Author Topic: 750 K2 Strip & Rebuild - help please  (Read 21001 times)

Offline Oddjob

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Re: 750 K2 Strip & Rebuild - help please
« Reply #165 on: July 07, 2022, 03:11:58 PM »
No 6 was chromed IIRC. All of them will rust but some are internal and so are protected to some degree. Axle nut will rust on the outside edges, the spacers will especially where the seal doesn't rub as the rubbing keeps the rust at bay. I had most of mine hard chromed, they grind them back to standard spec in most cases and they tend not to rust after as the chromes so hard. The speedo drive I'd plate, makes no difference in that case, the speedo drive plate you could try rechroming or BZP it.
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Offline K2-K6

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Re: 750 K2 Strip & Rebuild - help please
« Reply #166 on: July 07, 2022, 04:16:08 PM »
Thanks Johnny; did try this on another nipple problem using waxed sail thread… it basically cut through said nipple.  I may try it all again, but with a thicker / gentler cord.

(1) Today unlaced the hubs for polishing. When rebuild time comes back any comments on greases / anti seize lube etc to go onto the (SS) nipples where they sit in the chrome rim?

(2) the (front) disc mounting plate is to be repainted black. Should it be gloss, satin.. or matt pls?

(3) since I’ve got the disc in my hand, any ideas how to de-glaze it? Been through past threads here but not found much other than to buy a new disc.

Ta.

1/ a consideration regarding spoke breaking from a few post back. Make sure that the hub flange casting doesn't interfere with the internal spoke radius of those outside set of spokes to bring a high stress alignment with the new spokes. Carefully checking that they should be slightly "bellmouthed" to avoid pulling the spoke angle tight over a sharper radius than the spoke will help to distribute load along the spoke. Hope that makes some sense  :)

3/ disc deglaze, if you mean surface for brake performance rather than refinished surface to get level from irregularity? Then just using sintered pads is fine as it'll have no problems. Just clean with isopropyl alcohol before use or acetone/brake cleaner proprietary spray.

Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #167 on: July 09, 2022, 09:03:33 AM »
Thanks Ken / Nige, and yep, all makes perfect sense.

The wheel bits, barring # 6 above, were all zinc plated it seems…. as a check I pre-dipped them in a stripping solution and over 15 mins the zinc fizzled away. Don’t know if it was the original coating, but they were indeed a bit tired looking, prior of course, to all of this. (The polishing pic above gives a false impression!)

Anyways, all Cobalt-Nickel plated now, and whilst not perfect will hopefully provide a better protection than their failing previous coatings. Fingers crossed…

(btw: hub in the early stages of polishing - not coated in any way)
« Last Edit: July 09, 2022, 09:06:49 AM by Lobo »

Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #168 on: July 14, 2022, 12:57:51 PM »
Painting the support plate to the front disc…. today’s tech question is, “How hot might the disc typically get on your average gentle run?” I ask because I have a SATIN BLACK VHT paint in the cupboard, whose quoted max temp is 140 C.
Am happy to take recommendations on any particular paint of course.
Ta.

Offline K2-K6

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Re: 750 K2 Strip & Rebuild - help please
« Reply #169 on: July 14, 2022, 03:29:15 PM »
With a "licked finger in the air"  calculation, that appears ok to me. The centre generally stays much cooler than brake surface in use even at fairly extreme elevations of rotor temperature. 

When you see brake discs at very high temperature, indacated by blue colour, it rarely extends much into the centre structure even on single material disc and with much less transfer on composite aluminium/steel type.  Also probably significantly above your intended use range too.

Maybe someone has some real numbers that would give more accurate experience to contribute.

Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #170 on: July 14, 2022, 11:07:03 PM »
Thanks Nige - I’ll go ahead at that. I regularly use an IR thermometer for various things (eg plating bath, painted parts in the oven…); and first ride out, purely out of interest I’ll, check the disc temp.
« Last Edit: July 15, 2022, 01:27:19 AM by Lobo »

Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #171 on: July 18, 2022, 12:42:44 PM »
Wheels now done - the whole bike now fully reconditioned / painted / polished …and awaiting rebuild.

Begrudgingly I bought a wheel balancing / lacing frame last week (£120 thereabouts); the decision eased by knowing the MG Griso’s tubeless / spoked wheels (using o rings) will likely need replacing in the next few years.
TBH am pleased to have it. SO much easier / better / quicker than the wooden jig I DIY’d on the last occasion…

Anyone interested, the main tips I would suggest are (applic to CB 750)
TAKE A PIC < dismantling the old wheel.
(1) if you can justify a jig; go for one that will accept the rim + tyre dia; as adjustments / balancing then become possible down the track.
(2) Lace & true the wheel (initially) using the (20) A spokes only - ie those threaded from the outside towards inside of the hub. Fill all the alternate hub holes with those A spokes (ie both sides of the hub) and then lay it flat.
(3) Sweep all lower spokes in one rotational direction, and all upper spoke in the opposite direction…. iaw with the photo you hopefully took.
(4) Lay the rim over the hub & spokes, raising it appropriately so that it’s centreline  aligns with the hub’s, and lace the spokes in turn (upper / lower / upper etc) working around the wheel. (iaw your pic.)
(5) Mount the wheel in the jig, and true it for wibble and wobble (whatever the terms are)
(6) Now thread in the B spokes (it’ll be easy / obvious) and nip the nipples finger tight. (mine needed to be sprung in occasionally)
(7) Tighten B spokes (opposingly) to get a nice ping / pong sound.
(8) Check & adjust the wheel again for final trueness.

Well… it worked for me. Rebuilt / trued the second wheel in about 90 mins, inc the odd bit of help from the 2yo grandson…
« Last Edit: July 18, 2022, 12:48:41 PM by Lobo »

Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #172 on: July 20, 2022, 02:29:16 AM »
Anyone finding issues with the YAMIYA Starter motor cover plate? Fitted a new one today, and left with a significant gap, particularly the leading edge. To be fair, refitted the old one and it too doesn’t ‘sit’ on its circumference, but rather rocks about the 2 starter motor top mounts, and still with a gap. Any yup, I’ve the new packing washer in @ 3mm thick or so… noting though that a 5mm one would solve the problem, but be visible due its height.

So.. is it a pattern part problem with the cover, or the motor….. or am I missing something?

Ta
« Last Edit: July 20, 2022, 02:59:03 AM by Lobo »

Offline Nurse Julie

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Re: 750 K2 Strip & Rebuild - help please
« Reply #173 on: July 20, 2022, 08:06:16 AM »
Have you fitted the rubber gasket under it Simon?
I've just looked at all our 750's and the cover all fit flush with no gaps, all have original covers fitted though. It almost looks like your starter motor is sitting a bit proud but that could be the angle of the photo.
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Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #174 on: July 20, 2022, 12:32:37 PM »
Hi Julie. Yea, I thought that too (starter motor proud), but as far as I can ascertain there’s no other way of installing it. (& thanks for thanking the time to check)

Yep, a silicon gasket is in place; about 3mm thick…  a 5mm piece would solve the issue, though would leave the chrome cover visibly raised.

All a bit confusing… unless it simply boils down to pattern parts?

Edit… I’ve had an idea, & tomorrow will swap the lid over with the Sandcast…
« Last Edit: July 20, 2022, 12:35:10 PM by Lobo »

Offline Trigger

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Re: 750 K2 Strip & Rebuild - help please
« Reply #175 on: July 20, 2022, 01:42:59 PM »
Don't know why you have acorn nuts on as, they came with M6 x 10mm chrome bolts and chrome washers as per picture. Are you sure the bolts are not too long  ;)

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Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #176 on: July 20, 2022, 09:54:36 PM »
Thanks Trig… knew about the M6x12 bolts, but ‘deviated’ a little - I wasn’t aware the bolts were chromed and will now revert - appreciated!

When tightened down the cover is hard against the starter motor mounts, and consequently high of the casing, and more-so at the leading edge. It’s as tho’ the starter needs to drop a couple of mm, and roll forwards a coupe of degrees. When I get home today I’ll be taking the SC cover off and seeing if it’s simply this as otherwise I’m baffled….
« Last Edit: July 20, 2022, 10:01:00 PM by Lobo »

Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #177 on: July 20, 2022, 11:34:34 PM »
On topic here Trig / folk, pls how can you tell when a bolt set etc is chrome versus Zinc finish? I understand the colour code XW infers chrome, but don’t see it against fasteners.

Offline Trigger

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Re: 750 K2 Strip & Rebuild - help please
« Reply #178 on: July 21, 2022, 12:03:31 AM »
On topic here Trig / folk, pls how can you tell when a bolt set etc is chrome versus Zinc finish? I understand the colour code XW infers chrome, but don’t see it against fasteners.

You can not tell from part numbers on bolts and washers. Some nut have a S on the end of the part number to ID as chrome.

Honda superseded loads of nuts, bolts and washers from chrome to BZP, All the chrome bolts had smooth face apart from some JIS chrome screws.
The ones that spring to mind.
Fork drain bolts
Rear brake arm bolt
kick start bolt
Rear brake pedal bolt that had 0A on the end of P/N ( i have had them in Honda packets as, BZP and Chrome  :o
Chain adjuster bolt
Chain adjuster locking nut that had 0S on the end of P/N
Rear shock mounting bolts M10x32
And so on. The original general rule was a chrome bolt to a chrome part  ;) 
« Last Edit: July 21, 2022, 12:08:42 AM by Trigger »

Offline Lobo

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Re: 750 K2 Strip & Rebuild - help please
« Reply #179 on: July 21, 2022, 01:45:30 AM »
…good to know, and the ‘general rule’ is a big help, if not a little obvious now that I think about it!  Cheers Trig.

 

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