1977 Yz 400

[FenryHonda]

Does anyone out there have any idea as to how much hp the '77 YZ 400 puts out stock?

I love mine, and have a DG National pipe and Boyesen reeds.

 

[David Trustrum]

Well a friend dyno’d his brother’s TS400 at 18hp, so perhaps you don’t want to find out the real answer. Another friend had a YZ400 & always said it had “enough”.

 

[FenryHonda]

Well a TS 400 and a YZ 400 are very different animals.

 

[David Trustrum]

This I realise, my point being don’t be expecting 40hp

 

[FenryHonda]

I fully expect 40...... I have ridden a modern 250 and my 400 back to back, and my bike wasn't that far off, but harder to ride.

 

[OnAnySunday]

I dont know for sure what your bike is rated at BHP wise, but i'm sure it's well over 40.
My '82 XL500R is rated at 32bhp (according to my friendly neighborhood Honda dealer anyways.)
And i know my '79 YZ400 would absolutely incinerate it.
I would personally guesstimate closer to 50bhp.

Oh and just for grins & giggles.........
I did end up drag racing the 400 against a modern 250 once or twice.
It's not a pretty sight when those 1/4 liter guys breakdown in tears from being blown away........ :laugh: :laugh:

 

[FenryHonda]

Yeah, in a drag race there isn't even a comparison.

 

[billtx]

I also had a 79 YZ400..great engine on that bike! I think I saw an old test recently and recall HP number is the 40's.

 

[FenryHonda]

I know it has to be. I have a spec sheet for my Penton 400, and it is listed at 42, and the YZ is much more powerful.

 

[billtx]

Check this web site out - http://hometown.aol.com/vintageyz/index.yzmods.html

It shows the 1981 YZ465H HP to be 42.18@7000RPM, does not indicate what the source is however.

I'm sure it was faster than my '79 YZ400, just don't remember it that way.

 

[FenryHonda]

I read the same thing on the YZ site. Dyno numbers are variable anyway. What I remember about a 465 was it was a torque monster.

I'll keep mine, whether it has 15 or 40 hp. Either way, it will easily loop out in 5th gear, with my fat butt on it.

 

[jmics19067]

I dont think you will ever see an older big bore bike have high horsepower numbers like a modern 250. Horsepower is a function of torque x rpm and since the modern 250's will rev higher than the 7000 rpms. It throws horsepower into comparing apples to oranges. also talking watercooled which allows you to run higher compresion, better manufacturing processes and materials allowing tighter tolerances etc etc...
But the old big bikes should be more than enough fun when in that sweet spot of rpms when the grin factor is ear to ear :laugh: The torque from the bigger displacement should be more than able to make up for any technology advantages