Engine backfire

[Bob C]

Just been on a tour of Austria and Southern Germany, over 2000 miles and my 04 bike didn't miss a heart beat. Went out today for the first time since being home and my bike has developed a backfire on decelleration. Its not happening everytime only when I close the throttle fully when doing about 70 and then theres a bang from the cans. Bike also cuts out now and again when its ticking over during a run out. Any tips or ideas very welcome.

[VTRDark]

Is it a full on backfire or just a bit of popping. You may want to check the exhaust seals for any air leaks, this can cause some popping and banging. Start with the basics, check the plugs, ht leads. It could also be that the bike is running too lean, a fuel/tuning issue. Have you got an aftermarket exhaust on? Do you know what air filter it's got? Check the air filter is clean.

You say it's been cutting out. What's the idle speed set at, It should be at 1200rpm ish but you can up that to 1400 and see how it goes. For the idle speed adjustment there is a black knob on the front carb, on the right hand side through the triangular part of frame behind the rad. Turn this one way or another to increase or decrease the idle speed.

Hope that gives you some direction to go in.

(:-})

[sirch345]

Impressive tour Bob
All what Carl says, plus a carb balance may help. When were the plugs and air filter last renewed

Chris.

[Bob C]

Sirch and Carl thanks very much fellas. Air filter, plugs were all changed when I carried out a full service in April. Sirch, tour was awesome. Some of the best roads that I have ever ridden on in Austria.

[VTRDark]

A bit of a long shot but it won't cost you anything to check and it will be good to rule it out. There's a vacuum hose that runs from the left hand side of rear carb along the frame and up into the petcock on the fuel tank. If this has disconnected or damaged this will cause huge backfires and popping, especially if you have an aftermarket race exhaust. It will also affect how the bike idles.

All you need to do is lift the front of the tank up and from the left hand side of bike, check that this hose is connected to the petcock right behind the fuel line on that side (note it does not connect on the bottom which is a common mistake) It's hard to see, but you can feel it behind the fuel line. Just make sure this is connected and secure, it may have worked it's way loose.

Let us know how you get on.

(:-})

[Bob C]

Thanks for all the tips fellas, problem now solved. Exhaust seal from the rear down pipe into the collector box had disappeared. New ones fitted all round and it runs sweet as a nut.

Cheers

[VTRDark]

Good news, it was a nice simple solution then

(:-})

[skyman]

mine does that really want to meet up with some other owners to check if mine sounds right or not. but i must admit i love that burble and popping when i shut down especialy in tight enclosed streets or under bridges

[VTRDark]

especialy in tight enclosed streets or under bridges

I know what you mean. I once forgot to connect my vacuum hose back up and went out for a ride and managed to do roughly 80miles without any running problems except a hell of a lot more popping and banging. It was lovely in tunnels

Stick your hand over the end of your cans when you first start the bike up and carfully feel around the joins/clamps for any leaks before it warms up to the point where you will burn your hands. Also use you ears to listen for any air leaks. It's a simple thing to check and rule out before moving onto anything else that could cause it.

(:-})

[tony.mon]

Stick your hand over the end of your cans when you first start the bike up and carfully feel around the joins/clamps for any leaks before it warms up to the point where you will burn your hands. Also use you ears.

(:-})

Now my ears are burnt, and it still pops and bangs on the overrun.

Perhaps my car wasn't full enough.

[VTRDark]

Now my ears are burnt

(:-})