Are the DOHC's significantly faster than the SOHC's?

[seestheday]

I just read an article that was talking about an old drag racer that had a heavily modified SOHC in 1978 that he mothballed in 1979 because Honda released the DOHC version and it was already faster stock than his highly tuned/modded SOHC.

I found this surprising considering how the SOHC ones are preferred for the cafe modding.  I guess that is more about looks and simplicity though rather than straight up speed.

I also know that I haven't come close to the numbers that shiney has been able to achieve on his SOHC.  Not that I've tried though.  I have hit 150 KPH (93 MPH) on it ("closed track" of course) and that felt plenty fast for me.  I was nowhere near the redline in 5th and honestly felt like I was at the beginning of the power band.

[TOOLS1]

Maybe stock, but the SOHC is, so much easier to modify, and there are tons of hi-performance parts out there, for it.
TOOLS

[cdaiscool]

Oh they're much faster. Mine tops out at 70 mph. And it's bucking and moaning (not in a good way, either!) about it.



Wait, did you mean when running well?  Got nothing there.

[TOOLS1]

Have, you checked to make sure, you are getting all five gears? It might not be going into fifth.
TOOLS

[seestheday]

For what it's worth, here is a link to the magazine: http://caferacermag.com/

Maybe it only applies to the quarter mile?  

Here is an excerpt from the article:
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Back in the late 1970's, Reverend Jim was a hot-shot on the Deep South motorcycle drag racing scene.  Running a slammed and lowered CB750 Honda with a highly tuned single overhead cam engine, Jim, then in his thirties, had gained a reputation as both a fast man in the quarter-mile and a handy tech with the wrenches.

The winning racer had some big plans in the works during the 1978 season, plans that involved installing a rare and very expensive Goldenrod racing motor into the 1975 Honda.  The engine, featuring light-weight rods, overbore cylinders with high compression pistons and tall cams and a balanced crank, would boost Jim's performance into the realm then held only by Kawasaki's 1000cc Z1.  But technology has a way of usurping even the grandest plans; by the end of that racing season, Honda had introduced its latest CB750 motor, a new, dual-overhead cam model that, in stock trim, could outrun the costly and highly-modified racing motor that Jim had procured.
-------------------

[Re-run]

Well it does have a bit more hp and probably a couple more ft/pd torque but I don't think it was that much faster. Top speed was about the same.
So far, this is all I found http://www.motorcyclespecs.co.za/model/Honda/honda_cb750f_79.htm
This would make them about .3 - .5 seconds faster than a stock sohc f3 I suppose depending on rider as the f3 was a bout a 12.6 second bike.

[Piute]

                          I guess Shane was out of town during that print

http://www.youtube.com/watch?v=87Ca0CtGhro&feature=BFa&list=ULU38Ol4by4Qg


                    Ya might wont to E-mail him and let him know He's down in the puddle still I think

[shinyribs]

Just to clarify things...my achievements are merely claims at this point.We'll call them real when (if) i post the vid


Maybe it's my svelt 230lb figure that allows my bike to run good...or maybe it's just the Susie tank that does the trick...

I have read all sorts of numbers.I've seen the SOHC's rated anywhere from 67-72hp. I keep seeing 78hp for the DOHC. According to my math (which could very well be flawed.If you have a 67hpSOHC and install an836 kit it would probably bump power to around the 78hp mark.Factory hp rating numbers are usually either inflated or sand bagged.Who knows really. There is a chassis dyno nearby that I can get on for $50 and hour.provided i do my own tuning.Tuning costs more.Thats cool...dont touch my bike anyways! I plan on getting some numbers one day to see whats really up.

[Piute]

                                          Plan to get a couple new
                                 slips myself once she at the top of her game
                               Most I know gotta have the paper
                       or ya trying to hard on public streets make me / U 1 of thoughs ..A -

[shinyribs]

I hear ya.I cant afford no tickets.And slips are always fun

[cdaiscool]

Yes I have. I counted the gears, and the RPMs drop a thousand or more between gears.

[TOOLS1]

Are, you saying the bike will not rev up in the higher gears?
TOOLS

[seestheday]

I'm definitely getting all 5 gears.  Like I said though, I feel like there is a lot left to go after 150 - I just don't want to go there.

-----

Edit - Whoops, I didn't know that Tools was talking to cdaiscool.  

[Re-run]

I dont think you are going to go 150mph or are you talking kph?
Top speed was supposedly 125 mph.

[seestheday]

Yep, I meant 150 kph (93 mph).  If I had to guess I'd say that I could probably get it close to 125 mph.  Don't think I ever will though.  Far too fast for me on a 30+ year old bike.

Heck, if I was doing 150 kph on the street that is 50 kph over any speed limit here and that is an instant street racing charge.  Instant license suspension, immediately impounded vehicle (7 days), possible vehicle seizure depending on the judge, minimum $2,000 fine.  Maximum 6 month jail time.

Don't speed in Ontario.  

[Rusty Spokes]

Stock for stock, as in sohc vs dohc, dohc pull harder. After that, it just depends how much cash you got to modify. Also, you can't modify all dohc's but IMO KZ1000's, are the best for moding! That SOHC video nice, I had to see all ten of them. To tell you the truth, I like the DOHC sound better. http://www.youtube.com/watch?v=tdSl8QhtZkc&list=HL1335492516&feature=mh_lolz

[shinyribs]

Awesome video Rusty!

[seestheday]

Here's my 1981 CB 750K: http://www.bikez.com/motorcycles/honda_cb_750_k_1981.php

Lists 77 HP stock.

Here's the 1978 CB 750K: http://www.bikez.com/motorcycles/honda_cb_750_k_1978.php

Lists 67 HP stock.

That's a 15% increase in horsepower.  That is fairly significant.

You also have to account for the the 81 being 564 pounds wet and the 78 551, but that is only a 2% increase in weight.

Of course, modding will get you a lot more and it's all about how much money you want to spend.  If you really want to go fast get a ZX14 with 192 HP

[Re-run]

Crappy thing about those hp numbers is that they were done at the crank for both bikes. I wish they were accurate!  Oh well. It was common back then to use crank hp instead of rwhp.

[Piute]

seestheday wrote

Here's my 1981 CB 750K: http://www.bikez.com/motorcycles/honda_cb_750_k_1981.php

Lists 77 HP stock.

Here's the 1978 CB 750K: http://www.bikez.com/motorcycles/honda_cb_750_k_1978.php

Lists 67 HP stock.

That's a 15% increase in horsepower.  That is fairly significant.

You also have to account for the the 81 being 564 pounds wet and the 78 551, but that is only a 2% increase in weight.

Of course, modding will get you a lot more and it's all about how much money you want to spend.  If you really want to go fast get a ZX14 with 192 HP

              81 d.o.h.c. only 4 hp.diff.then a s.o.h.c. 1977 F2(73hp.),See what A good / diff.head job could do ?

Model: Honda CB 750 F 2
Year: 1977
Category: Sport touring
Rating: 66.5 out of 100. Show full rating and compare with other bikes
Engine and transmission
Displacement: 736.00 ccm (44.91 cubic inches)
Engine type: In-line four, four-stroke
Power: 73.00 HP (53.3 kW)) @ 9000 RPM
Top speed: 197.0 km/h (122.4 mph)
Compression: 9.0:1
Bore x stroke: 61.0 x 63.0 mm (2.4 x 2.5 inches)
Valves per cylinder: 2
Fuel control: OHC
Cooling system: Air
Gearbox: 5-speed