Topic: HP charts from the old days

[Rocking-M]

http://img.photobucket.com/albums/v85/dancecant/HPall.jpg

scroll down for the CB 750 (72)

[DammitDan]

Funny how the torque and HP charts cross at around 5k on every bike...

[mlinder]

Funny how the torque and HP charts cross at around 5k on every bike...

..........?


Also, that doesnt seem like much HP, especially considering their claimed output.

[Rhonda750F]

HP and TQ always crosses @ 5252

HP = (Torque x RPM) / 5252

[mlinder]

HP and TQ always crosses @ 5252

HP = (Torque x RPM) / 5252

Indeed.

[SteveD CB500F]

that doesnt seem like much HP, especially considering their claimed output.

The dyno is measuring rear wheel HP

The 750 is losing 27% on the claimed 67bhp at the crank, but this shows peak power at <8k revs. Is this right? Presumably lower power at higher revs was caused by valve bounce which may have been particular to that bike.

On the dyno charts that Mike Rieck sent me, the bike measured 98bhp at the rear wheel

Charts (pdf) here

[mlinder]

that doesnt seem like much HP, especially considering their claimed output.

The dyno is measuring rear wheel HP

The 750 is losing 27% on the claimed 67bhp at the crank, but this shows peak power at <8k revs. Is this right? Presumably lower power at higher revs was caused by valve bounce which may have been particular to that bike.

On the dyno charts that Mike Rieck sent me, the bike measured 98bhp at the rear wheel

Charts (pdf) here

27% would be a pretty large loss. 15% would be reasonable, in my guestimate, meaning that the cb750 in question si making maybe 57 or 58 at the crank. That's a far cry from 67.

[SteveD CB500F]

15% would be reasonable

I agree.

Any ideas why this bike was showing so low?  (maybe the owner had it set up rich so the tester wouldn't blow it up!)

[merc2dogs]

wasn't 72 about the time that they started detuning the bikes?
 That Kawi had a sweet torque curve, wouldn't have to do a whole lotta shifting with that one.

Ken

[Rocking-M]

wasn't 72 about the time that they started detuning the bikes?
 That Kawi had a sweet torque curve, wouldn't have to do a whole lotta shifting with that one.

Ken

That's what I'm wondering, I had a 71k1 and a friend had a 72 k2 and it would in no
way run with my k1 and he was always tuning on it, I just ran mine.
Mine also regularly kicked 900 Kawa butt, it was drag raced before I got it
and this is true. It was a stock bike too!

[MRieck]

that doesnt seem like much HP, especially considering their claimed output.

The dyno is measuring rear wheel HP

The 750 is losing 27% on the claimed 67bhp at the crank, but this shows peak power at <8k revs. Is this right? Presumably lower power at higher revs was caused by valve bounce which may have been particular to that bike.

On the dyno charts that Mike Rieck sent me, the bike measured 98bhp at the rear wheel

Charts (pdf) here

Steve...that dyno is actually measuring from the countersprocket so actual rear wheel readings would be even lower.

[SteveD CB500F]

I stand corrected.

Hardly a fair comparison though is it?  A '72 stocker on period kit vs the Million $ CB on a modern dyno...