Author Topic: 1972 CB750K2 - engine freshen up (Read 9301 times)

hotdog · « **Reply #25 on:** March 14, 2015, 10:34:46 PM »

Cases are split, the insides look really good. Need to get some plastigauge tomorrow to check mains and rod bearings.
Lots of degreasing/cleaning coming up. Once the bearings have been checked I'll start on the head.

Off with its head

The worst scores were on piston #2 - not bad at all and could easily be re-ringed and reused if needed

Studs came out with no issues

All apart and ready for inspection

Oh yeah...someone's been here before?

Later

hotdog · « **Reply #26 on:** March 16, 2015, 03:44:51 AM »

Got some plastigauge today, will be checking the bearing clearances tomorrow morning. Spent the afternoon degreasing and cleaning the cases, dishwashers are great for that final clean...

The cases came up great.

Later alligators

Retro Rocket · « **Reply #27 on:** March 16, 2015, 02:52:58 PM »

Looking good hotdog...

hotdog · « **Reply #28 on:** March 16, 2015, 03:24:24 PM »

Thanks for your reply Retro...wasn't sure if anyone was following

Another big push on today, I can then finalize my order for the last of the bottom end parts. Decided to change the primary's and re-bearing the box while I'm in here.

HD

Retro Rocket · « **Reply #29 on:** March 16, 2015, 03:25:35 PM »

Quote from: hotdog on March 16, 2015, 03:24:24 PM

Thanks for your reply Retro...wasn't sure if anyone was following

Another big push on today, I can then finalize my order for the last of the bottom end parts. Decided to change the primary's and re-bearing the box while I'm in here.

HD

You should put this in the project section mate, You'll definitely get a better response there.... This topic has had 992 views though, so people are looking....

hotdog · « **Reply #30 on:** March 16, 2015, 03:32:32 PM »

Reserved post

SOHC4 Cafe Racer Fan · « **Reply #31 on:** March 16, 2015, 03:45:07 PM »

Hotdog,

Is the K2 motor you are working on different from the one in the beautiful Rootbeer colored 750 at the start of the thread?

hotdog · « **Reply #32 on:** March 16, 2015, 03:50:28 PM »

Hi CB 750 cafe racer fan, it is the same bike/engine. Only pulled it down to stem the bleeding from the head really.
Bit I think I like to "spin spanners" as much as ride so some upgrades were going to happen.
Thanks for your comment.
HD

hotdog · « **Reply #33 on:** March 16, 2015, 08:30:26 PM »

The mains and rods have been plastigauged and all are well within spec

I have just placed the order for the remainder of bottom end parts required.

I had to make this stand first as there was no way I was working on this thing while it rolled around the bench - 3rd stand in 2 weeks, you would think I would be faster by now.

Crank in, plastigauge on ready to torque down.

Very happy, every main came in at under 0.001"

All the rods came in at under 0.0015"

Noticed the oil feed holes have been relieved, must have been done when the gallery plugs were installed.

Thanks for watching..

hotdog · « **Reply #34 on:** March 18, 2015, 01:24:13 AM »

Today was a fun day polishing all of the casings and tappet cover, polishing wheel on the bench grinder makes it easier.

Started to strip the head, it has the older guides including seal less exhaust guides.

I do have all new valves and guides to go onto this head however I thought I would check them anyway as Honda man says they are real hardwearing.

Unfortunately they were all out of spec, exhaust were .007" inlets .004" so they had to go...wonder if hondaman wants them?

The removal of the guides was pretty straightforward with no issues, action shot to follow.

All removed and ready for some porting.

Just have to wait for my 6" alloy burrs to arrive, anyone got any hot porting tips for me. Plan to reduce/eliminate the guide boss, taper the ampco guides if I can get my hands on a lathe. Unfortunately I don't have any equipment to bore the seat further. The seats will be cut by hand with my neway gear. And no plans to back cut the valves at this time, I need to have a better look at them first...

Later alligators

hotdog · « **Reply #35 on:** March 18, 2015, 09:40:00 PM »

Only a small update today. I bead blasted the head to give the chambers and ports a clean up, they need some work especially de-schrouding.

The ports are not to bad and I cannot wait to start to clean them up - just waiting on some burrs.

Its back to work tomorrow for me so there won't be too many updates for a while.

Catch ya later

hotdog · « **Reply #36 on:** March 18, 2015, 11:07:22 PM »

Spec sheet of the Norris D+ cam I'll be running, almost identical specs as an RC#240.

Bye for now..

flatlander · « **Reply #37 on:** March 19, 2015, 12:15:51 AM »

good work hotdog, keep it up!

hotdog · « **Reply #38 on:** March 22, 2015, 08:38:30 PM »

Masked up the cases and painted them today, I was not going to bother doing this but while waiting for parts thought "why not"...
It may be a wrong choice as it will make the average paint on the frame stick out like dogs balls, will have to see what the engine looks like when assembled and go from there.

Masked and pepped for paint.

Painted.

hotdog · « **Reply #39 on:** March 24, 2015, 12:42:30 AM »

While waiting for my Yamiya order to arrive I thought today I'd wash both cars and vacumn them out, after that I took a load of green waste to the dump. Upon returning from the dump the delivery lady was outside my house with my order...it has been a big day.

Yamiya order, 4 business days ex Japan to Australia - not bad.

All new OEM rod bolts and nuts and all seven gearbox bearings and some other bits and piece's.

So I started out by replacing all of the box bearings including the primary drive ball bearing.

The new oem primary chains and cam chain were fitted to the crank and installed into the cases.

The top case half went on and all torqued down with no issues

While I was on a roll, fit the shifter - "why not"
This is why not..

So ratted a spare from one of my spare lower ends.

Annnnd boxed up for now, that's all folks....

P.S. where's a good place to get nice hardware for a motor.?

Later

SOHC4 Cafe Racer Fan · « **Reply #40 on:** March 24, 2015, 07:37:59 AM »

Nice save hotdog!

Bigsam302 · « **Reply #41 on:** March 24, 2015, 11:30:44 AM »

Quote from: hotdog on March 24, 2015, 12:42:30 AM

While I was on a roll, fit the shifter - "why not"
This is why not..

Yep, I know the feeling. The exact same thing happened to me.

hotdog · « **Reply #42 on:** March 24, 2015, 01:35:46 PM »

Yes it was unexpected, it was coming up to torque and just screwed itself off. After looking at the stud it appears to have been fractured for some time. Currently waiting for an opportunity to pick up the barrels from the machinists, apparently he has finished my cb barrels but is still to re-sleeve a set of xs650 barrels I have there also, they should all be completed at the end of this week.

hotdog · « **Reply #43 on:** March 25, 2015, 03:29:23 AM »

Today my ultrasonic cleaner arrived, I've been wanting one of these for a while now & thought I'd test it out on my carbs.

10l capacity, it heats as well - from eBay.
Probably like a lot of guys here I've cleaned more carbs than I care to remember so anything that might make it easier is a good thing. The carbs were all there just crusty so I started to strip them down.

And placed some parts into the cleaner with a mix of water and diluted degreaser.

After 20 minutes @ 50c the results speak for themselves.

I also cleaned the hardware while on a roll.

All finished and assembled, just need to install them on the rack.

And done.

Anyone thinking about getting one of these cleaners you'll be happy with the results, I know I was hesitant about their ability. I am more than happy with the results and can see it getting a lot of use in the future.

Ciao

andy750 · « **Reply #44 on:** March 25, 2015, 03:40:26 AM »

Carbs look great and yes agree on the ultrasonic cleaner! Looking forward to seeing how this turns out.

good luck
Andy

hotdog · « **Reply #45 on:** March 25, 2015, 04:31:58 AM »

Thanks Andy, like most freshen ups "the more you dig the deeper it gets"
Still haven't decided once the motor is complete if the frame gets a re-paint or not........or just install and ride.

andy750 · « **Reply #46 on:** March 25, 2015, 09:44:08 AM »

Hotdog I know that only too well - check the link in my signature for my own K2 freshen up - particularly the page with lots of porting photos - thanks to MikeR - the 810cc kit + porting really helped my K2. Good luck, Andy

hotdog · « **Reply #47 on:** March 29, 2015, 01:52:07 AM »

Quick update - got the barrels back from the machinist's and they look good

Signs of a competent machinist, pistons measured in several places and each bore honed to match each numbered piston, .001" clearance for each piston so needs to be accurate.

Porting kit and burs arrived, as well as frame kit (thanks Gordon).

There wont be any updates for a while as the wife, myself and two kids are about to go on a three week holiday. 2.5 weeks will be in Tasmania ( Australia's southern most state) followed by a few days on Queensland's sunshine coast. I'll post some photos of Tasmania if anyone's interested.

Ciao

Retro Rocket · « **Reply #48 on:** March 29, 2015, 04:29:44 AM »

Enjoy your holiday Hotdog....

andy750 · « **Reply #49 on:** March 29, 2015, 06:39:02 PM »

Id be interested in seeing some Tasmania photos.

Have a good holiday!

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Author Topic: 1972 CB750K2 - engine freshen up (Read 9301 times)