Author Topic: 1972 CB750 Four K2 -- Rebuilt to NEW OLD STOCK -- PIX ON PAGE 50 (Read 243067 times)

edwardmorris · « **Reply #225 on:** January 05, 2014, 02:48:48 PM »

Quote from: 70CB750 on January 05, 2014, 02:10:59 PM

I would say pistons are fine and you could reuse rings if you put them back the way they were. I was going to to that on the F, but one ring was broken - reringed it all.

This thread is why I wasn't gonna ask

http://forums.sohc4.net/index.php?topic=126776.0

I was just cleaning the damned things and one of the #3 rings just snapped! Ugh, I guess I'll be re-ringing as well.

70CB750 · « **Reply #226 on:** January 05, 2014, 02:50:43 PM »

Everybody brakes a ring eventually

BPellerine · « **Reply #227 on:** January 05, 2014, 03:56:22 PM »

as for your main bearing shells they don't look too worn but you should measure or plastigage them same for the rod bearings .don't mix them up and try to see if you can see any color markings on them ie green yellow brown or black .IF they measure out ok some reuse them.also have you marked your rods 1,2,3,4 so they go back where they came from along with their shells?bill

RRRToolSolutions · « **Reply #228 on:** January 05, 2014, 04:00:11 PM »

Ed, while you're this far - I would suggest measuring the bores top and bottom for wear. Give us the bore measurements in line and 90 degrees to the piston pins (where most wear occurs). New rings is always a better way to go. If the wear is in tolerance, you could use a good Sunnen ball-hone and refinish the cylinders with a new cross-hatch so the new rings will seat. You'll have a happy engine too.

I'll go check, but I should have the snap gauges that you'll need for measuring and a ball hone in my shop for the new finish.

Regards, Gordon

RRRToolSolutions · « **Reply #229 on:** January 05, 2014, 05:57:25 PM »

Ed, I posted photos of your Rotor Puller Tool in the "For Sale" section. We made these from the best materials available and copied one I had in my tool cabinet so I know it works well. I'll get it to you this week.

Best Regards, Gordon

edwardmorris · « **Reply #230 on:** January 05, 2014, 08:06:40 PM »

Nice! Perfect timing Gordon, the crank and the rods are next on the removal, cleaning and inspection list and the rotor is still on, thanks!.

I can get the bore measurements if I can get those specialty tools. The pistons themselves I measured earlier for Terry with a caliper and they are the stock size (never bored). Honing was on my list anyway so I guess new rings will work out for the best. The busted ones are coming in handy to clean the ring lands

MCRider · « **Reply #231 on:** January 05, 2014, 09:03:05 PM »

Quote from: edwardmorris on January 05, 2014, 08:06:40 PM

Nice! Perfect timing Gordon, the crank and the rods are next on the removal, cleaning and inspection list and the rotor is still on, thanks!.

I can get the bore measurements if I can get those specialty tools. The pistons themselves I measured earlier for Terry with a caliper and they are the stock size (never bored). Honing was on my list anyway so I guess new rings will work out for the best. The busted ones are coming in handy to clean the ring lands

point of order: the "lands" are the part between the grooves. You are cleaning the grooves with the broken bits.

Carry on!

http://www.hastingsmfg.com/ServiceTips/piston.htm

edwardmorris · « **Reply #232 on:** January 05, 2014, 09:31:24 PM »

AH I see, thanks! About that pitting on the piston heads, should I sand it out with a fine grit paper and polish it or leave it be?

MCRider · « **Reply #233 on:** January 05, 2014, 09:39:28 PM »

asking me? never seen anything like the pits. from detonation? I'd say OK to ignore, but I don't really know.

Get some snow? we got about 12" and the wind begins to howl.

edwardmorris · « **Reply #234 on:** January 05, 2014, 10:08:02 PM »

Question was for @all.

A little worried, apparently pitting happens from the acid formed due to water and carbon mixing. Pitting (like I guessed) will increase carbon deposits too, so I'm trying to see if I can get away with polishing them.

And yes, don't know the official numbers but there is about a 4 foot tall mountain blocking my garage from all the winds blowing it around. Front yard looks about 15 inches of snow though, I really need to get me a snow blower. Four shifts of shoveling and it piles right back up. I live in between Lake Michigan and Wolf lake, so double the lake effect snow gets dumped here.

BPellerine · « **Reply #235 on:** January 06, 2014, 09:49:35 AM »

same here in Canada Edward!bill

MCRider · « **Reply #236 on:** January 06, 2014, 11:24:11 AM »

Quote from: edwardmorris on January 05, 2014, 10:08:02 PM

Question was for @all.

A little worried, apparently pitting happens from the acid formed due to water and carbon mixing. Pitting (like I guessed) will increase carbon deposits too, so I'm trying to see if I can get away with polishing them.

And yes, don't know the official numbers but there is about a 4 foot tall mountain blocking my garage from all the winds blowing it around. Front yard looks about 15 inches of snow though, I really need to get me a snow blower. Four shifts of shoveling and it piles right back up. I live in between Lake Michigan and Wolf lake, so double the lake effect snow gets dumped here.

I see. I'd polish them out till you feel good and move on. The water pitting makes sense.

All's closed in Indy, no unnecessary travel allowed. Maybe another day, too. Give an offering to public utilities and fan forced heat.

I had to downsize my snowblower. Still @ 20" with electric start and self propelled (forward only) it makes amazing short works of the sidewalks. A truck blade does my larger parts, for a fee.

edwardmorris · « **Reply #237 on:** January 06, 2014, 11:39:36 AM »

Looks like sanding IS an option, I'm going to try since mine don't look to be as deep.

http://forums.sohc4.net/index.php?topic=81955.0

MCRider · « **Reply #238 on:** January 06, 2014, 11:43:18 AM »

Nice search!

greenjeans · « **Reply #239 on:** January 06, 2014, 02:49:44 PM »

I've sanded some piston tops in the past with no ill effects. Not really taking much material off - I've also polished the tops thinking it would be harder
for the carbon to stick to a polished surface. I haven't actually torn things apart to see if it had any effect at all. I usually run so much seafoam and Chevron gas with Techroline that I just assume they stay clean. One day I'll have to tear things down just to see.

edwardmorris · « **Reply #240 on:** January 06, 2014, 09:48:34 PM »

Quote from: MCRider on January 06, 2014, 11:43:18 AM

Nice search!

Its a moody piece of crap, you either find everything or nothing

Today was the worst day. Absolutely zero progress today because I was stupid enough to go out and start shoveling. Snow wrapped up at 18 inches and wind chill of -42 F today. My fingers froze through the gloves so bad I think I have some busted capillaries in my finger tips. Can't do crap till they heal a bit. Oh well, guess a rest day isn't so bad. Garage is still inaccessible, no idea how to deal with the four feet mound in front of the man door. Too much for even a snow blower.

Terry in Australia · « **Reply #241 on:** January 06, 2014, 10:12:59 PM »

G'Day Ed, sorry I haven't replied earlier, I was away visiting my folks for the last few days. Gordon's right, buy new rings and give the cylinders a good hone.

Those main bearings are expensive to replace (around $100.00) but as you've come this far, I can't see the point in you not replacing them, the primary chains, and the cam chain and tensioner assembly. (CB750Supply.com sells the new tensioner assembly for $79.00 which is really cheap, and they look good, I bought two sets and am happy with the quality) http://www.cb750supply.com/products/4/engine/59/cam-chain-cam-chain-tensioners

Your weather is amazing, it must be great there in summer, otherwise I can't think of one good reason why you'd want to live there? I like my beer icy cold, but not frozen solid! Cheers, Terry.

edwardmorris · « **Reply #242 on:** January 06, 2014, 10:35:12 PM »

Hey welcome back Terry! I was thinking the same, I don't want to open this one again so I'm going to make an investment in it. Where do you get the main bearings? Same site? I could swear there was a thread that cb750supply ones weren't that great.

Terry in Australia · « **Reply #243 on:** January 06, 2014, 11:21:11 PM »

G'Day Ed, I bought my bearing shells, primary chains etc from Yamiya in Japan, they're all OEM Honda items. I've never used "Non OEM" bearings, so can't comment on their quality except to say that I probably wouldn't use them, any really close tolerance items like bearings are best left to the OEM manufacturer, IMHO. Cheers, Terry.

edwardmorris · « **Reply #244 on:** January 07, 2014, 08:58:21 AM »

Looks like motogrid has them locally for about the same pricing without the hassle of customs paperwork on delivery. Once I am able to go back into the garage, I'll take a closer look for damage. I recall seeing some ridges being scratched in at least one of them, so it seems more than likely I need new ones. I'll need to go read up on plastigauge again.

Kickstart · « **Reply #245 on:** January 07, 2014, 03:00:14 PM »

I think some of the favorites on this board for OEM parts are:

www.hondabike.com and
http://www.hdlparts.com

There a lot of online places selling OEM parts - definitely compare prices.

I'm a little bit of a hypocrite saying this, but your shells may be fine. Get some green plastigage from your local NAPA or autoparts store and take some measurements. If you're on a budget, and they look good, you may want to save a little money (and a whole lot of hassle - IMHO). That said, I'm not as experienced as others on this board.

Admittedly I'm replacing all of mine, on my build, (even though I really don't need to) but that's because I want to (both for improved performance and more realistically for the learning experience)... and I'm OK throwing some money at my bike.

edwardmorris · « **Reply #246 on:** January 07, 2014, 03:36:12 PM »

Quote from: Kickstart on January 07, 2014, 03:00:14 PM

I think some of the favorites on this board for OEM parts are:

www.hondabike.com and
http://www.hdlparts.com

There a lot of online places selling OEM parts - definitely compare prices.

I'm a little bit of a hypocrite saying this, but your shells may be fine. Get some green plastigage from your local NAPA or autoparts store and take some measurements. If you're on a budget, and they look good, you may want to save a little money (and a whole lot of hassle - IMHO). That said, I'm not as experienced as others on this board.

Admittedly I'm replacing all of mine, on my build, (even though I really don't need to) but that's because I want to (both for improved performance and more realistically for the learning experience)... and I'm OK throwing some money at my bike.

Yep, thanks for the hdlparts link, didn't know of that one. Budget is definitely tight, especially losing hours from all the snow nonsense all new year. I do want to get it done right and I know its going to cost me a bit. I can work towards the cost, at the cost of the losing time on the build. I just finished digging my garage out of the snow, and hopefully will be able to get out of the house tomorrow. I'll do the palstigauge test and then decide. From the factory manual, if even one is bad or has something embedded in it deep, the whole set needs replacing! And I'm afraid mine's going to come to that. The crankcase looks like it was never opened, so I believe a change is overdue??

calj737 · « **Reply #247 on:** January 07, 2014, 03:38:38 PM »

Plan on doing it; penny wise now to avoid expense and lost time later... Even if it delays your completon 30 days. Worth it in the long run.

RRRToolSolutions · « **Reply #248 on:** January 07, 2014, 06:58:22 PM »

Ed, according to Buzz of Dynoman whom I have a lot of respect for, the original factory supplied insert bearings are better than what you can get today. I can't remember exactly why that is, but he encouraged me to check the clearances on every bearing and use what was in spec. Mark, Terry, and others here may can explain this better than me, but before you mix those or lose track of where they came treat the bearings as though you will re-use them. Measure the clearance with plastiguage (available at most good auto parts places) and replace only as necessary. I wound up tearing mine down a 2nd time at only 600 miles and busting my budget with Buzz's help, but only because I grossly under estimated what porting the Honda CB750 head would do for a 40 year old engine. I know you're looking for a stock build, but if your insert bearings are good - reuse them.

Gordon

edwardmorris · « **Reply #249 on:** January 07, 2014, 09:25:47 PM »

Thanks Gordon, I'll do the plastigauge check as soon as possible and post back. I haven't removed any yet because they have been locked up in the garage last few days because of the snow. Its supposed to go back to 0C this weekend here so hoping to make some progress, at least on Sunday. So what happened exactly? I was planning on porting the head ( part of the performance on the budget thing), what should I be looking out for?

It was quite the battle, but the Honda snow blower took down the snow mountain today! Will get really busy next few days and catch up on work. My finger tips are better today so I sanded down the pistons. Stuck to the light side of things, didn't wan't to get greedy and sand away half the piston surface. Still have to wet sand with the finest grits and polish them out as smooth as possible. Look better than they did, so I'll take it. All mail has been delayed two days now, so no sign of the K2 head yet, hopefully it'll get here before the weekend.

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Author Topic: 1972 CB750 Four K2 -- Rebuilt to NEW OLD STOCK -- PIX ON PAGE 50 (Read 243067 times)