1000cc big bore

If you are only switching 59mm rod for 64mm long rod, then you can shim under the cyl. But you didn't stroke the motor and cc are still the same.

If you moved the crank pin kept the same rod, just adding a shim won't fix the port issue. If all you do is add a shim and keep stock port timing you'll likely make less hp then a good race 880 kit.

Input your new numbers into port program and run the simulations. It will show you how far off the port timing is, plus what loss in hp without using 800 boost port cyl. The intake on the 750 can develop crack's in the bridge, not sure what to like with that intake
 

OK Doc, no I not just change the con rod, I change the entier crank for a longer crank with 64mm of stroke. Many work on lathe for enter the new crank on the case and also many work on case.
With the new stroke I use rod with 18mm head and a original Yamaha piston. All the interne parts are Yamaha original parts. The reason for is easy to find and less expensive. For this reason it' s necessary to use a big shim under the jug. Also when I rebore the cylindre I expect the port timing lower a little bit and give to me more play for have the right timing port for the new port timing.
 
toydoc said:
If you are only switching 59mm rod for 64mm long rod, then you can shim under the cyl. But you didn't stroke the motor and cc are still the same.

If you moved the crank pin kept the same rod, just adding a shim won't fix the port issue. If all you do is add a shim and keep stock port timing you'll likely make less hp then a good race 880 kit.

Input your new numbers into port program and run the simulations. It will show you how far off the port timing is, plus what loss in hp without using 800 boost port cyl. The intake on the 750 can develop crack's in the bridge, not sure what to like with that intake[/QUOTE I think Dom is talking about stroke,not rod length.A stock Vmax4 rod is 110mm long.
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I would have to agree with toydoc on the cylinder choice. The exhaust time area lost using the 750 cylinders will hurt the performance limitations of this set up. The 800 cylinders would be a better choice but even with the 800 cylinders it can be a challenge to get proper time area #'s for a high rpm race engine. Good luck with the build and keep the posts coming.
 
It' s for this reason I looking for 750 jugs, the port timing are lower to a 800 and probably easyer to use with the new stroke.
 
First I think it super your taking on this big bore, very cool.
I just don't want to see you put all this work into this and it lays an egg and wont make big hp, or more hp then a stock stroke race motor.
So your this far into it, i'd put a bunch of time into port maps and see what works.
The other thing to keep a eye on is piston speed. Plug the numbers stock stroke and stock 8500rpm & 10,000rpm. Then long stroke & 10,000rpm. What piston used will be a issue
 
Thank you Toydoc. I make this project for 2 reasons. First I wish run Vmax 4 on imp 1000 class and the second it' s a fun challange for me.
For the piston speed the stock engine have 16.30 M/sec at 8250rpm. At 10000rpm the piston speed are 19.8666 M/Sec. In comparaison with a stock Vmax 600 or Mach Z the piston speed are 18.7M/Sec at 8250rpm and the engine run without fail. Also the Mach Z 800 on prostock version run at 10000rpm for 22.66 M/Sec. The max limite are around 22.5 to 23 M/Sec for the stock componement and around 25M/Sec for exotic material. On the fact the speed piston are not a problem on this project and respect the safe limite for the material.
The big challenge are the port maping. More stroke need a longer time for the port timing and more material betwin the top of barrel to the top of exhaust port. 4.4mm more stroke need a 2.2mm shim under cylinder, because the piston travel are 2.2mm longer on the top and 2.2mm on bottom for 4.4mm more total travel. I wish have a suffisant material on the exhaust port and transfert port for make a good porting with a performante mapping. A other thing i have calculated it' s when I bore to 70.5mm the exhaust port go down a little bit and the same thing for the transfert. But I dont know how much? One thing I sure the porting jod dont need to remouve a big quantity of material.
 
dominicturbo said:
Thank you Toydoc. I make this project for 2 reasons. First I wish run Vmax 4 on imp 1000 class and the second it' s a fun challange for me.
For the piston speed the stock engine have 16.30 M/sec at 8250rpm. At 10000rpm the piston speed are 19.8666 M/Sec. In comparaison with a stock Vmax 600 or Mach Z the piston speed are 18.7M/Sec at 8250rpm and the engine run without fail. Also the Mach Z 800 on prostock version run at 10000rpm for 22.66 M/Sec. The max limite are around 22.5 to 23 M/Sec for the stock componement and around 25M/Sec for exotic material. On the fact the speed piston are not a problem on this project and respect the safe limite for the material.
The big challenge are the port maping. More stroke need a longer time for the port timing and more material betwin the top of barrel to the top of exhaust port. 4.4mm more stroke need a 2.2mm shim under cylinder, because the piston travel are 2.2mm longer on the top and 2.2mm on bottom for 4.4mm more total travel. I wish have a suffisant material on the exhaust port and transfert port for make a good porting with a performante mapping. A other thing i have calculated it' s when I bore to 70.5mm the exhaust port go down a little bit and the same thing for the transfert. But I dont know how much? One thing I sure the porting jod dont need to remouve a big quantity of material.
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I would not be to concerned with piston speed factor. We have been exceeding them for over 8 years with the wiesco and have not had a failure. The cast piston will not last.
By trenching the case you have also increased case volume. This makes pipe design critical.
 
Yes CMR, it' s possible to outpass the piston speed limit but the life time of the engine and reliability are affected. The first failure when you excess the piston speed it' s the broken rod. And titanium rod have a extremely high cost for the small gain on power.
And yes the pipe desing are more tuff but it' s possible to make a great pipe with the rignt mesure.
 
CMR said:
I would not be to concerned with piston speed factor. We have been exceeding them for over 8 years with the wiesco and have not had a failure. The cast piston will not last.
By trenching the case you have also increased case volume. This makes pipe design critical.
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Hey Chris, when I read the "original Yamaha piston", I didn't know if that was as in "cast" or "size".
Also the PS800 machz at 9800 rpm with good forged pistons will collapse the piston dome quick and it's not fun to diagnose. Runs fine, everything checks out good, just down on hp. So piston speed and what it can do is something to keep a eye on.

When I ran into you at the world series in Bill trailer, that's what we were dealing with all that weekend. We switched carbs, talked about borrowing your reeds. Went home switched entire ignitions.. In the end we had collapsed piston domes
 
You have reason Toydoc the piston speed are a very important thing to mind when you built a engine. Also the forged piston are not the best choise for all apiquation. On the PS 800 Mach Z we use a stock piston to run at 10000rpm without issue. The CR and fuel quality are a other thing very important.
Many guys report the same thing on stock 700 with the F7. After 2-3 race programme with the programmed race box from A/C the piston dome collapse and the power down ant the engine do not longer take the clutch weight. The reason are not the piston speed because it' s a stock engine. The fuel are a little bit on cause but the main problem it' s the engine are too lean and make a verry little detonation and collapse the piston dome. And when the CR are a little bit lower the detonation stop and the engine run normaly but the power are not great. Around 75 pass and the problem start and after 100 pass the piston are collapsed. And effectively Toydoc it' s not easy to find.
 
It for sure could be a bit of deto over time. But it's not always a lean issue. You could add fuel, or back timing off, or run less CR, or even more race oct fuel, or even turn less rpm. All help stop deto, but also makes less hp. About the same hp as when the domes collapse.
 
more work done on the 1000cc v4 project. Probably more longer I expect because it' s very expensive to built.
The stroker crank have half left side done, also 2 cylinder bored to 70,5mm and the Yamaha piston for are arrival.
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I wish run half motor on my Stuska dyno this winter for test and developpe the pipe, timing curve and lot more.
 
CMR said:
I know of only (1) vmax 4 that is over 1000 cc that has been dynoed by somebody other than Darcy Rosentretter. That is A to Z engines at 301 HP. The other motors at that time are Ross' and mine and they were pulled at Darcy's on his homemade dyno so the numbers are not comparable.

And yes you can get over 1000 cc with out stroking and the max you can stroke a stock crank is 64mm with out trenching the case and 76mm trenching the case unless you have a Billet small lower rod pin crank built
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Is Darcey still around???
 
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