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I am conducting a CP2 Engine Experiment. 

I need to know the dimension between the center of the spark plug holes, to within a millimeter or so. 

If anyone has an opportunity to obtain this dimension, I would greatly appreciate acquiring  that information. 

Thanks in advance. 

Edited by FZ-R7-626
Adding description. Type-O.
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Do you know what the word “GENESIS” refers to with respect to YAMAHA and motorcycles?


 I am attempting to modify (genes-ize) the CP2 engine. I am creating a solid model of the CP2 engine cylinder head with a reconfigured valve array. After which I will generate a reconfigured head by means of additive manufacturing.


With the help of several co-experimenters, we will determine any gains in output and tuning flexibility.


It is a multi step process. The first step is to obtain a CP2 head for the purpose of 3D scanning. Those components are do to arrive here on Monday. The company who will perform the scan is conveniently located a short distance from these coordinates.


I will try and post regular updates here.

In the meantime, if anyone would like to donate to this experiment, you can do so through my PayPal account: aeronaut@aerobiker .us


Thanks in advance,



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So, from what I remember, the 'Genesis' engine was the 5 Valve technology.


I once (1998) modelled up an original YZ400F head for exactly your above noted reasons. Did a bunch of redesign, and then milled it out of billet. Takes a bunch of time, but cool project.

I think I have Yamaha disease...

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I don't have that file any longer. It was for a proprietary governor based variable valve timing technology that didn't use electronics. Governor on the cam actuated a lever that varied the valve lift and timing. I had to relinquish the files when I finished the project. Company promptly went broke when the investor was done for bribery and racketeering in Belgium...


I do have another design which is a twin cam 2 valve air cooled Ducati head, but not sure how much value you will find in that. Also have a couple of complete 2-stroke engines modelled (if I can find them) - a Rotax 600 and 800, and a Polaris 800.


Let me know if you are interested in talking further. I have designed a bunch of engine related components (including my own engine) over the years. Happy to help out or collaborate or whatever.

I think I have Yamaha disease...

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I found a broken, but complete, CP2 head on the eBay for cheap $. 

It is scheduled to be delivered on Monday. 

After I disassemble it, I will bring it to be scanned. I’ll add the valve array I scavenged from a TRX850 head file to the resultant scan model. The TRX information may end up being for reference only. The array needs to be scaled 88.46% to fit inside the 80mm bore of the CP2 engine. But I also intend to arrange for the largest possible valve diameter, so it may be a blank slate from the start. 

I hope to cover the costs of scanning and additive manufacturing via gofundme. I am recently retired from automated assembly machine design and this is an experiment. But I do see potential for performance upgrade kits. Homologation could be another goal but that might require finding a loophole in the rules. Or significant rule changes. 

It is also to keep my mind engaged in an effort to slow the advancement of Parkinson’s Disease. Exercise, both mental and physical are vitally important to achieve any resistance to the progression of PD. 


Hopefully I can generate some enthusiasm among the various CP2, 5-Valve, GENESIS and YAMAHA  powered groups in general. 

Wish me luck!?..

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So here is an article that kind of explains why Yamaha switched from 5 valves to 4. It is basically to allow better combustion chamber shape to allow increased compression, while reducing inefficiencies. It also aids combustion and reduces emissions. 


Although it appears to be largely unchanged, Yamaha has essentially redesigned the YZF-R1 for 2007 to give it more and cleaner horsepower and improve its handling all while keeping...


Somewhere I have a bunch of design info I obtained through various conversations with BMW and Toyota engineers back when I was working on VVT designs (circa 1999) that show optimum bore size, valve area, valve angle, compression ratio, etc for optimum flame travel yielding maximum efficiency. This was done using fully instrumented single cylinder development engines, and then simulated using dynamic 3D solid models. Valve area, swirl pattern, port size, etc effect air/fuel flow, but do little to optimize combustion. Optimizing combustion is what is allowing engines such as BMW's 1000RR, or Ford's 3.5L Ecoboost (specifically in the Ford GT application) to generate massive amounts of torque (which means maximum cylinder pressure and BMEP) without self-destructing due to detonation on standard (albeit premium) auto fuels.

I think I have Yamaha disease...

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Yet they continued to use the 5-Valve configuration on the TDM900 until it was discontinued in 2013, the YZ250F until 2013, and the WR450f until 2015.


Perhaps there were more motivating factors being considered by YAMAHA.?..


Certainly the cost to produce either  a twin cylinder engine, or a single cylinder engine, that uses the 5-Valve configuration as opposed to a four valve configuration, is significantly less than it would be to produce a four cylinder engine with a total of twenty valves. 

When you multiply that per unit cost by the number of R1 units sold in 2007, I believe that represents a significant savings in production costs. 

Without researching the amount of R1 units sold, compared to the amount of TDM, YZ-F and WR-F units sold in that year, I’m willing to bet that number is also significant. (a short caveat; while the TRX and the TDM model lines probably ever dominated any premier class competitive race series, at any point during their production runs, the YZ/WR-F’s certainly were. and, therefore, must have received much consideration when the topic of competition vs cost savings was argued during corporate meetings)  

I may be mistaken, but I’m fairly confident that the R1 is, historically, one of YAMAHA’s all time best selling, if not the all time best selling model, to ever hit the show room floor.

But I’m just speculating. After all, I can’t imagine the sticker price reflected any discount for the subtraction of those four valves. 😉

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