SOHC vs DOHC

[tenor66]

Hello everyone!

I'm new to the forum and new to motorcycles in general. I'm planning to purchase a CB 750 in the near future and would like to know if there's a general consensus about the SOHC vs the DOHC. Are there advantages and/or disadvantages to owning one over the other? I searched the forum but didn't find anything.

A little bit of background information: I've owned and restored several classic cars in the past and am a capable hobby mechanic. I always wanted to ride a motorcycle and I'm not particularly interested in speed but rather reliability and style. I might decide to do something in the direction of a café racer, but I'm not sure yet.

Thanks so much in advance!

 

[Dave]

The 69-78 SOHC are more reliable and easier to work on.

The 79-82 DOHC offer a little more power and better brakes. They are considered more difficult to maintain because of the vacuum carbs and use of shims for adjusting valve clearance instead of the screw and lock nut type on the SOHC.

It's my belief that it is these reasons that a SOHC in good condition is harder to find then a comparable DOHC.

The main disadvantage of the SOHC is the dual point ignition though there are many available kits to convert it to electronic with a wide array of options to choose from.

The main disadvantage of the DOHC is the lack of a kick starter.

 

[dirtdigger]

http://www.cb750.com/threads/506-SOHC-VS-DOHC

It has actually been discussed several times on here, above is one of the threads from before. It all comes down to personal experience and personal preference. To me there is no comparison I would take a sohc over the dohc every time. Its the grandfather to all the 4 cylinder bikes and I think it is plain and simple the best looking motor out there.

 

[amc49]

The SOHC is the simpler more reliable bike but the DOHC has more parts options available at this time as well as much bigger motors that bolt right in easily. But that makes those heavy in the 750 version as well since they are framed for those much larger motors. So weight offsets the power difference pretty much evenly. The SOHC won't strand you in the middle of nowhere like the DOHC can due to the crap rotor thing. Mine broke a rotor at 3K miles when brand new.

The SOHC being the grandfather like said is a keeper, while the more intense maintenance issues of the 'better' (riiiiight!) DOHC have launched it down the path that Honda has chosen for UJMs today. That being one of mediocrity and easily broken and misunderstood to break it worse to then be pushed outside with the view 'I'll fix it someday' so that it can quietly rejoin nature where it began.

 

[dirtdigger]

I can find far more aftermarket support for the sohc then for the dohc. Stock Honda parts maybe but not aftermarket performance stuff.

 

[tenor66]

Thank you all for the prompt responses. This is all very helpful! Is there a well-known site that sells the electronic ignitions as well as other parts for modification? i.e. Exhausts, gauges, air filters, seats, etc.?

Many thanks!

 

[dirtdigger]

Cyclexchange.net and dynoman.net are the two i use for engine related. cyclex does everything else also for customs, choppers, racing etc. You will have to do some searching if you are looking for oem parts, gauges, seats etc. cb750supply has got alot of the harder to find smaller stuff and they supply alot of aftermarket stuff for discontinued oem stuff. They also hold a monthly giveaway on this forum for free parts.

 

[amc49]

'I can find far more aftermarket support for the sohc then for the dohc.'

I was indeed referring to OEM parts, once the aftermarket figured out how flimsy the DOHC was they pretty much dropped all support after like 5 years. The main support now is the OEM parts that can make one bigger in size as long as the engine families thing is kept in mind again. All kinds of parts available from the aftermarket at first, but dried up pretty quick when nobody won to make publicity. The engines blow up too easy and too hard to build them really big yet dependable like Kaw or Suzi big inch ones, the bore centers were too close together. They spaced them to be about as big as you can get on the 1100 but to race big you had to be able to go 1200+. Puny rods and super long strokes out of the '60s made them break even faster. It takes quite a bit more money to build a high-perf DOHC simply because of all the extra needed parts.

 

[Flogger]

This question is like, what's the best oil? Helmet debates and the like... In most eyes, older is simply more desirable. SOHC is easier to customize but it was replaced by better, newer technology by Honda with a superior bike... I prefer the DOHC...

 

[amc49]

Either is fine as long as one recognizes the limitations of each. In fact one should do due diligence with whatever vehicle he buys to pick up on as much of that as possible. It can make the owner experience so much better......................

 

[madmtnmotors]

I've had my K8 for thirty years and I still like it:

The naysayers are just jealous because the 78's were the fastest!

 

[amc49]

Man I love that picture, it brings back some memories.

After the utter unpredictability of leaving the line on Kawasaki threes I learned to really bomb off the line and my DOHC wouldn't lift short like that in low, only when you went to 2nd. In fact, I left at around 8500-9500 rpm, and the bike was everywhere and pointed in 50 directions until I got to 3rd gear. Hazing the tire bigtime. I actually felt much more comfortable though like that as I always was scared of 500+ lbs. of motorcycle in your teeth, the bike just bit in too hard at lower rpm and snapped up way too quick.

 

[Dave]

Awww! I love riding wheelies. I don't do it on my CB750 but the last time I rode a Ninja 600 I was going through the gears on one wheel while looking underneath my left arm to see where I was going off every stop sign

When I was a kid I used to ride my dirt bike around the neighbor hood (literally, around corners, around the block, all the while on one wheel) trying to look behind/under me to see how close the rear fender was to the street.

 

[amc49]

I did the same on the dirt but there was something psychological about bigger bike and being on concrete I never could really get past in my head. I could ride my Yam YZ250 all day long and wheel in the air more than not. But on dirt only.

Crazy, huh?