Jetting 300ex carb for 250es

[RUNMEDOWN]

I know some of you have done this mod to your big reds. The choke plunger kept giving me fits so I picked up a 300ex carb QB01A. I have read to use the stock 250es jets but also read another post that said to run a 120 main. I have a 130 in my old carb. I just order a bunch of new jets (125-148) due to the 300ex carb using the long style jets and my jets were the shorties. Not sure what to start at. I’m in Omaha so 1100 ft elevation. Stock airbox, uni filter, aftermarket quad boss quiet exhaust so basically stock.

[Chasebet]

I’m also planning on putting a 300ex carb on my 250es I’ve read that it really helps out with throttle response. But I havnt been able to find any definite info on proper jetting. I would like something to go off of instead of just shooting in the dark and having to throw a bunch of jets at it, just wondering if you got it figured out and if so what are you running? Thanks!

[ATC King]

It gets expensive buying a handful of different jets, and then you'll always have some that'll never be used.

It's cost less and is less wasteful to use a jet drill bit set and soldering iron. Once the size is dialed in, replace the soldered jet with a new factory one. The solder isn't as tough as the brass, although I've used some soldered jets for years and they held up fine.

Start with too small of a main, then enlarge it for each test until it's too large. Solder it and go back one size with the bits, then give it a good test ride. Correct size is found and there's not a small bag of useless jets left over.

That's how people have been carb tuning since the invention of carbs. People who often work on the same type vehicles and carbs tend to have a decent amount of spare brass, but if someone is like most average people and doesn't own dyno or carb shop, they probably don't already have a bucket of brass to choose from.

[deejaycee_2000]

You can buy multiple size jets (20pc) on Temu for next to nothing (purely for the dial in process) and once dialled in, buy the OEM jet from Honda. Hard to believe but the Chinese jets are quite accurate I have found, but I only use them for dialling in and only use OEM for the long run.

[Chasebet]

Yea jet bit kit would definitely be handy to have. And yea jets aren’t all that costly I was just wanting an idea to start with instead of taking a shot in the dark. There is a really good website that’s worth checking out if you’ve got older bikes it’s called 223 cycles, and they sell a Honda keihin 300ex carb and will set it up for your bike, you just tell them what bike you have, what elevation you will be running at and any modifications you have done to it, exhaust, intake etc… they also have a 1 year warranty. The only thing is it costs about 400 bucks where as an oem 300ex carb goes for around 120 on eBay but then you have to get it all dialed yourself.

Here is a link to that carb just in case anyone is ever interested.
https://www.223cycles.net/store#!/Ge...or/p/446692759