Back Firing XJ600N 1998 UK bike

My Yamaha XJ600N 1998 UK model is back firing and popping. Everything is standard on her and has recently had oil, filter, air filter, chain, plugs etc done to it.

WHen giving it some welly and then releasing the throtal to slow to a junction, it starts popping. the other day it let out one almighty bang and i was shocked that i slowed down to 40mph.

Why could this be happening.

It runs well and is quite nippy around, but has no power at top end and find myself in 4th gear quite a lot to get it going. I did have a power band and at 8k it use to take off. this has gone now and says the same speed upto 13k.

The engine is quite ( well the noise sounds blug blug blug) when idle at stationary, but pulls off well and is a good starter.

I have no service history on this bike and has done 35k miles. all i have done in the 6mths of owning her is the basic service as mentioned above.

Are these motors blug blug blug when idle ( not electronic like my dads cbr) and why has this power band gone. what maintinence should i do on her to get her back to a service history and why is it back firing.

Alot to ask, but i'm sure some kind person will help a new comer on this site.

I do not really know anything about bikes and therefore any maintinence advice you give me , i would need it done at a garage and at cost. If you know the rough prices i would appreciate this too.

Thanks XJ'rs

 

Sounds like it could be a vacuum leak. I had similar problems on my bike the other day and it turned out that the vacuum hose that runs from the carb book to the petcock had split and come off. I didn't realize it because I had my petcock set to PRI (forgot about it when synching carbs).

Anyways, the one carb boot was sucking air big time and the backfire and popping you described was happening.

Check your carb boots for big cracks and your vacuum line for splits/holes.

 

The carb boots can be found between the engine and the carburators themselves. They often begin to crack over time and will suck air through the cracks causing running issues.

Have a look at your carb boots and let us know how they look.

When the bike is running, if you spray some WD-40 on the boots and the idle increases - then you definitely have a leak.