Z1000J max rpm ?

[rickm]

Hi,
Just curious as to what the general feeling is for "safe" rev limit on a recently rebuilt standard engine for a 1000J?
I thinking of a bog-standard engine here (no welded crank).
While the original redline was set at 8500, I believe the subsequent 1000R limit was raised to 9000? (same engine but with a small oil cooler added?)
I appreciate that the redline isn't necessarily the safe rev limit.

Any thoughts, experiences, recommendations?

Ta
Rick

[Julian_Boolean]

Until the valves bounce

If it's standard is there any point revving it beyond 8.5K, it won't be making any more power after that, I think the max power on the Unitrak engine is only about 8.5K, my one feels like it's time to change up by 9 at most.

[Pigford]

You can peak at the occasional 9.5k no sweat, but that's in racing mode

[Farmer]

I have a mate who regularly took his Z1B's rev counter straight down to 6 o'clock, he wrote the bike off before the engine !

[tlc]

An interesting topic here.
When I bought my untouched J I maxed it out on a downhill stretch of road local to me. I just worked out that on the standard gearing at 135 mph I was pushing 8750rpm. I would say that the limit was the road condition, other traffic around, tyres and bravery.
Any engine will rev on beyond max power, which in this case is at 8500 with max torque at 7000.
The issue with an non-welded crank is that in the event of a missed gear it can whip round alarmingly and twist the crank.

Without a welded crank it is best to not miss a gear.

[rickm]

So the real concern is missing a gear at high rpm and the torsional forces involved as the crank accelerates very rapidly, rather than actual speed of rotation? (up to a point)

[tlc]

I would say if you are stripping the engine it's worth having it balanced and welded.

[rickm]

The engine was rebuilt by KipKawa to standard spec, so not welded (as far as I know).
It's running fine, so my question is really out of curiosity.

[Big Fluff]

Personally I don't think you'll find it's speed that'll twist the crank, it's torsional force!
Turbocharging or any kind of big power hike will do the trick.