Author Topic: Brought home a K2 today (Read 4524 times)

VTCBike750 · « **on:** February 16, 2020, 06:35:14 PM »

I brought home a K2 today, 205115X, prod 7/72. 4,200 miles. Second owner bought it off the original owner 3-4 years ago, and it sat in his garage. It was last inspected in 1995 and I have the original title from 1973. The bike still has gas in the tank.

So far the transmission shifts easily, engine turns over. Pipes are in great shape with a little "patina". The bike was once dropped on its left side with minimal damage (stator cover looks rough though). Tank will probably have to be lined, but honestly thinking of getting a yamiya body kit. Sorry, not a fan of briar brown.

I wont pretend that I know everything about these bikes. Any advice/tips/recommendations to get this bike up and running would be greatly appreciated. My first goal is to clean and polish the bike. I also want to go through each electrical connection, clean them and add dielectric grease.

From what I know so far, the bike needs the following:

-Adjust the values
-Check the timing
-New air filter
-Kick start the bike about 40-50 times and change the oil and filter (its clean looking on the dip stick)
-Front brake master cylinder needs to be rebuilt
-Rebuilt front brake caliper
-New tires
-New battery
-Carbs need a full rebuild
-disassemble and grease swing arm.
-Check chain (With the history of 750 chains breaking, Im thinking of getting a new chain. which kind though? With only 4200 miles Ill use the same sprockets)
- Check rear brake
- New seat foam, its crusty (Maybe from yamiya, ideas?)

Any other ideas/tips/recommendations?

Here's to another one in the garage.

HondaMan · « **Reply #1 on:** February 16, 2020, 06:52:08 PM »

WOW! That's the brother to mine! The color should be Garnet Brown, though, not Briar Brown. It was made by spraying green over red: I discovered that when my tank bag wore thru the green layer, decades ago.

For the oil: pull the sparkplugs and hook up a battery charger (nothing bigger than 10 amps, though) and use the electric start, 5-7 seconds at a time, to bring the oil up. Much easier, works better. Then change the oil and filter: it will stay primed but you will have to spin it a little more again to fill up the empty oil filter then. It will hold 4 quarts, showing about 1/4" high on the dipstick afterward. That won't bother anything: mine has been that way forever.

The spark advancer will be the AD125 Hitachi unit, most likely. Someday, think about cutting 1/2 turn off one of the springs to increase the low-end torque about 10%-15% and also reduce sparkplug fouling, by increasing the low-speed efficiency a little more (and use regular grade gas in town, midgrade for freeway, premium only if touring interstate speeds continuously). When you take the carbs apart, all they should need is a good cleaning and maybe new float bowl gaskets: soak the float valves clean for a couple of days in lacquer thinner, and keep the float valve with the same seat.

The swingarm bushings might be zamac plastic (like mine were) as this appeared until about 2/1972 production on the K2. If so, the edges of it may chip when you wrestle the swingarm collar out. If that happens, I can help out with a swingarm rebuild that will probably outlast you and the bike.

Ah, the K2: zenith of the 750K design, IMHO. Write with any questions, would love to answer back! Send a picture of the tank and side covers, too. Mine are in such nasty condition....the K2 seat foam is unique, having a bead on the seat cover that dipped down along where your thigh presses against it when you are standing still. The cover is still available: I have a genuine K2 foam and cover, don't know if I will ever use it, if you go the stock route. The K0-K2 had the legendary seat foam with the punched-out cores under your tailbones to make the famous "superseat in disguise" as Cycle Magazine called it in 1971. I did many back-to-back-to-back-to-back 1000 mile days on mine before I wore the original one out (in 1984).

Mark1976 · « **Reply #2 on:** February 16, 2020, 07:24:03 PM »

Good lord, there's nothing like a stock bike from the early 70's, where does the time go. It'll clean up fine and be a real nice ride.

VTCBike750 · « **Reply #3 on:** February 16, 2020, 07:32:12 PM »

Quote from: HondaMan on February 16, 2020, 06:52:08 PM

WOW! That's the brother to mine! The color should be Garnet Brown, though, not Briar Brown. It was made by spraying green over red: I discovered that when my tank bag wore thru the green layer, decades ago.

For the oil: pull the sparkplugs and hook up a battery charger (nothing bigger than 10 amps, though) and use the electric start, 5-7 seconds at a time, to bring the oil up. Much easier, works better. Then change the oil and filter: it will stay primed but you will have to spin it a little more again to fill up the empty oil filter then. It will hold 4 quarts, showing about 1/4" high on the dipstick afterward. That won't bother anything: mine has been that way forever.

The spark advancer will be the AD125 Hitachi unit, most likely. Someday, think about cutting 1/2 turn off one of the springs to increase the low-end torque about 10%-15% and also reduce sparkplug fouling, by increasing the low-speed efficiency a little more (and use regular grade gas in town, midgrade for freeway, premium only if touring interstate speeds continuously). When you take the carbs apart, all they should need is a good cleaning and maybe new float bowl gaskets: soak the float valves clean for a couple of days in lacquer thinner, and keep the float valve with the same seat.

The swingarm bushings might be zamac plastic (like mine were) as this appeared until about 2/1972 production on the K2. If so, the edges of it may chip when you wrestle the swingarm collar out. If that happens, I can help out with a swingarm rebuild that will probably outlast you and the bike.

Ah, the K2: zenith of the 750K design, IMHO. Write with any questions, would love to answer back! Send a picture of the tank and side covers, too. Mine are in such nasty condition....the K2 seat foam is unique, having a bead on the seat cover that dipped down along where your thigh presses against it when you are standing still. The cover is still available: I have a genuine K2 foam and cover, don't know if I will ever use it, if you go the stock route. The K0-K2 had the legendary seat foam with the punched-out cores under your tailbones to make the famous "superseat in disguise" as Cycle Magazine called it in 1971. I did many back-to-back-to-back-to-back 1000 mile days on mine before I wore the original one out (in 1984).

As always, thank you for the help HM.
Not sure why, maybe because it first 750 was a K2, but Ive always liked them. I put out a WTB a K2 ad and the rest is history.

I had read that the brown was green paint shot over defective red tanks. My concern with the tank is the old gas and the surface rust inside. Its light, but there. Ill derust it first and see. I haven't taken the side covers off, but they arent cracked. Im going to hit the tabs with silicone spray before trying to gently take them off.

Thank you for the oil change tip. I have a MotoBatt gel battery on another bike that has worked and lasted a few years. Thinking of getting another one. Any opinion on gel batteries?

Im hoping I dont have to do a full carb rebuild. I havent taken the float bowls off and have no idea what the main jet holders look like. They are 657A carbs and I do have a spare set of 657A bodies if needed.

Ive been planning to send you my first K2s swingarm, life got busy for a while. I should send both now. We plan to buy a house soon and once we get settled my other K2 is being taken down to the frame and rebuilt. Its a project Ive wanted to do for a long time. Hopefully get this "new" K2 running while I rebuild my other. Im also considering your key switch saver relay for both 750s. I plan to keep using the round plugs

Regarding the seat. I read your comment to one of my posts the other day about the seat foam. I have 2 seats that need to be rebuilt. I'd rather rebuild them and go stock than buy a new reproduction. You say the seat cover is still available? Where?

Thank you for offering to answer questions, I greatly appreciate it.

VTCBike750 · « **Reply #4 on:** February 16, 2020, 07:34:15 PM »

Quote from: Mark1976 on February 16, 2020, 07:24:03 PM

Good lord, there's nothing like a stock bike from the early 70's, where does the time go. It'll clean up fine and be a real nice ride.

The engine bolt heads arent even messed up. Its never been taken apart. I cant believe its in my garage.

newday777 · « **Reply #5 on:** February 16, 2020, 08:06:44 PM »

Great find you got there indeed.

754 · « **Reply #6 on:** February 16, 2020, 08:31:38 PM »

Mark I thought it was Candy Garnet Brown for 71, Briar brown for 72.

andy750 · « **Reply #7 on:** February 17, 2020, 07:18:51 AM »

Quote from: HondaMan on February 16, 2020, 06:52:08 PM

I have a genuine K2 foam and cover, don't know if I will ever use it, if you go the stock route.

s

If the OP dosent want it HM I am def interested in buying this from you. I already have a stock seat it just needs to be recovered with new foam. I agree the K2 was the zenith of CB750s

Cheers,
Andy

Stev-o · « **Reply #8 on:** February 17, 2020, 07:42:47 AM »

Nice find

PeWe · « **Reply #9 on:** February 17, 2020, 07:59:20 AM »

Good find!
It cost a lot to restore an old CB750 to look like that.
A bike is only original once. This is.

A bike in that nice shape must have a good tank inside with no need of liner, right?
Clean the tank from old fuel, use fresh gasoline or diesel.

I guess the tank cap seal is dry and need to be replaced.

Petcock o- rings a good idea to replace too.

MauiK3 · « **Reply #10 on:** February 17, 2020, 08:37:38 AM »

The Yamiya body kit is first rate, I did tank, headlight, for ears and side covers.
Keep your original stuff though. It's original and in good shape.
Beautiful bike.

VTCBike750 · « **Reply #11 on:** February 17, 2020, 10:46:28 AM »

Quote from: PeWe on February 17, 2020, 07:59:20 AM

Good find!
It cost a lot to restore an old CB750 to look like that.
A bike is only original once. This is.

A bike in that nice shape must have a good tank inside with no need of liner, right?
Clean the tank from old fuel, use fresh gasoline or diesel.

I guess the tank cap seal is dry and need to be replaced.

Petcock o- rings a good idea to replace too.

There's surface rust on the inside of the tank from it being partially filled with fuel for the last 25 years. Plan is to clean it out, use Evaporust to treat the tank and see how it looks.

The tank cap seal is dry and needs to be replaced.

VTCBike750 · « **Reply #12 on:** February 17, 2020, 10:49:00 AM »

Quote from: MauiK3 on February 17, 2020, 08:37:38 AM

The Yamiya body kit is first rate, I did tank, headlight, for ears and side covers.
Keep your original stuff though. It's original and in good shape.
Beautiful bike.

That's good to hear about yamiya's body. If I take these off the bike Ill keep them. Never seen an old side cover that isnt cracked. This one has 2 uncracked ones. Badges look good too

PeWe · « **Reply #13 on:** February 17, 2020, 11:23:09 AM »

Rust remover should be the first step to save tank stored dry. It might be enough.

VTCBike750 · « **Reply #14 on:** February 17, 2020, 03:13:04 PM »

Quote from: PeWe on February 17, 2020, 11:23:09 AM

Rust remover should be the first step to save tank stored dry. It might be enough.

Removed the gas tank and drained the 1/2 gallon of old gas out of the tank resembling the color of an Amber Ale. Petcock was still in the on position, fuel lines filled. Can only imagine what the carbs are like.

Tank isnt the best but not terrible. Currently soaking in Evaporust

Opened the seat and found the original toolkit with red handled screw driver and inspection paperwork from the previous owner. Hit the rubber grommets holding the side covers on with silicone spray, they're starting to loosen up.

VTCBike750 · « **Reply #15 on:** February 17, 2020, 05:38:14 PM »

Popped off the float bowls, carbs arent terrible. A lot of fine gray seditment on the bottom of the bowls. They should clean up easily.

VTCBike750 · « **Reply #16 on:** February 17, 2020, 05:47:19 PM »

I wish I knew how to weld!

Taking a further look at the bike, I took the points cover off and instantly a screw didnt feel right. Half the threads holding the bottom bolt are broken off and fixed with silicone. Not really sure where Im taking this build, full restoration or an as is survivor, but I would like to have this properly welded.

Any ideas the best/proper way to fix this? Not JB weld. Need to source a good place in town who can weld aluminum.

scottly · « **Reply #17 on:** February 17, 2020, 07:11:38 PM »

That's the threads that hold the points cover, not the points plate, correct? My K1 has similar damage to the cover threads after a suicidal coyote jammed his head into the cover when I was traveling a 60 MPH.

VTCBike750 · « **Reply #18 on:** February 17, 2020, 07:30:00 PM »

Quote from: scottly on February 17, 2020, 07:11:38 PM

That's the threads that hold the points cover, not the points plate, correct? My K1 has similar damage to the cover threads after a suicidal coyote jammed his head into the cover when I was traveling a 60 MPH.

Correct, the points cover, not the plate. Edited my previous post.

What happened to the coyote?

scottly · « **Reply #19 on:** February 17, 2020, 07:48:43 PM »

My buddies that were behind me said he twitched once or twice, then was dead as a door nail. The point is, as long as there is enough thread to hold the cover on, it's not an issue.

754 · « **Reply #20 on:** February 17, 2020, 08:42:50 PM »

That is one area to always check, lucky its not at the cover sealing surface. I would put a 5mm ? Rod or drill in there, try to HB weld and carefully retap.
If you buy a body kit, what colorv? My first 750 wasa gold 72.. I have that color on my 74 now.

PeWe · « **Reply #21 on:** February 17, 2020, 09:03:04 PM »

My K2 engine build has same thread damage. There was some threads further in that was complete.
So I used a longer M6 bolt sprayed with teflon spray that dried, aligned it correctly and kept it aligned with block down missing piece up, a jar parked against bolt that could not move and filled the gap with JB Weld.

Bolt helped to shape missing threads. I needed to add JB Weld a few times to build up the thickness.

It should work now for the ignition cover. Not tighten too hard. Use long bolt filling the entire thread depth.

Surface filed flat after photo was taken. M6 tap carefully screwed down to bottom. Beginning of hole coned slightly by hand using a 10mm drill.

Maybe possible to see the damaged thread on this photo, up right beside Motul label. There is a piece missing.

VTCBike750 · « **Reply #22 on:** February 18, 2020, 05:26:44 AM »

Quote from: 754 on February 17, 2020, 08:42:50 PM

That is one area to always check, lucky its not at the cover sealing surface. I would put a 5mm ? Rod or drill in there, try to HB weld and carefully retap.
If you buy a body kit, what color? My first 750 wasa gold 72.. I have that color on my 74 now.

Yeah I looked over the cases before buying it, but didn't popped off the cover. I did removed the sprocket cover and check for chain damage. All good there.

As far as a yamiya body kit. Ill need 2 body kits. One for my other K2 and this one. I'm leaning towards Sunrise flake orange for my other K2. That was it's original color. For this K2, Im thinking Silver. I know it's not A US color, but always thought it looked great. My kids want it to be red.

scrambler · « **Reply #23 on:** February 18, 2020, 10:22:06 AM »

I`d get it fixed properly, this bike is really worth spending more time and money on. A good welder can fill that up and you can drill and retap. I dropped the case of my K1 and two pieces broke off close to where the damage is on yours. I found a welder nearby and he welded the two pieces back on pretty nicely for $40. My cases were apart though.

Quote from: VTCBike750 on February 17, 2020, 05:47:19 PM

I wish I knew how to weld!

Taking a further look at the bike, I took the points cover off and instantly a screw didnt feel right. Half the threads holding the bottom bolt are broken off and fixed with silicone. Not really sure where Im taking this build, full restoration or an as is survivor, but I would like to have this properly welded.

Any ideas the best/proper way to fix this? Not JB weld. Need to source a good place in town who can weld aluminum.

HondaMan · « **Reply #24 on:** February 19, 2020, 05:59:37 PM »

Quote from: VTCBike750 on February 17, 2020, 05:47:19 PM

I wish I knew how to weld!

Taking a further look at the bike, I took the points cover off and instantly a screw didnt feel right. Half the threads holding the bottom bolt are broken off and fixed with silicone. Not really sure where Im taking this build, full restoration or an as is survivor, but I would like to have this properly welded.

Any ideas the best/proper way to fix this? Not JB weld. Need to source a good place in town who can weld aluminum.

That happens when the bike goes down on the right side. The screw breaks out the thread housing. I get the area welded up, then file the face flat like it was, then redrill and tap it again, good as new! More common, though, is the rear screw threads for the back of the sprocket cover - but just as simple to fix back up.

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Author Topic: Brought home a K2 today (Read 4524 times)