i've got a 3ln and i've just been getting it in running order again. I manged to get it all working after replacing a few gaskets and o-rings etc, i've also changed the spark plugs, oil, etc. anyway my problem is that the bike would only rev to 14k and not 18k and it's difficult to start when warm. Basically i have to hold full throttle when i start it and gently ease off until i hear the revs climb a little, hold it then ease off a little again until it'll finally rev up then it'll idle no problem again! just difficult hot starts. I replaced the spark plugs to see if that was the problem and it did rev to 18k in 1st gear although i had a spirited ride up the hill and stopped to see if it would start again since it was hot but i noticed water streaming out and no it wouldn't start hot again (i had to try).. the water streaming out was water coming from the escape hole from the water pump housing due to the mechanical seal giving way/failing, most of the rubbers are perished on the bike but should have 99% of them replaced now. Was wondering what the problem could be? loss of oil pressure above 14k not allowing it rev higher due to the water pump seal? i don't have the proper rubbers from the airbox to the carbs so i'm practically running without an airbox and the 2 vacuum (i presume) pipes on the carbs are free-to-air (i think the hoses from the airbox are meant to go on here but they don't appear to go anywhere anyway) any ideas?
Replace water pump seals, clean carbs (pay particular attention to pilot jets), check to ensure pilot air screws are 2 1/2-3 turns out, look for air leaks in intake boots, adjust EXUP valve, and balance carbs. Start with these and see what happens
replaced the water pump seals and took it a run, revved it to 17k to see if changing the plugs helped then at the next junction i seen the water coming out again from the same hole?!?! i don't think the propellor shaft is worn, well i doubt it very much it's steel not aluminium. I'm thimking it's due to excess pressure as it was fine at idle and under 14k revs. Blockage somewhere in the system? could the radiator cap be dodgy?
Try running the bike to what ever rev you can get it to sit on like 12K and remove 1 spark plug lead at a time and see if your engine starts to cough and splutter, if so put the lead back on and move to the next one. if you get one thats not making a difference then that narrows down your problem to the cylinder , carb , plug etc etc. I remember having this problem with one of the race bikes and it got to the point that i stripped the head down looking for my mistake re did the shims like 4 times and in the end it was some yellow dried honey looking stuff in the fuel bowl's that was clogging the jets so it was being starved for fuel.. hope some of this helps.
yeah thanks for that i'll give that a go once i get the cooling system sorted out. the seal in the water pump is mechanical, i.e. you can push the propeller in a few mm.. would i be correct in thinking that if there's two much pressure in the housing the pressure will push the propeller in and let some of the water out of the hole to relieve the pressure to stop damaging other parts?
