Alrite guys as some may have noticed I swapped my zip70 for a 1993 Piaggio SKR125 (Old shape skipper, 125 2T typhoon engine). And it just doesent feel as sweet or as powerful as it did a few days ago.. Im getting 55mph top speed, 60 at a push.. Was getting close to 70mph on the clocks on friday! And power is down, theres not really any bogging going on but just feels like my 70 now. Ive been suspecting the 17year old carb is nackard, I think its a Mikuni carb as its an early piaggio (if someone could confirm this).. And it is leaking fuel slightly so Im thinking a rubber gasket or something is rotten. So I was thinking about getting a Dellorto 20.5 for it & wanted to know if it would be a straight swap over from my mikuni carb? Or would I need to buy another throttle cable or anything else to make it a straight swap over? Everythings standard, it had 16g rollers in which was causing it to bog out but Ive fitted 12.5's and that sorted it. Then 2 days later its loosing power and leaking fuel.
AIRC the Mikuni has a longer elbow on the carb top? You can`t swap mikky and Delorto jets. I know you did`nt ask this but for the record... Mikuni use 6mm metric course (1mm pitch)(same as Weber) and Delorto use 6mm metric fine (1.5mm pitch). Mikuni are the only manufacturer to use a metric jet sizing system. A Mikuni #100 jet is 1mm/ #200 is 2.00mm/ #80 is 0.80mm etc etc. All other makers have a specific jetting system based on flow rates or random testing and it would be a beautifull world if they all saw the light and followed mikuni! Back to you... Buy a delorto 21mm PHBG meant for a tuned 70. MAKE SURE that when you fit it or any other carb that the oil pump/throttle cable set-up is correct (unless you run pre-mix). Cheaper than the 25mm delorto and set-up for mega bucks that some companies are touting. It will do the job better than the 20.5 mikky or delly and is just as adjustable. Buy a new manifold for a 70, your rubber is probably corroded,strip your reed block out and fit Polini GREEN (0.35mm) petals. Please don`t ask about jetting this.....I have a set-up but it may not work on your scoot so i`m not going to suggest it. Be aware that the PHBG Delly`s take 5mm jets not 6mm but there is plenty of scope for tuning down to different size/length/profile needles and a choice of atomisers/pilots etc.
Cheers for the reply mate! Really helped quite alot, the reason I wanted to change carb mainly is because the power loss and Im 90% sure its the old carb playing up and mikuni's are a pain to change jets. I will take into account about getting a 21mm carb with 70 manifold, but id like to hear a few more views on this.. But probably gonna get a 20.5 still, I know about jetting so dont worry im not gonna ask! :thumbsup:
i found a 21mm to be good on my old 125 once setup with decent filter straight inlet and reedblock and l/c ignition it power wheelied alot more and was a way better bike deffo worth doing you can get those bits cheap too if you shop around
So I just need a Delly 21mm, manifold for 70cc (I dont want to use a straight manifold as im running the airbox.. And can I use the standard 125 reedblock with that? Or will I need an aftermarket reedblock? Cheeers guys!
can run a stock 125 one as there a good match to the reedblock and yeah can just change the petals in the stock block as the gaind performance with a aftermarket reedblock isnt huge
