only blast the outsides? (I left the counter shaft bearing in there, didn't wan't to bang it out until I have the bearing issues sorted out).
Anything to caution him when blasting the fins on the top end?

[MCRider]

No luck on finding a shop to widen the grooves on SKF replacements. Worst case, I'll leave the old ones in, or shell out for yamiya ones. Haven't had time to get back to the rotor yet but thanks for the tips Ron and Bill. Been working like crazy and got some good news today, the first oversize pistons from yamiya are in Chicago, so should make it home any day now.

Any particular tips/advice for properly instructing the machinist?
As for blasting of the cases, should I ask that they only blast the outsides? (I left the counter shaft bearing in there, didn't wan't to bang it out until I have the bearing issues sorted out).
Anything to caution him when blasting the fins on the top end?

When I did my cases, plastic beads, not glass, I bolted the 2 case halves together. I think at the time someone had warned me about not blasting the areas where the crank main bearings lie. But even at that, everything had to be removed, ball bearings and such, as the beads get EVERYWHERE. Clean up is a #$%*, though with plastic you have the comfort of knowing if you missed a few they won't tear anything up...much.

No caution on the fins, just don't break any handling it too rough.

[BPellerine]

you have the desired piston clearance in your hondaman book for your replacement pistons make absolutely sure they understand to stay within those tolerances!!! they should measure each piston to its bore and mark the ie 1,2,3,4 so that you will assemble them in the correct hole.if you have to bring your specs with you and be double sure they understand you.bill

[edwardmorris]

Thank you Ron and Bill, added to my notes. Will go through the literature and spell it out for the guy as best as I can.

Bits of good news trickling in, got a solid center stand with mounting hardware, ignition switch bracket and a correct K2 oil tank (mine had a K0 tank on it) from Bill/Benton-Racing and Stev-o very generously sent me a great looking shifter drum. Gotta call my welder and get a time to get the center stand lowered. Will take the ruined shifter drum with me in case he can salvage it on a lathe.

[HondaMan]

Thank you Ron and Bill, added to my notes. Will go through the literature and spell it out for the guy as best as I can.

Bits of good news trickling in, got a solid center stand with mounting hardware, ignition switch bracket and a correct K2 oil tank (mine had a K0 tank on it) from Bill/Benton-Racing and Stev-o very generously sent me a great looking shifter drum. Gotta call my welder and get a time to get the center stand lowered. Will take the ruined shifter drum with me in case he can salvage it on a lathe.

Was that K0 tank useable? I need one for my [very slow] K0 resto I'm attempting. It's rough. (That's kind...).

Make sure the shop knows you want .001" clearance for those pistons. Honda specs it as .0008"-.0012", so they let it have production tolerances of just 2 ten thousandths either way. In my experience, when using Honda's own pistons from ART, they run best at the tighter end of the spectrum.

The best part of all: you'll now have round bores that will last a VERY long time. When I took my .25mm oversize out last Fall for this rebuild, the bores are still round within any measure I can get, at 90k miles on the pistons. Once those sleeves are cured, they are amazing!

[Terry in Australia]

I think I mentioned it earlier Ed, but you don't have a K0 oil tank, you've got a K2 oil tank that someone had filled the dimples with bondo. Cheers, Terry.  

[tweakin]

Making great progress Ed.

[edwardmorris]

I think I mentioned it earlier Ed, but you don't have a K0 oil tank, you've got a K2 oil tank that someone had filled the dimples with bondo. Cheers, Terry.

Damn! did I miss this or completely forget? I'll dig it out and see if bondo is scraping off and put some pix on Sunday (wife mandated that I not work Sundays ). More than one person had pointed out it was the wrong tank so I started looking. The one from bill is in better shape than mine anyway so no harm owning a spare .

Mark, if it does turn out to be a K0, you can have it.

[edwardmorris]

Cases, cylinders and head are all ready to go, will drop them off on my way back in the morning. I printed out detailed instructions on clearances, honing and plastic bead blasting on the outsides only.

 I'm impressed with Yamiya, this stuff looks great, fast shipping and good packaging. But, that hole in the wallet is undeniable

Pic 3. Gotta run back so no time to look at the books, but this curious set of letters in the lower crankcase, what are they?

[Terry in Australia]

Looking good Ed, make sure you leave your pistons with the guy doing the rebore so he can match them to the bores.

[edwardmorris]

Looking good Ed, make sure you leave your pistons with the guy doing the rebore so he can match them to the bores.

Haha yep. I called him and asked what to bring with after Bill posted earlier and the machinist asked for all four pistons. I asked him why and he told me that he needs to match each to its own bore. Looks like he knows what he's doing so I'm hoping for the best.

I won't be getting anything back until next Saturday because there were nine other (car) heads  ahead of me

As expected, he was surprised how tight the clearance is so I handed him a print of notes from Mark and he went "REALLY? I learn something new everyday". I asked him to do mine carefully and separate, not in the "rhythm" of doing several car heads one by one, and he agreed

Snowed in like nuts again so home for the remainder of the weekend. Too many things need attention, not sure what to pick up.....

[BPellerine]

looks like you are on the way up now Ed now the wait begins!bill

[tweakin]

Pic 3. Gotta run back so no time to look at the books, but this curious set of letters in the lower crankcase, what are they?

I think the letters in cases are a worker with too much time on there hands...  I have damn nearly the alphabet in my 71.

[edwardmorris]

looks like you are on the way up now Ed now the wait begins!bill

Haha, I wish Bill. Still not motivated to touch the electrical stuff, that's not going to be fun, along with the aluminum covers to sand and polish, and no lead on the transmission bearing situation yet. Capitalizing on bad weather to rack up as many work hours as I can, because I KNOW once the start the climb, my finances are going to take a diiiiiiivve.

Tweakin, thanks for the info, I wondered if it was some kinda code like the crank bearings...

[Kickstart]

How bad is the electrical stuff?  Was the wiring harness chopped up?

Let me know if you have any questions on bearings... I spent a lot of time researching them (and arguing with bearing shops), but I got it all worked out.

Keep up the good work!

[edwardmorris]

Nothing chopped up thankfully but slathered in 40+ years of gunk. Need to clean out the harness and apply some dielectric grease to rejuvenate it a bit. I searched a lot about new sleeves and it looks like there isn't an exact match available (either slightly light or loose) and if I do decide to change it, then I'll have to redo all the bullet connectors as well because all the wires won't just slide into a new sleeve.

I searched a ton on the bearings too and believe it or not, one of your posts is what definitively told me that modern day SKF NR suffixed bearings are not drop in replacements, and enlarging the grooves costs an insane amount of money.

I am curious however, about how to even get to the bearing between the primary drive sprockets and the clutch basket? The shaft pulls out but the rest of the assembly looks pretty tight. And for that matter, how to get the needle bearings out? The tips and trick section had a post where someone used a large socket and hammered a bad bearing out that way but not sure if that's a good idea for a bearing that isn't damaged....

[edwardmorris]

You were right Terry, looks like there's bondo paste on the tank. I'm gonna clean up the new tank and use that as is, the paint looks excellent.

[Kickstart]

...
I am curious however, about how to even get to the bearing between the primary drive sprockets and the clutch basket? The shaft pulls out but the rest of the assembly looks pretty tight. And for that matter, how to get the needle bearings out? The tips and trick section had a post where someone used a large socket and hammered a bad bearing out that way but not sure if that's a good idea for a bearing that isn't damaged....

There's a circlip inside the basket that holds it onto the primary sprocket.  Once you remove that you can get to the bearing.
I used a cheap bearing puller tool to remove it.  I figured I'd save myself some grief and just buy the tool.  Came in handy for the bearings on the final drive:
http://www.harborfreight.com/bearing-separator-and-puller-set-93980.html

Oh, those needle bearings are tough to get out! 
I think I spent half a day trying to get those out using a brass drift, screwdrivers, needle nose pliers, plenty of penetrating oil, heat (from a electric griddle) and I could not get them out.

I finally broke down and purchased a blind bearing puller:
http://www.harborfreight.com/blind-hole-bearing-puller-95987.html
IMO, this tool is necessary to get those bearings out.  It's not cheap, but it works (actually I might have picked it up on sale now that I think about it).  If you pull these bearings, make a note of how deep each one sits in the sprocket unit.  I damaged a new one installing it because I thought it wasn't in there deep enough.  When installing the new ones, heat the sprocket unit up on an electric griddle  (I put it between the 200-250f setting) and use lots of gentle taps rather than harder ones.  There's really not much case strength to those needle bearings.  The bearing on the one side is recessed some, so save the old bearings so you can use one of them to help drive the recessed bearing into place.

And yeah, no matter what method you use, I'm pretty sure these needle bearings will be damaged upon removal.

You may be able to rent those tools for free from you local Pepboys/autozone/advancedauto/etc.


All that said, do you think your bearings are in bad condition?  I replaced, mine, but honestly mine were ok. When I took the old ones to my machinist (as reference for the groove) he was like "what's wrong with these?"  I did it because I'm trying to make my engine "like new" and I wanted the learning experience... but all this stuff starts adding up to a lot of money

[edwardmorris]

Thanks Kickstart(Chris?), will take a look tomorrow, its been bugging me because I KNOW I saw a thread with pictures here but I can't find it for the life of me.

The bearings yes, it will be an all or nothing deal. I have no way of telling how many miles are on the engine and what condition the bearings are in. I wan't to change those out with SKFs (costly but permanent and available withing a mile from my residence) and not think about them for 80-100K miles. But unless I figure out an economical option to get the standard SKF grooves widened, tranny is on the back burner.

The needle rollers, same story (pardon the "while its open" thinking), change them out with SKFs and  forget about them. With these I might be in luck, my local auto shop has a great blind bearing puller similar to the one in the second link.

You are right about stuff adding up, but I'm hoping this is a good investment to make so I always have a reliable rider while go parts hunting for my next project

[edwardmorris]

Yamiya is out of K2 body sets? There goes that plan. Have they restocked these in the past? I suppose I should get my back up plan in motion, suggestions on renewing my gas tank? Visually there isn't much rust on the inside as it seems to have always had some gas in it. Don't have the set up for proper electrolysis, so what chem treatment to try?

[edwardmorris]

I'll have to read up on the electrolysis method again. Also, how do you get the petcock off the tank? Search didn't help much (moody piece of crap).

I made some time today to clean up some hardware. This weekend is grocery shopping weekend so I'm thinking about picking up some zinc plating ingredients. Grepper posted a great step by step, sounds easy with outstanding results, so worth trying.

[seanbarney41]

I can't say for sure on your tank as I have 500s, but mine are all threaded on. Should be a large nut that threads onto a neck from tank, the petcock comes free with the nut. Then further disassembly once free from tank is possible. A pic would help me confirm whether my advice is accurate on your tank.

I'm sure someone with 750 knowledge will correct me if I'm steering you wrong.

yep, you are wrong!  If your tank is correct for your year, Ed, you have to unscrew the sediment bowl, pull out the sediment sceen that is held in by an o-ring...then inside the petcock are two JIS screwsthat hold the petcock body to the tank

[edwardmorris]

yep, you are wrong!  If your tank is correct for your year, Ed, you have to unscrew the sediment bowl, pull out the sediment sceen that is held in by an o-ring...then inside the petcock are two JIS screwsthat hold the petcock body to the tank

Thank you Sean and Calj, mine is the correct year tank. I will gather some supplies this weekend to set up the electrolysis. I assumed that the petcock needs to be removed before doing this, that's why I asked. I'll have to find a way to plug the holes well. Hopefully some progress report this Sunday.

[seanbarney41]

Ed, it's kinda tricky 'cuz you got two screw holes and the actual fuel outlet hole...so what I have done is make a little metal plate, drill it for the two screws and then screw it on with some rubber(I cut a piece out of a heavy duty rubber glove) or gasket material sandwiched between the plate and the tank.