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RB Designs head mod


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Best bang-for-buck mod for a YZ250 (versus a pipe, etc)? I've read some good things about it and I'm thinking I might do it before I even ride the bike.

Thoughts?

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Best bang-for-buck mod for a YZ250 (versus a pipe, etc)? I've read some good things about it and I'm thinking I might do it before I even ride the bike.

Thoughts?

had rb do my head and carb and bike has been impossible to jet since..... working on it since august, including 3 1/2 hours last night:foul: Made the bike super sensetive to clip, needle and a/s changes. I have tried it all, mains pilots etc......

OH WELL gave me a good one liner "It ran great before i fixed it":bonk:

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Try it stock first. Then do the head mod.

I woudl hold off on the carb mod as I dotn think its necessary. Eric Gorr is taking these up to 300cc's with the stock carb. It should be fine for anything were doing.

The head mod makes jetting easier, btu to appreciate it, you need to ride the stock bike first.

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I have had good luck with the RB carb mod. Runs great, but requires a small jetting change for each 20 degrees of temp change. He did my head with tighter squish but slightly more volume (euro spec-22.5cc I think) for a little less compression. That along with correct timing has mine about perfect. I highly recommend it. That said, the most power increase I felt was putting on a PC works pipe. It kills some low end but has a huge hit in the midrange. I still prefer the stock pipe for MX.

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The head mod is the best thing you can do to a YZ250. I haven't tried RB Designs, but I've done my own head at .045" squish.

Your jetting should not change much from standard with the head mod. It should be easier to jet too.

As for the carb mod, I don't plan to spend any money there. The OEM carb is easy to jet, and works well if set up properly.

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The head mod isn't exactly a power increase. More of a livability thing.

I could not jet my bike until having the head worked... opposite of Rollie's experience. There was no more power though.

Best bang for the buck power wise for me was the 285 top end. No surprise there.

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stop reading and ride the darn thing!! 🙂

the head mod helps with throttle response mostly. you are coming off a 4-stroke so the bike will feel ungodly responsive compared to the slow reving 450 you were riding. + you can't see the benefit of a mod until you have ridden the bike stock. just my 2 cents.

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I had the RBD head mod AND the carb mod done on a stock engine. I had the carb bored to a 39mm and a divider plate installed. Definitley increased my bottom end. The head mod made it run a little cleaner/crisper. jetting & spooge is a PITA regardless!! I am really enjoying the stock pipe set up. Not looking to change that unless I get a major dinger!

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I had Ron mod my head to narrow down the squish to around .045-.050 and maintain sufficient volume so I can run pump gas. Compression is right around 200 psi.

As PC notes, it hasn't necessarily boosted power, but the engine runs cleaner and is more responsive. My motor was a spooge monster before the mod and now it hardly spooges at all, indicating more thorough burn.

It's definitely worth checking your squish and making you decision from there. If you're at .060 or so you might be ok. In my case, I was at .090+, so it was no brainer.

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stop reading and ride the darn thing!! 🙂

the head mod helps with throttle response mostly. you are coming off a 4-stroke so the bike will feel ungodly responsive compared to the slow reving 450 you were riding. + you can't see the benefit of a mod until you have ridden the bike stock. just my 2 cents.

I'd ride it if I had it......still trying to track a bike down!

I know what to expect with a stock bike.....I had an '07 YZ250 before the 4-choke.

Anyway, thanks for the info guys. I'll probably just ride it stock for a while and see how she runs. My '07 spooged a lot, but then again I never bothered to mess with the jetting because it ran so good.

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I'd wait on the head mod (and any other mods) until you simply ride it.

From there, I'd work on getting your controls set to where you like them (including new bars, raised/lowered bars, footpegs, etc.). This includes clutch and throttle tension/response.

I'd get the jetting in line before seriously riding, too.

THEN I'd go for a suspension revalve set up for your weight and type of riding - if necessary. Stock might work for you, and there's no sense reworking new suspension if you don't need to.

After that, I'd consider the head mod if only to improve jetting. The power increase or change is really kind of hard to notice unless you're keen on those sorts of things.

Then maybe go for a pipe or silencer.

RCannon said it best: mods are really pointless unless you have a goal in mind and a direction worked out. You need to know what you're aiming for and how to get there.

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