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The 2-Stroke Garage => Turning Wrenches => Topic started by: RD350NL on February 03, 2025, 06:56:09 AM

Title: RD250 with 350 top end jetting
Post by: RD350NL on February 03, 2025, 06:56:09 AM
Hi all

I am in the process of converting my rd250b to a 350. For the jetting I referred to the manual, which indicates I should use 25 pilot and 130 main. Currently I am running 27.5 pilot and 120 main, the 250 top end runs great with this jetting. The concern I am having is that virtually everywhere I read the main should be 140 when running 350.

Can someone confirm the manual has a typo? Or should 25 pilot and 130 be fine.

PS: Bike is bone stock (does have a Vape ignition)

Thanks already
Title: Re: RD250 with 350 top end jetting
Post by: sav0r (CL MotoTech) on February 03, 2025, 07:47:42 AM
Just go rich and see. It can't hurt.
Title: Re: RD250 with 350 top end jetting
Post by: m in sc on February 03, 2025, 10:48:20 AM
that jetting also applies to a stock airbox, stock 350 carbs. us market rd350s were indeed 140 73& 74. so, the jet tubes have to be the same as a 350 and all sirbox parts in place w a stock filter, etc. otherwise,  the jetting will need to be figured out. 250/350 airboxes etc are the same as are the carbs,  but I'm pretty sure the jet tube and needle for both are 0-8 and 514 in the middle clip
Title: Re: RD250 with 350 top end jetting
Post by: stresa on February 04, 2025, 05:14:09 PM
@RD350NL
I have a couple of carb charts, parts lists and manuals, both USA and Europe versions, but not in one is a #130 stated for a 350. For a 73/74 350 always the numbers Mark stated or a #105 main jet, 5L3 needle, 2.0 carb slide with a baffled airfilter for the 1975 Europe B model which was a slightly different model to the USA B ones.
But carb fine tuning always depends on your own engine.
As @sav0r wrote. Start rich and work down if needed.
Regards Uwe