Topic: Build of CB750 K2 1975 - Europe had K2 until 1975 - Engine started feb 17 2019

[PeWe]

K2 build started. It will be 736 close to stock, no hp increasing engine mods.
It will get Honda std carbs and airbox from my K6!
K4 tank and side cover style in Freedom Green Metallic waits on the shelf. Yamiya No number 4-4 pipes too.

Cases are cleaned and painted earlier this week. I continued the cleaning process by blowing the cases with high pressure washer and ended with compressed air to be sure no dirt inside any oil channels nor threads.
Painted cases with rattle can Motip engine paint 150* C. I have used that on my K6 with good result

Head is a refurbished K1 head with no ex guide seals. Let's see if it will smoke some. Shop that did the head saw no problems with guides.
Gasket surface is done, seats cut and valves lapped and leak tested.

Installed thread inserts today for the cam holder studs before the threads go bad. Checked threads on other side of the bearing cap, all good when doing a test mount tighten 10Nm.

Next is to deburr all new cruzinimage pistons that have rather sharp edges. Check/adjust ring gaps. I'll measure all bores and pistons to verify if they need to be arranged in a specific order like thickest piston in widest bore.

[PeWe]

The puzzle
I have almost all parts laying around in my small garage. Frame and swing arm plus other small parts are 2k painted years ago by PO before the PO I got it from but never assembled. Frame cut by PO PO for easier top end access. Franks kit will keep it together. This kit allow future closing of frame welding it together if needed.

Refurbished wheels are soon here from Germany, polished hubs, new bearings, new rims and spokes with yellow spoke nipples. New tires needed, old stock style.
I looked for good old wheels but all had some small rust. I remember mine after long storage where chrome flaked off when pressure washer them. Bearings I had to replace despite only max 35.000 km. SKF bearings I installed correctly with a press 1983.

Finding rear wheel or hub however very difficult. Just a few on eBay in bad shape for too much. I have a hub with cracked brake surface so I know what can happen with rear hubs. Crack visible when cleaning and grinding the steel, not before.

I had planned to use GS1000 fork with dual brakes and molded wheels. I changed my mind to make a stock look instead of a strange bastard that might have worked for 40 years ago. Stock style shocks in same shipment as the wheels. I had planned to use my old Marzoochi AG Strada. Stock style look better. I'll restore the Stradas to their stock style and might sell them. I have rebuild kit and new labels.

The work with engine will hopefully go quick.  All parts that block my garage here and there will be stocked and bolted together in a configuration called Motorcycle. Below photos of the mess.

[PeWe]

Thread testing day!
I have to verify all thread before assembly. Cases are unknown and needed to be tighten together. All threads OK. Only one thtread bottom popped that need WB Weld where alu popped to ensure no oil leak. Thread for gear shift cover.

Threads for valve cover in head refreshed with M6 tap. 3-4 threads need time sert thread insert. That valve cover need fresh paint and will do better on my K6 with hot cam. Cover swap in winter.

I'll do the ring gap and decide piston to bores when I'll get bore micrometer and std micrometer with me from my job.

[PeWe]

Got a wild idea today... the bike must have a Honda std handlebar with wiring inside.....
I hope I'll no get ideas about OEM bolts all the way, X heads on all covers except oil pan....

[BPellerine]

you are living on the edge,pewe,stock handle bars,haha.bill

[PeWe]

Yes... This bike was planned to be built on my leftover parts from my K6 bike only. Maybe 836, 900cc with VM29 smoothbores, nice cam and a ported old head I have. But changed my mind after seeing and hearing some CB750's in stock style without any engine mods sounding as sewing machines. A friends nice setup of 736 cylinder with new pistons and a restored head, both with nice paint helped me to find the path. Std cam and sprocket will make install easier with no need of timing, just bolt on.

Wiring inside the handle bar will make a smooth build. There are euro bars with holes for wiring.

But I have one more set with tank, side covers etc. etc for my additional tuning parts. Need a 3:rd bike 

[BPellerine]

yes,having a nice stock engine as a second bike will be good,less issues to worry about and cheaper too!bill

[SOHC4 Cafe Racer Fan]

Nice sweep the garage bike.

[PeWe]

I look forward to feel the stock bike and sound again. It was 38 years ago my K6 was stock, now a little bit wilder.
I planned to use my old speedo and tacho from My K6 and use NOS meters on my K6. It feels wrong to remove the speedo from my K6 that have had it since new amd have wrong color for a K2. Cable broke a few times, some km missing otherwise the complete history.

I think I'll give the bike new replica setup from Z1 that are not that far away from K2 style. K3 which was not an option in Europe. I have an upper fork bridge for K3-K6 meters.
https://z1parts.net/honda-gauge-set-cb750-cb550/

New cool low K0 seat from Yamiya, not exactly K2 but will look cool and almost stock.
http://www.yamiya750.com/index.php?main_page=product_info&cPath=246_251_182_81&products_id=2955

K1 look OK too (This one will probably be the seat since it will fit frame and have the matching look)
http://www.yamiya750.com/index.php?main_page=product_info&cPath=246_251_182_81&products_id=3512

These bikes can suck $$$ when the owner has been bitten by the CB bug!

[PeWe]

Measured bores and pistons yesterday. Verified rings and weights today.
Cuzinimgare 61mm pistons are 0.03mm under 61mm. All 4 very close too each other, weights too. My scale show grams only. 2 pistons might be 0.5 grams lighter. All rings very consistent sizewise too. No need of grinding ring ends, gaps around 0.2-0.30 mm

Bores had max size of almost 61.040 mm. All  4 bores were min 60.025 at the bottom were no rings have gone, then 60.035 to about 61.038 mm.
Clearance around 0.06-0.07 mm which must work fine.

Fix some thread inserts and ready for assemble the engine when parts and bench are cleaned and no burrs after fixing the threads.

[Stev-o]

These bikes can suck $$$ when the owner has been bitten by the CB bug!

No joke!!!!   Looking forward to progress on this...

[Terry in Australia]

Looking good Per, not "Redneck" enough for me of course, but I do like that you're mixing parts from other models, that's a good start! Cheers, Terry.

[PeWe]

It is a parts bike.  Mostly K2 from several bikes.
My first plan was a hillbilly style with 16" Henry Abe rear wheel, GS1000-78 front end with GS1000-81 molded wheel. 836,849 or 900cc + ported head + VM29 carbs+ 4-1.  "I met Jesus" and found that I must make go closer to stock since I have one screaming high powered CB750.

Frame, steering stem, swingarm, battery holder is the registration bike.
Engine cases from a bike scrapyard not far from here. Crankshaft w rods + carbs + airbox from my K6.  K2 transmission + clutch + oil pump + some covers found in Germany.  Primary hub from a low mile F bike 1975 USA, restored in Germany where they replaced the cush rubbers www.fourever-classic-parts.de
Primary chains will be BMW timing chains (VAICO V20-0251).

Small parts in engine + cylinder + head + fork from a friends stash of CB750 parts nearby.
Cam with holders also from eBay USA.
(I could not resist extra cam holders and rocker arms as spareparts  when finding for a OK price)

Tank + side covers from eBay 4 years ago, repainted old tank K4 style.
Restored std wheels from Germany
+ various new parts from Yamiya (K1 seat), Davidsilver (K2 headlight ears + steering bar + K2 grab bars ) + more will come. Maybe a center stand to be added too.

I'll spend my NOS front fender and NOS K1 rear fender on it, probably my new plastic inner rear fender from Yamiya too.  It will look newer than my K6.

It will get my No Numbers 4-4 with baffles mounted for smooth rides.

[Terry in Australia]

Nice! And thanks for the tip on the BMW timing chains Per, I'll check them out for my K0 build! Cheers, Terry.

[PeWe]

Terry, MessnerMoto started a thread about stronger Primary chains and gave me the hint to find an alternative. I have compared the BMW timing chain with my old Honda chains (had 67.5mm slack when removed) and Classic Cycle City's thick heavy duty chain I have in my K6.
http://forums.sohc4.net/index.php?topic=154183.100

[PeWe]

Got a few hours in the garage today.
1.) Fixed some threads for valve cover in head. 6-7 time-serts where threads looked bad and weak. I know how boring it is when the bolt will rotate when tighten the cover on a completed engine. The long holes at front where the dowel pins sit are better do to with head on the bench.

2.) JB Weld under the cam holder studs in the head. Filled the holes from the plug cavity to make sure it will be tight. All 4 studs got time-serts earlier just for sure.

3.) Checked all M6 threads on cases for side covers with an M6 Tap. All were good except one with the bottom popped due to a too long bolt used by PO long time ago. That hole plugged with JB Weld after an M6 bolt with grease on bottom is mounted.

4.) Prepare for mount a new bottom case ball bearing, 6204 bearing in the freezer. I'll heat the case another day this week and drop the bearing in place.

I'll build the engine by filling the bottom case with parts as I always have done.  I have only done the kick starter stuff so far, very easy if follow the manual, spring done with help of a screwdriver.

I will use JIS M6 bolts as fasteners for all covers! I have ordered a set of JIS bits. 1,2,3 !! 

Yamiya has the set of  bolts. 2 sets I can not understand the difference of.
http://www.yamiya750.com/index.php?main_page=product_info&cPath=158_283&products_id=126

or this set with red tape? It cost 1000 YEN more, but what is the real difference? I think I'll ask them at Yamiya750
http://www.yamiya750.com/index.php?main_page=product_info&cPath=158_283&products_id=3491

[Terry in Australia]

G'Day Per, one of the members here changed all the cam tower hold down bolts to 8mm awhile ago, with excellent results, if I was building a high performance engine I'd do that. I bought the Yamiya screw set with the red thread tape, only because I didn't see the cheaper one when I ordered it. It looks to be very nice quality.

I also bought all new bolts from Yamiya, all the frame bolts, including engine mounting bolts. Not real cheap, but as I bought my bike in a thousand pieces (or thereabouts) I didn't have the luxury of using the original bolts, and it looks way better than non-original fasteners. Cheers, Terry.

[PeWe]

Hi Terry,

Have you figured out the difference between the bolt sets? If I do not know, I'll might order those that cost more as long as they are not stainless steel which I do not trust with the alu. Is it thread tape only? For the going thru bolts for valve cover and avoid leaks?

The proper screwdriver or bit for the Yamiya bolt kit is JIS size 3? Philips will harm the X when slipping, right?

New bolts make the build easier and feels better! New long hanger bolts made everything easier on my K6, the old bolts were banana shaped. This build has also new hanger bolts.

I have ordered various bolts from Yamiya before that I have to this build too, some M6 flanged bolts in various lenghts that make the engine cases to look better.
This engine will be stock power, the cam holders will not fight harder springs or high lifting cam. The head has insert threads in all cam holder threads except the threads other side of each stud. I might insert a time-sert in all 4.
I saw that the alu is rather grainy when I did the other time-serts.

Using M8 is another way to solve the problem with broken threads, right? 

I fixed my broken old helicoils with Big-sert in my ported K6 head. 1 thread needed the next step with self tapping/cutting insert. Hole 8,2-8,6 mm. I guess that the stud with big-sert must have got a slap when the guides were replaced.

[Terry in Australia]

No worries Per, yep, all the screws appear to be zinc plated like the originals, no stainless steel, and JIS heads. I've just ordered a new JIS Screwdriver set for the K0 build. OK, at work, so better pretend I'm doing something!

[seanbarney41]

Pretty sure those red tipped bolts are pre-loctited for staying put and sealing.  At work, I end up prepping for installation quite a few Mercedes industrial diesel engines.  All the Mercedes hardware supplied is pre-coated with blue loctite.

[PeWe]

This kit for valve cover has all the bolts with seal. I think the half threaded bolts are closer to Honda bolts. Bolts with threads all their lenghts feels not like stock.
http://www.yamiya750.com/index.php?main_page=product_info&cPath=158_283&products_id=3676

I have vague memories about half threaded bolts when I removed all stock bolts on my K6 for 35 years ago.
Correct looking bolts but too long threads...can I live with that?

[Terry in Australia]

Bloody hell Per, it's a bitsa bike, so who cares? Just buy them mate!

[PeWe]

I'll have problems enough with the knwowledge about 4 countersunk allen heads inside the engine, countershaft bearing holder. If I'll service the oilpump, same there, allen head countersunk bolts.

Next problem is to find correct yellow marker to apply on certain bolts....

One more thing about K2 here. It must use ONE small grab bar only,  left  side for getting the bike on the centerstand.

Not the later loop going around the seat and better for the passenger. A friend (A CB750 repair and horder guy since many years) here knew when I asked him, he has the parts needed too. Blinkers have different bracket I suppose.

I have to think about it since the tank and side covers I'll use have the later graphics, badges. Color is Freedom Green Metallic which is K4 only, right?

The meters will have the later bracket too, maybe I'll order the K3 set from Z1 parts.
This might end up in a better combo than Honda shipped to Europe 1975 named K2.
Look as a K4 will match the year better!

But Honda CB750 purists guys here can find things, complain. I will then tell them about the ugly allen heads inside the engine and that there is a crank from K6 too. What a shame!! I might need to take the bike to the Vatican and let the Pope bless the it and let a specialist to perform an exorcism.

OK, the bike will look more than a K4.

Future project:
I need to paint another tank I have, find new sidecovers and use K2 graphics, the beautiful CB750 Four chrome badges.
Optional: Find fresh K2 meters (Km speedo) with the rhino horn upper tree
Then use one grab bar only and matching rear blinker fastener.

Is it Ok to use new OIL? I must find NOS Castrol GTX from the 70's? 

[Terry in Australia]

Ha ha, don't worry about "purists" Per, no-one gave a Fcuk about originality back when our bikes were new, and when I built my gold K2 with an 836cc F2 engine, alloy rims, FZR1000 front end etc, so many old guys came up to me to tell me that they had one just like mine, back in the day.

 I giggled to myself but said nothing, they were happy re-living their youth. In my humble opinion, most "purists" are d1ckheads who would rather ponce around a bike show talking sh1t than actually ride their bikes, so tell them to get fcuked.....

[PeWe]

Thing is that I feel the purist disease entering my mind...
But it would be nice to have a bike stock as it just had left the Honda factory.
Maybe they had free sake days when the bikes were different built?

I'm thinking about to use rear tire, Continental K112 which I did not like early 80's due to the good grip and sudden no grip at all (hopefully better rubber mix today).
Just for the look together with RB2 front. Metzeler ME77 might work too with RB2 front.