Rather than call this a tech page, lets call this a useful "tid-bits" page.
We do not see any reason to talk about Hondas timelines and changes they made unless its useful.
We do not see any reason to copy and paste a bunch of tech articles about theories that do not pertain to the Honda cb750 engine.

Under heavy construction.
More to come

 

Pistons and Rings
 
Ring seal is one of most important things people should pay attention to.

So important, that NASCAR engine builders will actually bore and hone their cylinder blocks to a preheated full temperature to insure things are consistent when racing. What happens during cold start-ups?
They don't, the motors are pre-heated before start-up.

So important, most performance engine builders will use vertical gas ports to expand and push the rings against the cylinder walls. With introduction of modern oils, the gas ports will not clog up like the olden days.

So important, vacuum pumps were mainly introduced to keep the ring seal connected at higher RPM.

So important, due to the fact that rings are main contributor to disperse piston heat. (Aside from under the piston oil sprayers) Ring thickness has been reduced from the olden days to a happy medium for specific applications.
Thick rings cool better and thin rings have many advantages until cooling is a problem.

So important, ring tension against the cylinder wall for the compression and oil rings is measured when installing or building performance motors and is something that only high-level builders have access to. (Meaning a verity of rings to choose from)


Anyway...
Let's stay to perimeters Honda has given us and the parts available to us, to keep it simple.



  



Leak path #3 will be talked about below and is critical to get ring seal as good as possible.

Leak path #2 is what many people experience when using old technology pistons or used pistons.
New rings will never help if the ring grooves are worn, distorted or not perfect. Worn ring grooves can only be measured with the best and most accurate measuring equipment.
Using new rings with bad rings grooves will have you leave plenty of horsepower on the table.
 



Too vertical or steep of a angle can create excessive blow-by. Also, there could be high ring rotation speeds that could lead to ring end gaps to align on the piston.

In the Honda world with cast iron cylinder liners, here's what we do!


After boring the cylinder.
We use 220 grit stones to create valleys for oil. Generally about .002 from final size.
We use 280 grit stones to eliminate peaks and maintain valleys.
Then we follow up with a cylinder finisher, heavily oiled and about 18 strokes per cylinder.
The cylinder finisher kinda looks like a chimney sweeper. (We will get you a photo soon)

When assembling it would be advised to oil the inside of the piston ring grooves.
In the break-in period the rings can get too hot and cause a bit of micro-welding. Generally seen as light speckling on the sides of the rings. (Aluminum)
The pistons are now shot.

Here's what we do...
When first starting the motor, we will cover start-up in greater detail later. But, this is ring talk right now.
Start the motor and run for 15 seconds and let it cool.
Start the motor for 15 seconds and let it cool.
Start the motor for about 60 seconds and let it cool.
Start the motor and run for a few almost full temperature several times. (Until you feel heat in the lower cases)
This is ring thing, our break-in and running procedures will come later.
 
 

 

Some basic static ratio guidelines:

7-8 to 1: This range works for blown or turbo-charged engines. These engines typically use later closing inlets to over fill the cylinders.

9-10 to 1: This range is very easy to work in and gives good results in power output and general manners.

10-11.5 to 1: This is a range we use in our high output street engines when we can control all components as a total package. By using piston squish and quench to our advantage, exceptional power can be obtained on a street driven motorcycle.

11.5 +: These high compressions are used in racing applications and the overall performance.

   To be continued  (Break-in and piston configurations)

 

 

It is the sole and exclusive responsibility of the purchaser to determine the suitability of any part, product or work for his or her use.
The purchaser shall assume all legal, personal injury risk and liability and all other obligations, duties and risks therewith.
There is no warranty on High Performance products.

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