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  #1  
Old 24 Feb 2007
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r850r backfire problem help please.

Hi need some help please. I have a 95 r850r (25k miles). Owned it for 6 mnths and its been great so far, up until this week when it has suddenly developed terrible backfire under deceleration. Generally by the time it gets down to 2k revs the thing sounds like a shot gun going off. There seems to be a slight misfire/surge when you try to hold a steady throttle as well(I would not describe this as surging it seems to quick).I am worried it will blow the exhaust so am not riding it at the moment. I have changed the plugs, checked all the connections etc and as per advice on this site I have checked both cables are seated correctly. Air filter is good and I have read all the stuff on syncing the TB's and resetting the TPS. Anyone any ideas before I take the plunge and really mess things up?? Cheers. Strodius.(by the way this is an excellent site thanks for all those posting great info)
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Old 24 Feb 2007
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backfire

check the exhaust for leaks, loose joints at the clamps are the usual cause of a backfire. run your hands over the exhaust before it gets too hot you should be able to feel any leaks. if not it could be carb balance or any number of other things
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Old 25 Feb 2007
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backfire problem solved

Thankfully I have sorted this backfire fire problem. Turned out to be the RHS throttle body out of sync. Used a pair of borrowed vacuum gauges to find the balance was miles out. Tweeked the brass screws which made little effect and then adjusted the cable to recify. Reset brass screws to original settings and hey presto, back to normal running. Will have to buy myself a set of gauges to keep now.
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Old 26 Feb 2007
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Since this occurred suddenly I'd check the cables carefully. Perhaps one is about to snap?
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Peter.

Europe to NZ 2006-10
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Old 26 Feb 2007
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Quote:
Originally Posted by strodius View Post
Thankfully I have sorted this backfire fire problem. Turned out to be the RHS throttle body out of sync. Used a pair of borrowed vacuum gauges to find the balance was miles out. Tweeked the brass screws which made little effect and then adjusted the cable to recify. Reset brass screws to original settings and hey presto, back to normal running. Will have to buy myself a set of gauges to keep now.
not gauges...vacuum gauges aren't sensitive/accurate enough.
...make a U tube manometer out of clear plastic hose for pennies (Home Depot, Lowes ect...) a manometer is dead on accurate and instantanious sensitive as it acts on pressure (negative) against pressure. I used red auto trans fluid as the liquid since it's similar to water and easy to see, but you could use any liquid...even water. light water is more sensitive than heavy mercury...the beauty of that is you can carry the compact coiled hose and add liquid on the road when you want to use. I would use 1/4+" ID hose with bushings for the connections...that allows some forgiving from bigger diameter...the danger is sucking the liquid thru if it's way way off to begin with.. the beauty of a manometer is you only have to compare easily seen liquid levels.

this quick easy solution is more accurate than both mercury or gauges.
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