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Blog - Brute force backfiring

Kawasaki valve problems and what to do about it

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     We have read a lot about supposed problems with Kawasaki Brute force intake valves being soft and losing their ability to seal. On many occasions we have encountered all sizes of Brute and Tyrex engines with bad backfiring through the carbs at low speed operation, and we believe that many people mistake this backfiring to be caused by bad intake valves. 

     One thing we noticed is that Kawasaki does not have jetting charts for change of altitude meaning that their jetting is supposed to cover all altitudes. We are at sea level here in Alvin, TX and we have found that going up half a step on the idle jet and shimming the slide valve needle with a .5mm shim makes nearly all the backfiring disappear and makes for much better throttle response. 

     The bottom line is, with as many rebuilds as we have done on these engines we have not seen any real indicator that there is a problem with the factory intake valves. It is more likely a problem with the engine being too lean at very low throttle opening. Not to say it is not a possibility to have bad valves, but I would certainly recommend to try re-jetting before having your engine rebuilt if backfiring is your issue. Also, if possible have a leakdown test performed to determine if valves are causing your issues. 

Thanks for reading, Christian

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