derbi gpr

[coggie]

i brought a derbi gpr im fully rebuilding it. it has a 70cc kit in and i just brought a 21mil carb to replace the standard 14mil carb,
i will be running the standard air box.

i would like to know if any one has any idea what main jet size i should start at?

cheers

i will up date this as the bike comes together
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2005 Derbi Gpr Replica, Airsal 70cc kit, K&N, Doppler Racing Crank, Metrakit Pro Carbon Exhaust, Metrakit Carbon Reeds - Currently Being Build (Project)
(SOLD) 2005 Derbi Senda SM Limited Edition 656/999 (SOLD)

[SpannerMonkey]

-Facepalm- So many people come on here asking us to recommend jet sizes... do you really think many people on an open forum about ALL of motorcycling (Not a specific area like 50-70cc) will know what jet size goes in a random carb (You havent even told us the brand or model of it) on a 70cc engine in a state of tune that we have no idea about?

Too many variables there my son. Normally I'm prettytolerable with all the 50-70cc questions, but this one KEEPS cropping up and as always people supply no information

Best bet, Fit it, see if it runs, run it for a SHORT time and read the plug.

Read this...This'll help https://www.theultralightplace.com/sparkplugs.htm
Sorry if I'm taking out my frustration on you my 70cc'd friend. I just wish some people would do more research themselves first before buying a part.
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My bike? A YX140 powered one-off Monkey Bike, something a little different!

[coggie]

thank you,

i had looked all over this site and couldnt find a post related, proberly me not looking hard enough. i phoned around but all replies i got were go from standard work up or down, problem is standard was a del'orto14 mil with a 50cc kit which i know would be too lean for a 70cc kit, im quite clued up as i am studying a level 2 motorcycle course.

was just interested where to start, if anyone else had done the same thing and could give me a rough idea.

i know im sorry for my mistake, i am not very good with writing and i didnt realise i didnt state it was a del'orto 21 mil, in a state of tune its being build with a metrakit 70cc kit metrakit pro carbon exhaust, and currently trying to find a replacement crank, (parallel drive) they all seem to be tapered.

thanks
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2005 Derbi Gpr Replica, Airsal 70cc kit, K&N, Doppler Racing Crank, Metrakit Pro Carbon Exhaust, Metrakit Carbon Reeds - Currently Being Build (Project)
(SOLD) 2005 Derbi Senda SM Limited Edition 656/999 (SOLD)

[SpannerMonkey]

To be fair, the size of the carb wont cause it to run lean, it'll just only be able to supply smaller amounts of the mixture. As stated, I think it would be best to start with the standard jetting then work up or down. it's the only way you're really going to find out =/
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My bike? A YX140 powered one-off Monkey Bike, something a little different!