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Discussion Starter · #5 ·
hi test

Oh my! You think you will be able to run 91 octane safely? Any other mods like cams? Jevers
The only fuel my bike has ever seen is 100 octane racing fuel. I'm pretty sure premium would be fine with the bump in compression.
cannot find anyone making cams for that bike. they would have to be custom ground.
 

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So 10.5 SCR I'm sure is based on an all factory config, chamber volume, pin compression height, etc, but you really won't know what actual SCR is until you actually measure.


Point is, curious as to what SCR actually comes out to.


That will also be needed to correctly have a cam ground, and you can compensate for SCR some and control detonation that way.


Many street cars have that type of SCR and run on pump gas, just to say. But, they are liquid cooled.


Considering the head is aluminum, running 91 shouldn't be difficult at all, but will still take some planning.


.
 

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So 10.5 SCR I'm sure is based on an all factory config, chamber volume, pin compression height, etc, but you really won't know what actual SCR is until you actually measure.


Point is, curious as to what SCR actually comes out to.


That will also be needed to correctly have a cam ground, and you can compensate for SCR some and control detonation that way.


Many street cars have that type of SCR and run on pump gas, just to say. But, they are liquid cooled.


Considering the head is aluminum, running 91 shouldn't be difficult at all, but will still take some planning.


.
Being a bit of a novice when it comes to engine building, I have to ask.
What is does " SCR " refer to? Thanks. Jevers
 

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Discussion Starter · #14 ·
Scr

I know..... Now if they only made 12.5:1 piston's i would be doing the math. These pistons are 10.5:1 up from 9:1 can't image there is going to be a substantial difference. we will see. hopefully it might sound a little better...:smile2:
 

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Yes, static compression ratio, sorry about that!


Anyway, since it has to come apart to install those, you can CC the head volume, and the OE piston relief volume(s) and pin compression height. Also check compressed thickness of head gaskets.


My understanding is the tolerances are not very good, and that could be part of the reason they choose to make the compression ratio lower from the factory. Poor fuel availability is also a possible reason.


Point being, I bet there's differences between the two cylinders. Getting them as close as possible can actually be a noticeable power gain. Some simple head/port cleanup can provide considerable gains too.


Do me a favor, when you tear into it, post pics please. Maybe even start a new engine thread.


I like the fact the pistons to have the coated skirts.


.
 

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If you have the part number of the ones you got post that too please, as well as the spec sheet that came with them, would be a great reference.


.
 

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Discussion Starter · #18 ·
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Yes, static compression ratio, sorry about that!


Anyway, since it has to come apart to install those, you can CC the head volume, and the OE piston relief volume(s) and pin compression height. Also check compressed thickness of head gaskets.


My understanding is the tolerances are not very good, and that could be part of the reason they choose to make the compression ratio lower from the factory. Poor fuel availability is also a possible reason.


Point being, I bet there's differences between the two cylinders. Getting them as close as possible can actually be a noticeable power gain. Some simple head/port cleanup can provide considerable gains too.


Do me a favor, when you tear into it, post pics please. Maybe even start a new engine thread.


I like the fact the pistons to have the coated skirts.


.
The stock pistons are 9:1 the wiseco 10.5:1
 

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Yeah, what i was trying to elude to is that the listed CR for the pistons mean pretty much nothing, there's too many variables, and you have to measure to know for sure.


Yamaha lists the generic SCR for the engine at 9.1, but actual is probably more like 8.6-8.8, they round numbers, just like with displacement.


Sure, as long as they have blanks, most cam grinders will grind you a cam, but can check with Cuervo Racing, Web Cams, HPS, Megacycle, and the likes. I'm kind of newly getting back into bikes, so not familiar with the manufacturers involved, but will look into it.


I see a lot of cams for the V-Star 950 & 1100, so would have to research the engine families and see what is interchangeable. If they are compatible, might be able to do a jug, piston, rod upgrade for a 'big bore' type upgrade, and go to 1100.


.
 
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