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Originally Posted by Brewmaster
Good reply and pictures for the comparison. A few questions:
1) can you use a lighter pin?
2) how much are the Carrillo's?
3) how much lighter(if at all) are aftermarket pistons?
4) can you get a longer than stock rod and piston combo to work?
5) what would you consider a safe piston to valve clearance with a stock rod, with a carrillo, with a TI?
6) How much does a lighter combination allow you to increase the rev's too?
Sorry for the questions, I just don't have any experience with the Duc's internals YET! Stock has been fine for my abilities but that could be changing next season I hope  . |
1. Most aftermarket pistons come with a lighter pin as part of the piston overall design.
2. You can call Carrillo directly for a price, but if your having a shop doing the work purchase them through your engine builder. Support your builder! Don't cut the throat of the engine builder who is making your dream come true.
3. It depends, if you stick with the stock bore size and bump compression you can save some weight with a quality aftermarket piston. If you bore the barrels out to 95mm with MBP HC pistons it's a push. Remember your still saving weight on the rods and reworking the crank makes the assembly much more efficient, as well as getting a huge increase in bore and cylinder volume. Bigger slug means more mass!
4. Sure you can. Plan on reinventing the wheel though, and where do you get spares for your one off motor? Especially if your going racing. You better know what you are doing and be sure that in the end it will develop the power you are expecting from all of the work being done. We are talking engine designer here. If you have the bucks and the knowledge I'd say go for it!
5. The norm has been 1mm or .040 of an inch with stock rods on squish. It's really more than just the rods. Main bearings have a lot to do with the assembly process. The OEM bearings wear and get sloppy so you loose the ability to maintain the tolerances required for safe operation. Steel rods will hold up better to abuse over time. Cast Ti rods will stretch over time while forged Ti rods are the ticket. $$$$$ Ti makes a great light weight spring on my rear shock! I have one on my 996. Done right you can shrink that 1mm number even much tighter. Also valve to piston clearance needs to be taken in to consideration when swapping to a more aggressive profile. Then there is always valve timing to consider as well and how it effects valve to piston clearance.
Larger valves diameters will effect all of the above as well. Still game?
6. Lighter parts will help in keeping things together at high rpm, as well as allowing the motor to spin up faster due to reduced inertia. Port work, larger valves, more aggressive cam profiles, will do more for increasing the RPM of a motor. A motor is an air pump, the faster it gets air into and out the head, the more power and performance gains you will realize.
My advice is to find an builder chat him up then talk to others. See what folks are doing with their motors and who they are sending them to. Most important is to find someone who thinks like you. Learn from them and heed their advice. More than likely they been down this road many times before and their experience is valuable in ways I can't even begin to describe!
Reliability of motor in a race bike
I too am an ex drag racer (from quite a few years ago...) and have worked in a machine shop for a bit (plus a M.E. degree). I totally agree with letting the guys most familliar with the specifics to do the job. Buce Meyers is not too far from me (well at least during racing season) and has a good reputation for the 2V's. 
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