Z1a BHP

[BigZCas]

Does anyone know what the BHP should be at the rear wheel for a 1974 Z1a. (rebuilt engine).
Thanks

[chrisNI]

Anybody's guess? I'd have thought 80bhp at the back wheel would have been good for a standard motor, a bit less not neccessarily a problem, a bit more very good. 50 or 60 not so good. Be interested to know are you taking one to a Dyno?

[ZedHead]

Manual says maximum 82 @ 8,500 RPM. It does not mention where from, I would assume it is at the crank?

[zed1015]

Around 80 to 83hp at the CRANK for a stock 900 depending on year and what manual you read.
A little bit less at the wheel due to losses through the drive train and knock about 20 hp and 40 mph off the top end if fitted with one of those iffy restrictive pattern 4x4 pipes that were produced a while back..

[tlc]

I took BunnysZ1a to the local dyno.
It made 78 rwhp which I thought was very good.

[ZedHead]

I took BunnysZ1a to the local dyno.
It made 78 rwhp which I thought was very good.

I would live with that. What pipes does it have Chris?

[BigZCas]

Looking at the readout I think the low HP (under 60), was due to the low RPM @ under 7000

[Crofty]

Guy that dynoed my 650/810 told me to get at least a 1000 miles on the engine before giving it a hard time. He did some basic jetting to get it running ok to run engine in. Did your guy deliberately keep the revs down because it's been rebuilt or did it not want to go over 7000.

[BigZCas]

Rev's delibereatly kept low due to being a classic bike.
It was dyno'd to set up engine and carbs as they were only bench set previously, my bike has covered only 250 miles since full restoration.

[Ultim8pc]

I have a dyno printout of my ST somewhere. 59HP...

[rickm]

I'm sure there must be plenty of dyno charts out there that folk can pitch in with.
I recall (back in the day) seeing in an American mag a dyno chart of a freshly run-in J which gave 79bhp at the wheel (Kawasaki claimed 102). They were speculating at the time whether this was reasonable transmission loss or maybe just a weak motor?
It would be interesting to get some more expert opinions here.

[ZedHead]

Rev's delibereatly kept low due to being a classic bike.
It was dyno'd to set up engine and carbs as they were only bench set previously, my bike has covered only 250 miles since full restoration.

Still running in at 250 miles

[rickm]

This is an interesting site, with dyno charts on some of the tests:

https://www.yeoldecycleshoppe.com/?offset=1489078859052

http://www.yeoldecycleshoppe.com/roadte ... -road-test

[wheelysteve]

Rev's delibereatly kept low due to being a classic bike.
It was dyno'd to set up engine and carbs as they were only bench set previously, my bike has covered only 250 miles since full restoration.

Hi Steve, I trust you will be riding it down to the Ace Cafe .......that should run it in nicely and gain another 10 bhp !!
Steve

[BigZCas]

I certainly will be Steve
We are planning for an early start, will be at the Ace for 9am ish.....