Paulwhite Posted March 25, 2011 Share Posted March 25, 2011 hi all been a while since iv asked for help but iv managed to get the project going right.... iv given it a test run today and have noticed that at 9000 rpm the engine sort of splutters then kicks in again (like iv changed gear) but its a little rough from 9000 up the plug is reading ok if not a little lean....its a weird problem that i havent come across before so was just wondering if anyone has an answer to why its spluttering? cheers. Paul. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 25, 2011 Moderator Share Posted March 25, 2011 Fuel starvation, partially blocked filter? is there a filter screen inside the petrol tap, or inside the tank? Link to comment Share on other sites More sharing options...
Paulwhite Posted March 25, 2011 Author Share Posted March 25, 2011 Fuel starvation, partially blocked filter? is there a filter screen inside the petrol tap, or inside the tank? there is a filter on the petcock in the tank .....but its clean...im usin the xvs 125 tank (turned it to prime to test run it plus it dont have the pump on ...just a straight line from tank to carb) il double check tomoz but its only doing it at 9000 rpm sort of pulls to 9k rpm then drops off for a split second then pulls again to 10500 rpm but its a little rough from when it drops off. could it be a flat spot do u think? i have got a pod filter and race exhaust Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 25, 2011 Moderator Share Posted March 25, 2011 yeah Paul if its not fuel starvation it could be caused by the pod filter I suppose. What degree of throttle opening are we at? try lifting the needle one notch if it isnt the screens. Link to comment Share on other sites More sharing options...
Paulwhite Posted March 25, 2011 Author Share Posted March 25, 2011 yeah Paul if its not fuel starvation it could be caused by the pod filter I suppose. What degree of throttle opening are we at? try lifting the needle one notch if it isnt the screens. well i did originally have that bit of pipe (48mm silicone u bend) between the filter and carb but found that the engine ran rich and wouldnt go past 8k rpm (got quite hot too) , but with the filter straight to carb, the engine revs to 10500 rpm (which it should do) and the plug is looking ok. im just touching full throttle when i get to 9k rpm i get what ur saying about fuel starvation but surely that would cause the engine to bog down once i hit 9k rpm?? (not sure on that one ) and i would love to change the needle position but i cant as its not adjustable (well suppose i could make it richer using washers) its a keihen carb by the way.....dont suppose you know of any websites to take a look at for jets and things? could try re-jetting i suppose.... but id rather figure out why the engine dips b4 i start making changes. im gonna have a play tomoz and put the fuel pump back on, then il report back oh forgot to mention, is there a way of making the tank gravity fed instead of it needing a vacuum? Link to comment Share on other sites More sharing options...
Paulwhite Posted March 26, 2011 Author Share Posted March 26, 2011 right iv put the pump on and moved the needle up a notch (ended up putting a washer on ) but the problem is still there. iv taken the filter off to have a look at what the carbs doing when it revs.....and found at 9k rpm it spits out the air/fuel mix through the filter. i reckon the timings out but would like a 2nd opinion b4 i start taking the engine to bits. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 26, 2011 Moderator Share Posted March 26, 2011 Could it be valve bounce? 9k is quite high revs. Might need new valve springs Just a guess tho Link to comment Share on other sites More sharing options...
Paulwhite Posted March 26, 2011 Author Share Posted March 26, 2011 Could it be valve bounce? 9k is quite high revs. Might need new valve springs Just a guess tho posably and come to think of it...it makes a sence. im gonna check the timing at some point, wont hurt to check iv got some new springs in the shed that might do the trick but there 24lbs racing springs for a honda gx 160 engine il do some reading/research to see if there compatable or not (probably not lol). cheers OG ur a time saver il report back once iv had a play Link to comment Share on other sites More sharing options...
Recommended Posts