bjmst07 Posted January 1, 2013 Report Share Posted January 1, 2013 Hi folks Is there anybody out there who has an idea as to why my bike won't rev out fully !! I've cleaned the carb out , changed the plug . It revs fine to about half throttle they just fluffs up ! Also the fan is constantly running !! Poss stat problem ? Running it on 80ml of oil to 5 litres of shell v power fuel Any help would be much appreciated Quote Link to comment Share on other sites More sharing options...
closeybeta2011 Posted January 1, 2013 Report Share Posted January 1, 2013 Hi folks Is there anybody out there who has an idea as to why my bike won't rev out fully !! I've cleaned the carb out , changed the plug . It revs fine to about half throttle they just fluffs up ! Also the fan is constantly running !! Poss stat problem ? Running it on 80ml of oil to 5 litres of shell v power fuel Any help would be much appreciated dose the bike rev out with the choke on ? Quote Link to comment Share on other sites More sharing options...
bjmst07 Posted January 1, 2013 Author Report Share Posted January 1, 2013 Still exactly the same with the choke on Quote Link to comment Share on other sites More sharing options...
huski Posted January 1, 2013 Report Share Posted January 1, 2013 Check the ignition timing Quote Link to comment Share on other sites More sharing options...
bjmst07 Posted January 1, 2013 Author Report Share Posted January 1, 2013 How do you check the ignition timing ? Quote Link to comment Share on other sites More sharing options...
dombush Posted January 1, 2013 Report Share Posted January 1, 2013 (edited) Hi sound like a number of possible causes... First question is.... what has been done to the bike since it last ran correctly? Here's a few ideas that might trigger some further investigation. Cant supply enough air at higher revs.blocked filter Wet filter something blocking the airbox. [*]Supplying too much fuel at higher revs Main jet loose Float bowl flooding at higher revs (difficult to see what might cause this) Needle position incorrect (needle clip come loose or similar) [*]Not rich fueling causing the blubbering, but pulling in oil from the grearbox. Damaged crank seal on the clutch side Damaged crankcase joint gasket (very rare unless reassembling a split engine) Cracked or damaged cases Would be useful to know what has occured since it last ran correctly? Dom Edited January 1, 2013 by dombush Quote Link to comment Share on other sites More sharing options...
copemech Posted January 2, 2013 Report Share Posted January 2, 2013 Sounds like you are running a bit much oil, needs to be in the 62.5-70ml range as I recall in liters. Not the issue though. One might inspect for a broken intake reed as well. I have never broken one, but I seem to recall the bikes going lumpy like that when it happens. Otherwise, I would be looking at the ignition. Do you have anyone near to swap some parts? Quote Link to comment Share on other sites More sharing options...
bjmst07 Posted January 2, 2013 Author Report Share Posted January 2, 2013 Thanks for the help so far gents Firstly I've only recently returned to trials after a 15 yr gap. The last trials bike I fiddled with was a yam ty250r They've changed a bit since then !! I've done nothing to the bike since I bought it, Apart from oil change etc etc On tick over its sweet but when you pull 3rd up a climb it just will not peak !! I will start by stripping it all down again and going through the carb and air box again. I have noticed the mixture screw on the carb is virtually fully out !!!!! I know someone who has a 250 so if I need to rob some bits I'm sure he will let me try them I've come across something similar on a tyz when it wouldn't rev out, Removed the air filter and it was fine New air filter fitted and same prob again !! To be honest the previous owner didn't / couldn't use it to its potential so it needs sorting out Any ideas as to why the fan is constantly running ? When I changed the plug I noticed a wire linking the terminals on the stat ?? I removed this but it's still on all the time :-( Looks like this evening I will be taking it to bits again !! Happy new year to you all Quote Link to comment Share on other sites More sharing options...
tony27 Posted January 2, 2013 Report Share Posted January 2, 2013 The fan being on all the time is 1 of 2 things, the wires which fit to thermoswitch have been joined together which sounds like what you describe although you say that the terminals have been linked. This is normally done if the thermoswitch fails & doesn't switch the fan on The other is that the thermoswitch has jammed internally making fulltime contact, mine does that from time to time Most likely you need a new thermoswitch which is the same as fitted to gas gas' that have the inline thermoswitch http://www.splatshop.co.uk/in-line-thermostat-sherco-Gas Gas.html Quote Link to comment Share on other sites More sharing options...
dombush Posted January 2, 2013 Report Share Posted January 2, 2013 (edited) OK, some good information in your last post. There is no step change, the bike has been like this since you owned it The issue is seen when asking for maximum revs for instance up a climb. That the carb may not be running standard settings. This changes things somewhat. Some other questions will help further diagnosis. What carb is fitted to the bike (to determine the design)?. The model number is normaly stamped onto the side of the carb Dellorto PHBL Dellorto VHST Keihin PWK Regards Dom Edited January 2, 2013 by dombush Quote Link to comment Share on other sites More sharing options...
finn Posted January 2, 2013 Report Share Posted January 2, 2013 Food for thought.. I picked up a sherco 125cc years ago that had the same problem, ran fine on tick-over but wouldn't rev out on demand. Took me a couple of days to find that the previous owner had stripped the carb at some point a managed to snap the atomiser emultion tube and loose the main jet, yep it ran fine on tick-over without a main jet! What jogged my memory was the air screw was wound right out... Does the bike bog when you open the throttle fast from tick-over? Have a look on the sherco website for part diagrams - very helpful.. Good luck Nick. PS, as for the fan, Tony has the measure of that one.. Quote Link to comment Share on other sites More sharing options...
outlaw dave Posted January 2, 2013 Report Share Posted January 2, 2013 Check that carb for sure - if the the FUEL screw is nearly all the way out - you likely have too small a pilot jet - a #36 or #38 is used by most over this side of the pond - the screw should only be about 2-3 turns out. - Get that fixed then do as the other threads suggest & check ignition. Quote Link to comment Share on other sites More sharing options...
copemech Posted January 3, 2013 Report Share Posted January 3, 2013 Should normally be a PHBL, so also ck to insure the slide needle is set UNDER the retaining plate! Quote Link to comment Share on other sites More sharing options...
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