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Discussion Starter #1
So I was thinking about rebuilding my engine next year. I have a few things i want to do a few things while i have it all apart. Two things i really want to do is to have it bored out a bit, and i want to raise the compression ratio to somewhere around 11.5:1. i have a few other things i'm gonna do like port and polish and some stronger clutch springs.

Does anyone know how much i can bore it out and where to get pistons to match the new bore?
And does anyone know how i can increase the compression by that much?
And are there any other things i should do while i have the engine pulled?
 

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increasing compression ratio wont take much, its already 10.5 to 1. might be as simple as remove a bit from the head (I dont know how much, but probably not much more than a few thou

not sure on how much bore it will take, or where to get oversized parts
 

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In all my parts searching, I don't think I've ever seen an oversize piston, even the standard bore size is hard to find. Wiseco doesn't even list the VN750, but they may build a couple for you. $$$

One problem I see with more compression, you can't adjust the ignition timing (in stock form).
 

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Check/replace the balance dampers while the engine is removed.
 

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If u press out the sleeves and put bigger ones in u can go to about 1000cc,i went to 890. u'll need machine shop work to match sleeve to piston( prob.wiseco),custom head gasket,another set of brushes in starter,stock carb.isn't enough,shave heads and a machine that spits out money.Go for a good shave and a thin gasket will be happy enough with that
 

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FREEBIRDS MC CENTRAL NY
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If u press out the sleeves and put bigger ones in u can go to about 1000cc,i went to 890. u'll need machine shop work to match sleeve to piston( prob.wiseco),custom head gasket,another set of brushes in starter,stock carb.isn't enough,shave heads and a machine that spits out money.Go for a good shave and a thin gasket will be happy enough with that
I was waiting for you to chime in...

Sent from my LGL34C using Tapatalk
 

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Discussion Starter #8
I would also like to know how much this would cost. I can do most of the work my self including doing the port job. But about how much would it cost to get new high compression pistons (if I can find one) or to get the head milled down?

Also how much can it be safe to mill the head down to without the valves coming in contact with the piston and wreaking the engine?
 

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Also how much can it be safe to mill the head down to without the valves coming in contact with the piston and wreaking the engine?
I'm also waiting for an answer on this, as I'm replacing a head gasket this winter.
 

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I'm also waiting for an answer on this, as I'm replacing a head gasket this winter.
Probably best just to lap the surface.

If you're milling to increase compression, you need to spend time with clay checking the clearances. Or find someone that has, and I'm not aware of anyone that's milled this one.

It's 10.5:1 stock, and manages to take regular gas. Much beyond that and you need fuel and ignition tuning, along with higher octane most likely, maybe even racing gas.

Ignition tuning is something nobody has cracked on this one, and that limits getting this mod right.

This engine will bend valves too.
 

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Don"t remember the clearance but there is enough metal that i did it twice and used thinner copper gasket
Recall how much you took off?

Tried to remember your handle yesterday, but knew I'd butcher the spelling.
 
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