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2007 CRF450X EARLY Rev Limiter

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Ok guys, I know the bike doesnt have an "early rev limiter." I just needed a headline to get your attention. My question is jetting based, I have an 07 450x that ran awesome when it was cooler out at about 3K feet. Now, I'm back home at almost sea level with the temps much higher and my bike falls flat on it's face at full throttle in every gear. The motor misses immediately at WOT and almost sounds like a rev limiter. The bike sounds like it doesnt get enough fuel and needs a larger main jet so I tried going bigger, starting out at 150, then 160, and then 170, all with the same result but it seemed to get slightly better with each larger jet. My settings are as followed;

Main: 170

Pilot: stock

Leak: Blocked off

Needle: stock third clip

Backfire screen: off

airbox: snorkle removed

Emissions blocked off too

I dont know if the blocked off Leak Jet is causing it? I went to the sticky and no one else blocks their leak jet off, am I wrong for doing so? thanks guys!

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Sounds like your engine is shot. Just sell it and buy a new X. I'll take this one from you for $500. 👍🤣

Not sure how much affect the Leak as at WOT. Could be alot, just saying I don't know.

I find that I have to make small changes to the fuel mixture when riding in drastic temp changes. 1/4 turn to 1/2 turn. I can be in Low 40 degress to 110+ degree heat. Been told that means I probably don't have my jetting dialed in.

If you think you have a clogged jet have you pulled them to take a look.

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Ok guys, I know the bike doesnt have an "early rev limiter." I just needed a headline to get your attention. My question is jetting based, I have an 07 450x that ran awesome when it was cooler out at about 3K feet. Now, I'm back home at almost sea level with the temps much higher and my bike falls flat on it's face at full throttle in every gear. The motor misses immediately at WOT and almost sounds like a rev limiter. The bike sounds like it doesnt get enough fuel and needs a larger main jet so I tried going bigger, starting out at 150, then 160, and then 170, all with the same result but it seemed to get slightly better with each larger jet. My settings are as followed;

Main: 170

Pilot: stock

Leak: Blocked off

Needle: stock third clip

Backfire screen: off

airbox: snorkle removed

Emissions blocked off too

I dont know if the blocked off Leak Jet is causing it? I went to the sticky and no one else blocks their leak jet off, am I wrong for doing so? thanks guys!

The leak jet works everytime you 'whack' the throttle: the Accelerator pump engages and squirts fuel right down the bore.

A closed leak jet means you are squirting the maximum fuel amount the pump can provide. A 50-55 leak jet should be fine.

If you turn the throttle wide open, but slowly, does it still miss/stumble?

Is you pipe stock?

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No matter what, once I get to full throttle, it falls flat. I have to keep the throttle less-than for the bike to keep power and limiting the ability to ride WOT in every gear sucks. I was riding in sand this last weekend so WOT was quite often, and made the problem more evident.

Do I need to mess with the needle or clip? Possibly go fatter on the Main?

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No matter what, once I get to full throttle, it falls flat. I have to keep the throttle less-than for the bike to keep power and limiting the ability to ride WOT in every gear sucks. I was riding in sand this last weekend so WOT was quite often, and made the problem more evident.

Do I need to mess with the needle or clip? Possibly go fatter on the Main?

165-170 main should be fine. You probably have fuel delivery problem, or an air restriction problem. It sounds like all of your jetting is just fine.

The only way to know is to disconnect the airbox boot from the back of the carb, and watch the carb in action with the motor running.

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Good Ol JB Weld...When I had the emmissions thingy off I blocked that off with JB weld and kinda went a little wild and did the leak jet too.

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Good Ol JB Weld...When I had the emmissions thingy off I blocked that off with JB weld and kinda went a little wild and did the leak jet too.

you should probably take the JB-weld out of your little bag of tricks

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Not sure if you have the stock exhaust, but check the screen for blockage. May be choked up in the bunger.

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Good Ol JB Weld...When I had the emmissions thingy off I blocked that off with JB weld and kinda went a little wild and did the leak jet too.

Did you take the jet out to do it?

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The bike has the stock exhaust but the guts have been removed from it.

Haha, Yes, I took the jet out, JB welded it, let it set over night, then reinstalled it. I then took the bike to Coal Creek, TN. Which is up in the mountains some. THe bike ran like a raped ape. Then I got home and took it riding in much warmer, lower elevation, and first time out the bike would fall flat on it's face at full throttle. I tried putting a 180 main in the bike last night, cleaned the air filter, made sure no lines were pinched, and after starting it and twisting the throtte wide open; with the same result. I'm lost

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The bike has the stock exhaust but the guts have been removed from it.

Haha, Yes, I took the jet out, JB welded it, let it set over night, then reinstalled it. I then took the bike to Coal Creek, TN. Which is up in the mountains some. THe bike ran like a raped ape. Then I got home and took it riding in much warmer, lower elevation, and first time out the bike would fall flat on it's face at full throttle. I tried putting a 180 main in the bike last night, cleaned the air filter, made sure no lines were pinched, and after starting it and twisting the throtte wide open; with the same result. I'm lost

Could your airfilter be wet?

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Nope. Airfilter is good. I'm starting to think it may be a TPS problem. I've heard some guys disconnect it. Can I give this a shot on my 07? The missing is perfectly incrimental and sounds exactly like the rev limiter. I'm starting to think there is a throttle position problem.

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Eddie Sisneros, the jetting forum moderator, recommends brazing or otherwise blocking off the leak jet completely. I was temporarily skeptical, but tried it on my son's 450R and the throttle response is great.

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Eddie Sisneros, the jetting forum moderator, recommends brazing or otherwise blocking off the leak jet completely. I was temporarily skeptical, but tried it on my son's 450R and the throttle response is great.

is blocking off the leak jet go for an 06 crf250r too?

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In doing some more looking, I found another member who had a problem similar to mine and he found foam had gotten down into the 90-degree bend neck on the carb, where the fuel like connects and the float bowl was not able to refill fast enough. That leads me to believe mine is draining on full throttle and not able to refill in time. I'm going to check the fuel lines, filter, float bowl all again and try again. I'm also going to try with and without the TPS sensor. Will report more later...

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No luck no luck no luck. This is driving me crazy. The fuel filter in the tank looked somewhat collapsed near the bottom of it, like in the Reserve portion. I tried keeping the bike on ON and RESERVE with the same result.

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No luck no luck no luck. This is driving me crazy. The fuel filter in the tank looked somewhat collapsed near the bottom of it, like in the Reserve portion. I tried keeping the bike on ON and RESERVE with the same result.

You need to pull the fuel hose off the carb and WATCH the fuel come out for the time periods you are talking about.

Perhaps your float is sticking, not letting the float bowl fill up.

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Do you have an aftermarket breather on your fuel tank ? These can get blocked and cause problems with fuel delivery. Not sure if it would do what your saying...

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i took the entire bike apart two nights ago, inspected everything, dissassembled the carb and put it all back together. Everything checked out ok except I had a vacuum line vent hooked up to somewhere I Wasnt supposed to. So I disconnected that thinking that was my issue. Took the bike out yesterday and it acted the exact same.

My needle is a NTSU or something to that effect. It was not adjustable and not one I've seen listed in the jetting sticky. Could this be my issue?? I'm going to order some JD needles this week.

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