Topic: greasy's re-rebuild 'the utilitarian transcendentalist' 71 cb750

[greasy j]

ok, haven't updated for a while. been super busy. get ya guys up ta speed...

so I'm about to separate the cases, but I had some stripped(rounded) screws in my 'layshaft bearing holder' I think it's called? under the shifter. they were impossible to get out. I used a trick the teach showed me after rounding out the heads pretty bad on 3 of them, using a center punch to push the metal back into the rounded out hole then find a good impact bit and make a new +. then whack the impact driver very hard. I kept making it worse, but teach was able to get them out. he has magic powers when it comes to this stuff.





got all the screws out of the top and bottom of the case, had to flip it over and realized I still have to deal with the oil pump down there...





broke one of the screws...


here she is hangin out upside down on her medieval cart that I use as an engine stand it has metal wheels

[greasy j]

and I cleaned up the pistons, polished the sides a bit w/ 2000 grit and checked the fit in the cylinders w/ feeler gauges.

before and after cleaning




a 1 1/2 feeler(.0015", I think, might've missed a 0) fit in there very snug, so the pistons and cylinders are very usable. yay, no re-bore necessary.


the 1st piston was a lot more beat than the rest, it may have had a big chunk of carbon in there bashing it up. there are little dents all over the top and scratches on the sides. but it's still good to go, just pock marked on top.

it had bad acne when it was young.


and I honed my cylinders

before...



after...


left side unhoned, right side honed




after honing cylinders, you must clean them out w/ soapy water and keep doing so until you can wipe them with a white rag and have it come out white still. this is important because of the metal bits that will be left from honing. could be very bad for your engine.

also fixed a few more busted fin areas with Devcon brushable ceramic





and the mating surface here


got em all filed down last night but haven't taken pics yet.


gonna order parts in a few days. at least what I need to put the cylinder head back together. I'd like to get that done before class is over, but I only have 2-3 weeks left. and 2 different jobs going at the same time.

I will prolly have to put it all back together at home by myself because of time being short, so I'm gonna be askin you guys all the ?'s that I won't be able to ask the teacher.
more to come soon...

[paulages]

Josh-

You really want to measure your piston/wall clearances a little more accurately than with a feeler gauge. You need to check the hole for taper as well roundness. I've rebuilt many engines that had pistons in spec in one direction but were worn beyon tolerance in another. Taper is common on a worn engine.

Anyway, you might be fine, but if I were you i'd mic the piston in both axes as well as the skirt, and use a quality bore gauge to measure the bore at top and bottom, and in both axes. For what it's worth, I've measured the bores with a telecoping bore gauge and micrometer and found as much as a half thou inaccuracy when compared to the measurements taken by my machinist with his very nice bore gauge used on his boring mill. Now I always send my piston/cyls to the machine shop for measurements. Surely your school has these tools?

[greasy j]

Josh-

You really want to measure your piston/wall clearances a little more accurately than with a feeler gauge. You need to check the hole for taper as well roundness. I've rebuilt many engines that had pistons in spec in one direction but were worn beyon tolerance in another. Taper is common on a worn engine.

Anyway, you might be fine, but if I were you i'd mic the piston in both axes as well as the skirt, and use a quality bore gauge to measure the bore at top and bottom, and in both axes. For what it's worth, I've measured the bores with a telecoping bore gauge and micrometer and found as much as a half thou inaccuracy when compared to the measurements taken by my machinist with his very nice bore gauge used on his boring mill. Now I always send my piston/cyls to the machine shop for measurements. Surely your school has these tools?

the teach said to put the feeler in there, then the piston and pull it out, see how tight it is. it's lined up right and the 1 1/2 is a lil too tight all around so it's less than that, the tolerance spec is 2.2 or something like that, so it's well under. also this bike ran great before a gasket blew, so I'm kinda expecting everything to be cool. hopefully.

yeah, they have micrometers and stuff. don't know about the bore gauge, but I will check. I trust your judgement so I'll take some more measurements on thursday and see what I find.

I kinda figured I didn't have to know the exact measurements, just that it was within the tolerance. I mean if it's under the limit, what does it matter to know exactly how much it is?

thanks, Paul

and I may want to get a hold of you at some point w/ some ?'s once school is out...

[greasy j]

I got the teacher to explain the bore gauge and show how it works. measured my cylinders and double checked the pistons and they seem well within the tolerance. I don't think this bike had very many miles. the crankshaft bearings are like new.

I got some other stuff done as well, but I gotta get to work so I don't have time to post pics right now. more tonight or tomorrow.

I just bought a domain and updated my website so you can just go to www.dimalepainting.com, whereas the old address was a lot longer. I added some pics of a pedestrian slicer I just painted.

and I'm almost done painting a gas tank for a sohc member. no pinstriping or lettering, though, so nothing too fun. and I'm building a deluxe chicken house/coop for a customer that matches her house, same roof and whatnot. pretty big.

those will be up on the site soon.

if any one wants some lettering or pinstriping done I like doing that stuff so I'm likely to make time for you. I make a living doing houses, the striping is more for fun so I don't charge a lot as long as it's something I want to do. just a little advert, there.


ok, no time at all. monday comes the rain. I'll update this then.

[laminarflow]

Greasy,

I have been quite motivated by your rebuild--too much really.  Tonight, with wife beside me, I bought a 75 CB750 on CL.  So, the journey begins.  The girls said with a smile, "Its smaller than your other projects, but I doubt it will be less costly.  I also live in SF and am curious about the class you are taking--seems great.  The ye olde CB runs, but boy does she need help.  Did you take the prereq class to get into the rebuild course at CCSF, or do you think they would take a student if we could somehow "test out" based on existing knowledge?  Hope to see you around.  Be well. 

[rustrocket92]

Thanks for posting all the pictures in your project. I am sure i will be down this road soon enough .

[greasy j]

Greasy,

I have been quite motivated by your rebuild--too much really.  Tonight, with wife beside me, I bought a 75 CB750 on CL.  So, the journey begins.  The girls said with a smile, "Its smaller than your other projects, but I doubt it will be less costly.  I also live in SF and am curious about the class you are taking--seems great.  The ye olde CB runs, but boy does she need help.  Did you take the prereq class to get into the rebuild course at CCSF, or do you think they would take a student if we could somehow "test out" based on existing knowledge?  Hope to see you around.  Be well.  

thanks!

I got your email and sent you one back.

welcome to the club!

Thanks for posting all the pictures in your project. I am sure i will be down this road soon enough .

tryin to make it easier for the next guy. if ya need help get the hondaman book. a lil spendy, but very worth it.

[greasy j]

ok, class is over this week, so I do the rest myself at home.

got my cyclex gasket kit.

here's pics of the case apart and the guts and gears exposed. looks really nice inside, mostly. I have found 2 bearings that are a lil rough I'm gonna replace. the rest are smooth as silk. plastigaging the crank tomorrow night in the last shop class of the semester. and trying to get the head put back together as well.
















more photos to come soon!

[vorhese]

Lookin good, man. Is the head work something someone can do at home without the cool tools you have access to? And do new valve guides come in the Cycle X set?

[73nancy]

nice work seems like your doing it the right way keep the pics coming

[zzpete]

NICE WORK!! Can't wait to see it run!!

[greasy j]

Lookin good, man. Is the head work something someone can do at home without the cool tools you have access to? And do new valve guides come in the Cycle X set?

you mean the rubber dealies for the valve guides? yeah, it comes with 8, for all 750's. mine only needs 4.

you can do have someone else cut or grind your valves and seats, then lap them yourself. I've heard it's really cheap at a machine shop. or if they are not too bad you could just lap them a lot, I think. they sell lapping tools, but that's kind of silly. all you need is a rubber hose.

school is out for 3 mos. but after that I go back for another class. I'm just going to keep taking stuff so I can use the shop and tools. and learn everything. muahahaha. but I can help ya out maybe, if ya need to cut valves or something I might be able to do them in class for you when I'm back in there.

I'm going in right now. to plastigage the crank and assemble my head. which I painted last night. pics later. gotta go.

[HavocTurbo]

Lookin good, man. Is the head work something someone can do at home without the cool tools you have access to? And do new valve guides come in the Cycle X set?

you mean the rubber dealies for the valve guides? yeah, it comes with 8, for all 750's. mine only needs 4.

Um..... pretty good insurance to replace them all in my opinion. Then just keep the older good ones if you evern need a spare in a pinch.

I mean.... you already paid for them...... right?

[greasy j]

Lookin good, man. Is the head work something someone can do at home without the cool tools you have access to? And do new valve guides come in the Cycle X set?

you mean the rubber dealies for the valve guides? yeah, it comes with 8, for all 750's. mine only needs 4.

Um..... pretty good insurance to replace them all in my opinion. Then just keep the older good ones if you evern need a spare in a pinch.

I mean.... you already paid for them...... right?

the intake valve guides are of the type that use the rubbers, the exhaust valve ones are the smooth type which don't use the oil seals. don't know why they set it up that way but there were only 4 from the factory. later 750's had them on both sides. cyclex also included a different variety of seals that look like they would work with the smooth guides, but I figured I should leave it the way Honda intended.

reading Hondaman's book I found out that they did a lot of head work on these engines up to 1/2 way through the k1. after that they got rougher and rougher and lost hp because of it. mine was one of the early k1's. the ports are nicely smoothed out, and the boss around the guide and the pocket area are all cut down/shaped after casting for better breathing. the marks are visible inside. the intake side was polished as well.

I got my superior k1 head painted and got my valves and stuff reattached. valve springs are held in the same way as your stock rear shocks. there are keepers held in place by the tension of the springs. if you release the tension they will fall out. some people even remove valve springs by putting a socket on there and whacking it with a hammer. then I guess you just hope to find the keepers when they fall out. I used the valve spring compresser(big c clamp slightly modded). also used it to put it back together.

everything I have measured is right at or just a fraction off of the specs for brand new. the springs were all very close to the exact same height, inners too. plastigaged the crankshaft/bearing fit and it is not even a little bit worn. the pic didn't come out that shows the smashed plastigage.

basically you get a bit of green toothfloss/waxy thread that comes in a paper envelope with 4 width markers on it. you put the bits of thread where the space to be measured is, then put the parts back together, torque down. disassemble and look at the now smashed tooth floss. the width of the smashed thread indicates the clearance you just measured. the smaller the clearance the greater the width as it gets smashed more. if it is unsmashed you need to use the next size up, if it is oversmashed you need smaller plastigage.

pics:

@havocturbo- you can see the guides in this pic, 1/2 of them are smooth, so only 4 have lips for the seals











torquing the case to check crank/bearing fit


reading the toothfloss

[traveler]

Looks great man!

What color, if any will you paint your cylinders and case?

Good info on the K1 head....I had no idea, other than reading on here that K0-K1 had more power.

~Joe

[lostinthe202]

Great thread, thanks for explaining as you go.  I'm throwing in with the tank and seat lot, they look great.  Looking at the houses on your website really made me homesick, I lived in the bay for years.

Keep 'em comin!

Will-

[greasy j]

Looks great man!

What color, if any will you paint your cylinders and case?

Good info on the K1 head....I had no idea, other than reading on here that K0-K1 had more power.

~Joe

I'm doing the cylinders black also, but the rest same as stock silver. polishing the alum covers a bit. nothing too groundbreaking.

thanks for the comments! I wanna get to the 'riding it' part so I will prob get the engine, wheels, suspension and brakes, frame stuff all sorted, then ride it with the current tank and seat for a while. see what happens.

and I decided to keep the stock swinger, add bronze bushes, maybe have hondaman do it, for one less thing to do.

[greasy j]

I've been working a lot, no time for fun stuff. I'm finishing up the engine at home. I needed more workspace, so I decided to build an engine stand/workbench with left over wood from a chicken coop I just built (http://sites.google.com/site/dimalepainting/home/photos)

I can use blocks to balance out the engine and also use it for other stuff afterwards. I added some tool pockets and places for bolts and parts and junk. it's pretty sturdy. I smoothed out the top and painted it black. white or safety yellow might've been better for visibility of bolts and stuff, but it's what I had and grease won't show up as quick.

[greasy j]

engine bench is workin out nice.


I noticed in the 2 manuals I have and in Hondaman's book no one really shows how the shift drum comes out. I was a little confused but figured it out.

you have to remove the neutral switch which screws into a housing that is held on with a clip and another screw. the housing/neutral detent thing looks like a 21 mm wrench would fit on it but there is no room. it actually just pulls out and then that releases the shift drum. so after you unscrew the switch/lead you still have to pull out the thing it is screwed into.

[greasy j]

now I need some help with what to do next.

I had a busted screw from when I first separated the cases. I tried to get it out now that they are apart and I had a bit of it to grab onto. I ended up busting the bit of the screw off that was poking out still while trying to get it out w/ vise grips and my girlfriends awesome creme brulee torch. it was in very well.





so I used a stupid screw extractor and more heat. ended up busting off the tip of the extractor in the screw, so I'm even more screwed than before .




sorry about fuzzy pics.

so... do I drill out the screw and extractor and re-thread with tap/die set. now that the extractor tip is in there, is it going to be a nightmare to try to drill it out? I assume it would be made of harder metal than a screw.

the screw hole does go all the way through and there is a bit of room on the other side, so if I just drill it out larger could I use a longer engine bolt and a nut on the other end?

what to do?

[traveler]

The easiest way to fix it now, is to drill it out and re-tap.  This might require you to go a size larger on the bolt.  You might also have to use a carbide bit to drill the hardened steel.

Good luck!

~Joe

[greasy j]

thanks joe

[RAFster122s]

How much room is there around the extractor bit?
If you can you can use diamond tipped bits to remove the metal around the extractor bit and then grab it with needle nose pliers and remove it.

My advice is never use a screw extractor...they rarely work as intended and often cause more trouble than they are worth.

You can get a pack of 15-25 diamond bits from Harbor Freight in a little card sized pack. They fit dremel tools very well or a die grinder shaft drive.

A machine shop can use an electrical discharge machine (EDM) and get them to remove the remains. They'll cut the extractor out in nothing flat, very precisely.
The EDM is a process of electrically disintegrating a broken tap, drill, bolt, screw or pin. An alloy tube of various sizes is lowered drill-press style onto the broken component. An electrical current then disintegrates the broken component until it crumbles and can be chipped out, leaving the threads/hole undamaged. Provided your drilling and tapping didn't damage the threads.

Just a thought...

David

[greasy j]

thanks for the info. my engine teacher said the same thing about extractors, shoulda listened.

there is not enough room for your needle nose vise grip idea. good one, though. the machine shop tool sounds awesome, do they sell those at harbor freight?

I wonder if I just drill it out carefully, without hitting the threads if I could then just brush out the remaining crap in the threads with a wire bottle brush or something?

just looked closer and there's no way I could fit a nut on the other end unless I ground out a lot of metal. the threads are too close to the outside wall. I thought the boss stood out further.

poopy.

I also have 2 of the locator dowels stuck in to parts of the case. I was just going to leave them in there. the ones I have taken out have brown stains on them like they rusted or seized in the holes. does this indicate a prob or normal wear?