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

[PeWe]

Maybe I rotated the rubber stacks different. I really tried the other position hard before change.
Lash is same. 1"= 25.4mm
0.002"= 0.05mm

Honda say 0.08mm on Ex, std feeler gauge set here has 0.1mm

[Terry in Australia]

Maybe I rotated the rubber stacks different. I really tried the other position hard before change.
Lash is same. 1"= 25.4mm
0.002"= 0.05mm

Honda say 0.08mm on Ex, std feeler gauge set here has 0.1mm

No worries mate, even though they're a metric bike, and we're both from countries that use metric measurements, most of us older guys on Oz (and the US, of course) still measure clearances in thousands of an inch. Humans are so complicated..........

[PeWe]

Bike runs better now with richer needles and 110 mains!
These carbs sat once on my K6 with 40 pilots, needles middle (3:5), mains 105.

Never this should work today. Maybe the fuel... Needles must sit 1 step richer 4:5 and 110 is a must with 4-4. I guess 115 might work without the wool on diffusers.
My K2 has more open 4-4  (HM300 replica), but they have diffusers in and packed with the wool so they are hardly free flowing. My K6 had the restrictive HM341 without the endplugs.

I'll open up air screws a little now since I smelled rich when it idled when coming back home with warm engine.

[PeWe]

About air box... I should have searched about it and found how to since this is a common "problem".
http://forums.sohc4.net/index.php/topic,74061.0.html
The carbs here are a little bit angled forward.Float bowls not exactly horisontal as it look like. Risk that it can flood over if float height is at max.

Carb boots orientation ending up in correct angle is the first one. I aligned them all to be parallel. Numbers 1-4 readable as sitting on the bike. I tried to get the ends against carb rack vertical. I'll adjust next time to avoid the wrestling match to align the few mm missing for bolting up in ears.

[PeWe]

We have sh!t weather over here I had  planned a test ride on my K2 after adjusting rear shocks that were too hard. Now swampy soft, one step lower springs.

Road felt bumpy that my K6 can handle really well. I realized that the stock looking shocks have no dampers, only springs. My K6 Ikons feels hard but have dampers take care about bumpy roads or bad done asphalt roads with waves. I see a 500 euro bill coming     

I have also replaced the HT leads with NGK caps since I have had bubbling carbs at idle/low rpms that most likely is ignition problem on one cylinder.  Feels like bad connection in one lead - NGK cap. I swapped them all 4 with another set I have.

I have started the engine in my garage and it sounds better.

It ran fantastic with good throttle response last time with needles 4:5 and 110 mains. Legal speeds now drinking 0.5L/10km (47 MPG).

[Terry in Australia]

Good work Per, and yeah, those replica shocks (even the genuine Honda shocks from that period) are sh1t, that's why we all threw them away back in the day and installed Koni's. Ikon's are great shocks, I've got them on a couple of my bikes, and I think they're as good as anything out there. I've got a couple of pairs of old shocks in my garage, but I think I'll just clean the rust off the old OEM shocks on the swamp rat, I'm not really interested in making it handle, just look like a "Barn Find" original bike that needs some love.

[PeWe]

Terry, the jumpy handling is in low speeds 50-90 km/h.

I have had another ride today with the shocks one step lower pretension. Still a jumpy experience when riding in legal speeds. The handling overall is OK, even on curvy roads in 140 km/h.

The shocks can't have oil dampers taking out the bumps in the road.

I have my finger on the order button for Ikon shocks, the version with stock look.

I have my old Marzocchi AG Strada from the 80's with a repair kit.
They do not look stock though.

[PeWe]

Replaced the shocks today with new Ikons.
I hope they will make this bike as comfortable with good handling as my blue K6 that also has Ikons, purchased 2014.
They are not exactly the same.

Different springs. I hope the new Ikons are good too. I did same settings, damping 2, springs 2.

My older on the blue is progressive springs, right?

The new set look more as stock old Honda. It is the damping that was the problem with the knockoffs.

The stock knockoffs rests on the seat.

[PeWe]

Added a new gadget today, volt meter.
I have so far focused on charging to work so battery will not discharge as it can when cruising around for a longer distance on lower rpm.

I have finally realized that using GEL battery might be less good as wet lead acid battery. GEL battery max charging voltage is 14,4 V. It can get bubbles at too high.
Normal wet battery can do a little bit more.
My LED flash for overcharging after 15V.

So a Volt meter is needed during a period when regulator can be adjusted.
I'll see if I have to connect it direct over the battery. Now green and black wires in headlight bucket which was  quickly done. Hopefully not that much voltage drop. I'll see when LED flash for 15+ Volt and learn eventual difference.

[Terry in Australia]

Good job Per, I think I might install one on my "Bitsa" this year.

[PeWe]

Terry, I recommend this good gadget which will inform that the battery will support your ride.

I'm currently on a test ride. It work really good. I see the voltage constantly.
Strange high voltage raise when switching off the headlight, from 14,1 to +15V.
Battery was fully charged before the ride.
Headlight is a LED 30W, rear std 5W.
Charging system a little bit weak?
I'll check the Honda shop manual ch.8 when back home. There is a voltage chart there, headlight on vs off.

I found this LED volt meter on eBay. Nice with green light. The plastic cover need to be sealed/ glued since it is easy to snap off.
Rainy ride might be an issue.

[PeWe]

Here is the LED voltmeter I bought and fit nicely. I attached it with double sided tape, the thicker version.
Note! Camera does not show how good the voltmeter lit. Its update frequency is fast for they slow eye with sharp and clear green light. Camera is quicker and take the photo while the update flicker.

https://www.ebay.com/itm/LED-Digital-Motorcycle-Car-Voltmeter-Indicator-Voltage-Volt-Gauge-Panel-Meter12V/223531707201?ssPageName=STRK%3AMEBIDX%3AIT&var=522283515352&_trksid=p2057872.m2749.l2649

I saw that bike has electrical issues with sudden low voltage when riding, OK direct when switching off headlight. After a while it can work fine even with headlight on.

- Photo at idle headlight off. The multicolour LED change from yellow to green at 12.4V

My first measure was to replace headlight bulb when back home. LED H4 to a std halogen H4. I only started the bike and switched light on-off, 1V voltage drop when on at idle. Next ride will show if the sudden low voltage will occur again. It must be something that limit the current if still a problem or the circuit between switch and headlight.

I know that there is a problem, that's why I installed this voltmeter. I have recently replaced battery since it drained under a ride so it hardly started on the starter. I continued with light off. Replaced battery when I was convinced that 6 year was its lifetime.

I forgot the most important part of today's test ride after work. Not many bikes there today. It can be hundred or more other weeks.

There is a burger (150grams minced meat) in there between the layers of pickled cucumber, tomato, lettuce, onion, dried fried onion, dressing, ketchup and mustard

The brown K2 in the background

[Terry in Australia]

Thanks Per, I'll order one. Whats the button(?) under the volt meter for?

[PeWe]

The yellow button?
That's the charging supervision. It has 3 wires. battery - and +, another + to ignition 12V.
It has 2 modes, blinking when ign is off, steady when on. It look like an alarm when ign is off. Green and battery is OK, yellow time to charge.

When riding, it must be steady green for OK charging, turn to flashing green/red when voltage exceeds 15V, yellow under 12.4V.
This was my first charging control to get enough charging. The new voltmeter to verify no voltage over 14.5V volt during a longer period. Good setup to ensure good charging and see if something strange happen when turn on-off things.

I'll see if the voltage will be more stable after bulb replacement, the LED bulb might be defective.

[PeWe]

I think I have solved the charging issues. I visited a friend that has a lot of old CB750 parts,  back home with 3 regulators. One look like never opened before, really clean inside.
Adjusted core gap. Test ride and decreased voltage screw by 1/4 turn counterclockwise. Better, much better.

Edit: I use the LED H4, No problem with it.
The voltmeter placed between speedo and tacho make the charging behavior very visible.

 I can guess that many good batteries are replaced due to wrong adjusted or faulty regulator that can't do the job charging the battery.

[Terry in Australia]

That burger looks good Per, you're making me hungry!

[PeWe]

Terry, what about a tasty Kebab plate with fries and medium hot chilli paste?
Here 2 different restaurants along my usual country roads for road tests, or just enjoy the bike and hunger

[Terry in Australia]

Looks fantastic Per, I think there should always be time for food on a good ride!

[PeWe]

Correct Terry, find a nice restaurant with food you can enjoy for not that much money and let that be one more reason to enjoy the ride.
That is what Guide Michelin did giving restaurants stars making cars to worn their tires so they could sell more tires.
1 star worth to stop for, 2 stars worth to take a detour, 3 stars reason for the trip.

Restaurant get 2 stars, my bike 3!!

[PeWe]

Next sub project to this one,
1975 cylinder. From an F bike but must be same as K2 got 1975 here.
It look a little bit swampy.. a light hone and ready to go with the crispy crust... Or update it when the nearby shop's mechanic will be back from a very long vacation.

It will get a beautiful and refurbished K6 head ready to be used.

[Terry in Australia]

Wow, that looks just like my swamp rat's cylinders before I replaced two of them Per, you might get away with boring them out, although some rebore shops would just reject it, as it'd be a horrible surfaces to bore, you might need to replace the sleeves? Find some good used sleeves and just swap fhem out, give it a hone, and re-use.

[PeWe]

I think it will work to remove the rust crust that has grown over the bore.
Wire brush on my drilling machine with light hand.
Then hone with 2 3 stone hone which will show if it will be grinded evenly.

Maybe I'm optimistic, I have 0.5mm oversize in mind. So I hope the rust is max 0.2mm deep into the 61.0mm sleeve.
https://www.cruzinimage.net/2017/08/17/77-78-honda-cb750k-k7-k8-0-5mm-over-size-pistons-set/

If rust is deeper, next size up and use +0.5mm pistons to my K1 cylinder it has now .
https://www.cruzinimage.net/2017/08/17/77-78-honda-cb750k-k7-k8-1-0mm-over-size-pistons-set-62-00mm/

The  cylinder head surface will get a table grind. A few rounds of grit 240 followed by 400 to be able to use MLS head gasket.
As I did on my K6 836 cylinder (replaced by billet block), head and  upper case to use RCS base gasket. No leaks.

[Terry in Australia]

Best of luck with that Per, I have my own boring bar so I can re-bore my own cylinders, but to set it up I need to be able to properly centre the cutting tool, and with crap like that in the bore, it'd be a nightmare. You could buy some good used sleeves from someone for only a few bucks, then just heat up the cylinder block in an oven, and pop the old sleeves out and install the new ones, and you'd be good to go. Up to you mate, it's your Kroners.......

[PeWe]

I'll see how it will look like when brushed. Most rust has grown outwards. I hope no deep pittings.
The shop guy that will do this is an old bike mechanic that is working overtime, no retirement yet, soon. He has worked with these engines since the beginning. He need a challenge.

[PeWe]

Now ready for the bore guy!
Bores are 61mm by caliper. + 0.5 mm pistons must work fine. Even +0.25 should work except for cyl 3 that has some pits that can be deeper than 0.1mm.
Remove 0.2mm material must make the bores clean and even.
I'm not a bore specialist

I have 2 old 836 kits (one not much used, AF pistons a little bit sloppy grooves) so cylinders are needed!