backfires



8 replies to this topic
  • Fast Freddie

Posted June 17, 2003 - 07:16 PM

#1

My bike will backfire on deceleration a few times a ride.

I have read others with the same issue. How can it be fixed? And does the odd backfire hurt the bike at all.

Thanks

  • Kot

Posted June 17, 2003 - 08:00 PM

#2

My bike backfires the same way. I also noticed that it happens more when humidity is higher then normal, like just before the shower rain starts or when riding on a beach. IMO this is due to the rich gas mixture, but I don't think it hurts the engine anyhow. I'll watch the bike for another month and then will try to adjust the mixture.

  • yamahasocal450

Posted June 17, 2003 - 08:06 PM

#3

i would have to say its normal because on my friends factory yz450 it also backfires on decel and on my 450 it also backfires... nothiin to be worried about unless it bugs you, but if your under hard acceleration and it back fires then you need to rejet :) :D :D

  • yamaharichey

Posted June 18, 2003 - 12:20 PM

#4

Are you saying its a little popping when you let off the throttle or is it a big bang like a gun going off? if its the latter then its too lean and its not good for the bike. increase the pilot jet size and raise the needle one clip. Trust Me.

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  • tctrailrider

Posted June 18, 2003 - 12:35 PM

#5

Fast Freddie,
A small backfire is not uncommon and most do not worry about it. Most say popping on decel is lean, a bang is rich. I have just finished rejetting my bike, tried about 30 combinations and the only bangs I got on decel were when the needle was to rich. Some say its the pilot but with me it was allways the needle.

  • Fast Freddie

Posted June 21, 2003 - 04:01 PM

#6

It is not a popping it is banging, on decel.
I changed the Pilot Jet from a 48 to a 42 and made the backfire problem worse. I am at about 3500 ft and an running a 155 (stock 160) main jet, dropped the needle 1 notch (moved the washer up). This is bugging me now. I am not sure if I am too lean or rich. Changing of the main jet and dropping of the needle seemed to give me more top end.

Also a large bog with quick twists of the throttle; and nothing seems to fix it. :)

Anyone have a wr450 in the Calgary area? What jetting/settings have you found to work?

  • John_Lorenz

Posted June 21, 2003 - 04:18 PM

#7

The best thing to do is place everything back to a stock setting. Only change one item at a time. It seems you are running way lean in the bottom 48 to a 42 is a big step down.


Dropping the main from 160 to 155 is a big step as well.

What di it run like prior to your jetting?

Do you have an after market pipe or insert?

  • Fast Freddie

Posted June 22, 2003 - 06:26 AM

#8

The best thing to do is place everything back to a stock setting. Only change one item at a time. It seems you are running way lean in the bottom 48 to a 42 is a big step down.


Dropping the main from 160 to 155 is a big step as well.

What di it run like prior to your jetting?

Do you have an after market pipe or insert?



The bike ran fine with stock jetting, but seemed to choke a bit at higher revs. The bike came with extra jets, so I thought I would play. Because of the altitude I ride, 3500-4000 ft, I assume the bike needed to be leaned out a bit. Once I put the 155 main jet and dropped the needle 1 notch, it seemed to run a little smoother and have more top end power. However, the bottom end seemed to be less after. I also have the famous bog on quick throttle thumps at low rpms. Also, backfire bangs the odd time, with a 42 pilot jet from a 48 made the thing backfire constantly.

I am happy with the bike, I just like to play with things to see if I can make it any better.

  • Beta_Man

Posted June 22, 2003 - 05:07 PM

#9

On my wr 450 i am running a yz 450 pipe and for jets i got a 162 main, needle in stock position and the stock 48 pilot with the fuel screw around two turns, it runs good no popping or banging on decel still has a little bit of a bog when idling and given a shot of fuel but when ridding it's good. it is still running a little rich i think, i am going to play with it a bit more and see what i can get out of her. :)




 
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