any thoughts please on why the valve timing should be wrong on b25ss. inlet is not opening until the piston is nearly at the bottom of its stroke and not closing till past tdc on what should be compression stroke
HI THERE > I WOULD CHECK THE VALVE TIMING MARKS INITIALLY > SOME CAMSHAFTS HAVE 2 MARKS , A STRAIGHT LINE AND A V SHAPED MARK > IF MEMORY SERVES I THINK YOU NEED TO USE THE V MARK TO LINE UP WITH THE CRANK DOT MARK ON THE PINION ON CAMSHAFTS WITH 2 MARKS OTHERWISE IF JUST ONE MARK LINE THAT ONE UP . ALSO CHECK YOUR TAPPET CLEARANCES ARE CORRECTLY ADJUSTED WITH THE ROCKER SPINDLES IN THE CORRECT POSITION . RUPERT RATIOS B25 ENGINE BOOK IS A GREAT HELP HERE IF YOU ARE UNSURE > ALSO THE CRANK PINION TIMING MARK COULD BE OBSCURED UNDERNEATH THE TAB WASHER IF YOU CANT SEE IT INITIALLY . THEN AGAIN IT MAY BE THAT AN INCORRECT CAMSHAFT IS FITTED OFF SOMETHING ELSE BUT IM JUST GUESSING HERE . HOPE THIS HELPS A BIT . REGARDS JOHNBOY
thanks for the reply;just to let you know that i made a silly mistake; every bike i have ever restored has started first kick (no bull).this one however refuses to start. when i rechecked ignition and valve timing the points cam rotates anticlockwise so i assumed that the timing marks on the primary drive side would be running clockwise.not so. which is why i thought the valve timing was so far out. having pulled it all apart and rechecked everything i then discovered my mistake. so- everything back in place valve and ignition timing all seems correct;new carb;electronic ignition;fat spark; fuel getting through; still won't start. can't believe it.
HI THERE THIS MAY SOUND OBVIOUS BUT IS THE FUEL FRESH ? AN ENGINE GENERALLY NEEDS 3 THINGS TO WORK > COMPRESSION , FUEL AND A PROPERLY TIMED GOOD SPARK > CHECK SPARK PLUG GAP IS WITHIN LIMITS > POUR A LITTLE FUEL DOWN THE PLUG HOLE AND SEE IF IT FIRES . REGARDS JOHNBOY
This may not help in this case but just for information.. Two of the biggest mistakes on these engines (both have happened to me!!) is firstly not checking you have cam end float after fitting the inner timing cover. With little or no end float the Inlet cam follower sticks as the clearance between it and the inner timing cover is way too small.. The other thing is to make sure the pushrods are fitted the correct way.. If I remember correctly, you use the saying IN,OUT, IN,OUT, so Inlet pushrod on Outer cam follower and Exhaust on Inner follower. I assume you have the correct length pushrods fitted and valve clearances are set at 0.008" Inlet and 0.010" Exhaust? HTH