mike1 Posted June 23, 2011 Report Share Posted June 23, 2011 Hi , Just recently got back into trials and enjoying immensley, now ride with my son who as just purchased a new Beta Evo 4t 300. problem he is encountering is a loud backfire often , (almost every time he gets past half revs. ) had back to shop who have sealed exhaust but problem still persists, will be taking back and shop very heplful, just wondered if any other beta 4t evo owner encountered same problem, many thanks Mike. Quote Link to comment Share on other sites More sharing options...
mattholmes Posted June 23, 2011 Report Share Posted June 23, 2011 Yes mine does same if I've been above 3/4 revs for more than 30 seconds and drop the revs off quickly usually on a road section think it's just excess fuel burning off ??? Doesn't seem to have any side effects just makes you jump now and again lol Quote Link to comment Share on other sites More sharing options...
fivemeister Posted June 23, 2011 Report Share Posted June 23, 2011 see here..... http://www.trialscentral.com/forums/topic/23670-beta-evo-4t-250300/page__hl__evo4t__st__30 Nothing to worry about - common with large capacity 'thumpers' and twins. Its the ignition of excess unburnt fuel introduced when doing what you describe (and sometimes made worse by an air leak into the exhaust system - like if you had the system apart then didn't seal it properly) My BMW R1150GS was a bugger for it - scared the bejeesus out of many a blue rinse waiting at the bus stop. Found one to watch with this bike though. The engine breather exits into the bottom of the air box. After a big off and the bike being upside down - then going down a steep hill, my bike began popping and farting all over the place. I later discovered the engine had spat some oil out of the breather into the bottom of the airbox and this must have then been pulled / poured through the carb when going downhill causing the popping and banging. Worth checking if ever you have a big off. Quote Link to comment Share on other sites More sharing options...
mike1 Posted June 24, 2011 Author Report Share Posted June 24, 2011 Many thanks for your replies , i will pass this info on to my son who was concerned, seems its quite the norm so he will be pleased to hear it . Thanks again Mike. Quote Link to comment Share on other sites More sharing options...
dgshannon Posted June 24, 2011 Report Share Posted June 24, 2011 Many thanks for your replies , i will pass this info on to my son who was concerned, seems its quite the norm so he will be pleased to hear it . Thanks again Mike. Interesting feedback. I had the Rev4T 250cc bike for about 18 months, and never experienced such a problem. Always ran clean and quiet. Quote Link to comment Share on other sites More sharing options...
mattholmes Posted June 24, 2011 Report Share Posted June 24, 2011 Yes I had a 250cc 08 4 stroke and never had it happen its only when I've moved to the 300cc that it's started Quote Link to comment Share on other sites More sharing options...
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