Porting question

Hi guys,

recently I've enlarge ports on PK125XL with DR130 kit. Since then the engine just isn't the same. In first gear it doesn't rev as high as it did and top end speed isn't good at all. I've tried different jet's from 78 to 87 on 19 carb, but no good. I tried changing the timing but still no improvement. Also I noticed that now it won't run in idle (if I remove the 90°knee from cylinder then it runs OK - loud as hell though :-). Should I go for 24carb or did I f*** it for good. I tried to be careful and to match the ports as much the same as I could but . . . this was my first time. Any thoughts would be greatly appreciated.




Cheers Jim,

I guess I just needed to hear that. I'll also switch from 0,5 mm base gaket to 1,0 mm and increase commpresion to 10,5:1.



Thanks Jim,

I've already changed clutch + exhaust (Sito Plus). I just don't want to buy new carb if it won't help. I'm concerned about lack of power in first gear (which was there before) and same if not lower top end speed. Spark colour is right (that rich brown). I will check the compression rate, but apart from that I have no clue.


I think you will need a bigger carb, plus maybe some other bits.

If you download the SIP catalogue there is a section on smallframe tuning that tells you what you need to change when you put a kit on, for a DR130 it says:

Upjet carb, reinforced clutch, tuning exhaust, upgear kit 2.56, racing crank, 24 carb kit.

You should definately notice a difference if you change all that - don't know what else you have done already.


definately think a bigger carb will help.

The gearing would only help if you were revving too high.

cut crank would help but wouldn't make THAT much difference.

Before considering spending more money on big carbs etc; lets consider what you have done so far .

have the transfers been matched to those in the base of the barrel ? Is your timing, jetting done in line with the DR instruction leaflet, is everything sufficiently torques up and sealed.? have you set the cylinder head squishband ?

no worries good luck with it


Sorry for late reply,

I've tried to match ports to my best. There were marks on the casing where the base of barrel sat. Timing seems OK as I played with different settings. Everything is sealed and torqued as it should be. Jet looks to be right size. Kit was already on when I bought this Vespa so I don't have leaflet. Squishband - so far I only seal the head straight on. I was wondering when you know to mount bigger carb ? And when porting is done poorly ?