RB head/carb mod, or EG300 kit?

If you were going to throw money at your YZ to get more power and crisper/more torquey low-end out of the motor, what would you do? Looking for more pull below the hit on hillclimbs, and more low end pull through loose sandy stuff without having to scream it, but still have the wild top end there.

The EG300 kit looks to be ~2X as much as the RB mods. Not opposed to having the carb modified along with the 300 kit either.


Desert/singletrack bike. Might be on a track once in a great while. Pretty sure it has the WR gears from the previous owner already. Run 14/47 gearing at the moment, but may throw a bigger rear sprocket on for certain things.

Like they say, "There is no replacement for displacement"and as an EGyz295 owner I definitely say go with Eric's engine, it is awsome


How easy was it to jet correctly? Pump gas or race gas?

What sort of fuel range were you able to get compared to the stock motor?

Hey GHill, I've been wondering the exact same thing, I do GP races with a dead engine start though, so I wonder how much difference in ease of starting 250 vs EG295? I'm really pretty happy with the stock powerband, but isn't more allways better?

A dead engine start with a well-jetted 250 and a properly set-up Rekluse is a breeze!

Hey GHill, I've been wondering the exact same thing, I do GP races with a dead engine start though, so I wonder how much difference in ease of starting 250 vs EG295? I'm really pretty happy with the stock powerband, but isn't more allways better?

Yup, more is always better:thumbsup:I also race offroad with dead engine starts, I have had absolutely no issue w/ 2nd gear dead starts.


I had the rb head on my yz 250 as well as the single ring wiseco piston. These mods were great and I woudl recommend them. Still, they are no match for the 300 kit. Both are very fast, but the 300 kit has torque that you cant get with 250.

Not a sif I expected them to be and that comment about displacement is right on. Theres no reason to stay at 250cc;s unless a rule makes you.

You guys are killing me, I guess I'll have to drop another $600 on the YZ to EG this winter.

The rb carb mod is still well worth it to ez jetting and Get him to grid your slide to an #8.

Already running a #8 slide with the NE3J, 2nd position. Made a good bit of difference.

Any commentary about ease of jetting with the 300 kit with the better-all-around porting?

Has anyone got a good jetting or setup solution for the off-idle detonation issues that I'm reading about with the 300 kit?

What off idle issues are you talking about? My bike runs perfect. The correct jetting and a number 8 slide work well for me.

Just read through some old threads. Seemed to be an issue that came up a few times, and moreso with the setup for pump gas.

Good to know on the slide though.

Probably send my stuff off next month. After some other very gucci mods to the bike, it's going to be probably the nicest damn YZ around....can't wait.

The 8 slide is great for the kit, or it has been for most. The slide lets you dial in the pilot much easier.

Its hard to say, as I only have experience with my bike. Oh, one other issue is timing. Its been way off the factory spec and I believe that makes pinging worse.

That was one of the first things I sorted out after buying this bike last year. It was definitely way off, and setting it back to stock, then 2 degrees retarded made the powerband a lot nicer.

I've performed that same check on 5 other late model YZ's since then, and every single one of them have been off by around the same amount.

I think some people experiance some deto on the pump gas deal at around eighth to quarter throttle at about sea level to 500 ft.

I use a JD red needle pos 2, a std slide #7 and a 50 pilot.

The JD needle has a richer straight section at that throttle pos, i tried to fix it with pilots but just ended up with spooge and didnt really fix the deto.

have you tried an octane booster? Worked for me.

I did the RB head mod and carb mod--I did them at separate intervals to see the gain of each. The head mod did not make as big of a difference as the carb mod but still worth it IMO. The carb mod increased my bottom end alot--the best mod I have done to increase bottom end.

Both mods together gave me very noticeable gains in power throughout--more so than my pipe and RAD valve--probably still not as much as the EG300 will give you though.

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