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aharm117

popping on stock 06 yz450f exhaust

30 posts in this topic

my bike pops alot when i let off the throttle, really loud. how do i fix this

The 06's come really lean from the factory. Put a 48 pilot and 168 main in and adjust the fuel screw as necessary.

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Pends on your elevation, too. I'm at 700 ft and mine took a 50 pilot jet. Yamaha mechanics at the local shop say Yamaha recommends 48 for my area. I know of others resorting to the 50 as well. Higher elevations, where the air is thinner, will probably require a leaner pilot jet than the 48-50 for my area. Check with your local Yamaha mechanic.

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My elevation is from 2500 to 6000...

I put a FMF pipe on my bike and then it started starving for fuel when I gassed it. It would stall the bike and it popped badly! I went down to my shop to pickup a 50 pilot jet and they told me to use a 55 pilot jet since the new pipe is on it. I put the 55 pilot jet in and one of them red fuel screw that is set to two turns. Everything else is stock. I rode the bike but only on flat roads, because I can't ride over rough ground right now (my shoulder trashed). Anyways, when I rode it the power feels linear now unlike before, it is easier to ride now. Before it used to have a hard hit in the top end that felt like a two strokes power band.

After reading all of these jetting questions, a 55 seems kind of high. Wondering if I am going to start fouling plugs when the weather starts to cools off?

What would happen if I were to changed the fuel screw to 1.5 turns, can someone tell me what the fuel screw effects? Will it run at 1 turn, 3/4 a turn?

Thanks!!!

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I noticed my bike doing this also, not a lot but a little more than normal so I'm going to try and mess the fuel screw before i do anything. Then if its not fixed I'm definitely going to have to re jet it. Other than that the bike is awesome.

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Also, put some slack in your hot-start levers cable. My bike has been rejetted, but sometimes I was getting alot of popping on decel, since I've put some slack in the cable (there was none) no more popping :thumbsup:

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can someone tell me what the fuel screw effects?

Thanks!!!

Bottom end.

Out is rich

In is lean

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Look under the carb.....use a flat tip screw driver end from a socket thing.

lightly seat the pilot screw. set the pilot screw to 1 1/2 turns to 1 3/4 turns out.

Use the RPM adjustor and adjust the bike to a fast idle. turn the pilot screw so the bike idles slow and bogs down a little (idles rough, generally screw inward)...slowly turn the pilot screw in the opposite direction...the idle should get faster and faster...and the exhaust pitch should start sounding smooth and tuned. Find the position where the bikes rpms are maxed out and the exhaust sounds tuned. do a quick ride around to cool the engine down and shut the bike off..... count the number of turns to seat the screw. If its over 2...you need to rejet the carb. If not....retune the engine the way you just did.

After that....just do the above when the bike starts popping again.

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Look under the carb.....use a flat tip screw driver end from a socket thing.

lightly seat the pilot screw. set the pilot screw to 1 1/2 turns to 1 3/4 turns out.

Use the RPM adjustor and adjust the bike to a fast idle. turn the pilot screw so the bike idles slow and bogs down a little (idles rough, generally screw inward)...slowly turn the pilot screw in the opposite direction...the idle should get faster and faster...and the exhaust pitch should start sounding smooth and tuned. Find the position where the bikes rpms are maxed out and the exhaust sounds tuned. do a quick ride around to cool the engine down and shut the bike off..... count the number of turns to seat the screw. If its over 2...you need to rejet the carb. If not....retune the engine the way you just did.

After that....just do the above when the bike starts popping again.

HUH? :thumbsup:

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I just rejetted mine this weekend as it was lean as well. I went with the 45 pilot and left the main alone. Runs much better on the limited testing I did.

I had a hell of a time getting to the carb :thumbsup: . It's a lot tougher than my 03. Anyone have any tips in getting the carb turned enough to get to the jets? Very little room to work. It took me about 2 hours :ride:

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Excessive decel popping is almost always the result of one or both of two things; lean idle mixture or an air leak in the exhaust. In some engines it can be brought on by a very excessively rich condition, but this is much less common. You should usually troubleshoot it by looking for the air leak first, because otherwise, you will end up with a bike that's too rich to run right because you fattened it up to cover over a pop that was actually caused by something else. FMF has a slip fit midpipe/header. Check it.

Lean idle jetting can be as simple as a fuel screw adjustment, or it can be an undersized or clogged pilot jet. Another, less common cause is a hot start plunger stuck partly open.

Besides, a little bit of popping on decel is normal for a YZ450, and IMO, any YZ450 that never pops at all is too rich on the pilot.

The '06 is, as was pointed out, built lean. I run a 45 pj/165 main, and it's worked well so far. When the bike first came out, in the cold months, a lot of guys immediately went with a 48/170 set up, and many of them dropped down to the 45/165 as the weather warmed up.

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Decel popping is almost always the result of one or both of two things; lean idle mixture or an air leak in the exhaust. You should usually troubleshoot it by looking for the air leak first, because otherwise, you will end up with a bike that's too rich to run right because you fattened it up to cover over a pop that was actually caused by something else. FMF has a slip fit midpipe/header. Check it. Besides, a little bit of popping on decel is normal for a YZ450.

The '06 is, as was pointed out, built lean. I run a 45 pj/165 main, and it's worked well so far. When the bike first came out, in the cold months, a lot of guys immediately went with a 48/170 set up, and many of them dropped down to the 45/165 as the weather warmed up.

48/170 is definitely the below 65 degree jetting start for the 06.....the 45/168 works great from 70-85 and then the 165 is all out 85+...degrees

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ya mine does that shitt wen i wasnt used to the decomp starting it from what im hearing its normal ?

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Decel popping is almost always the result of one or both of two things; lean idle mixture or an air leak in the exhaust. You should usually troubleshoot it by looking for the air leak first, because otherwise, you will end up with a bike that's too rich to run right because you fattened it up to cover over a pop that was actually caused by something else. FMF has a slip fit midpipe/header. Check it.

Besides, a little bit of popping on decel is normal for a YZ450, and IMO, any YZ450 that never pops at all is too rich on the pilot.

The '06 is, as was pointed out, built lean. I run a 45 pj/165 main, and it's worked well so far. When the bike first came out, in the cold months, a lot of guys immediately went with a 48/170 set up, and many of them dropped down to the 45/165 as the weather warmed up.

That is the same jetting i am running on my 06 except for an NFLR needle- Dr D pipe. Works perfect for So Cal Tracks.

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One way is to have a helper hold a rag over the outlet, raising the pressure in the pipe and making the leak more obvious. Careful of burns.

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Need Help!!! Ok so I bought a 2006 YZ450F that only had 3.5 hours on a fresh motor from a vet pro rider..the bike was meticulously taking care of it never had fuel in it till 2010 when he bought it from parts unlimited it was a display bike...heres the issues popping n backfiring on decel, hanging idle, boils over (within 30 seconds) the worst part is it starting smoking (white smoke) and has a horrible bog from idle two about 1/8 throttle!! I've cleaned n the carburetor 3 times replaced pilot jet with a #45 had a #42 replaced hot start cable, plunger, spring, seal advanced the ap timing about a half turn in, o-ring mod and have tried every 1/4 turn out on my air/fuel thumb screw from 1 turn out to 3 with no difference...somebody PLEASE before I have a $3000 bonfire!!!!

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Here's the weird part it starts first kick hot or cold n absolutely rips up the road but falls on its face out of every corner on a mx track and yes I roll on the throttle but still will bog..not some much concerned with the popping n backfiring as the (white) smoke n bogging!

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