Topic: how to get more power out of 82 cb650sc?

[82cb650nighthawk]

this winter im building my 82 cb650sc into a cafe racer. i plan on port and polishing the heads, 4 into 1 exhaust, air filter for each carb, and jetting the carbs. is there anymore tricks i can do. and what can i get for hp out of my engine

[cb650]

You covered about all of it unless you want to search for other pistons to put in it.  Soos has a thread on his.
Try not to cut to many of your old parts up and sell them to others who want them.

[mlinder]

...cam?

[CBJoe]

...cam?

I'm not sure there's such thing as an out of box performance CAM for the 650.  Given the fact that the 550 and 650 cams can be swapped, i'm not sure how a HiPo 550 Cam compares to the stock 650 Cam.

I'd love to know though.  I thought that member Soos had investigated this, but a quick search didn't turn it up.

Joe

[Pinhead]

GM High-Energy Ignition (HEI) is a very good upgrade.

Soos can machine various pistons for overbores but I haven't seen him online since December.

Straight-pipes end up waking the motor up a bit. If you don't want to replace the pistons, run without the cylinder base gasket to raise your CR a hair.
 
I cut "Powre Lynz" in the intake ports (don't polish the ports!) GM HEI, '78 CB750 pistons with no base gasket (11:1 CR), "Surface Turbulence" valves pistons and chambers, and straight-pipes. The bike runs absolutely amazing!

Send me a PM if you're interested in Powre Lynz ports...

I hope you don't plan on cutting up your tank/seat/sidecovers up; the Nighthawks are gettingpretty rare and are, IMHO, the finest-looking SOHC4 made!

[Retro Rocket]

(don't polish the ports!)

I understand what you are doing with your engine but you shouldn't be telling people to "not polish the ports", this method has proven successful and is still used on a wide scale and there are plenty of happy SOHC { and millions of other applications},riders riding around with polished ports, myself included. I don't want to get into a discussion about your method as i have read all your posts about it, just don't be so dismissive about a proven method of improving flow.....

[Pinhead]

(don't polish the ports!)

I understand what you are doing with your engine but you shouldn't be telling people to "not polish the ports", this method has proven successful and is still used on a wide scale and there are plenty of happy SOHC { and millions of other applications},riders riding around with polished ports, myself included. I don't want to get into a discussion about your method as i have read all your posts about it, just don't be so dismissive about a proven method of improving flow.....

I didn't mean to start a war but you're simply wrong. Not that I'm saying what I'm doing is the only way... Just that it's been proven again and again by real professional engine builders (not me) that  a mirror-finish only serves to cause large rivulettes to run into the chambers which ultimately cause detonation or simply add heat to the exhaust.

I admit that what I'm doing is "extreme" when compared to what has been done conventionally, though; most use rough-grit sanding scrolls to keep the ports rough.

As most good head porters say, mirror-polishing intake ports only sells more port jobs to people who don't know any better.

[mick7504]

Here is a "birds eye" of a job that Mike did for me.

[Retro Rocket]

Nowhere did i say "mirror polishing" , the term "port and polish" is still widely used, and polishing usually refers to "de-burring" the ports.
Micks ports are what we refer to as port and polish, so what i said isn't wrong unless you take it out of context, actually i have NEVER seen a mirror polished port at all, but i know plenty of people, including racers that "port and polish" their heads....If i'm wrong their are still thousands of businesses world wide that port and polish and and i am sure that they all know what they are doing....

[Pinhead]

Nowhere did i say "mirror polishing" , the term "port and polish" is still widely used, and polishing usually refers to "de-burring" the ports.
Micks ports are what we refer to as port and polish, so what i said isn't wrong unless you take it out of context, actually i have NEVER seen a mirror polished port at all, but i know plenty of people, including racers that "port and polish" their heads....If i'm wrong their are still thousands of businesses world wide that port and polish and and i am sure that they all know what they are doing....

I've seen heads taken back to head porters because they "forgot" the polish part of their expensive "port and polish" job. That's why I mentioned it. I have no idea about the OP's engine knowledge so I was trying to reduce possible confusion.

But I still stand by my recommendation for PowreLynz for a hot street engine. Especially if you want to raise the CR.

[BLUE71TURBO]

 In my experienced years of engine building, all of the cylinder heads that i have ported and seen ported, the intake ports
 were never polished ( mirror like )  Just the combustion chambers and the exhaust ports were mirror polished.
         The original reason for mirror polishing was that the head was easier to clean during tear downs. Just like you see
 in the picture of Mikes ported intake port, it's smooth but not mirror polished. Thats for better atomization of the fuel on
 normally asperated engines.  Porting and combustion design is very very important on normally asperated engines, not
 as much so on turbocharged and supercharged engines because they force feed the engine with way more air and fuel.
     A very easy way to gain horsepower is to use nitrous oxcide.  With a small 50 HP setup it will work great on a stock
 motorcycle, with better valve springs.   

[82cb650nighthawk]

thank guys for the port and polish info i hear with today's gas you shouldn't shave heads on an air cool bike because the fuel burns a lot hotter and you can run into problems. is that true? and what about getting my cam machined?

[mick7504]

Lightly decking the surfaces to get them billiard table flat should be fine.
These guys may be able to help with regrinding the camshaft.
http://www.coltcams.com/

[mlinder]

...cam?

I'm not sure there's such thing as an out of box performance CAM for the 650.  Given the fact that the 550 and 650 cams can be swapped, i'm not sure how a HiPo 550 Cam compares to the stock 650 Cam.

I'd love to know though.  I thought that member Soos had investigated this, but a quick search didn't turn it up.

Joe

If the cam his higher lift, longer duration, or both, then yes, it will add power (where and how much depends on the cam.)
The mildest hipo 550 cams are similar to the stock 650 cam.

[mlinder]

Also, the 'polishing' part of 'port and polish' generally refers to chamber and exhaust port. The smoother the exhaust port is, the faster the exhaust gases can move out.

Just because it's port and polish, does not mean you polish everything.

When you 'wash and wax' your car, do you put soap and water in your engine to clean it? Do you wax your upholstery?

[cb650]

I only ever found one "hot" 550 cam that was more than a stock 650.    Only 1 mm more.  And  it is 400 bucks so I wont be trying it.   Was thinking more of a regrind.

[Retro Rocket]

Also, the 'polishing' part of 'port and polish' generally refers to chamber and exhaust port. The smoother the exhaust port is, the faster the exhaust gases can move out.

Just because it's port and polish, does not mean you polish everything.

When you 'wash and wax' your car, do you put soap and water in your engine to clean it? Do you wax your upholstery?

Yep, i was referring to the inlet side, nothing wrong with highly polished exhaust ports...

[mlinder]

I only ever found one "hot" 550 cam that was more than a stock 650.    Only 1 mm more.  And  it is 400 bucks so I wont be trying it.   Was thinking more of a regrind.

A regrind is pretty much what you will be doing (and should do.. the weld and regrind gives you a harder surface), regardless.

Yes, they cost upwards of 400 bucks.

I believe someone said the first one on this list is very close to a stock cb650 cam.

1mm is a lot, by the way.

[82cb650nighthawk]

i hear with today's gas you shouldn't shave the head on an air cooled engine it can lead to problems. is that true?

[mlinder]

i hear with today's gas you shouldn't shave the head on an air cooled engine it can lead to problems. is that true?

This question is asked incorrectly.

What you heard is that with todays gas you shouldn't increase COMPRESSION on an air cooled engine.

Depends.

It's not like the 650 is a high compression engine to begin with, the combustion chamber design isn't terrible, etc. 10.5:1 is probably just fine with an unaltered combustion chamber. Much higher compression is fine if someone like Mike Rieck gets ahold of it and does his magic.

[Pinhead]

i hear with today's gas you shouldn't shave the head on an air cooled engine it can lead to problems. is that true?

This question is asked incorrectly.

What you heard is that with todays gas you shouldn't increase COMPRESSION on an air cooled engine.

Depends.

It's not like the 650 is a high compression engine to begin with, the combustion chamber design isn't terrible, etc. 10.5:1 is probably just fine with an unaltered combustion chamber. Much higher compression is fine if someone like Mike Rieck gets ahold of it and does his magic.

Agree'd. IMHO if I'm going to tear into the engine anyway, 10:1 is pretty much the minimum I'd build.

[82cb650nighthawk]

im new to this performance stuff on four stroke bikes(you guys can probable tell). i had two stroke dirtbikes all my life. this is my first street bike. i only know so much so thanks for the help.   

i probable need to do something with the pistons so the valves don't hit right?

[mlinder]

im new to this performance stuff on four stroke bikes(you guys can probable tell). i had two stroke dirtbikes all my life. this is my first street bike. i only know so much so thanks for the help.   

i probable need to do something with the pistons so the valves don't hit right?

.010" to .020" probably wont be enough to see valve and piston interaction. You can use some clay to make sure.