05 crf 450r popping, help!!

moore433
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525
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11/2/2011
Location
Denton, TX US
2/25/2013 7:48am Edited Date/Time 3/5/2013 9:02am
We went to the track yesterday (Swan mx) and when we started my 05 crf 450r, as soon as you'd crack the throttle it would back fire and pop and the throttle response seemed very slow. I took the pilot jet out and cleaned it, same result. I installed a larger pilot and had the same result.

could the little jet thats made into the bottom housing of the carb cause the popping I'm having?? I forget the name of that little jet...

Thanks for any help..

PS. the last time this bike acted similarly, I had to replace all of the electronics on the bike.
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slipdog
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10043
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7/25/2009
Location
Nor Cal, CA US
2/25/2013 8:33am
I think you mean the leak jet. Actually it's less likely the leak jet and more likely the accelerator pump nozzle that may be plugged up. The jet bleeds(leaks) fuel away from the nozzle, but when the nozzle gets plugged you run very lean on throttle openings. It would also bog real bad when you crack the throttle because that's what shoots the first shot of fuel into the carb.

Also could be the cam is miss timed or jumped a tooth, that could be big trouble.
moore433
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525
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Location
Denton, TX US
2/25/2013 9:27am Edited Date/Time 2/25/2013 9:29am
Thanks! That's the name of that jet , I couldn't for the life of me remember the name of it..
I'll check the accelerator pump when I get home, thanks for the tip....It had a full rebuild less than 5hrs riding time ago and a new timing chain tensioner was installed at the time. I'll check the timing too...
JCollins762
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2/28/2013
Location
Ringgold, GA US
2/28/2013 1:46pm
As he said, check your timing just to be safe.. You'll regret it if you keep testing it assuming it's a carb prob and you bend a valve.

As for the carb, check for Airleaks using WD40 (Spray the carb boots with WD40, it will surge if their is an airleak and the WD hits it. Also check your AP diaphram, if they crack it's been known to cause backfiring. You seem to somewhat understand jetting, so check that out along with your fuel mixture.

Also try the BK mod, some people have fixed bog probs with it.



All else fails, check to see if your stator has found it's way off time some how, it's a long shot.. but it's plausible.
Chad198
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40
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2/28/2013
Location
Huntington Beach, CA US
2/28/2013 2:09pm Edited Date/Time 2/28/2013 2:11pm
Put a new seal on the slide plate. It is an often over looked part that should be replaced every few years. Contact with carburetor cleaner destroys it.

The Shop

moore433
Posts
525
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11/2/2011
Location
Denton, TX US
3/4/2013 8:48am
Ok, I took the carb all apart and cleaned it very well. The accelerator pump is fine, the jets are fine, I checked the valve timing and its ok. I also tried a old cdi box I had from the last time it acted up. Still running the same.

I believe the stator is going out again..

What do you guy's think?? Thanks for all of the help guy's!!!
4stroke4DWIN
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Location
texas city, TX US
3/4/2013 1:57pm
Make sure the hot start is closing/working right. Mine stuck open once and ran like shit. Also make sure the fuel screw on bottom hasn't fallen out, if its an aftermarket one make sure the o ring is good. But could be plug is about to shit it's pants also.
moore433
Posts
525
Joined
11/2/2011
Location
Denton, TX US
3/4/2013 5:17pm
Make sure the hot start is closing/working right. Mine stuck open once and ran like shit. Also make sure the fuel screw on bottom hasn't fallen...
Make sure the hot start is closing/working right. Mine stuck open once and ran like shit. Also make sure the fuel screw on bottom hasn't fallen out, if its an aftermarket one make sure the o ring is good. But could be plug is about to shit it's pants also.
4stroke4dwin, That's one thing I haven't checked is the hot start. The fuel screw is still in the carb and the oring is in good shape. I haven't tried the plug either.

Thanks for a couple more obvious ideas that it could really be, but are so obvious you don't always think of them. I'll give them a try as soon as I get my new cam chain tensioner comes in. This is the 2nd stock Honda one that has broken on me. I'm getting a manual one & will never run a stock one again..

Thanks again for the tips...
Arkmx
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1625
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10/6/2006
Location
35 miles west of PHX..., AZ US
3/5/2013 6:13am
.

Valve seats may be bad.

One of the boys has one and it was hard to start and if it did it would pop etc... Changed the valves and it worked for a short time then it started again...

Long story short.... Purchased a new stock head, put it all back together and presto! Good running bike! Cheaper to buy a new head than have the seats replaced.... Honda's are soft or were soft in the valve seat areas....

Hope this helps too...

.
4stroke4DWIN
Posts
2767
Joined
1/15/2012
Location
texas city, TX US
3/5/2013 9:02am
Make sure the hot start is closing/working right. Mine stuck open once and ran like shit. Also make sure the fuel screw on bottom hasn't fallen...
Make sure the hot start is closing/working right. Mine stuck open once and ran like shit. Also make sure the fuel screw on bottom hasn't fallen out, if its an aftermarket one make sure the o ring is good. But could be plug is about to shit it's pants also.
moore433 wrote:
4stroke4dwin, That's one thing I haven't checked is the hot start. The fuel screw is still in the carb and the oring is in good shape...
4stroke4dwin, That's one thing I haven't checked is the hot start. The fuel screw is still in the carb and the oring is in good shape. I haven't tried the plug either.

Thanks for a couple more obvious ideas that it could really be, but are so obvious you don't always think of them. I'll give them a try as soon as I get my new cam chain tensioner comes in. This is the 2nd stock Honda one that has broken on me. I'm getting a manual one & will never run a stock one again..

Thanks again for the tips...
I wouldn't run a manual one unless you are super confident on your ability to have proper chain tension. I had an manual and went back to the stock auto. I havent had any problems myself with them though.

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