250sx mods

**ChrisB** · 03-09-2015, 06:24 PM

Hey guys, I know this topic has come up a few times but I can't seem to find any real concrete answers on some stuff. So far I have the 200x front end on and a dg muffler on the way (not even sure if it's for an sx but I'll make it work) just wondering if any body has tried the bigger carb (350x?) in they're sx, if it worked or not and if anything else needed to be done. My sx is running fine now but there is something up with the carb and it is lacking a little power when I really lay into the gas and its bothering me haha. Was thinking about ordering a carb off wincycles, but also couldn't find anything concrete on that. Figured I'd ask about the bigger carb see if anyone here had any input. Also anything else that you guys know could be done for any sort of improvement I'd love to hear it. Thanks

**Flyingw** · 03-09-2015, 07:10 PM

The aftermarket carbs are hit and miss. Guys have reported success but most have reported problems from cables not fitting right to running issues. The 350X carb is the same QA series carb just bored larger for the bigger engine. Yes they do improve performance but rejetting is usually required otherwise they drop right in. Even with a stock carb, the DG muffler usually drives rejetting so going to an X carb and DG muffler, I will say rejetting will be required. The most important thing to do to your stock carb is the synchronization adjustment of the linkage. This adjustment ensures the butterfly and slide actuate at the same time. Over time, the slide tab will bend knocking the synchronization out of adjustment. Also, keep in mind that the CDI has the timing curves built in to it and that has allot to do with rapid acceleration. The SX is nothing more than a sport version of the ES with different gearing otherwise the engines are very similar in performance. One last thing, the QA series carbs have a nasty habit in that when you stab the throttle right off idle, some carbs hesitate and some just flat out fall on its face. I have been looking in to this and thus far, have no concrete explanation as to what is causing it. Here is my tutorial on rebuilding the QA series carb and the synchronization adjustment is addressed in it. http://www.3wheelerworld.com/showthr...54#post1257154

**Flyingw** · 03-09-2015, 07:13 PM

One last thing. If you do go with the X carb, the stock SX choke assembly drops right in and works exactly the same so the X choke lever and choke valve should be omitted and use the SX choke valve and cable.

**ChrisB** · 03-09-2015, 07:27 PM

Thanks a lot, lots of helpful stuff.. X parts aren't the easiest to get around here so it would probably cost me. Do you think anything I might gain would be worth the money or just tune and rejet my carb so it's top notch would be my best bet, considering I don't have piles of cash to throw into this. Also what jet size would be appropriate with the dg muffler? I haven't messed around with jets much so I'm not to familiar. Also it gets fairly cold here in the winter say around -20 Celsius if that would effect your jet opinion at all I'm not sure

**Flyingw** · 03-09-2015, 07:45 PM

Since every motor breathes differently, I would suggest getting a rebuild kit for your stock carb and do a complete cleaning and rebuild on your carb and see what you get. You may or may not need to rejet. With the sx keep in mind they are built for torque and not speed.

**ChrisB** · 03-09-2015, 07:53 PM

I did have a 250es motor in before, with a different carb which I no longer have and that had more top end power and speed than the sx motor I have in right now, that's mainly how I know it's not giving me the power it should. You still selling rebuilt carbs? Was looking through your post and it looks like you would do a much better job than I would haha. I get into some stuff and have a hard time taking my time with jt. Just wanna get it back on and get the bike out of the shed. Not the way I should be I know but that's it. If you're still selling them how much do you ask for them?

**Flyingw** · 03-09-2015, 07:55 PM

That's unusual because the ES is lower geared than the SX. I don't have any ready built carbs now but I can rebuild yours if you like. 95.00 and that includes the return shipping.

**Flyingw** · 03-09-2015, 07:57 PM

Look on the bowl rim under the hose nipple and tell me what carb you have. QA01, 02, 07, or 08

**Flyingw** · 03-09-2015, 07:59 PM

Opps, your in Canada. It will be a little bit more as shipping is more than the lower 48.

**ChrisB** · 03-09-2015, 08:02 PM

Yeah I knew the sx should be a little peppier that's why I was a little let down when I finally got my sx motor in and went for a ride. And I'm actually going to be away working for a while, was hoping you would have some there cause im probably not going to be home for a few months.. Was hoping to have whatever parts I needed waiting for me when I got home so I could put it all on and be ready to go in no time. I'll see what I can do though maybe I'll take a look on eBay for a good priced one and just get it sent to you?

**redsox** · 03-09-2015, 08:02 PM

I've had 3 rebuilds from FlyingW. Worth the $$ all day long. he does a better job than I would on my own and in less time. $95 is well worth it. can not go wrong.

**ChrisB** · 03-09-2015, 08:07 PM

Sounds a lot more reliable than an aftermarket carb and probably run me around the same price. Any other additions you guys can think of for the sx I should maybe consider?

**ChrisB** · 03-09-2015, 08:20 PM

Just looked at e bay doesn't seem to be much good on there. Maybe I would have better luck with finding someone on here with an old one to sell

**Flyingw** · 03-09-2015, 08:41 PM

I'm easy. whatever works for you. You can always get me at jamesbaldwin99@gmail.com. My ship to address is:

James Baldwin
14712 SE 77th Terr
Choctaw, OK 73020

Any one of the QA carbs I mentioned above will work.

**ChrisB** · 03-09-2015, 08:46 PM

Thanks a lot. We'll be in touch

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250sx mods