[250Renvy]

Neil,

Maybe they can make you a sticky, but could you explain what kind of cylinders you can re-port?
Or maybe a better way of putting it, is what type of port jobs you can re-port.

I'm currently looking at 2 motors, one with an ESR trx 9 port job and one with a Boyessen Low end port
job and I would like a good all around low to mid port job. Can the TRX9 (mid to high) be brought down or can the Low be brought up to low - mid?

 

[C-Leigh Racing]

Neil,

Maybe they can make you a sticky, but could you explain what kind of cylinders you can re-port?
Or maybe a better way of putting it, is what type of port jobs you can re-port.

I'm currently looking at 2 motors, one with an ESR trx 9 port job and one with a Boyessen Low end port
job and I would like a good all around low to mid port job. Can the TRX9 (mid to high) be brought down or can the Low be brought up to low - mid?

Let me see if I can answer it all.

What type,
Re-porting can be done on any cylinder that has porting lower than upper midrange.
Depending on how high the midrange port is, as to what you will end up with.
Upper midrange is kinda the breaking point where some changes can be made.
Drag porting, depending on how radical the port job already is, wheather any changes could be made to it or not.
If you have a bottom end ported cylinder, most any other level higher of porting can be done to it.

You see, when your doing porting, you got to do the cylinder to fit the person that will be using it, thats how I look at it. I want it to fit you.
I could, on every cylinder I port, just do a full drag port & then when you recive it, got it running, it would be the badest & fastet thing you ever throwed a leg over, but, could you use it or would that engine work well for the type of riding your intending to do.

When your thinking of cylinder porting & the different levels or stages of porting you should think of full drag as the last step, the highest level of porting the cylinder can be taken to.
Full drag is the highest & thats all the cylinder can be for from that point.
Only way any changes could be done to a full drag port to lower the porting, would be lots of machining work on the cylinder & at a very high cost, machinings not cheap.

Heres one question I get asked a lot.
Can I just install a stroker crank in my ported engine to up the power.
Using a cylinder thats been ported for a STD stroke crank & then wanting to take that cylinder & install a stroker crank under it, thats a whole different ball game altogether, lots of work & cost, but, it can be done on some cylinders, not every one though.
Ported, STD stroke cylinders that could be used over a stroker crank, bottom end & midrange, depending on how high a midrange.
Normally midrange porting, or anything higher, it turns the engine into a drag engine.


Sometimes, even a cylinder that ported & performs right well, some changes could be made to it to make it perform even better, it all about flow & angles.

Normally what I can change is the ( generic ) port jobs that you would recive from the big name builders, run of the mill porting.
There have been some though, I got to say that was right good porting, but still could use some improving.
To get a eye opening port job from most of the big name places, you would need to be one of their sponcered riders.
I'm not saying, that every place that ports, cant give you an eye opening port job, they more than likely can but its about how much attention they will recive afterwards.


On the 2 engines you have asked about.
The TRX 9, depending on how good the ESR porting is, probably some changes could be made to it to improve the output.
ESR TRX 9, suppost to be a little above midrange, but all I have seen so fars not to the ultra midrange level.
I could change flow & angles some & install a higher compression done, you would be surprized.

The Boysene port, I got to admit, I dont think I've ever seen one, not to my knowlage but would be interesting to check out.
A good bottom end to midrange pulling engine needs lots of compression along with a complementing pipe.
250Rs are just a happy long lasting engine when you can make them pull down low, as well as not beating the rider up as much as a high strung one.


Can sombody do a sticky on this, I dont know how.
Thanks Neil

 

[250Renvy]

Thanks Neil.

That's unfortunately not what I wanted to hear. I was hoping the ESR would be easier to re-port, but it sounds like it could be a gamble. The Stock cylinder with a Boyessen port job is running at 250psi with a PT type 6 pipe. I was hoping to steer away from High compression because the race fuel is incredibly hard to come by in my area and I'd never get to ride except on race days.

I was leaning toward a Pro-x cylinder but I know that stock cylinders can be worked pretty good to be just as good if not better than any of the aftemarket cylinders. I guess I'll keep looking.

 

[iwem]

a little off subject for what you were talking about but i have a 86 250r that is 50 thou over and the cylinder has only the intake cleaned up a bit it looks like they sharpened (like a knife) the botom of the aluminum runners that go for the transfer ports but they did not have the exhaust side cleaned up at all im thinking that this is hurting my power and am wondering if this cylinder would still be ok if i cleaned and polished the exhaust and maybe stightly roughened the intake with a die grinder ?

 

[C-Leigh Racing]

a little off subject for what you were talking about but i have a 86 250r that is 50 thou over and the cylinder has only the intake cleaned up a bit it looks like they sharpened (like a knife) the botom of the aluminum runners that go for the transfer ports but they did not have the exhaust side cleaned up at all im thinking that this is hurting my power and am wondering if this cylinder would still be ok if i cleaned and polished the exhaust and maybe stightly roughened the intake with a die grinder ?

When you have a bridge in a transfer port & put a knife edge on it, it cause that bridge to create a direction of the flow. A more blunt curve shape to that edge is far better because it causes the bridge in a sence to act like the leading edge of a air plane wing. The shape of the leading edge of a wing, when the air flows over it creates a void once it goes past that edge & causes a lift.

A straight flow of air & gasses will have sort of a cling to the surface that its being directed by & with the blunt edge on the bridge & it creating the void you wont have that cling.
A texture in all the areas where you have flow is important, texture on the surface will remove the cling & promote better flow.
Exhaust ports, reason you see most of those polished up, is to some extent trying to stop any build up of carbon on the walls.
Carbon build up in an exhaust port can cause differences in how the pulse wave acts as its traveling through that area. Anything other than a flat surface could send the wave off in the wrong direction & distort the wave.

On the intake side of the cylinder, a texture is needed & a knife edge is somewhat important because, on a 250R the carb & manifold is setting at an angle & will cause most of the flow to go on the right side of the engine. This angled flow can cause more fuel air charge to pass up through the ports on the right side & cause a imbalance in the top of the cylinder, lean on the left side rich on the right. Even though this is something thats so small of a item that it would seam unimportant, its just one of the many millions of things when you correct it has a difference in the power output, very small, but some.
When I port the intake side of a cylinder, I try to direct as much flow as I can to the left side of the engine in an atempt to slove this problem.
Some of you that I've done cylinders for may have noticed a difference in the intake & wondered why it looked like that, this is why.
Neil