Popping sound and occasional spitting of fire

[Seeychellesoffroadracer]

Hey guys gt my new to me 03 wr 450f n the only problem seems to be backfiring during deceleration. Wat to do?

[FORMA MOTO]

Read the pinned posts at the top of the forum

You need to verify jetting, get a remote fuel screw, learn to adjust it, check for carb corrosion, and air leaks.

[RMK800]

Get a Merge fuel screw..... The temperature here has dropped 15 to 20 degrees.... I was getting some popping/backfire on decel, didn't have this problem when it was warmer. I turned my fuel screw 1/4 richer and the popping has gone away...without the fuel screw you would have to almost remove the carb. One of the must add ons for a carb if your changing altitude or tempauture.

[JDLowrance]

For spitting flames, unburnt fuel is entering the exhaust header and mixing with oxygen (most likely from aworn or damaged exhaust manifold seal). Have you had the header off recently? If so replace the seal with a new one. You can try tightening the header but a new seal with a little silicone should do the trick.

 

Pilot may be part of reason for popping on decel.

[Seeychellesoffroadracer]

I took it out for one ride and then engine seized, I kickstarted it it came on for 5 seconds with a knocking sound in the engine n then just seized, the kickstarter is completely locked and the e start just makes a ticking noise. It all seemed fine had been riding for like 2 hours on and off, put the bike on the stand to have some water and relax and when I go back to start it ths happened. I just spent 3300 on the bike now I have to send it to a shop to get it fixed and am a uni student saved all my money to get this. Everything was fine engine oil coolants everything I had checked everything.. I don't know what's wrong.

[JDLowrance]

Well first off, it's a 2003.  Having lived there, I know how hard some of you guys ride. Personally I wouldn't buy a used four stroke unless I knew the person I was buying from and they were as meticulous as me with regards to maintenance. They cost thousands to rebuild which unfortunately sounds like what you are in for.

 

Two strokes on the other hand are relatively cheap to fix usually requireing no more than a piston and cylinder to get running if they sieze.

 

Good luck!

[FORMA MOTO]

Well first off, it's a 2003.  Having lived there, I know how hard some of you guys ride. Personally I wouldn't buy a used four stroke unless I knew the person I was buying from and they were as meticulous as me with regards to maintenance. They cost thousands to rebuild which unfortunately sounds like what you are in for.

 

Two strokes on the other hand are relatively cheap to fix usually requireing no more than a piston and cylinder to get running if they sieze.

 

Good luck!

 

Oh please.

I took it out for one ride and then engine seized, I kickstarted it it came on for 5 seconds with a knocking sound in the engine n then just seized, the kickstarter is completely locked and the e start just makes a ticking noise. It all seemed fine had been riding for like 2 hours on and off, put the bike on the stand to have some water and relax and when I go back to start it ths happened. I just spent 3300 on the bike now I have to send it to a shop to get it fixed and am a uni student saved all my money to get this. Everything was fine engine oil coolants everything I had checked everything.. I don't know what's wrong.

 

It sounds like oil starvation.

 

Did you check or change the oil before riding it?

[JDLowrance]

Oh please.

 

Oh please what?

[Seeychellesoffroadracer]

Ye man I checked the oil it was all good. I just have to wait another few weeks now to get some money to get it fixed, hope it doesn't cost too much

Thanks for all Ur replies guys

[FORMA MOTO]

Oh please what?

 

Oh please....why are you bagging on four strokes in a four stroke thread and promoting two strokes......we all have four strokes so get over it.

 

...and it will cost at most $600 for a new piston and cylinder, period. Nothing happened to his valve train.

I doubt it even needs a rebuild, just some scotch brite and new rings.

[Seeychellesoffroadracer]

I hope you're right trannie.. I really do. Will let you guys know but won't be soon maybe in 2 weeks or more.

[Seeychellesoffroadracer]

I mean krannie sorry typo

[Seeychellesoffroadracer]

Are you in WA wud you be able to recommend a good place to get it repaired?

[JDLowrance]

Oh please....why are you bagging on four strokes in a four stroke thread and promoting two strokes......we all have four strokes so get over it.

 

...and it will cost at most $600 for a new piston and cylinder, period. Nothing happened to his valve train.

I doubt it even needs a rebuild, just some scotch brite and new rings.

 

Bagging on four strokes? Really, forget who you're talking to? I love four strokes...been riding and racing them since 1999. Two strokes since 90.

 

 

 

I hope you are right in that all he needs is cylinder and piston. I've found that older four strokes that are ridden hard and put away wet are ticking time bombs that will fail catastrophically and cost unsuspecting buyers of said used bikes thousands more than the initial cost of admission. Two strokes, not so much.

 

 

 

Again, my observations over time and I hope you're right, hope it's something simple but based on the description the OP provided I'm not so sure.

 

If you can tell nothing has happened to his valve train, crankshaft, etc. from 7000 miles away based on a brief description in a forum post, you're powers of mechanical diagnotics are quite impressive. ? 

Edited September 15, 2013 by JDLowrance

[FORMA MOTO]

 

 

If you can tell nothing has happened to his valve train, crankshaft, etc. from 7000 miles away based on a brief description in a forum post, you're powers of mechanical diagnotics are quite impressive. ?

 

Yup. I'm amazing.

[JDLowrance]

Have you had a chance to take a look at the bike? How bad is it?