Question about 2003 Yamaha YZ 250 F

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My bike won't start

It back fires out of the exhaust,good comp,and i cleaned the carb but still won't start just brought the bike need help asap ALOHA

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Is the hot start lever on the bars seized if it is seized open will struggle to start and if thats ok could be valves need checking and setting

Posted on Apr 02, 2009

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Why is my bike backfiring?


a back fire on a bike is usually the cause of timing being out or damaged carburettor ( too much petrol going through ) in the case of the carb you can adust the air screw to see if that helps ( small screw in the side of the carb ) screw it right in and then bring it out 1 and a half turns ,this will get you very close to the right mixture. in the case of timing being out you will need to take the fly wheel off and adjust the stator plate ( turn it to the timing marks ) as a rule its usually . back fire through the exhaust is timing,back fire through the carb is fuel mixture. if you rev it when it starts and it pops through the exhaust the problem is within the fly wheel . if it pops through the carb the problem is with mixture.

Nov 09, 2015 | ATVs

1 Answer

Backfiring and trouble starting


If you change the exhaust pipes, you have to sync the carbs (if you cant sync them, you have to change the carb jets), usually it is backfiring because the carbs are not in balance.

May 18, 2013 | 1996 Honda VT 600 C Shadow

1 Answer

Motor cycle popping and smoking on start up


The old gas needs to be drained. Also the intank filter probably needs to be cleaned as well. The carb will need to be cleaned too.

Aug 26, 2012 | Motorcycles

2 Answers

My echo pb-2601 leafblower wont start


if you have spark then you have a fuel delivery problem or exhaust clogged

Nov 12, 2011 | Garden

1 Answer

Hello i have a aprillia sr50 and i brought it from brand new i ran the bike in for 300 miles and then i fully de-restricted the bike and placed a de-restricted exhaust on and a bigger jet and had the...


Hi,
That looks like a REED VALVE leak.
If your 2 stroke kept coming out from the carb air intake and as you say that sometimes a back fire in the exhaust.

Check these....
  • Reed valve
  • Crank oil seal ( there might be air leak in the block )
  • Exhaust pipe ( might be already blocked )

Hope that helps you out!

Aug 29, 2011 | 2011 Aprilia SR 50 R Factory

1 Answer

Sir can i clean carburator and carban in fuel give me advice what can i do plz reply


jes get ur self a can of carb cleaner and remove airfilter and stard the bike then spray it thru the carb wile reving the bike,carbon is not in feul in builts up in exhaust if u want to remove it in exhaust u need to remove the exhaust and worm it up to melt carbon and let it drip out.u can make fire and put the exhaust in fire to melt corbon in exhaust if its a 2stroke bike

May 21, 2011 | Honda Unicorn Motorcycles

1 Answer

Bike sits a lot,Hard to start, will only continue to run with choke on. Bike backfires alot.


You need to clean your carburetors. The ethanol that is in gasoline turns to an orange colored film
and it clogs the jets. The prevention for this seems to be seafoam added to your gasoline after your carbs are clean.
It does work. If your bike sits a lot, i would also suggest that you start it up weekly and let it warm up. Sitting is the worse thing for gasoline.
Judging from your description and other problems, the backfire is probably bad gas not burning and igniting in the cylinder when overloaded with gas.
A good carb cleaning, consists of taking the carbs off the bike, taking out all the jets and soaking everything in a good carb solution.
I would start with the carb cleaning, drain the old gas out of the tank, start with fresh 93 octane and add the recommended dose of seafoam listed on the back of the botlle to your gasoline.
Put a set of new spark plugs in it, and fire it up.
Your back fire should be gone as well.

Nov 29, 2010 | 2004 Yamaha V Star 1100 Classic

1 Answer

I just replace a broken exahust valve on my 02 yz250. While I was in there I also replace the piston and rings. The bike had been sitting for several years by the time I aquired it. As a result I...


I would squirt some fuel in the cylinder to see if it fires, then if it does, blame the jets in the carb being set wrong. Get some fresh gas, and a new plug if you have one. The carb settings might be fixed but still wrong. If they are adj, take them all the way in, then out 1 1/2 turns, this should get it running, if the jets are fixed on the inside, they might need some deep cleaning, did you make sure they were real clean??? Poke a wire through them and blow through them?? Check it out.

Oct 11, 2010 | 2004 Yamaha YZ 250 F

2 Answers

I have a 1992 Suzuki GSX-R 750, that wont start


It is in the carbs, A bike will act like that when it needs to be jetted, most jets are not adj, but whoever built the bike, must have messed with the carbs, you can go back to factory settings, which is about 1 1/4 turns out, and try it, you might need to get new jets, you might want to try dyno jet kit, they are adj and work great.. I had to do my bike, the exhaust was burning my eyes, backfired, wouldn't run, factory jets didn't work. But I found a dyno jet kit on ebay, and it works great. But before you take the carbs off, take a piece of heavy paper and cut the air intake in half with the paper to see what it does, then cut by 1/3, then 1/4, just to see if the intake is messing with you. Check it out, hope it helps.

May 09, 2010 | 1985 Yamaha XJ 700 X Maxim

1 Answer

Raptor 660 2003 choke on bike idles good but when off the bike starts to back fire


Your bike is running too lean. If you have not made any changes to the air intake or exhaust then your pilot jet may have something blocking it. (probably a piece of dirt, or just tarnish build up of fuel if the carbs aren't drained while in storage) By turning the choke on, you are reducing the ammount of air allowed into the "Fuel / Air" Mixture. This allows the bike to idle properly. Once the choke is off, the mixture has too much air and not enough fuel causing the backfire. If you haven't changed anything like the exhaust or air filter it sounds like a good carb cleaning is in order. Otherwise, you will need to change jet sizes to accomodate the difference in air flow.

Jan 10, 2010 | 2004 Yamaha XT 660 R

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