[tovar]

Imo, only reason to go 1mm over is when you race and rules allow 1mm over as max you can go. Even than I choose busa or OEM .5mm over.
But, if you already want to bore it you may as well go with 2mm and get some power .

 

[JaredP]

I guess it comes down to me being convinced that the +2mm will be a suiteable replacement for a street bike. More reading and learning is in the works.

 

[cRaZy8]

Good thread.

Just pulled my SV into the shop yesterday to start the build.
Mine has a blown engine in the frame right now, and I have another engine ready to go in.

And our new waste oil heater at the shop is the BOMB.

 

[smoothclutch]

subscribed

 

[Kind]

Imo, only reason to go 1mm over is when you race and rules allow 1mm over as max you can go. Even than I choose busa or OEM .5mm over.
But, if you already want to bore it you may as well go with 2mm and get some power .

Does + 1 or even +2mm pistons yield that much more power when all else is equal (c/r, cams, intake etc.)?

I know at a race you want to take advantage of any and all the rules allow. 1 more hp than the guy making a move on you coming out that last turn could mean crossing the line before he does.

For those who aren't competing for the nationals that are just looking for some more reliable power for faster track day laps are big pistons even worth it?

 

[tovar]

If you look at hp per displacement 2mm over would give you 3-4hp increase. 1mm over you lucky to get 2hp. So, using 1mm over is not worth doing alone considering you putting lesser quality part that is in most cases heavier than stock.
With sv you can get power in many ways and don't need to push envelope to squeeze every little bit possible, there simply is no need for it. Goal is to make maximum reliable power without crossing red zone. Which path you take to get there will decide how reliable motor will be.

 

[JaredP]

I ordered my +2mm pistons today from Greg at Spears Racing. I am very impressed with the customer support. He was willing to talk with me for a long time an had answers for all my questions jetting, plugs temps, blah blah..... He even discounted the gaskets and valve seals. Waiting for the pistons to get here to bore the cylinders.

Here is my original Dyno chart
134 mains, needles on 2nd clip from bottom.
Cam swap
about 16K on the stock engine
Slip-on Pipe
K&N filter

 

[JaredP]

I unshrouded the valves a little, the intake turned out great, the exhaust will clean up with my valve job.

 

[JaredP]

Maybe a different day I'll have a little more ambition to do some port work on it. Gotta get my porting guy to show me what to do though, as I have never ported anything before.

 

[JaredP]

Just to clear up the reason I went with the +2mm pistons I did.
The front cylinder was oxidized/rusted/damaged and I want a clean start with this engine.

 

[marka83]

I understand the basic theory behind enlarging the bore size of the cylinders to increase hp, I was wondering how you guys learned to do the hands on stuff like this? Should I just dive in and learn as I go or do you guys do this stuff or something similar for a living?

Also, given the block of the engine was built for the specific pressures of combustion from stock pistons, engine displacement, intake and exhaust valves, etc, how far do you know you can push it till boom? What other mods will you need to ensure stability of the engine? Different head gasket? Exhaust manifolds? Some combination of various tweaks?

 

[JaredP]

I do this for a living on sport quads. I've been messing with this kind of stuff since junior high.

By pressures, you mean compression ratio? If so, increasing the compression ratio will yield more power across the rpm range. So you ask why didn't Suzuki increase it from the factory? With raise in compression comes the need to for higher octane. This allows Suzuki to be safe with a production model where people are going to run dog **** gas.

I chose a piston with an increased static compression ratio 12.5 and a increased bore +2mm. The reason I chose Spears Racing was because I felt comfortable with his ideas and experience. And his pistons are 220 grams, I'll do a side by side comparison later.

 

[champer]

I unshrouded the valves a little, the intake turned out great, the exhaust will clean up with my valve job.

What did you do to clean those heads up? I have some I am starting to clean for use in a rebuild but they are full of what I assume is carbon buildup in the combustion area in those crazy places around the valves.

Worth cleaning that up?

I am very gently taking a razor blade to the mating surfaces to clean up the leftover gasket.

 

[JaredP]

Porting tools for the removal of material about four different ones.

Worth it to me.

Keep your razor blade at a 90* angle to the head it will clean the surface with out gouging in to it.

 

[ebrammer252]

sub'd

 

[marka83]

I will just follow along and learn from this build, thanks for putting it up for us.

 

[JaredP]

No problem, I kinda like to document my progress and this is a good outlet. I do not know everything, just enough to get me in trouble. So take my information for what it is worth.

 

[marka83]

we learn best from trouble, it just hurts like hell sometimes

 

[champer]

Keep your razor blade at a 90* angle to the head it will clean the surface with out gouging in to it.

So the razor blade should be straight up and down basically?

 

[steveSLO]

In similar situations, I had an old brass punch that I ground down to a chisel.
I could do pretty much anything without damaging hardened valve seat surfaces.
Same for brass wire brushes and drill attachments.