YZ465 Horsepower

This is great, and thanks for actually looking and sharing opinions, it is only chatting and that helps us to make progress, no matter how good any of us are, we are all better together, so thanks for your input.
The climb is rapid, and I had thought of that, I didn't think we had a slipping clutch, and without doubt the revs rise rapidly. we ran a road tyre to increase grip and reduce the bouncing, I think I have the torque curves also somewhere to see the climb, and will add them when I dig them out. I agree the train loss is about 15%, but ultimately we wanted to get the set up better rather than have more horses than we could handle. The pipe was made for torque and it delivered well, so much better than stock!
I am embarrassed to add that I have not ridden the bike since it was re-jetted, we are virtually closed in the UK due to such heavy rain, but I am booked in to ride one of our Nation Twinshock rounds next weekend. I will let you know how the riding experience feels.
As for timing, I tried a 490 cdi, and just got a top end misfire, also tried small advances and retards on the timing, we got the best results from stock settings. I was thinking it may be a bit retarded as the pipe was beginning to go blue, eventually accepting it was just expelling moisture.
I am aware that V-force make a reed system, but opted for Boyesen as they were the hot ticket in the day and wanted to keep pretty close t standard. Perhas a better rider could handle more, but I thought 'one step at a time' was my best option.

This was a photo of me handing the bike to Josh Coppins to try, he didn't like the power delivery, I wish I had set it up on the dyno first.
Jetting is 50 pilot, 350 main, standard needle and slide, regular unleaded pump fuel with synthetic oil at 38:1. More HP was found with a 330 Main, but made a huge hole in the mid.
I am totally aboard with your drum to tyre slippage comment, on the first run when we added resistance to the drum, we could actually stall the bike, but the surge of low to mid was overpowering.
Glad you like it and have been willing to share opinions, I will definitely keep you up to speed after the race to talk about the sensation of riding it.
Regards
Rob

Hi Project racer,
I loved your suggested clip, also respect your statement about the possibility of being 'dead wrong'. I think you are a true expert and politely offer possibility. I agree with your suggestion, but enquire if you feel an open class two stroke has a sanppier power than an open class four banger? I think you are right that we have traction issues which are showed in the power dip on the graph. I do however think the smoother power may not be as aggressive, but more tractable on the track. This makes me search even harder for the torque graphs as I feel they are right up your street to help diagnose.
Of interest the first Dyno I ever used was a water brake crank pto, it was mind blowing, seriously old but totally effective. We ran a YZ125 on the dyno, after my work we got 22BHP to memory, raised rear transfers and re-shaped head, most significantly a hand formed pipe! Likely tame by todays standards, but back then we were making headway. That YZ125 won many British Championship races!
You have got me thinking, and probably excited to delve deeper into the tuning I had left behind. Fortunately, it looks like 2 strokes are making a strong return!

We share the 'foggy brain' bit, that's for sure! The cylinder is a 4V4, and the carb is a stock YZ465 is the VM38SS fitted to that bike, or certainly to European issues.
My header pipe is long and slim, purposely designed for torque, you may have hit the nail on the head.

We made the pipe to have its header tucked out of the way as this was a vulnerable area on the 465. The parallel section, rather than being on the right angle bend where the cdi is located, is a bit further along, just tucked under the tank




I don't suppose the rider trying the bike is as famous in the USA as he is in the rest of the world, Josh Coppins was believed to be the fastest rider to never win a World Championship, perhaps one of the few racing in Europe who could beat Everts, he lead the MX1 world champs until injury lost him his title with 3 remaining rounds. Sort of a James Stewart or Ricky Carmichael standard rider, or European Races equivalent.
I think the bike, other than a +50 re-bore, Boyesen reeds and the pipe could be described as standard. The fuel knock which Yamaha's had is nothing like as noticeable as I remember the bike to have when I raced it in the 80's, probably flame retardants in the lower grade fuel or composites substituting the lead. I guess that can even be the reason for missing power. Like I say, I will know better when I race it, or even ride it for that matter!
Did you take a tour of my site www.yz465.info ? its a glorified blog, but shows what we have done to the bike.