Topic: CB750 K1. Dont drink and ebay project....

[jaguar]

well i was drinking one night and playing on eBay with my iPhone and saw this 1971 CB750....
it had a video of it running and listed that it had a title, but sat outside for years
i placed a super lowball bid and i figured someone would snipe me last minute and take the bike.
well that didnt happen!!  lets just say ive bought blown up junk parts bikes for what i got this thing for.
but to be honest it doesnt look that far from a parts bike.
tank is rusted to hell but only on the out side.
spokes are toast.
seat is shot.
frame and wires are in good shape and will clean up really good.

as far as i can tell the bike was valley green
plan is to ride the hell out of it for the rest of the summer and then do a factory resto over the winter.
i got a corbin seat and better wheels for it


need to find side covers and an origianal exhaust....those should be easy right?....lol

do have a few questions though
-how pitted is too pitted to rechrome?
-what should i know about k1s vs other sohc bikes?

[srook]

The K1 is a bit different than the later bikes 72 onward.  It is more like the sandcast and K0 than the K2-K6.  The obvious differences are the plastic chainguard, taillight, turn signals, and painted fork ears/headlight bucket.  Not so obvious are the wiring harness, seat latch, and handlebar switches.  The motors are a bit different as well depending on where they were made.  Cams depend of the factory they were made in.  I pulled a cam out of a my K1 motor and it looked exactly the same as the cam in my K5 motor.  The cylinder studs won't have all the rubber o-rings around them like the later bikes.  The rocker shafts aren't held in place with bolts, they are free to pivot.  The cam chain tensioner blade is shorter and the tensioner spring is stronger than the later bikes.  Cam timing is a little different as well.  The K0-K1 bikes were quicker than the later bikes but not as much as many people think.  The later motors were made less noisey which made them a little slower and were really focused on touring.  The F bikes were supposed to carry the performance mantle for Honda and the K bikes were left for the touring crowd until the Goldwing was introduced.  The K bikes were actually supposed to go away after 1975 but people reacted negatively and Honda introduced the K6 and even restyled the K bikes for 77-78.

Keep us updated on the project.
Scott

[traveler]

From ym experience having built a couple of bikes.

Before you tear it down, you need to plan on $5,000 to $6,000 for a proper restoration.

As far as pitting....really depens on how much the metal has been "chewed" on by the rust.  if it is smooth after sandblasting, then all is well....if it isn't, then you either replace, or powdercoat it glossy silver and live with it.

What is the VIN# on the frame and engine?  K1's were built in one of two factories for a time, the factory one bikes, were built like a K0, with more hand assembly going on.....about midway through the K1 production, they shut facotry one down, went to facotry two, and mass production commendced to keep up with growth and demand.

Hope that helps.  Just want you to realize what a "full on factory restore" entails cost wise.  You better love the bike, because you will never get the money back on resale.  a MINT K1 is worth maybe $5,000 on a good day lately.

~Joe

[jaguar]

I'm not really looking to do a 100% factory crazy resto.
The goal is to have a nice factory bike to ride and enjoy.
I've been down this road before on other bikes and cars so I know how the cost and time thing goes.
My build date is 1/71 I don't have the frame numbers with me.

I do hope that if im carefull I can build this bike and not spend huge money.

[mycb750k6]

At first glance this bike looks like it will need a LOT of work, not just bunches of money. You'd pretty much need to take it completely apart to determine where you are. Make a plan with a list of things to be done and their costs and see where you are. That's what I would do anyway. You have the impossible to find chain guard, switches, gauges, tail light, tank, carbs and air box, and seat pan so you have the big ticket items except the side cover. They just need work. What is the VIN and the mileage on the speedo??

[jaguar]

its really not as bad as she looks.
most will clean up well.
and like you said most of the big ticket parts are there.

frame
 CB750-1075385
motor
 CB750E-1075684
build tag
 1/71
milage is
21k

all of the electrical stuff works.

is this an early bike?
how do you decode the vins?

[mycb750k6]

Doubtful. VINs are decoded here: http://www.sohc4.net/index.php?q=content/serial-numbers
71's were 104xxx to 200xxx. You're at 107xxx which probably places it in the new factory so no big deal.

With the amount of rust I would be most concerned about:
swing arm bushings
triple tree bearings
Water in the carbs and general goo
Water in the engine 
frame down tubes rusting inside - a real possibility.

The fact that all electrical works is huge. I'd still clean all the connections on the harness.

Many chromers will tell you they can chrome that fender and handlebar but what you may end up with is a chome fender with lots of bumpy pits. I'd try something throwaway first with whoever you go with.

[jaguar]

oh yeah i am going to assume that the swing arm bushing and triple tree bearings will need to be replaced.

no water in the carbs or in the motor.
under the fork ears has rust. but nothing at all in the travel of the forks.

im not trying to make light of the amount of work it needs as it will be alot of time and money to get this thing to a good looking bike.


really would like to know more about at what point they changed from the old to the new factory.
they made 77,000 K1s?  so that makes mine about 21,000 into that?

[mycb750k6]

I'd like to know the switchover number when they started manufacturing in the new factory as well. Could be hard to nail down. Apparently the old factory was shut down at that point. How did you calculate 21000? You have a frame date of 1/71 with VIN  107.... I have a frame date of 9/70 and a frame number 105xxx one month after K1 production. That's about all I know. Others here are more knowledgeable.

[jaguar]

i just took my engine number and subtracted the starting engine number listed in that link you posted.
my mental rounding was alittle off.  but not by much.  i get 22,285.
i have no douht at all yours is much earlier then mine

[mycb750k6]

Well I hope you bring it back to it's former beauty as I'm sure a lot of the folks here do. My favorite year is the 71. In fact it's almost customary to document your progress with photos. Sometimes folks here even have parts you need.

[jaguar]

I'll do my best to do the right thing for the old girl.
Going to enjoy her as is right now and start the big project in a a a few months

And yeah the guys here are great!

[jaguar]

cleaned her up a bit the other day.  i was happy with how she is turing out.
cleaned out the tank using "the works" toilet cleaner.  all i can say is WOW that stuf works and its only a $1!

checked the frame welds too.  i would really say that they were done by hand.  they are not as nice as on my other bikes.  but i really dont know.  ill post some pics and maybe we all can figure this out.

starting to think about a plan for the bike.  i go back and forth about doing a full factory resto or a mild(IE only bolt on, no cutting and normal color) cafe or just a clean rider.

trying to find out what pipe is on the bike.

funny that it has K81s and a Hella light...

[mycb750k6]

Pictures. You gotta have lots of pictures.

[jaguar]

chrome is cleaning up enough to use for a bit.  will need to be replaced or rechromed down the line though


flash rust after the "works" cleaning.  i really thought that the tank was going to be junk.
very happy that i will be able to use it


helped out a friend and he hooked me up with this seat and two good wheels.
not the best looking seat but is nice to sit on


not really sure about the welds. 
if you ask me they look hand done but that just might be me telling me what i want to hear


looking forward to riding the bike for a few weeks before the weather gets cold. 

[mycb750k6]

In that case I want your old seat or seat pan. I don't have one for this K1 project and maybe I could recover yours and put some foam in it. Worth a try?

As far as the welds go, shoot a picture of the Y in the front of the bike , where the horn goes, And the welds under the tank and seat looking down from the top.

"few weeks riding before it gets cold"? What do you mean cold?

[jaguar]

I'll try and get those pics

I'm heading back to school in a week
I'll be in Potsdam ny.  We are 20 min from Canada.  Winter comes early...
I need alittle time to get the bike ready and after that there will not be much time this year for riding

[srook]

Hi All,
I have a K1 frame number 1076XXX.  The build date is also 1/71.  Here's some info about the motor that I found when I tore it apart.  The cam was marked R6 and looked identical to the cam out of a K5 that I had.  I did measure the lift on both cams and they were the same.  The lobes did not look any fatter between the cams.  The ports had lots of hand finishing marks in them.  The rocker pins did not have the extra 2 bolts to hold them down.  The cam chain tensioner spring was stronger than the K5.  Everything was consistent with the differences between a K1 and K5.  What does all of this mean?

Bikes built on or after 1/71 did not have the hotter cam of the Sandcast, K0 and early K1.  That doesn't mean they weren't quicker than the later bikes.  The cam timing (advance curve) was different on the K1 as well as the main jets.  Together with the factory port job and the little differences, that made the K1 a little hotter than the K2-K6 bikes.

Another observation.  There are alot of K1s that seem to be made on or afetr 1/71.  There are not that many 10/70, 11/70, or 12/70 K1s.  The large majority of the K1 production happened after 1/71. 

I think all of this means that the new factory probably came online in late 1970 or early 1971.  But......

"Ultimately, though, the production of engines and bodies was transferred to Suzuka Factory-in July and October 1971, respectively-as part of the company's endeavor to satisfy customer demand."

That quote comes directly from Honda's website and is part of an article that detailed the early history of the CB750.

http://world.honda.com/history/challenge/1969cb750four/text/04.html

Could the article have meant July and October 1970?  Maybe because I don't know how many 1971 model bikes would have been built in July or October of 1971.  I would think their production run for 1971 would have stopped by April or May and they would have been onto 1972 models by October.

Scott

[jaguar]

bike is torn down now and the frame is ready to be refinished.

[jaguar]

been doing some work on the bike

needs timing rollers replaced, parts are on order

here is the frame stripped down.  some times i look at it i think its hand welded others im not so sure




Started to polish up the cases



they are looking very good.

[jaguar]

painted and cleared the frame.
will get more pics soon



pulled the swing arm bushing out as the bike was sitting for years and wasn't traveling nice
this is what i found

how bad is this?
not really sure where to get parts.....

[jaguar]

been working slowly on the bike
havent solved the swingarm bushing issue yet

moving more and more toward a mild cafe on the bike.
working on a deal to trade my NOS HM341 pipes for some cool parts for this bike.
not going to trim off anything or cut the bike up so one day it might be able to go back to stock

going to sell off some parts and other toys and try and track down a clean stock bike to start with for a factory project


still doing some polishing

[brandEn]

Looks like your off to a good start. I hate polishing so I went with powdercoat! Looking forward to watching your progress.

[jaguar]

cant lie.....one of my friends is helping out alot with the polishing the bike.
i told him that i would help him get his project on the road.

[jaguar]

slow going right now.
cracked the motor to replace the tensioner.

kinda changing direction from my first thought on this bike.
frame is now being powdercoated black.
going to do a mild cafe with the bike
tarazi rearsets
cool tank.
not going to cut the frame or anything just want a fun bike for the summer