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Discussion Starter · #1 ·
Hey there,
I have a completely stock 06 Rhino 450 with an odd carb issue that I’ve been hitting my head over. I got the rhino about 6 months ago and it had a massive backfire on decel. I tried a bunch of jet tuning to fix it, but had no luck. I then found out the o-ring on the needle valve housing was not sealing, causing the carb to overflow. Which I then figured is my backfire issue. I found a new niche carb for almost the same price as a rebuilt kit, so I put that in. Then the engine would idle but would die if you gave it any throttle. I fought at that for a while and figured it was just a cheap carb. So I bought the rebuild kit for my factory carb. Installed all the new jets, o-rings and the needle valve assembly. Tested and the valve sealed perfectly no longer leaking. Then I went and fired it up and it now does the same thing as the new carb did… idles great but dies with any throttle. It does rev with the choke on though. Which makes it seem like it’s lean. But it’s all factory with factory jets. Only 1000ft above sea level. It should run great. I then tried putting a richer pilot jet in and had no changes. Float level seems good. Fuel pumps working good. No vacuum leaks that I can see. I’m kind of stuck. Seems it ran perfectly with the fuel overflowing, other then the backfire, but now working as it should it’s way worse. Anyone have any thoughts??? Thanks!
 

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Captain Zoom Sand Pirate
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Hey there,
I have a completely stock 06 Rhino 450 with an odd carb issue that I’ve been hitting my head over. I got the rhino about 6 months ago and it had a massive backfire on decel. I tried a bunch of jet tuning to fix it, but had no luck. I then found out the o-ring on the needle valve housing was not sealing, causing the carb to overflow. Which I then figured is my backfire issue. I found a new niche carb for almost the same price as a rebuilt kit, so I put that in. Then the engine would idle but would die if you gave it any throttle. I fought at that for a while and figured it was just a cheap carb. So I bought the rebuild kit for my factory carb. Installed all the new jets, o-rings and the needle valve assembly. Tested and the valve sealed perfectly no longer leaking. Then I went and fired it up and it now does the same thing as the new carb did… idles great but dies with any throttle. It does rev with the choke on though. Which makes it seem like it’s lean. But it’s all factory with factory jets. Only 1000ft above sea level. It should run great. I then tried putting a richer pilot jet in and had no changes. Float level seems good. Fuel pumps working good. No vacuum leaks that I can see. I’m kind of stuck. Seems it ran perfectly with the fuel overflowing, other then the backfire, but now working as it should it’s way worse. Anyone have any thoughts??? Thanks!
Sounds like a you may need to go bigger on the main jet (stock they are on the lean side) and/or move the needle richer. Just a though.
 

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Hey there,
I have a completely stock 06 Rhino 450 with an odd carb issue that I’ve been hitting my head over. I got the rhino about 6 months ago and it had a massive backfire on decel. I tried a bunch of jet tuning to fix it, but had no luck. I then found out the o-ring on the needle valve housing was not sealing, causing the carb to overflow. Which I then figured is my backfire issue. I found a new niche carb for almost the same price as a rebuilt kit, so I put that in. Then the engine would idle but would die if you gave it any throttle. I fought at that for a while and figured it was just a cheap carb. So I bought the rebuild kit for my factory carb. Installed all the new jets, o-rings and the needle valve assembly. Tested and the valve sealed perfectly no longer leaking. Then I went and fired it up and it now does the same thing as the new carb did… idles great but dies with any throttle. It does rev with the choke on though. Which makes it seem like it’s lean. But it’s all factory with factory jets. Only 1000ft above sea level. It should run great. I then tried putting a richer pilot jet in and had no changes. Float level seems good. Fuel pumps working good. No vacuum leaks that I can see. I’m kind of stuck. Seems it ran perfectly with the fuel overflowing, other then the backfire, but now working as it should it’s way worse. Anyone have any thoughts??? Thanks!
Clogged fuel filter can cause those symptoms. Changing the filter is a cheap easy try before you start throwing money at it.
 

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Discussion Starter · #4 ·
I have gone richer with the needle and pilot but not the main. I will try and see but the main should have little to no change off idle.

As far as the fuel filter. It has a new pump and filter and I also tried running it off a separate gravity tank system to isolate just the carb and it behaved the same way.
 

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Hey there,
I have a completely stock 06 Rhino 450 with an odd carb issue that I’ve been hitting my head over. I got the rhino about 6 months ago and it had a massive backfire on decel. I tried a bunch of jet tuning to fix it, but had no luck. I then found out the o-ring on the needle valve housing was not sealing, causing the carb to overflow. Which I then figured is my backfire issue. I found a new niche carb for almost the same price as a rebuilt kit, so I put that in. Then the engine would idle but would die if you gave it any throttle. I fought at that for a while and figured it was just a cheap carb. So I bought the rebuild kit for my factory carb. Installed all the new jets, o-rings and the needle valve assembly. Tested and the valve sealed perfectly no longer leaking. Then I went and fired it up and it now does the same thing as the new carb did… idles great but dies with any throttle. It does rev with the choke on though. Which makes it seem like it’s lean. But it’s all factory with factory jets. Only 1000ft above sea level. It should run great. I then tried putting a richer pilot jet in and had no changes. Float level seems good. Fuel pumps working good. No vacuum leaks that I can see. I’m kind of stuck. Seems it ran perfectly with the fuel overflowing, other then the backfire, but now working as it should it’s way worse. Anyone have any thoughts??? Thanks!

Have you checked the carb boot between the carb and the engine? it could be leaking. Crank it up and let it get warmed up enough that it has a steady idle. Shield between the intake to your airbox and the carb boot. Spray starting fluid, wd40, or carb cleaner ALL around the boot. If the engine rpms changes you have a leak.
 

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Discussion Starter · #6 ·
Have you checked the carb boot between the carb and the engine? it could be leaking. Crank it up and let it get warmed up enough that it has a steady idle. Shield between the intake to your airbox and the carb boot. Spray starting fluid, wd40, or carb cleaner ALL around the boot. If the engine rpms changes you have a leak.
Yes I have, with both wd40 and carb cleaner, and had no rpm change. Also inspected the boot and it has no visible cracks.
 

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2005 660
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If the carb, exhaust and air filter are all bone stock, stop fiddling with the jetting. You'll create more trouble for yourself. The stock jets, needle position and mixture screw setting should be left alone if the carb is indeed stock.

Speaking of the air filter, I see no mention of what you have. If there is anything aftermarket in there, get rid of it and try the stock filter.

Replace the spark plug and gap it correctly. Make sure there are no cracks in the plug wire or cap. Make sure the cap is fully seated.

Check the valve adjustment.

If you still have this issue with all of the above addressed, my next thoughts would be a plugged pilot passage inside the carb that has not been thoroughly cleared, the tip of the mixture screw is broken or bent, or the mixture screw o-ring is missing. (I have seen all 3 cause this problem).

Let us know what happens...
 

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Discussion Starter · #8 ·
If the carb, exhaust and air filter are all bone stock, stop fiddling with the jetting. You'll create more trouble for yourself. The stock jets, needle position and mixture screw setting should be left alone if the carb is indeed stock.

Speaking of the air filter, I see no mention of what you have. If there is anything aftermarket in there, get rid of it and try the stock filter.

Replace the spark plug and gap it correctly. Make sure there are no cracks in the plug wire or cap. Make sure the cap is fully seated.

Check the valve adjustment.

If you still have this issue with all of the above addressed, my next thoughts would be a plugged pilot passage inside the carb that has not been thoroughly cleared, the tip of the mixture screw is broken or bent, or the mixture screw o-ring is missing. (I have seen all 3 cause this problem).

Let us know what happens...
Thanks for all the thoughts.
I have a stock air filter. It’s clean.
Has a new spark plug, wire is fully seated.
Checked and adjusted the valves, then rechecked again.
Carb can’t be plugged, cause the new carb also has the same issue and I cleaned the old carb about 4x and then a 5th time I put in the carb rebuild kit.
The mixture tip isn’t broken cause it is brand new.
The o-ring is brand new. Not missing.

I think jetting is the only available fix left. Even though it shouldn’t be.
 

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2005 660
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Well you said it will rev with the choke on so that normally points to a fuel delivery problem in the idle circuit. The fact that you have tried 2 carbs should eliminate that though.

Is it drivable with the choke on?
Does it stumble/backfire when you rev it up?
 

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Discussion Starter · #10 ·
Well you said it will rev with the choke on so that normally points to a fuel delivery problem in the idle circuit. The fact that you have tried 2 carbs should eliminate that though.

Is it drivable with the choke on?
Does it stumble/backfire when you rev it up?
It idles pretty high with the choke at first, and the warmer it gets the less it runs well. You can get around a bit with the choke 1/4 on while its warm. It does stumble occasionally, but doesn't backfire. But I haven't driven it much at all like that.
 

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Discussion Starter · #11 ·
So I put in a dynojet kit. With one step larger main jet then what’s recommended for factory, as well as a 22.5 pilot jet (20is factory) and had the a/f screw out 2.5. And it now runs and drives normally which is great!
But on decel from high rpm I still get one large backfire. I swore that leaking o-ring on the needle valve housing was going to fix that. Maybe I’m a bit to rich at idle?
 

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So I put in a dynojet kit. With one step larger main jet then what’s recommended for factory, as well as a 22.5 pilot jet (20is factory) and had the a/f screw out 2.5. And it now runs and drives normally which is great!
But on decel from high rpm I still get one large backfire. I swore that leaking o-ring on the needle valve housing was going to fix that. Maybe I’m a bit to rich at idle?
I had a similar problem with my 06 450. I have an electric fuel pump now and had the same problems. I put a tee in the fuel line between the pump and carb to send and extra fuel back to the tank fixed my issues. Maybe this will help you also. Good luck
 

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Discussion Starter · #13 ·
I had a similar problem with my 06 450. I have an electric fuel pump now and had the same problems. I put a tee in the fuel line between the pump and carb to send and extra fuel back to the tank fixed my issues. Maybe this will help you also. Good luck
That's a good idea. I was wondering why the 660 had a T and return, when it uses the same pump and uses more fuel then the 450. I will give that a shot. Did you also have to put the 660 "fuel pipe joint" in? That has the 2 fuel line fittings? Or did you plum the return in another way?
 

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That's a good idea. I was wondering why the 660 had a T and return, when it uses the same pump and uses more fuel then the 450. I will give that a shot. Did you also have to put the 660 "fuel pipe joint" in? That has the 2 fuel line fittings? Or did you plum the return in another way?
That's a good idea. I was wondering why the 660 had a T and return, when it uses the same pump and uses more fuel then the 450. I will give that a shot. Did you also have to put the 660 "fuel pipe joint" in? That has the 2 fuel line fittings? Or did you plum the return in another way?
I would suggest you replace the coil ,i had the same problem and this solved my problem
 

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Hey there,
I have a completely stock 06 Rhino 450 with an odd carb issue that I’ve been hitting my head over. I got the rhino about 6 months ago and it had a massive backfire on decel. I tried a bunch of jet tuning to fix it, but had no luck. I then found out the o-ring on the needle valve housing was not sealing, causing the carb to overflow. Which I then figured is my backfire issue. I found a new niche carb for almost the same price as a rebuilt kit, so I put that in. Then the engine would idle but would die if you gave it any throttle. I fought at that for a while and figured it was just a cheap carb. So I bought the rebuild kit for my factory carb. Installed all the new jets, o-rings and the needle valve assembly. Tested and the valve sealed perfectly no longer leaking. Then I went and fired it up and it now does the same thing as the new carb did… idles great but dies with any throttle. It does rev with the choke on though. Which makes it seem like it’s lean. But it’s all factory with factory jets. Only 1000ft above sea level. It should run great. I then tried putting a richer pilot jet in and had no changes. Float level seems good. Fuel pumps working good. No vacuum leaks that I can see. I’m kind of stuck. Seems it ran perfectly with the fuel overflowing, other then the backfire, but now working as it should it’s way worse. Anyone have any thoughts??? Thanks!
Hey there,
I have a completely stock 06 Rhino 450 with an odd carb issue that I’ve been hitting my head over. I got the rhino about 6 months ago and it had a massive backfire on decel. I tried a bunch of jet tuning to fix it, but had no luck. I then found out the o-ring on the needle valve housing was not sealing, causing the carb to overflow. Which I then figured is my backfire issue. I found a new niche carb for almost the same price as a rebuilt kit, so I put that in. Then the engine would idle but would die if you gave it any throttle. I fought at that for a while and figured it was just a cheap carb. So I bought the rebuild kit for my factory carb. Installed all the new jets, o-rings and the needle valve assembly. Tested and the valve sealed perfectly no longer leaking. Then I went and fired it up and it now does the same thing as the new carb did… idles great but dies with any throttle. It does rev with the choke on though. Which makes it seem like it’s lean. But it’s all factory with factory jets. Only 1000ft above sea level. It should run great. I then tried putting a richer pilot jet in and had no changes. Float level seems good. Fuel pumps working good. No vacuum leaks that I can see. I’m kind of stuck. Seems it ran perfectly with the fuel overflowing, other then the backfire, but now working as it should it’s way worse. Anyone have any thoughts??? Thanks!
A crack in the exhaust pipe can cause a big backfire as well. If it ran ok with the stock jets in the past i don't think that is your problem. 1 more thing there a very small air bleeds / passages in the carb that you should run a small pcs. of wire threw all theses tinny holes as they tend to get plugged up and just spraying them will not always clean them out. and last thought is just because the spark plug is new it still can be bad. same with the fuel pump. OEM parts are your best bet, as non oem are some times not worth the problems. good luck,
 

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don't forget the Carb Heater. Make sure wire is connected and if it is replace the heater.
 
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