How is the correct port timing achieved?

[GGRider01]

I don't see it changing durations. The piston is going to pass by them at the same rate at a given RPM despite the cylinder height.

Granted, I'm in the shade-tree mechanic category (quite literally) and learning these things myself - this is just as I understand it so far.

 

[(F5)]

That'sentirely what its going to do. Draw a picture at ddifferent stages.

Its all about the port roofs. The higher they are the more duration. The ultimate manifestation is if you raise the port roof to the top of the piston stroke. Port would be open 360 degrees.

 

[GGRider01]

So, raising the cylinder does have an affect, depending on what is desired? Making it flush at BDC is more of a baseline setting rather than an ideal setting? Once the characteristics are desireable, that is the time to modify the squish and CR, I'm guessing.

 

[(F5)]

Some people report that when they raised the barrel to where, on their bike the port floor was flush, that they liked the results.

There are several issues with this. The most crucial you might resolve if you find the part number for the barrels stays the same throughout the model life. And in fact there are 125s,200s,250s,300s. That's drawing a long bow.

Its like saying, my mate sez . . . well Iccan't think of anything

The bike won't run worth a damn if you raise the barrel a whole heap and leave the squish with a greatly increased height.

 

[motopsycho87]

I agree with that most certainly, but if you're going to do one, you may as well do the other. Any machinist worth his salt will do the work for an hours labour.

 

[GGRider01]

I agree with that most certainly, but if you're going to do one, you may as well do the other. Any machinist worth his salt will do the work for an hours labour.

That's definitely what I take away from this. Better to have a lower barrel and a tighter squish until I decide what I'm going to do with the machine.

If I decide to throw more money at it, I'll raise the barrel and have the squish and C/R corrected. Otherwise, I like riding it now that it's got some top end power again.

 

[motopsycho87]

I agree with that, but getting the squish done won't cost much, if you're in the UK I'll do it for ?50+p&p. So long as you take the necessary measurements.