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Tore down.. at 20k once again

14K views 95 replies 16 participants last post by  JaredP  
#1 ·
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New heater in the shed is proving to be a nice addition. I had the carbs off for a rejet and started thinking about my first engine. It only lasted to 24k when a con-rod bearing had a slight misunderstanding of what frequent oil and filter changes are supposed to do. So engine is out once again, I am going to tear it down to check the top end and possibly try my hand at porting the heads. This will be my tear down and build thread.
 
#15 ·
I'd also consider just doing 'busa pistons. They require a heavy hone, but not a bore. And quality is great.
 
#25 ·
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?
 
#26 ·
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.
 
#27 ·
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
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#33 ·
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.
 
#31 ·
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?
 
#43 ·
The weakest point on SVs is the crank, especially if you don't lighten the flywheel (which is part of the charging system as well). Rods on 2nd gens aren't too strong either.

You can get billet cranks, but even they break on a strong enough engine. The issue is that there's an oil hole that acts as a stress riser, so with each power pulse the crank twists a little, and eventually can crack and the flywheel end breaks off. You can also lighten the stock flywheel - in some cases retaining full charging ability, in some cases retaining minimal charging ability, enough for track but not street, in some cases getting rid of charging system entirely. You can also buy an aftermarket flywheel/stator assembly, brand slips my mind right now, that drops a lot of mass and gives charging system that's marginal for street but fine for track.

Anyway, the basic story is that it takes big bucks to build a reliable high power SV engine, but you can get a reasonable increase without spending a ton of money.
 
#32 ·
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.