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red7

Surging/bog...jetting issues.

9 posts in this topic

I've been reading tons of threads on bog and surging but I'm still confused on how to diagnose my problem. I just got my '06 YZ450 back to Mexico and broke it in yesterday. With stock jetting it seemed to have crisp response when snapping the throttle but with tons of popping on decel. So today I changed to the 48/170 as recommended and the popping was much better (though still there a little) but I'm now having problems where it bogs (to the point of stalling occasionally) if I snap the throttle open quickly. I didn't notice this yesterday. What's even worse now is that the engine doesn't want to run steady in any gear at 1/4-1/2 throttle without surging/cutting. Should I keep the 170 and go back to the 42 pilot? Should I try a 172 to totally eliminate the popping or is it enevitable? Should I change the clip position? The surging at a constant 1/4-1/2 throttle is my biggest problem as I can live with the little bit of popping. What would be causing this. Oh, I also added a zipty FMS and played around from 3 turns out to all the way in and didn't notice a big difference. BTW- I live at sea level and it's about 70 degrees. Thanks!

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Try a 45 pilot and a 168 main. Live with a little popping. Jetting is very much trial and error. Everyone runs different gas, altitudes vary, temps and humidity vary. Going from a 170 to a 172 main is not going to effect the popping. The popping is happening when the throttle is closed and the bike is decellerating, correct? The main jet is not in play under this scenario.

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I've been reading tons of threads on bog and surging but I'm still confused on how to diagnose my problem. I just got my '06 YZ450 back to Mexico and broke it in yesterday. With stock jetting it seemed to have crisp response when snapping the throttle but with tons of popping on decel. So today I changed to the 48/170 as recommended and the popping was much better (though still there a little) but I'm now having problems where it bogs (to the point of stalling occasionally) if I snap the throttle open quickly. I didn't notice this yesterday. What's even worse now is that the engine doesn't want to run steady in any gear at 1/4-1/2 throttle without surging/cutting. Should I keep the 170 and go back to the 42 pilot? Should I try a 172 to totally eliminate the popping or is it enevitable? Should I change the clip position? The surging at a constant 1/4-1/2 throttle is my biggest problem as I can live with the little bit of popping. What would be causing this. Oh, I also added a zipty FMS and played around from 3 turns out to all the way in and didn't notice a big difference. BTW- I live at sea level and it's about 70 degrees. Thanks!

You need to adjust your fuel screw and possibly your idle. Do a search on how to adjust your fuel screw and you'll be fine. The jetting that you added is also fine. I assume you added a new aftermarket screw?

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The stock AP squirt is huge. This is why the bike is jetted so lean on the pilot. Basically they leaned the pilot to make up for the huge shot of fuel from the AP. If you richen the pilot to get rid of the popping and leanness on decel, the bike will be way too rich at the crack of the throttle. That is why doing the AP mod or at the very least, getting the AP squirt down with a larger leak jet and timing the squirt correctly, is so important. Doing the AP mod decreases AP duration and makes it much quicker in response, this way the AP has a minimal effect of the rest of the jetting and every other circuit can be tuned correctly without fear of the AP screwing things up.

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You need to adjust your fuel screw and possibly your idle. Do a search on how to adjust your fuel screw and you'll be fine. The jetting that you added is also fine. I assume you added a new aftermarket screw?

Yes, I added the zipty FMS. I tried it all the way in and a ways out and nothing changed the bogging or missing at constant throttle. I can live with the popping but this surging/missing thing at constant throttle is new 'cuz it didn't do it with the stock jetting.

The AP mod sounds cool. I wish there was a write up on it for Yamahas. What leak jet would you guys recommend for my '06? Problem is I just got back to Mexico so getting them is a hassle. Maybe I'll just go back to stock jetting and live with the popping for now because this surging is strange.

Is it the main jet that causes the popping? Couldn't I just up the main and go back to the stock pilot (or maybe a 45 as a compromise). It just seemed like the throttle was so much crisper yesterday before rejetting. The popping went way down though so if I can go back to the crisp throttle, no surging and keep the popping down I'd be happy.

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Eddie recommended I just unhook the TPS to get rid of the surgin/missing issue. Would that just be a bandaid fix to improper jetting or are a lot of you doing this. I searched the subjects but you really have to get specific feedback since there are so many variables that effect jetting. I'd like to do the AP mod. Where can I get leak jets (tt store?) and what all ones should I get? Again, sea level and I'm currently running 48/170 jetting with the others stock.

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Is it the main jet that causes the popping? Couldn't I just up the main and go back to the stock pilot (or maybe a 45 as a compromise). It just seemed like the throttle was so much crisper yesterday before rejetting. The popping went way down though so if I can go back to the crisp throttle, no surging and keep the popping down I'd be happy.

Again, the main jet has nothing to do with the popping. I went through this same stuff with my bike. Going to the 45 pilot and 168 main and tuning the fuel screw cleared mine up. Jetting is not the same for everyone. Conditions are constantly changing. I don't know if you are still using gas bought in the USA or gas bought in Mexico. If you are buying gas in Mexico expect each tank to be different from the one before.

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Again, the main jet has nothing to do with the popping. I went through this same stuff with my bike. Going to the 45 pilot and 168 main and tuning the fuel screw cleared mine up. Jetting is not the same for everyone. Conditions are constantly changing. I don't know if you are still using gas bought in the USA or gas bought in Mexico. If you are buying gas in Mexico expect each tank to be different from the one before.

This bike is brand new so I'm just finishing up my tank of USA gas. Maybe it will run better when I fill it up with Mexi gas today.:lol: Actually, I haven't had any problem with my WR450 using the 92 octane gas down here.

Ok so main jet has nothing to do with my popping. Could it have brought on the 1/4-1/2 (heck maybe even 3/4) throttle stumbling/missing problem or is that from the 48 pilot and the AP issue Baron mentioned? Should I drop to a 45 pilot? A 168 or 165 main? Should I leave the 48/170 and raise the clip to the 3rd position to lean it out? I've been searching for the thread that tells you what jets effect what portion of the throttle. I can't find it but is it correct that the pilot effects 0-1/4 throttle, needle clip position effects 1/4-3/4 throttle and main 3/4-WOT? Given that I'd think my problem is the needle for the stumbling issue and that the AP mod should take care of the bog when I snap the throttle. Am I close?

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Ok so main jet has nothing to do with my popping. Could it have brought on the 1/4-1/2 (heck maybe even 3/4) throttle stumbling/missing problem or is that from the 48 pilot and the AP issue Baron mentioned? Should I drop to a 45 pilot? A 168 or 165 main? Should I leave the 48/170 and raise the clip to the 3rd position to lean it out? I've been searching for the thread that tells you what jets effect what portion of the throttle. I can't find it but is it correct that the pilot effects 0-1/4 throttle, needle clip position effects 1/4-3/4 throttle and main 3/4-WOT? Given that I'd think my problem is the needle for the stumbling issue and that the AP mod should take care of the bog when I snap the throttle. Am I close?

Read:

http://www.thumpertalk.com/forum/showthread.php?p=4210139#post4210139

As for info on the effect of jets vs. throttle position, your manual has all of that information in detail, beginning on page 7-3 .

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