DOHC Dyno

[motorhead715]

Has anyone had a dohc on the dyno? I checked out my bike a few months ago. It only pulled 56hp. Does that sound right? I have K&N pods, slip on mufflers, and jetted but other wise its all stock. It runs like a dream and spanks by buddies stock 1981 750f. I havent been able to find any info to compare it to, other than stock 72hp listed in the service manual.

[LukeM]

That is probably about right.  I have a 700CC Honda Shadow, and it's spec'd out at about 62hp from the factory.  Given that age and tolerances set in after 20+ years, I'd say you're right on the money.  

Luke M

[rrgunslinger]

There is a chart on this link, plus a lot of information/history.

http://en.wikipedia.org/wiki/Honda_CB750

[shinyribs]

I'm not really up on the DOHC bikes, but 56 hp to the rear wheel is considered a strong runner for an all stock SOHC. The best you ever see out of a stock engined SOHC with good exhaust and intakes is upper 50's . Sounds like you have a good strong bike there! The HP ratings you see in the FSM are flywheel HP numbers,not rear wheel HP

[motorhead715]

Perfect... Thats what I wanted to hear. I was told 15-20% loss threw the drive train.

[shinyribs]

A non-o-ring 530 chain (Or even a smaller 520...$$$)and an aluminum rear sprocket can free up a small amount of HP if you are really looking for maximum effort. The difference may be measurable on a dyno,but I doubt you'd feel it in the saddle. Hard to believe you lose that much HP in these small trannys,but I'm sure  the chain absorbs some of it.

I've been looking for a dyno in my area. Any chance you are in the SW Virginia area? Also,how much do thay charge for dyno pulls? If you don't mind me asking

[rrgunslinger]

anybody look at the info I posted? No guessing!

[motorhead715]

I have a non o ring 530 chain. It was a crappy day to dyno I hope to go back this spring with a few changes to see what I can gain. I live in WI and work at the place that has the dyno. We charge $100 for a base line (3 pulls) or its $400 for 4 hours. Its not cheap but working at such a facility has benefits.

[motorhead715]

I did check out the info. I dont know why the F modle shows more power. All of the searching ive done shows the C,K,andF all share the same engine components.

[shinyribs]

F models had a hotter cam and better exhuast-on the SOHC's at least. Well,the F's had a 4-1,I don't know if that is ''better'' or not,but it is supposed to produce more peak HP

[motorhead715]

[motorhead715]

[motorhead715]

[motorhead715]

[sgtslag]

Too bad your bike is not fully stock [pod filters, different jets, different exhaust (?), make a difference].  What I am really curious about, is one fellow posted on his web site that motorcycles' exhaust does not generate enough back pressure to require different jetting due to 4-into-1, versus 4-into-4.  That is something I've always wondered about.  Cheers!

[shinyribs]

Sarge,FWIW, I have pods on the chopper. It had 4-2 with baffles in them. I swapped over to wide open drag pipes and didn't touch the carbs.Plugs looked identical and the power was the same. There may have been some sort of dyno-measurable difference between the two of them,but the seat of my pants cant tell any difference. Now my ear drums...that's a different story!

[motorhead715]

[motorhead715]