Author Topic: Advice on buying a CB750 (Read 6162 times)

NP3 · « **on:** September 28, 2011, 01:35:17 PM »

Hey everyone,

I've been reading the posts and various materials on this site and have been impressed with the amount of member's knowledge, support, and resources. So, I want in! I've been considering building a cafe racer for some time now, and I think starting with a Honda CB platform makes perfect sense.

I've always been mechanically inclined, although it's not what I do for a living. I think with the little knowledge I have, the ambition, and the help of everyone here, I can accomplish what I'm after.

I have been searching for a CB to purchase and found an add of someone selling a '76 CB750K near my area. The add states that the bike was purchased from the original owner, engine doesn't turn over, and have title in hand. The price is $500.

From the pictures, the bike actually doesn't look like it's in bad shape. Little visible rust, all the parts are there, and needs a new seat. My concern is "engine doesn't turn over". I'm guessing this means it is seized. I have full intentions of rebuilding the motor, but is there anything I should be aware of; anything that is common and irreperable when it comes to seized CB motors? Obviously, no deal if a connecting rod is hanging out of the side of the motor, but is there anything that is less obvious? Anything else in general that I should look out for that might make this a deal breaker.

Thanks,

Nik

phil71 · « **Reply #1 on:** September 28, 2011, 02:20:38 PM »

people often say 'doesn't turn over' when they simply mean 'doesn't start', it's just a terminology gap. You might get lucky and it not be stuck at all! The biggest advice I can offer about these is that they were remarkably trouble free and hard to break. ALWAYS start from the simplest possibly cause and work your way towards the complicated ones.
Let us know what you see, when you see it! Good luck.

seanbarney41 · « **Reply #2 on:** September 28, 2011, 02:36:54 PM »

...my advice to you if this would be your first old bike, and especially if this is your first bike of any kind...spend a few extra hundred and get something that, at least runs...really, you should try and get the best bike you can afford...your gonna have tons of fun just keeping an old bike maintained, safe, and reliable...then you can learn to actually ride the dang thing and know what it needs to improve it, 'cuz really, cafe bikes should not be just another custom build style...check some prices on engine rebuild 'cuz these little motors ain't no small block chevy...also, I didn't notice where you are located and prices vary wildly depending on region, but in my neck of the woods $500 ain't that great a price for a seized bike...

jmo
Sean

Tugboat · « **Reply #3 on:** September 28, 2011, 02:40:22 PM »

KRONUS0100 · « **Reply #4 on:** September 28, 2011, 04:27:50 PM »

+1 to all above

NP3 · « **Reply #5 on:** September 28, 2011, 05:21:36 PM »

I'm hoping that "doesn't turn over" means that the engine doesn't start and not that the motor is seized. I called the phone number listed in the add and left a message, so we'll see what the story is if I get a call back.

This is going to be my first old bike. I currently own an '09 Yamaha R6, and have owned an '04 Honda CBR600RR, but I really like the CB750 mainly because of simplicity, availability of parts, and customizing options. I'm really looking for a project, so I'm not looking for a running motor. But, I was hoping to at least get a motor that turns over and is not seized. However, if the motor is seized, worst case, what might it take to get it back to running? Ideally, I'd like to keep most of the motor. I'd like to avoid major service that I wouldn't be able to do myself (i.e. cylinder boring, complete cylinder head rebuild). I am prepared to open the engine to remove carbon deposits, replace all gaskets, cylinder honing, valve lapping, piston ring replacement, and other things I can do myself.

As far as price goes, I haven't been able to find anything as low as $500, except 1 add for $50, which gets you a '71 CB750K frame, seized engine, trans, and wheels. Here are a couple of pics of the '76 for $500 that I've been talking about. I'm not sure how much you are able to tell from these, but it's better than no pics. Plus, I'm still waiting for the owner to get back to my questions.

Thanks for the advice so far guys. Keep it coming.

Stev-o · « **Reply #6 on:** September 28, 2011, 09:18:19 PM »

First off, welcome!

I recently bought a bike very similar to the one you are looking at. But, it has a nice, recent paint job and it runs. Paid $600.

Make an offer or keep shopping.

NP3 · « **Reply #7 on:** September 29, 2011, 10:29:29 AM »

Here is another one that I found: 1979 CB750. $750, but this one runs. Only thing is it's a 1979. How are these different from the earlier models? Are they less reliable, less desirable, built different, etc? I noticed this '79 is still SOHC. I know that after '79, CBs went to DOHC, which are considerably cheaper to purchase in the adds that I've seen. But, I'm specifically after a SOHC.

Tugboat · « **Reply #8 on:** September 29, 2011, 10:33:10 AM »

That's acutally a 77-78 F bike.

78whiteorbs · « **Reply #9 on:** September 29, 2011, 10:55:27 AM »

+1 Keep shopping, find a ugly runner with a title or at least one that just doesnt start and has good compression. I recently gave 200$ for a 73' with a clear title , that wouldnt start. I cleaned the carbs popped in a fresh battery and this is the best running CB I have ever owned .

also F's are nice in the fact that they have the triple disk brakes which is a leg up. If you are gonna do some remodeling anyways go for it !

Stev-o · « **Reply #10 on:** September 29, 2011, 05:00:14 PM »

Yes, that is an F model, last year made was '78. It was probably titled in '79, hence the owner thinking it.
The F's are good bikes, not as popular as the K models. They are good bikes to Cafe. Note it has the Comstar wheels, rather than spokes.
Go look at it and ride it and see if you feel for it!

Click here for more model info:

http://www.sohc4.net/?p=36

BobbyR · « **Reply #11 on:** September 29, 2011, 05:53:53 PM »

The first thing I did when I went to look at my bike, a $100 get it out of here deal. I pushed down on the kickstarter and the motor moved, I knew I had something to work with. There is enough work to do on these without tearing into a torn up motor. King is right, with a seized motor, $125 and use the parts for the bike you are gong to restore/customize.

NP3 · « **Reply #12 on:** September 29, 2011, 06:52:44 PM »

Thanks for the advice. I think I might go and check out this CB750F. If it's in decent condition, maybe I can talk the guy down a bit from $750. I was a little bit hesitant at first about considering an F over a K because I was concerned about parts availability. But, I've looked around and it looks like most F and K parts are interchangable, and if not, both models have plenty of aftermarket support.

Stev-o - good point on the wheels, I did notice those. I like the spokes better, but I guess I can live with comstars if the bike is a good deal.

78whiteorbs - I did not know about the triple disc brakes, and those are definitely a nice bonus.

MCRider · « **Reply #13 on:** September 29, 2011, 07:16:35 PM »

Quote from: Tugboat on September 29, 2011, 10:33:10 AM

That's acutally a 77-78 F bike.

Yeah it was leftover in dealer inventory, sold and titled in 79.

the technological J · « **Reply #14 on:** September 29, 2011, 07:23:26 PM »

if you end up going with the 78 f i would love to trade you wheels if you want a spoke set.. ill even throw in an extra set..

things to look for on the non runner would be condition of the fork gators(the rubber over the forks they can dry out and tear and also can hold water and rust the forks(150ish).... most likely you'll have to replace all the seals besides just the gaskets like the shifter seal and the clutch seal(close to 100 for both)... possible things that need rebuilt are the oil pumps and the hopefully not the cam chain because that will have you open up the bottom end..... if your comfortable putting another 5 or 600 into her outside of the mods you wanna do go for it.. that is if it kicks and moves... if the engine is siezed you can count on a rebore and a larger set of pistons (theres an awesome deal on ebay for some 836s right now only 110.... well worth it) but then you'll prob wanna port and deal with carb jetting.. oh yah a carb rebuild is around 40 bucks also... plus what ever else you run into like electrical issues... i would bring a battery and some starting fluid..if she turns give her a little either and see if she sputters....
thats all worst case scenario but likely on a non runner... i dont think its too much at all if your up for the project and with the help of this forum you could have her on the road by spring!

Good luck you could prob get both bikes for cheaper though

ekpent · « **Reply #15 on:** September 30, 2011, 05:19:20 AM »

If the 77-78 F bike you are going to look at smokes at all, blue - white smoke not black or has high mileage tread carefully. That particular model has a history of excessive valve guide wear and things could get expensive or labor intensive in a hurry. If your looking for your first 750 I think you should stay with a K model.

NP3 · « **Reply #16 on:** October 02, 2011, 04:25:07 PM »

Ok, so after a lot of searching, some patience, a little luck, and some good advice from the folks here, I ended up with this bike: 1978 CB750k for $595. The bike needs a lot of work, as you can see. But, when I went to check out the bike, I hooked up a battery, sprayed some starter fluid in the carbs, hit the electric start and the bike cranked over. Gave it a little choke and the bike started and ran for a little bit. It sputtered most of the time, RPMs kept coming down, and it really wanted to shut off, but the important thing is the motor turns over and has good compression. It definitely needs a new battery and a good carb refresh.

Someone at some point put a Harley Sportster seat on it, which will be coming off. Also, someone welded highway bars (I think that's what they're called) to the frame in front of the motor, those too will be coming off and the frame cleaned up.

One downside is that the PO did not have a title. I got a weak bill of sale from him, but I don't know how much clout that has at the DMV. The guy I bought the bike from was actually in the process of getting a new title, and he says the owner before him simply lost the title. So, he had the police run the VIN and it came up clean. He is actually going to the DMV tomorrow to see how to go about getting a new title. He said even though he sold the bike, he's going to keep that appointment and give me a call to let me know how he made out. I have little faith and it will most likely be up to me to title this bike once I'm ready to put it on the road.

For now, I'm happy to have a good base to start my project. I think I got a pretty good bike for the buck. Let me know what you guys think.

BobbyR · « **Reply #17 on:** October 02, 2011, 04:59:26 PM »

Nice bike. I have a 78K also, so i know some of it;s quirks. You have an accel pump on the carbs which unique to 77-78 so they take some additional attention. Change the oil, replace the plugs and you need some air filtration, those stacks will give you heartburn.

the technological J · « **Reply #18 on:** October 02, 2011, 06:56:52 PM »

bikes not too bad i hope the titling isnt a nightmare.... whats that exaust? it would look pretty sweet wrapped in some exaust wrap back to that weld by the hanger.... theres a thread on here that some one is selling side covers if you end up going that route

Stev-o · « **Reply #19 on:** October 02, 2011, 07:21:25 PM »

The bike looks good! Give it the full 3000 mile tune up. And call the DMV yourself tomorrow and ask exactly what needs to be done.
In Texas, it's not a big deal to get a bonded title, about $150.

Good luck!

NP3 · « **Reply #20 on:** October 07, 2011, 12:33:44 PM »

Bobby - Yes, those stacks will be out. Ideally, I'd like to find a stock box and not worry about some of the headaches associated with pods.

the tech... - the exhaust looks better in pictures than it does in person. I have no idea what it is, but it sounds terrible. I will most likely be replacing it. And, I will look around for that side covers thread. I plan on keeping the oil tank and electrical where it is, so I definitely need new side covers.

About the title. In NJ, the only way to get a new title in my name is by court order. But, I first have to show and provide documents proving that I have confirmed with the local police that the motorcycle VIN is clean and that the bike has not been reported stolen, and I also have to initiate an "owner of record search" through the DMV. If the police check is clean and DMV search yields no results, you can then ask for a court order, and I have no idea if that means showing up in front of a judge to explain or simply filling out a form and mailing in the supporting documents. I hope it's the later and that it's straightforward. I mean, it's a 1978 that I got for $600. It's not a 2010 bike worth $10k. I would think this sort of thing is common for older bikes.

Cheffish · « **Reply #21 on:** October 07, 2011, 02:44:22 PM »

Welcome aboard! It looks like you got a great deal. Good luck with the title

Really? · « **Reply #22 on:** October 07, 2011, 05:34:30 PM »

I hate you guys sometimes!!!!!

Y'all find such good deals!

the technological J · « **Reply #23 on:** October 07, 2011, 10:37:02 PM »

heres that side cover thread
http://forums.sohc4.net/index.php?topic=74022.msg822417#msg822417

i would like to hear the bike run with that exaust... you might not be used to the cb sound yet or the engine might be outta tune and not sound right.. but that exaust should sound pretty interesting....... take a vid of her running from about 25 feet behind the bike.. get her warmed up and running well

NP3 · « **Reply #24 on:** October 08, 2011, 06:22:14 PM »

the tech - you read my mind. I made these videos with my phone and loaded then to YouTube. The quality may not be the best, but hopefully you can get something out of them.

I installed a new battery, new plugs, and cleaned the carbs. When I first picked up the bike, it would turn over, start, but bog down right away, and shut off completely as soon as you though about touching the throttle. As you can see from the videos, I managed to get it running and idling ok. I don't know what CBs are supposed to sound like, but it sounds rough to me. I'm going to go trough the ignition the next round.

Let me know if you can tell anything from these videos.

At idle: 1978 Honda CB750K at idle

With throttle: 1978 Honda CB750K with throttle

That's my dad whaling on the throttle and messing with the blinkers in the videos. He's in love with the bike, and won't leave me alone when I'm working on it. It's kind of nice. My generation is only used to fuel injection and he has quite a bit of experience with carburetors from owning older bikes back when, so I appreciate his help and I'm glad he's enjoying the bike too.

Stev-o · « **Reply #25 on:** October 08, 2011, 06:42:25 PM »

Sounds good, idle might be a little high...

the technological J · « **Reply #26 on:** October 08, 2011, 06:53:44 PM »

i cant really tell you should stand about 20 feet behind and redo the rev vid.... do you have any exaust leaks? and the idle sounds a little high... take it almost as low as it can go...

NP3 · « **Reply #27 on:** October 09, 2011, 11:03:41 AM »

Alright guys, here are some better videos.

The first video is taken just as I started the bike. The engine is cold, choke lever all the way up, and the engine is idling at about 1,500 RPM. If you apply steady throttle, the RPMs climb gradually. Abrupt throttle results in the motor flattening out and almost shutting off. The exhaust system on there is wide open, no baffle or muffler, and remember that the carbs only have those stacks and no filter. I'm not sure that the PO paid any attention to the jets, so I think the stacks, open exhaust, and stock jets are not the greatest combo. You can hear the bike struggling at the end of the first video and in fact it shuts off just as I stopped recording.

In the second video, the engine is warm, choke lever is all the way down, and the engine idles at about 1,200 RPM. I lowered the idle to about 1,000 RPM, and it sounds like anything lower would cause the bike to just shut off. Motor is still flattening out at throttle, but not as bad as when the engine is cold.

Also, there is a crack in the exhaust. I attached a pic, you can see the crack right in front of the weld.

Video 1: Cold Idle

1978 Honda CB750K, cold idle, full choke

Video 2: Warm Idle

1978 Honda CB750K, warm idle, no choke

Stev-o · « **Reply #28 on:** October 09, 2011, 11:17:47 AM »

Warm idle sounds good, actually surprising good since you have stacks and no baffle (no back pressure).
I wouldn't be concerned about the old idle, they don't always like to run cold, but do warm up quick.
I would get the crack welded and get a baffle in there. And you have an air box, right?
That bike is gonna be a good runner!

NP3 · « **Reply #29 on:** October 10, 2011, 12:46:09 PM »

No, Stev-o, I don't have an airbox, yet. Actually, I'm missing quite a few things that I'll have to pick up. I started taking some of the bike apart. I focused on the front brakes to start. I'm having to drill out every 2nd bolt. But, I guess that's part of the fun.

the technological J · « **Reply #30 on:** October 10, 2011, 01:21:34 PM »

use a number 3 head on the phillips screws.... if i feel its gonna strip i crack it real good with a hammer and try again

NP3 · « **Reply #31 on:** October 10, 2011, 02:59:47 PM »

Hey guys, I need a little bit of help with my brakes. I've loaded some shots of one side of my caliper for reference. In short, my piston is shot, and I wanted to change it as well as the seal. I've been looking for a piston for a '78 CB750K, but all I find are pistons that fit K models up to 1976. Are the 77-78 K model's brakes the same as the previous years? The calipers on my '78, look just like those on prior year models. The same goes for the master cylinder rebuild kit; I find that they fit 69-76 K models, and then I can't find anything for 77-78 K models.

One more thing; any advice on how to remove the C-clip holding my master cylinder plunger in place, if the C-clip is rusted and one of the holes to fit the C-clip pliers is broken off?

the technological J · « **Reply #32 on:** October 10, 2011, 05:54:17 PM »

i had a pick set that I used... i put the point down in the one hole and kinda wrenched it outta there

Cheffish · « **Reply #33 on:** October 10, 2011, 06:00:30 PM »

Looks like the pistons are different. Here they are side by Side
http://charlies-place.com/PAGES/Store/store_brake_pistons.html

jaguar · « **Reply #34 on:** October 11, 2011, 08:55:45 AM »

best advice is to buy the best bike that you can afford.
If you are searching for the cheapest bike then you get what you pay for. After time and knowledge you will be able to weed through tons of listings and find good deals but for now the goal should be to get a bike and ride. Its winter soon so something that needs some work is fine....but locked up, seized, not turning over is more then just alittle work. Sure there are stories of people getting lucky and with a can of WD40 they rode it cross country.....and others bought sandcasts for $100.....yes it happens but lets be realistic.

An old bike will give you plenty of things to mend or chances to learn how to work on a bike. If you have to ask how bad a seized engine is fix chances are you are not up to that....its not a bad place as everyone starts some place but if you get in over your head then you will be spending tons of money and having no fun.....this should be fun above all.

What is your realistic budget for everything?
ill tell you this.....buying a $500 bike and then putting a grand into is will normally net a bike that is not as good as if you had just spent the whole $1500 on the bike in the first place. this is because the guy selling the $1500 is $2500 into it.....

you are in north NJ?
Phil has a 78K bike that runs and is cheap. needs some work but might be be a good place to start for you.
Im on long island and can help if you need it

NP3 · « **Reply #35 on:** October 12, 2011, 04:36:08 AM »

King and the tech... - thanks for the advice about getting the beat up screws and bolts out. I'll definitely use that technique.

Cheffish - great link, that's exactly what i was looking for!

Jaguar - thank you, these are all solid points. I did end up scrapping the idea of buying a seized bike and I ended up getting a 78k that I cleaned up a bit and got it running. Still needs some work, but its been fun and I look forward to continue the work on it.

News:

Author Topic: Advice on buying a CB750 (Read 6162 times)