CB750 --- DOHC vs SOHC?

[BCBarker]

Still looking for that next project... The CA95 lady still wants way to much and won't detach her emotional connection. She thinks it's worth half of what a restored one is going for and that giving it to me for 300 is a deal! NOT!

But I've found another possibility! Since I'm a cheapskate and I've never paid more that $25 for a bike, I was wondering if you all thought this was worth it...

1980 cb750F DOHC $200
Missing side covers and air filters. Bonus would be the flat bars!

CRUSTY with no title... owner says it ran 6 months ago.. I honestly have never heard anything about the DOHC CB750s... Any major issues that would make this a crappy project? I have read that the 78 CB750F is the best "late model" to get because if it's head design.... but it's a SOHC... So should I?

 

[Tim]

Actually if memory serves me, the 1978 CB750F's head was a problem, not a benefit.

That being said I prefer the SOHC Honda's. For $200 or so you should be looking for a bike that hasn't been sitting outdoors for long periods of time. Plenty out there - don't rush yourself. You're better off spending $500 on something that's in way better physical condition than to spend $200 on a rusty hulk.

Things like replacing rusty rims/spokes, fork tubes, nuts and bolts add up $$$ really really quickly.

 

[VonYinzer]

I hate to say it, but the later years of the 750 were not great... The DOHC models could be built into nice bikes, and werent bad bikes really. They just werent great. In researching my 77' 750 ive found that the DOHC models were somewhat less reliable, and actually made less power than earlier models. That combined with the cost of replacing/rebuilding all those rusty parts will kill ya in the end. Tims right on point in saying that you could find yourself a better starting point. Sorry man. Theres tons of killer bikes out there on the cheap though. Keep on searching and youll find one. Last year I picked up a killer 72cb500k1 for next to nothing. It was lighter, easier to work on, nearly as fast, and handled better than a 750 (magazines of the day actually called it a better bike all around). Keep your eyes open and youll find something nice. Everyone goes goofy over the 750s which makes them pricey. Look for something else that isnt so high up on the "must have" list.

 

[boingk]

Never understood the hype around the 750's either, although the SOHC engine is quite pretty IMO.

I've heard that Honda weren't too good with their DOHC conversion, and that Suzuki and Kawasaki were somewhat better in that regard. I've also heard that you can tune the GS bikes more heavily if that is your thing.

Go for another bike, but if you'll be stripping the whole thing anyway then ask the guy if he'll take $100.

Cheers - boingk

 

[Swagger]

Having owned both, SOHC and DOHC in the 750cc variant, there's simply no comparison.

The SOHC is an iconic bike, it was the first real superbike though there are some crusty limeys that'll squawk about the 750 Nortons but that's not really relevant. It's well supported by the aftermarket and anyone who was around and or riding age in the late 60's/early 70's still holds some lust over them. They are nostalgic....like an old rusty car that someone remembers getting laid in back in highschool. More myth than reality. I've heard guys squaring off and demanding to be taken seriously when they tell stories of smoking their neighbor's FZR750 plastic bike. Yeah....I laughed too.

The DOHC 750 is a logical extension of the older lump with a dramatically better engine. Sorry to all the SOHC guys......but it's true. Far better flow thru the entire system, easier revving, higher revving and more horsepower, electronic ignition yada yada yada. Generally speaking the Japanese aren't known for NOT improving bikes over the progression of it's model run. Yes I know there are always exceptions but this is not one of them.

DOHC: http://www.bikez.com/motorcycles/honda_cb_750_f_1983.php

SOHC: http://www.bikez.com/motorcycles/honda_cb_750_f_1971.php

Both bikes are old enough to easily be nostalgic and vintage racers which is what we're all mostly emulating here anyway. Both when stripped down to the level that most here do will run around 450 pounds give or take your level of commitment and insanity and that extra 10 ponies will always be welcome, never mind the far more developed chassis design.......

 

[jonescafe72]

If your heart isn't set on the 750, there's a CB350 in a little better shape here in the middle of southern Kansas that can be had for a mere $100. I can post pics if you want. It's not mine, but I know where it is.

 

[BCBarker]

I appreciate it but I already have a 350f stocker and a 350-k4 cafe. If I get another 350, I'll have to bob it... And I think I want something bigger and faster. I'd be up for a 500F, 550F, or a 750F... Plus Kansas is a two day drive!

Tempting though!

 

[BCBarker]

Re: CB750 --- DOHC vs SOHC now a '74 550F?? Know anything about em?

AS luck would have it, I passes on the '80 750F, and now I found 2 CB550's up for sale.. I was hoping for something with comstars... but maybe I can find some and make them work. I just think they look cool.. Plus no tubes right?

Anyway, If I get them (which I most likely will) I'll have spare parts. If you need anything Let me know! I'd love to make a little to pay for the initial purchase!

BCBarker

 

[Swagger]

As far as I know there are some comstars that require tubes. Worth looking into if that's a requirement. Have fun man!

 

[Swagger]

They are still forged rims, the valve stem hole is different size.
You can fit tubeless tyres but have to use a bolt in valve stem and don't get the MT rim section.
I'm pretty sure there was a service bulltin about it in 78~79

PJ

Well there you go! I dunno where I heard tube/tubeless for Comstars....perhaps it was Geeto?
Hey you probably know.....
are the beads different between tube and tubeless style rims? I never once bothered to look..

 

[crazypj]

Yes, the MT rim has a 'bump' to prevent tyre falling off if you lose pressure.
The other rim is smooth ( makes tyre changing a lot easier)

PJ

 

[BCBarker]

So Comstars are tubeless right? Regardless I think they look cool and want to try and find some that work with a CB550. I don't know the condition of the spoked wheels, but if they are decent they will be up for grabs. I should be picking up the bikes Sunday. I'll let everyone know once they are mine.

BCB

 

[diesel450]

Hey, I know you're off the '80 750 but just to follow up. they changed the frame for the DOHC and "cafe" parts, seats in particular are alot harder to find if you want to do a conversion. Though they are starting to come around.

 

[builder]

If your heart isn't set on the 750, there's a CB350 in a little better shape here in the middle of southern Kansas that can be had for a mere $100. I can post pics if you want. It's not mine, but I know where it is.

Is bike really cheap in US?, i cant get any Honda four for less than AU$1000 here in Australia, any condition!

 

[crazypj]

So Comstars are tubeless right? Regardless I think they look cool and want to try and find some that work with a CB550. I don't know the condition of the spoked wheels, but if they are decent they will be up for grabs. I should be picking up the bikes Sunday. I'll let everyone know once they are mine.

BCB

I've got a 2.15x19 reverse spoke Comstar off CB900 or CBX for tubeless tyre. takes a 3.25~4.10 tyre.
I can check if axle diameter is same as 550 (think they are both 15mm?)

PJ

 

[bikeboy]

I've got a 2.15x19 reverse spoke Comstar off CB900 or CBX for tubeless tyre. takes a 3.25~4.10 tyre.
I can check if axle diameter is same as 550 (think they are both 15mm?)

PJ

Fronts are 15mm, rear is 20mm

cheers
ian

 

[DrJ]

So Comstars are tubeless right? Regardless I think they look cool and want to try and find some that work with a CB550.

Comstars look cool? Ya gotta be shittin' me One of the worst looking things Honda ever designed. They were an attempt at mag wheel that was cheap to manufacture and boy did they look cheap. Comstars are so not cafe.

 

[bikeboy]

Comstars look cool? Ya gotta be shittin' me One of the worst looking things Honda ever designed. They were an attempt at mag wheel that was cheap to manufacture and boy did they look cheap. Comstars are so not cafe.

While I agree they are so not cafe, the three-spoke 'boomerangs' look alright on the right bike (like mine ). Never cared too much for the 5-spoke series. Especially the first generation "un-reversed" units.

cheers
ian

 

[VonYinzer]

I gotta side with the Comstars are aweful contingent here... Too each there own and all, but they remind me of the wheels that came on old matchbox cars. There are other options out there for the non spoke set that are pretty cool imo though.
The mags that came on my buddys xs500 are cool as hell. His are unpainted natural finish. Theyll be getting done up though..
NOT HIS BIKE....

Ant the COOLES GODDAMN AFTERMARKET WHEEL OF ALL TIME! It would be a bitch to get em to work with a Honda but...
THE INVADER!!! More of a chopper kinda deal but they are killer.

 

[midnightcafe]

I share your cheapskate attitude. I bought my gs750 for $200, ratty, rusty, you name it!

That said, I'm never doing that again. I mean buying a bike really cheap that needs a lot of work, you end up spending a significant amount that likely outweighs its allure.

No title? add another $300 for title recovery service. Cracked tires? Another $200. Sidecovers for the f model sell quickly, without them the bike's worth less. So far that's a $700 hole on your pocket. $700 can buy you a bike in much better shape.

The DOHC is a great running bike, but plan on keeping the bulky airbox because that motor will NEVER run well with pods. The motor runs too good stock to mess with the intake, carbs are CV and have accelerator pumps which will suffer in performance when you have pods. guys at cb1100f.net are very knowledgeable and are conservative when it comes to intake.

I find the DOHC cb engine hideous in comparison to the SOHC. First generation cam cover is gorgeous, but the dohc is mechanically superior as anyone will tell you (I'm not too knowledgeable on the SOHC mechanical background). It doesn't have a kickstarter- my cb750's starter clutch badly needed a rebuild I used it so much when i was restoring it.

Both motors pale in comparison to any current gen middleweight motor so there's little reason to bicker about the performance aspect. The SOHC bike is the way to go if you're going for the nostalgiac appeal