Topic: Colombian 1975 cb750k2 restoration

[joseimport]

hey everybody, i finally bit the bullet and purchased this cb750 in Colombia, south America.

back before the quarantine started i was planning on purchasing this bike. but had to pospone the purchase until last friday, i traveled to pick it up 2 hours  away from my home.

here is my old post http://forums.sohc4.net/index.php/topic,181269.0.html.

to sum things up this cb750k´s are extremely rare here in Colombia, the last time i saw one for sale was 4 years ago and most of the ones i have seen are completely chopped up and have had 40 plus years of bad parts replacement and terrible owners that before the internet era, had no way of getting parts for them,  here this cb´s are not cheap, even old ratty ones.

this example comes like this:

frame number is cb750-2104309

and engine number cb750e-2423247

so in USA terms, it's practically a k2 frame with a k5 engine.

in all the research i have made, this is how this bikes where sold here, in the manual this would be a general exports bike.

i traveled last march to see the bike for myself, i was worried that the frame had been chopped up, but to my surprise the frame is in very good condition. and the bike is almost complete.

i had 4 months to dwindle on this bike.

did tons of research, and got the "my cb750 book" from our man hondaman from Lulu's (still reading, got it last week). i also whatched the entire Hackaweek cb750 restoration on youtube. and have pretty much read back and forth the http://honda750expert.com/ website which has helped quite a bit also, so this is all the experience i have restoring cb750k´s.

[joseimport]

the bike has not been started in 4 years, that's when it had its last mot.

the engine turns fine with the kick start (only tried it once when i went to check the bike for the first time)

so the first order of business is trying to start it.

i will remove and clean the carbs, ordered new carb gaskets.

will drain and change the oil.

then try to sort the wiring harness and all the electrics to see if i can get some spark. hopefully i wont have to rebuild the engine just yet.

first i need it to pass our Colombian MOT so that i can transfer the title to my name, before investing on the restoration. i don't know how it works in the US, but here you can not transfer the title of  a vehicle if it does not pass our Colombian MOT.

as soon as it's under my name, i will start the real restoration.

the k2 frame comes with the unicorn style top tree. it came with cb350 gauges that where fitted to the top tree by a plate. they were off the bike when i got it. but wont be using them.

sourcing the k2 gauges has been really hard, they are scarce and expensive.

i already got a good used top tree from a k3-k6 as suggested by some members on my first post, and will get those years gauges. this wont be a concourse restoration. but will come as close as my wallet allows it over the next few years.

my end goal is to have it look as original as possible, use as many original parts as i can afford. but some parts i don't mind if are excellent replicas.

so my main missing parts from what i can tell are:

-gauges
-new foam and seat cover
-tail light and tail light mount bracket
-airbox
-side covers
-main stand
-turn signals
-points cover
-mirrors
-4-4 exhausts (this i will skip they are extremely expensive, will eventually get some good aftermarket exhausts)
-front fender (the one it has has been)
-fork ears
-headlight

[joseimport]

OK after some research and getting some work done....  i renamed this thread, before it was cb750k2k5 1975.

its simply a 1975 k2.

as all of you know only the US got the k3-k5 models, my model is very similar to the UK's k2. which were sold as k2 until the k6 came along.

what gave it away was the left hand switches, which do not have the canceling buzzer from the us k2.

ok that is settled.

the bike had all of it's electronics butchered, the harness was a mess and missing the correct ignition.

so i decided to renew the entire electronics, keep what works and buy everything else.

had to read and learn a lot about wiring and electronics. learn how to read a wiring diagram. once you get into it, and a few videos it all becomes pretty clear. extremely important is learning how to use a multimeter.

from eBay:
wiring harness
used rectifier, starter solenoid
nos points ignition

from 4into1 got:
nos fuse box
new 5ohms magna coils
alternator wire harness
spark plugs and cables
k2 replica ignition switch (will try and get a whole set later)

as you can see in the pictures, i installed everything i think this is the correct routing for the wire harness.

[joseimport]

i stripped the carbs and sent them to the vapor blaster


the quality of vapor blasting here is not up to par with what i have seen US and UK vapor blasters do.

but still is a great finish compared to how i got them.

#4 carb had the "emulsion tube holder" broken and filled with some sort of epoxy, i had to get a replacement off eBay, so i got a good deal on some k5 complete carbs with no bowls.

ended up using my original internals as they all were the original stamped keihin. i might need to replace some of the jets and needles depending on how it works if the bike starts.

[andy750]

Carbs look great! Looking forward to following along on your restoration.
Good luck!
Andy

[joseimport]

i was wiring everything on the headlight yesterday, and came across something:

the idiot lights were missing from the bike so i got a used replacement in good condition from a 1973 cb750k3.

thinking they were the same across all of the k bikes.

now, looking at the k2 wiring diagram the neutral light only has 1 green red wire and grounds directly to the engine on the neutral switch.

the k3-k6 diagram shows the neutral and oil pressure lights sharing a black wire (key-on positive).

this is because the neutral wire goes to the starter motor safety unit present on the k3+ bikes.

my question would be....  do i plug this normally?  i would be using a k3 pilot-idiot lights on a k2 harness, so the neutral would be on the key-on positive black wire without a safety unit

would this create any problems?

[joseimport]

i installed all the wiring by myself, this is my first dwelling with wiring and electrics, and felt really good to just see all the lights work, learnt how to use a multimeter, learnt about how electronics work in general, i can say i'm now wiser than before      working on this bike is just a joy.

i had to rewire and crimp the handle switches, as the wiring was in bad shape. the wiring goes inside the bars, had to use a 10usd fish tape from amazon, this way was really easy getting them trough, many people have problems with this i had read. the fish tape really helps, would recommend it to anyone.

installed the carbs, and tried to install the airbox i got off ebay in really good condition but the rubber stacks are just rock solid and seem smaller than the only new one i have. not realizing that they would not go in the carbs, they have shrunk a lot,  i just purchased the missing one, should have ordered all 4.

what do you guys think about oem intake and airbox rubbers, is the difference from original Honda ones THAT big? been thinking about getting oem ones, and save a few bucks.

In the meantime the bike came with a set of k&n filters, i will start the bike with them, i know it might not run properly, but it will start, later i can buy the new rubber.

[joseimport]

from the start i wanted the bike to have the k3-k6 clocks, as getting original ones is way easier  and i think they are more solid than the unicorn type gauges.

i removed the unicorn tree, i got a top and bottom tree on ebay, for the k3-k6. i will sell this unicorn tree.

found a good set of gauges for 70 bucks, in the future i plan on restoring them with a kit from cb750faces.com, they are in the netherlands, is there an American company that carries them? it would be easier and cheaper to order form the US.

[joseimport]

the field coil was toasted.

the stator had the correct 0.5 ohms resistance, but the three yellow wires had been rewired.
also it was missing the bracket that holds the wires inside

the stator cover had been welded, probably from hitting a curb or a fall, who knows.

to  my luck i found on ebay a used cover at a good price, it came with the field coil, stator AND the bracket, the wiring seemed good, so i got it, checked it with a multimeter and everything is in really good shape.

[MauiK3]

Following
Keep your chin up and take your time. It's worth it.

[754]

Welcomr aboard.  Have you ever bought parts from Canada, I may have a few bits. 
 Not sure how bad shipping is ?

[joseimport]

Welcomr aboard.  Have you ever bought parts from Canada, I may have a few bits. 
 Not sure how bad shipping is ?

before i got this 750, i have been restoring an rd400g for the last 5 years, which is the Canadian version of the daytona special.
i got the most important parts from a bloke from the aircooled forum from Canada.

i had them shipped to Miami then i imported to Colombia, so i could do the same.

with the cb750 my main goal this year is to start her up and put the title under my name.

right now I'm derusting and cleaning the fuel tank with vinegar, might start her later this week.

next year as things normalize a little bit, and money is more plentiful (here's hoping) i will buy the bits and pieces left to restore her.

it needs:

turn signals
seat foam and cover.
front and rear fender.
complete tail light
side covers (the ones i have have were broken and somebody fixed them, but in the process removed the indentations for the emblems)
headlamp (don't know if i should get the sealed beam unit like the us models, or the one from the UK which has the bulbs separate)
the exhaust is something i don't know what to do, getting the original 341 costs more than the bike itself at this point. all the used ones i have seen on eBay have too much damage. and there is no place to restore them as they should be restored here in Colombia.

this is if i don't have to do a full engine restoration.

[joseimport]

got the bike started

here are two videos i made yesterday

the original air filter rubber velocity stacks were rock hard, i could not get them on the carbs, will order replacements soon. But in the meantime i started it with the k&n pods it came with. (cleaned them and added oil)

i checked before adding fuel if the oil pump was working and followed some advice from members here on a different post (http://forums.sohc4.net/index.php/topic,184527.msg2138073.html#msg2138073), so i connected the old battery (yuasa 14bl) but id did not have the cranking power expected so i connected my car's battery and cranked the starter, the oil pressure light went off, checked exhaust tappet on number 4, and oil is flowing fine.

so on to my first start, i made a DIY external fuel tank, with a washer liquid holder from a car,fittings and hoses.

at first with the choke ON the bike did not want to start, as soon as i opened the choke it lit right up. WHY WOULD THIS BE?

also the bike seems to not want to idle, it did for a little while at the beginning but as soon as it heated up and i release the accelerator it turns off.

i set the air screws 3/4 of a turn.

my altitude is 5250 feet.

it has 4 into 1 exhausts but i have no idea which brand they are.

i have been focused on just getting the bike started, now comes the tuning part of it, but i don't have a strobe light to check dynamic timing, also i don't have a way to sync the carbs, i will read Honda mans section on carbs, also if there are good articles or videos about this that any of you can recommend let me know.

[joseimport]

i had the speedo but the chrome plate that holds it was in bad shape, so i got a new set from Yamiya.

got a k2 handlebar to replace the flat bars and replaced the switches, got new grips and throttle tube.

replaced the cheapo mirrors for original ones.

here are some before and after pics

[Jerry Rxman Griffin aka MuthaF'er]

Sounds really good! Congratulations.

Remember these beasts are very cold natured at first until warmed up.

"Bench sync" the carbs using 1/8" drill bits initially. You can find this procedure on this site also.

You checked the oil flow on #4. I would also recommend checking #1 as the cam towers are independent of each other.

Next time I travel to Colombia (not sure when) perhaps I could bring items for you.

[joseimport]

Sounds really good! Congratulations.

Remember these beasts are very cold natured at first until warmed up.

"Bench sync" the carbs using 1/8" drill bits initially. You can find this procedure on this site also.

You checked the oil flow on #4. I would also recommend checking #1 as the cam towers are independent of each other.

Next time I travel to Colombia (not sure when) perhaps I could bring items for you.

i did as you said i bench synced the carbs, I'm waiting on a set of keyster carb repair kits that arrive next week, the main jet's holes seem to be of different sizes when looked up to a light.

i don't have a vaccum carb sync tool yet so the basic syncing will have to do.

 

[joseimport]

i got a used front and  rear fender on eBay. unfortunately, the seller did a piss poor job on the packaging and the parts arrived in bad shape, twisted and like if they had been stepped on.

whoever packed it did not take the braces off the front fender and did not even put the whole thing on a box as any rational human being would do. he just wrapped the whole thing on bubble wrap.

he is a recommended seller on eBay, and to his credit had great costumer service and we agreed on a partial refund for the parts. fortunately i know and old school metal worker here in my city, that says he can mend them.

[joseimport]

i just got the rear fender back from the metal worker he did a great job. here is the bike with the whole rear fender installed.

(this how our licence plates look like in Colombia=)

IMG_9103 by manuel caicedo, on Flickr

yes i hate this seat, but don't have the money for a new one yet, i wish i could get a NOS seat at an affordable price.

or does anybody knows who sells  the best replica seat out there for a k2? there are just so many options.

David silver has two replica models, one for 125USDA another for 195usd.

there are a bunch of Vietnamese ones on eBay, but the trim on all of them look somewhat off.

would be good if people shared their opinions on all the different replica seats out there.

[Jerry Rxman Griffin aka MuthaF'er]

Save your original carb parts for potential re-use. Many of us have had bad experiences with new Keyster kit parts and reverted back to our original parts.

[newday777]

Nice work so far on this Jose.
You mentioned you didn't know what exhaust it has on it, that is the Kerker 4into1. It sounds good in the video for the start up but yes it will need a vacuum sync to dial the carbs in better to quiet the slap of the primary chain at idle.
As to correct jetting you'll need to get out on the road and do a spark plug color test. I don't remember from the 70s what jets I had in my 76 K6 at 9,000' in Colorado with my Kerker and stock air box, built motor with 811cc kit and a cam which would be different than a stock motor anyhow.
I agree to use Honda brass carb parts only, not the keyster kits.
As to the seat, just get one of the David Silver seats.

I noticed the way you put the wire harness was outside the brace, but it should be inside the brace(to protect from the tank tunnel chafing it). See the second picture below.

Keep up the good work.

[joseimport]

Nice work so far on this Jose.
You mentioned you didn't know what exhaust it has on it, that is the Kerker 4into1. It sounds good in the video for the start up but yes it will need a vacuum sync to dial the carbs in better to quiet the slap of the primary chain at idle.
As to correct jetting you'll need to get out on the road and do a spark plug color test. I don't remember from the 70s what jets I had in my 76 K6 at 9,000' in Colorado with my Kerker and stock air box, built motor with 811cc kit and a cam which would be different than a stock motor anyhow.
I agree to use Honda brass carb parts only, not the keyster kits.
As to the seat, just get one of the David Silver seats.

I noticed the way you put the wire harness was outside the brace, but it should be inside the brace(to protect from the tank tunnel chafing it). See the second picture below.

Keep up the good work.

you really think it's a kerker?

will take more close up pictures, they dont have any type of lettering or stamps.

i was thinking on switching to delkevic, because i thought this was just an exhaust made here in colombia. but thinking about it they i dont know anybody who could have made them here.

i tried routing it the way you say, but the coils get in the way, and it would be a tight fit against the trianlge.

but i think i can move the coils a little forward, will check that later tonight.

[Alan F.]

Sounds and looks like a Kerker to me, check YouTube.

[newday777]

Nice work so far on this Jose.
You mentioned you didn't know what exhaust it has on it, that is the Kerker 4into1. It sounds good in the video for the start up but yes it will need a vacuum sync to dial the carbs in better to quiet the slap of the primary chain at idle.
As to correct jetting you'll need to get out on the road and do a spark plug color test. I don't remember from the 70s what jets I had in my 76 K6 at 9,000' in Colorado with my Kerker and stock air box, built motor with 811cc kit and a cam which would be different than a stock motor anyhow.
I agree to use Honda brass carb parts only, not the keyster kits.
As to the seat, just get one of the David Silver seats.

I noticed the way you put the wire harness was outside the brace, but it should be inside the brace(to protect from the tank tunnel chafing it). See the second picture below.

Keep up the good work.

you really think it's a kerker?

will take more close up pictures, they dont have any tipe of lettering or stamps.

i was thinking on switching to delkevic, because i thought this was just an exhaust made here in colombia. but thinking about it they i dont know anybody who could have made them here.

i tried routing it the way you say, but the coils get in the way, and it would be a tight fit against the trianlge.

but i think i can move the coils a little forward, will check that later tonight.

I had the Kerker on my 76 years ago. I remover the stick on label that said Kerker when I installed it in 1976.

[joseimport]

OK,i have been trying to take the bike for a spin, but had some trouble with the clutch, the cable was an aftermarket one which did not have the adjustable nut on the cover, the clutch felt weird and was not engaging correctly, plus the clutch lever was also aftermarket and was weirdly shaped.

i dissembled the clutch just to be sure everything was OK, and to my surprise the concave washer was backwards, the nut that requires a special tool came out with my hands after removing the lock tang. fortunatelye it appears this did no damage.

i checked the plates and friction discs and they are in good spec.

i purchased a brand new clutch cable, lever, and new EBC springs. so i installed everything making sure the clutch went in fine.

today i took the bike for her first big ride.

what a difference in the clutch feel and grab from how it was before.

2021-01-19 by manuel caicedo, on Flickr

maybe i forgot to mention, that i have never ridden road bikes in my life, my experience with motorcycles was a small Honda z50r,  an xr100,  but this was 25 plus years ago when i was 15, and always off road.

i took my license test 3 months ago. so i can literary say that this is my first bike.

today i took her to work since it finally stopped raining here in Popayan.  and after the clutch fix, it feltcompletely different.

well i guess everything they say is correct, i had a huge smile on my face the whole day, i have been taking it really slow and will probably continue to do so until i get more confidence on the bike, it feels heavy as hell, the brakes are not good, but the only thing i have to compare them to is a car....  im riding like a total noob, little 125cc bikes overtake me all the time, but who cares.

one thing i really noticed is everyone that goes or that i pass by looks at the bike as if an alien had just landed. not many bikes like this one i can tell you.

i got a new master cylinder, stainlees steel brake lines from 4into1 and EBC brake pads since i have no idea how many years or what brand are the current ones. will connect them tonight.

i had gotten a used front fender with the rear one, but arrived twisted, it had not been packed correctly and the seller did not take off the braces. so i sent it to a metal shop, and they did a fantastic job, i fitted it and they fit perfectly, later this year i will have all fenders re-chromed.

[Jerry Rxman Griffin aka MuthaF'er]

Congratulations 

Watch out for the taxis as you know.