Scooterotica

Bit of advice needed guys, if your opening out the transfer ports in the engine casing, what's the maximum you would take them out to? Ie the wall thickness?
Ps its a Spanish Jet 200 casing

Just enough to match the transfer cutouts in the barrel but should be less than 2-3 mm really

Dont go to big you dont have too, take your time and get the shape right https://m.facebook.com/AbsolutelyScoote ... &source=42

Use a base gasket on barrel and craft knife to cut it and then overlay on crankcase and scribe that.
You probably don't need telling that you "can't put it back" once you've taken it off. Slowly and carefully. Just blueprint it and while you're at it, match the inlet manifold in the same way.

Whats the best bits to use to rough out aluminium.
Anyone got any pics.
Cheers.
Boo

But is it bit of a myth of opening up your casings to match the barrels transfers. I appreciate that you are increasing the area, but you will get a drop in velocity (the speed that the air/fuel passes into the transfer ports).

Just wondering.

paulnobodyimportant wrote:But is it bit of a myth of opening up your casings to match the barrels transfers. I appreciate that you are increasing the area, but you will get a drop in velocity (the speed that the air/fuel passes into the transfer ports).

Just wondering.

Massive thread about this on face book recently some serious hp engines over 35 hp just matched them, some great input from darrel taylor , years ago it was all about making everything massive re ports then it went welding on cases now with input from tuners who were not originally scooter tuners it seems like intelligent porting is the way its going it about port angles, taper, velocity ,crankcase compression ,same with carbs I shudder when I read about 34mm carbs on a 200

paulnobodyimportant wrote:But is it bit of a myth of opening up your casings to match the barrels transfers. I appreciate that you are increasing the area, but you will get a drop in velocity (the speed that the air/fuel passes into the transfer ports).

Just wondering.

+1 "Gas Flow Velocity"

relate it to carbs. A small carb will flow gas quickly initially due to its narrow "choke" but will reach a situation where it can't flow any more.

A large carb will flow slower initially, but will flow more at high RPM.

Therefore, in theory a small carb CAN be better in some circumstances.

Chris

Thanks for the replys guys , I took my time and as stated gently matched the gasket to the barrel and then the gasket to the casing. Fingers crossed all will be good. I have another issue now ie ive just gone to fit the crank, mec 60x110 and con rod is picking up on the internal bore of the casing, just tried to measure it and it seems to be a interfeance fit.is it common to have to open up the casing ?? And if I do what clearance shoul I go for between the rod and the casing?

Whereabouts is the conrod catching on the casing? Is it the big end eye that's rubbing at BDC or all the way round? Sometimes it is necessary to cut a relieving channel in the crank case with some cranks.

Bear in mind the little end will determine the path of the rod I.e. In the centre of the barrel, so if it catches in an odd aposition it will never get to is that important?