Topic: CB750 K2 engine + bike project, frame will come

[scrambler]

What is the ignition off of?

[PeWe]

Just tested the fitment of Daichii point plate and Dyna-S to see if adjustments of the bosses were needed.
Points will probably complete the build when ready.

[scrambler]

Regarding installing time-sert/helicoil inserts: in my cylinder head all the threads are good, but apparently many engine builder replace these threads. Is it necessary/recommended to replace them even though they are ok? Or just most of the heads were taken apart so many times that there`s a great chance that these threads are stripped? 

[PeWe]

If all threads are good, no need to fix them.
Important to verify them by tighten bolts in all to check. They can look good but fail when tighten the bolts.

If engine will run a hotter cam with harder springs, reallly good threads needed for cam holders.

These are threads that can be overtightened. Max torque for M6 grade 8.8 bolt is 9.8 Nm (7.2 ft lbs). This is for steel bolt, the threads however is aluminium which is weaker. Even if using 10.9 bolts, alu is the weak point.

[scrambler]

Ok, thanks, I`ll double check those threads before assembly if they can withstand that torque.

[PeWe]

Valve cover about 20% less, retighten later when gasket has compressed.
Last time i tightened cam holders i tightened 8Nm (6ft lbs) on bolts without thread inserts..
https://www.unitconverters.net/energy/nm-to-ft-lb.htm

[HondaMan]

Regarding installing time-sert/helicoil inserts: in my cylinder head all the threads are good, but apparently many engine builder replace these threads. Is it necessary/recommended to replace them even though they are ok? Or just most of the heads were taken apart so many times that there`s a great chance that these threads are stripped?

The 'mixed reviews' about these threads are due to the K0-K2 (early) engines having just 7 threads in the holes that hold the long bolts which locate the rocker shafts. The only purpose for those bolts was to hold the shafts in place, and the specified torque was much, much less than the usual 90 in-lbs (more like 50-70 in-lbs max). So, lots of them are stripped after a rebuilder got in there because not many folks knew about it. In all of the heads with the little 5mm bolts holding those shafts, the bolts were not even needed, but were continued anyway and the threads were lengthened to the entire hole depth to stop the damage.

[MauiK3]

It never ceases to amaze me the level of deep dive detail that Mr. Hondaman shares with the rest of us, always rewarding to follow any of his posts.
Many thanks.

[PeWe]

Yes, these fragile alu threads must be OK to hold cam with holders in place. It can be expensive if not.
The trick is not to tighten the M6 hard.

[PeWe]

Last time assembled the cases with all covers to verify good threads, repair if needed. No bad threads !

Today crank and bearing clearance test before cleaning and paint the cases.
All clearances good with an AAAAA crank, BBBBB cases and green bearings. 0.050mm / 0.0020" or just under. My K6 has similar and its oil pressure is good according to the oil pressure gauge.

Did a second test with oiled bearings and case crank bolts tightened 25 Nm as earlier. Crank rotates fine.

Weight of Super rods ~30 grams more than stock with bolts. ARP vs F2 bolts + nuts. More meat too keep rods streight. They will go on later.

[ctcycleworx]

Cool SOHC points cover!

[PeWe]

Yes, from 4-1 when ordered handlebar switches to my K2.

[PeWe]

This K2 case has just got a frame, with registration. K2 -1975 almost matching the case number which is late 1975, frame is early 1975, registered here February.

Uncut one so it should be stock?

Time to use what I have. GS1000 -78 fork with dual brakes. I have All Balls tapered bearings to marry fork and frame.
GS1000 -80 front cast  19" wheel that has a design like my new Henry Abe 16" rear wheel.

My K6 can donor its K2 swingarm getting the refurbished K6 swingarm I have.
K4 tank set in freedom green metallic.....
Frame hidden in garage...

Need to find a good looking GS1000 front fender....
A slow project....
It has a ported refurbished early head, 849 or 900cc.
Some cams....
Smoothbore 29...

[PeWe]

Update:
My finished and well running K2 will get the frame which is not cut. The stock bike does not need a frame kit.
It will be easier to sell.

The running K2 frame with frame kit is better needed by a modified engine as this K2 engine project.  No worries for vehicle inspection if using GS1000 fork. No more inspections needed.

My last frame will have no issues with all stock parts when getting that registration back on the  road again after soon 30 years.

Lots of work coming winter.
Time to grind off the old paint on frame and paint it.

[PeWe]

Time to update this project.
Somehow easier to start with the engine.
 
Finally cleared the bench from last years use.
Engine top case need to get case bore for big bore. Why not adapt it for the Billet block 77mm "sleeves"?

I have prepaired it for an 890cc kit I have. With Billet block resting, good idea to adapt top case just for sure and future possibilities.
Good idea to clean up top case as the lower. Paint after  case bore.

This build has CycleX Super rods so it can handle  bigger bore.
Carbs probably VM29.



Parts shelves. Transmission i yellow jiffy bags. Need to be undercutted.

[Terry in Australia]

Jesus Per, I thought there was some problem that I wasn't receiving notifications for updates for your thread, then I realised tyou haven't updated it in over a year! Are you trying to compete with Ron for the longest running build thread in SOHC4.net history? Ha ha, anyway, good to see that you're moving forwards, so are you going to use the billet block? I thought you were having problems with oil leaks with it? I don't remember, but I know you told me that there was an issue.

I was ratting thru my collection of parts today looking for a speedo drive gearbox and I realised that I have pretty much everything I need to do a quick and nasty K2 build to make some fast cash, but I've promised myself that I'll finish my Kawasaki Z1-B build next, as I'll need it for all of the "50 Years of the Z1" celebrations in 2022.

[PeWe]

Hi Terry, now I see this. I did not get update on this.

Yes, I did not tighten the head hard enough so the MLS did not seal as it should. Took loads of oil after a while when warm.
Head and cylinder had to come off for cleaning.

Good opportunity to test an 890cc kit on the K6. Compression too high, pistons crowns off 2mm. I hope my measurements are right.
 I compared with an RC 836 piston same head used before with OK compression with thick gaskets.

Measured volume in cylinders with pistons in and could verify the volume of the 836 piston over the upper piston ring. After subtracted it with the total volume that piston height took in cylinder.

Did same with 890 piston in its cylinder.
This piston has same height to outer edge of crown from wrist pin as the 836. Same height to upper side of upper ring too which made the volume affecting parts easier.

The 890 need same volume and slightly more to compensate for the head chambers now opened a little bit more for clearance.
A burette helped to measure with accuracy this time.

2mm is the 890 piston cut off I hope will work fine. Sparkplug clearance too. It had double plug washers when tested as 12.5:1 for clearance!

I got also the chance to buy new 970cc JE 12.5:1 pistons for a good price. Used in a build but never started.
So CycleX sale of their 74.5/69mm sleeves,  good timing.
The billet block with pistons left to the shop as a template when that was in the right compression range.

Stock cylinder milled 1mm before installing the sleeves. The grooves for sleeves and o-ring area for oil feed milled to correct depth.
The compression jumped up a little and better power on dyno.

So the billet block is now in the shop where the K2 upper case is to be opened up to take billet block too just for sure. The build will get super rods.

The 890cc kit will go on first.
It has its own head. Billet block has another head.

Here how the 890 pistons look after cutting 2mm off.

First a little bit optimistic dome.
Next adjusted 890 piston side by side with the 71.25mm piston billet block use. 67 - 71.25 mm

I have now 3 different bigger bore cylinders + pistons with a ported head for each, 890, 970 and 1005cc.
My blue K6 use the 970.

This engine build has a frame...

890 piston side by side with compared 836. 
890 to have a little bit more crown volume. It is 2mm wider too, 67 vs 65 mm.

[Terry in Australia]

Looks good Per, what is that swingarm? Looks nice. That side by side pic is interesting, I bought some Cruzinimage CB350 pistons for one build, and Frank said that I'd have to trim some material off the skirts, but looking at your RC(?) pistons with quite long thrust faces on the skirts, maybe I don't need to? I thought I had a set of RC pistons here, but I can't find them. What's the height of the piston from the bottom of the skirt to the bottom of the crown?

[PeWe]

Hi Terry,
I do not know to wich bike the swingarm is made for.
It look like a  chromed Dresda.
It is narrower than a  CB 750, same bolt pattern for chain guide.
220mm inner,
stock K2/K6  240mm.

I bought roller bearings for it, same size as Dresda for CB750 has but not the expensive Timken.

Mounted it on my bike with shocks but saw that wheel did not have space enough to align with chain.

Maybe if using another wheel or another Honda?
I wrote about it 2012, bit fid not get much wiser.
http://forums.sohc4.net/index.php?topic=107856.msg1207657#msg1207657

The RC pistons same as you also have I suppose. Marked RC  HP6450 inside.
Full dome so head must be massaged to open up a little to 65mm. (Or 64.5 might work, top is narrower.)
Pistons delivered with one ring oil ring.
I reused my 3 rings for my old RC forged pistons melted 1984, worked fine.
So same rings as many other 836, CB350 rings.

[Terry in Australia]

Thanks Per, I'll have to see if I can find my RC pistons so I can measure the height from the base of the crown to the bottom of the skirt, I haven't seen them in years though, so wish me luck. Pity about that swingarm, if you want to sell it let me know, it might be good for my Suzuki T500 racer project.

[PeWe]

You need this height?
See photo.
I prefer short skirts!!
For hot rides!!
Those pistons were sold for $250US/set on eBay 2012. The seller had some kits.

Good idea to know what the swingarm is made for.

But it is like a CB750 swing that is 20mm narrower where wheel axle is.

I have no use for it. I can save it for you Terry. No need to hurry so you can think about it.

[Terry in Australia]

Thanks for that measurement Per, much appreciated, I'll measure the skirts on the CB350 pistons I bought, and if they're less than that I'll know they don't need trimming. Let me know how much you want for that swingarm and I'll see what I can get for my kidney.....

[PeWe]

I do not know how much or little for the swingarm

[Terry in Australia]

No worries, just send it to me then, and when it arrives I'll tell you what it's worth.......

[PeWe]

I'll check around, shipping price too.
It will not be expensive.
I know what I have invested in it.
I guess this is not needed asap, or is it?