Hi Paudap,
Yes - I agree - those instructions are difficult to decipher precisely - but I know what they are suggesting.
These are instructions to open up the inlet.
This operation needs to be done very carefully.
It is essential that the inlet overlaps your new crank on the inlet's long sides
Most on this forum believe that the minimum overlap should be between 1.2 and 1.5 mm on each side.
Every case is a little different - so the best way to determine this is to install your crank and mark it.
I've included some pictures below as an example.
I find, for best results, that if I paint the crank blue with a sharpie, and then use a very thin sharp pointer, I can lightly scribe the exact edges of the inlet onto the crank.
You can keep the pointer still - and rotate the crank to achieve these marks (like the two blue marks below).
The edge of the blue market must be at least 1.2 - 1.5 mm in from the edge of the crank
The front and back edge of the inlet can also be opened up.
This affects your "inlet timing"
Longer is generally better for peak power - but as you get longer, you can also start to take away some low end power.
With your larger cylinder - you can afford to be a little longer with very little compromise - perhaps no compromise at all.
There is some more - but let's figure out first what the Malossi suggested set up is.
The image you posted of Fig. 3 is telling you their suggested openings for length - it appears.
Can you post the rest os the information so we can read what it says?
Maybe we can give you some direction.
Here is a thread where a guy did a very careful and nice job with shaping his inlet. His measures are all calculated - which is a whole other can of worms.
Let's start by seeing what Malossi says...
Over a Barrel (BGM187) (Page 3)
