Scooterotica

i will soon be the proud owner of a gp 200 and just wondering whats the best cheap way to get a bit more umph with out major surgery or expense

simple.........cut 3mm off piston skirt (on inlet side)...........

port and polish, open things up a bit. that doesn't cost a thing - just your time.

sean brady scooters wrote:simple.........cut 3mm off piston skirt (on inlet side)...........

happy days whats all this stage four talk tho using the standerd barrel?

f@@k me Joe, you don't half seek out strife pal.

The SIL barrels are "stage 4" out of the box mate.

Juan wrote:f@@k me Joe, you don't half seek out strife pal.

The SIL barrels are "stage 4" out of the box mate.

ok ok just fancied a change tis all doubt ill have it for long anyway

sean brady scooters wrote:simple.........cut 3mm off piston skirt (on inlet side)...........

I was going to do this to my GP150 with 175 kit fitted and a mate offered to do it in work for me but when I got it back he had done it on a Lathe and taken 3mm of all the way round Plus he took 1mm of the top of the barrel.
But on fitting it and road testing it it flew with 6mph better top end (67mph sat nav ) and lots more mid range I was happy as hell

Then 9 weeks ago it was pinched :flaming: and only tonight the insurance said the cheque is in the post so my next Lammy will be a Li 150 special with 175 kit again but this time ill just cut one side by hand.
Will I still get the same results there abouts
I only did it last time because I read about it on here and in a shop and fancied a cheep boost in power

Lazarus wrote:

sean brady scooters wrote:simple.........cut 3mm off piston skirt (on inlet side)...........

I was going to do this to my GP150 with 175 kit fitted and a mate offered to do it in work for me but when I got it back he had done it on a Lathe and taken 3mm of all the way round Plus he took 1mm of the top of the barrel.
But on fitting it and road testing it it flew with 6mph better top end (67mph sat nav ) and lots more mid range I was happy as hell

Then 9 weeks ago it was pinched :flaming: and only tonight the insurance said the cheque is in the post so my next Lammy will be a Li 150 special with 175 kit again but this time ill just cut one side by hand.
Will I still get the same results there abouts
I only did it last time because I read about it on here and in a shop and fancied a cheep boost in power

I would like to know this as well, at the end of the year the std gp150 engine comes apart and transformed to a 175.

So 3mm off the inlet side..

Oohh... I was hoping someone would add to this, it's quiet interesting....

ok .......i,ll add to it a little more.......
cutting piston skirt to extend inlet timing really is a bit of a bodge...(from a tuners point of veiw).....but one that works very well
........
it is as i say ......the best gains you could obtain for no cost ,in the quickest time.........

cutting the skirt increases inlet timing but NOT area................
it is therefore much better practice to lower inlet port..........this increases time and area........
in fact ......lowering inlet port by 2mm would be far better than 3mm off skirt.............because timing and area have been increased............

having said that..........skirt chopping is something that most folk could do ......and is after all relativley reversable.............in that if you go to far .........just get another piston.....

the best way for most to approach this ,considering the vast assortment of barrels/kits available ......is to first measure your std inlet timing........you then have a base figure from which to work from.......
and then cut your skirt to suit what timing you would like..........say maybe 155/160 etc
or.......just cut a bit off at a time........try it ..then cut a bit more off .............and try it again..............and keep going until you know you have gone too far..........
and if you have kept notes........all you have to do is .........buy another piston and cut it to the best optimum that you found that suits you,your riding needs,and existing gearbox etc.................
all said.............chopping skirts is never as good as a proper stage 4 tune................

with a proper tuned barrel..........inlet would be modified.......and matched to manifold.
exhaust port will be modified..........as well as trans..........and usually ex port matched to ex manifold/u pipe etc...........all of which makes a difference............

good luck .......
sean