CB 750?

I'm going to look at a CB 750 for sale this week and was just wondering how similar they are to my XJ as far as things to check in the pre-buy. Also, the engine is out at the time. Is it possible to do a compression test without the bike running? I know you can on an aircraft, not sure if the procedure is transferable... Thanks for the help!

 

Any idea how much he is wanting?

 

A Honda CB 750 is a 4 cylinder with one major difference, it has only one camshaft. Another difference is it does not have constant velocity carbs and the primary drive is chain instead of gear. Other than that they are much alike.

 

before 78 or 9 they were sohc after that they were dohc just like the yamaha but chain drive and a bit slower. They are a bigger bike with a taller seat height and all the dohc have cv carbs. There was the f model was kinda like the seca and the k 4 pipe kinda like the maxim

 

It's a '75 model so I guess that's the SOHC then. I've got a 550 Maxim so I'm used to the chain drive (I'll never go shafty ). He's asking 300 bucks, but it's all disassembled. I haven't seen the pile yet, just a couple shots of the engine and frame (which has been hardtailed and raked already, looks like a good starting point). As far as the carbs go, if they aren't CV would that eliminate some of the problems people have on the XJs with aftermarket intake/exhaust systems? Thanks again!

 

As long as the engine isn't disassembled, and the starter is in place (or it has a kick-starter), you can compression test. Put any 12V source on the starter and it'll turn the engine. Something like a car jump starter works great, because they have a switch on them.

If I'm not mistaken, cb750s are popular bikes, so even if it's a dud you could probably profit selling it for parts...

 

That's how you do a compression test. As long as you can spin the motor, you can test it.

 

XJPilot, I'm curious, what issues do you have with shaft drive? To me it's like someone doesn't like cell phones because they are used to the rotary dial. If it's a preference thing, OK but maybe you are just misinformed. My first bike was a chain drive Honda 350 and it did it's job; but then I got a BMW 750 and it was so much nicer with a shaft drive. Please don't assume I'm bustin' yer ba**ls, just curious. I would appreciate a response, thank you.

 

I can tell you why I'M not a big shaft-drive enthusiast; but my reasons are likely different than his:

-Unnecessary, from a pure engineering standpoint. Chain drive transfers crank/transmission rotation directly (as in the same direction) to the rear wheel; a shaft drive has to change the "drive angle" by 90 degrees, spin the shaft, then transfer it back 90 degrees again. No real need from a power transmission standpoint, and inherently inefficient by comparison.

-As a result, excess weight. My 650 Seca weighs about 100lb more than my 550 Secas; most of that is the "middle gear" box, shaft, and final drive assemblies.

-Adverse effect on handling, via "jacking" from the driveshaft. This is inherent in a shaft drive; yes, some manufacturers have dealt with it better than others, but it's still there. Not so with chain drive. This is the reason that most "serious" high-performance sportbikes over the years have been chain driven and still are (I realize there are exceptions.)

Those are MY reasons, and I even own one. Let's see what OP has to say...

 

You can do a lot to those old 750s, check out this web site.
http://www.cyclexchange.net/index.html

 

I don't know, I guess I'm just weird, I like the jacking effect and use it to my advantage; in curves when you roll on the throttle you gain ground clearance Clarance.

 

Fitz, if they built the 650, 750, 900, 1100, with a chain drive, that is what I would buy, but..............................

 

I once bought a 750 four banger CB. The guy that owned it before me had done a lot of custom work on it with turn out mufflers, custom tank ect. but he couldn't get it to stop Poppin and Pissin so he sold it to me for $300. I didled with it all winter and finally got it straightened out with my stick for tuning the carbs. The old style with mercury in the tubes. It was a fast machine, dumped me once, actually the first time I rode it, dumped me going right out my garage door. Had very quick throttle responce! I liked it but the next morning a man came to my door offering me $1,300.00 for it and I took it. I never saw the bike or the guy again and to this day I don't even know how he knew I had the bike but that $1,300.00 cash bucks in my hand sure made my day. I still have a picture of the bike some where which I would show you but I still don't know how to get a picture on here. grunt007, XJ Seca750 R, Mi. I sort of am sorry now though that I sold that bike.

 

Ok, just wanted to make sure I could still do a comp test. LVSteve, the chain drive is strictly a personal preference. I've researched the pros and cons, I've rode both, but I just like the nostalgia of a chain drive, the way God intended haha. I meant no offense by it tho

 

No offense taken XJ, I see your point. I think I like shaft drive because it's exotic, maybe futuristic, just look at the final drive on an XJ 900 and you can see what I mean.

 

Like you say a matter of preference,for me a shaft is quieter,cleaner and the only time I touch the rear wheel is to change a tyre.Changing the diff oil is a 5 minute task.

 

Had a honda 750 single cam, did a lot of k's on it, never let me down fond memories of th time we spent together. Followed by th xj , apart from it's youth at th time, shaft drive appealed. Had done a lot of sprockets, chains, adjusted, oiled,replaced etc.. maybe 80lbs of scrap metal..th difference between xj chain and shaft. Now..check th diff' by wiping finger across th bottom, no oil leaks..must be ok.

Hope you enjoy the cb.