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Drz400sm Bogging on throttle snap.

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Hello, I've searched the forms and cant seem to find an answer to my problem.

The problem is when I snap the throttle(EX: rev matching for a downshift) the bike bogs down and dies, if i roll on it gently its fine. It was running fine today and at the end of my ride it started doing it. I've played with the fuel mixture screw but that didn't make any difference. I got the bike about 3 weeks ago and it came with the following mods.

 

bsr 36

3x3

K&N air filter

rs2 exhaust

JD jet kit(not sure which needle and whatnot was installed, but it ran great when i got it)

If anyone has had this problem or knows the cause of it I'd appreciate the help.

-Thanks in advance!!

Edited by GavinGarner

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Fuel mixture screw wont solve your problem. When you first turn on the bike in neutral and rev the engine does it bog then rev or rev immediately like it should? Try going for another ride, does the bog happen later on in the ride or at the start of it and continue?

If the bike always did this I'd say check out the needle and rejet the carb but if it was running good then started sucking that's something else..

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2 minutes ago, dspy21 said:

Fuel mixture screw wont solve your problem. When you first turn on the bike in neutral and rev the engine does it bog then rev or rev immediately like it should? Try going for another ride, does the bog happen later on in the ride or at the start of it and continue?

If the bike always did this I'd say check out the needle and rejet the carb but if it was running good then started sucking that's something else..

Well if i try to open it all the way up in neutral really fast it just bogs and dies. Earlier when I rode it did fine for about 20 min. then on the way home I did a quick throttle snap to downshift and it bogged and died(kinda sounds like it does when it runs out of gas), And now it does it all the time if i get on the throttle to fast.

I don't think it could, but could a loose cam chain have anything to do with it? when i was messing with it earlier i thought i heard it rattling a little bit. I haven't gotten the manual cam chain tensioner yet(my first bike so i'm not to familiar with working on them yet).

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Just now, ohiodrz400sm said:

What other bikes are you experienced with? The stock CV carburetor isn't going to respond to "snapping" the throttle wide open like a MX bike or Fi bike can.

none really, but before today it responded 10x better, now it will die if i give it to much throttle to fast. Like if i just give it a quarter turn blip it doesn't rev at all just bogs down.

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if i give it to much throttle to fast.

I think that may be key. The bike is new to you. Is it possible that you just discovered it would bog if you snapped it open and have become fixated on it?

 

Are there any other symptoms? New sounds, low fluid levels? Was the weather different than any of the previous rides? Did you do any work on the bike since the last riding session?

 

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Sounds like a jetting issue, but the fact that it wasn't happening earlier makes me think it is something else. Has airflow to the motor become restricted somehow? Maybe check the air filter for blockages?

10 minutes ago, ohiodrz400sm said:

What other bikes are you experienced with? The stock CV carburetor isn't going to respond to "snapping" the throttle wide open like a MX bike or Fi bike can.

Yes, but it shouldn't bog down and die either.

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If it's a real dog on the response and if it just happened recently I'd look for a air leak around the intake manifold boot and the vacuum line near the top of the carb that goes to the petcock,that it's not cracked,split or disconnected.Also the main vacuum diaphram and the tiny o-ring under the top cover is in place.The diaphram for the slide cannot have any pinching or pin holes.

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1 minute ago, ohiodrz400sm said:


I think that may be key. The bike is new to you. Is it possible that you just discovered it would bog if you snapped it open and have become fixated on it?

Are there any other symptoms? New sounds, low fluid levels? Was the weather different than any of the previous rides? Do you do any work on the bike since the last riding session?

No I've ridden it almost everyday since i've gotten it and its never bogged like this. even today i was blipping it to revmatch for downshifting and it was fine, then out of nowhere I do it and it dies... all fluids are good, only thing ive done to it is oil change and petcock replaced with on/reserve one.

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4 minutes ago, bumtarder said:

If it's a real dog on the response and if it just happened recently I'd look for a air leak around the intake manifold boot and the vacuum line near the top of the carb that goes to the petcock,that it's not cracked,split or disconnected.Also the main vacuum diaphram and the tiny o-ring under the top cover is in place.The diaphram for the slide cannot have any pinching or pin holes.

I've plugged the vaccum port on the carb when i installed the raptor petcock, but ill check those other things and see if i can find the problem.

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7 minutes ago, ohiodrz400sm said:

If you have any starter fluid spray it around the carb while it is idling

 

20 minutes ago, bumtarder said:

If it's a real dog on the response and if it just happened recently I'd look for a air leak around the intake manifold boot and the vacuum line near the top of the carb that goes to the petcock,that it's not cracked,split or disconnected.Also the main vacuum diaphram and the tiny o-ring under the top cover is in place.The diaphram for the slide cannot have any pinching or pin holes.

i've checked and it has no leaks i can find... im adding a video to the post of it. it seems to be worse when cruising then down shifting but you can still tell.

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14 hours ago, Vaughan Penney said:

Hey did you ever figure out what was wrong.  My

 bike is doing the same thing and ive checked everthing

No. I've tried everything i can think of and cant figure it out... think im just gonna upgrade to the fcr39.

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