Cycle World Redux....

[madmax-im]

http://www.cycleworld.com/yamaha-xs1...src=SOC&dom=fb

[Bonz]

Thanks for that! As to the cost of parts limiting the engine RPM? Everything I have seen and heard is these engines can be run higher than 8500 RPM. And survive willingly.

Thoughts?

[TopCatGr58]

Hey Howard,

From what I got from that article, they were talking about Cast Pistons and con rods vs. the Forged ones, and Steel/Titanium rods.

As for the engine taking 8500+ rpms, I know I've hit that a few times with misshifts, but not intentionally, besides the spec sheets stated that the max power/torque occurs at 8K or less, so you don't really get any benefit from pushing it beyond that point, so why do it and risk floating valves?

T.C.

[Bonz]

I understand where the more modern bikes are in terms of parts material, quality and tolerances. What I am getting at is the Yamaha is over engineered in a huge way when it comes to using the plain bearings they chose, the one piece crankshaft, split and bolted con-rods, etc.

In one breath, the engine is touted as extremely stout and strong unlike the other "biggies" of the era, and in the other breath, RPM is now limited because the parts weren't there to support higher RPM.

Seems to me the parts that are being talked about aren't as much RPM "related" as the valvetrain and valve springs. And nothing is mentioned of the valvetrain. I guess that is how I should have phrased my post.

With that being said, in my ZRX 1200 I put the ECU and timing rotor from a ZX11 which has another 1,000 rpm up top to take advantage of the ZZR1200 cams I installed which are a huge torque/hp boost in the mid range and up top. Redline is now 11,500. And I had to swap over the double valve springs from the ZX11 because they are able to handle that rpm. -Yes I could simply stay at the old stock redline of 10,500, every once in a blue moon it's fun to twist the tail and it truly does fly. The stock ZRX springs risk float above 10,500. Being that the ZX11/ZZR/ZRX engines are identical other than the valvetrain, the crank and rods and pistons are just fine in this application.

So, I would believe the valvetrain is more the weak spot with the XS1100 than the lower end. Does that seem accurate?