3.5A running problem

[Tim Parker]

Hi, I've an elderly air cooled 3.5A, which always starts first pull, and runs below half throttle no problem. but if i run it at higher revs for more than 5 or 10 minutes it starts to die, as if theres a fuel starvation problem? could it be overheating?

I've a manual, but i'm a bit wary stripping it down without any spare gaskets etc.

Someone suggested the float may be sticking?

[Ken]

Tim,
Check the vent for the fuel tank - sounds like it may not be venting properly and causing a vacuum, and thereby restricting fuel flow.
Good luck [img]smile.gif[/img] ,
Ken K

[Tim Parker]

hi, i don't think its that as at one point i had the cap off the fuel tank

it seems temperature related, as first few minutes its fine ( runs better in the depths of winter), then it begins to stall. i'll get a few gaskets and have a look at the carb. i'll take the float chamber off, as last time i did i'm it looked like the float had been repaired (glued) in some way. I'll keep you posted.

cheers

[beluga]

Hi Tim,
I am interested in how you resolve this problem. I've just bought a P65 and am trying to find out more about this model. Does your prop rattle when it is started out of water? I'm yet to try it out in the water. Cheers Beluga

[catman2]

I seem to have the same problem as Tim with my 3.5 Yamaha - have added fuel filter but that made no difference - checked for spark - there is one, odd as it gives up but after being left for 10 mins starts fine for another 15 mins. what plug is it meant to have mine has a NGK BP6HS? could I run a cooler plug? any help appreciated! oh and do most not have any gears??

[smokey]

sounds like your float bole is draining faster than it can refill. check your needle seats and you may have to readjust your float

[smokey]

sounds like your float bole is draining faster than it can refill. check your needle seats and you may have to readjust your float

[Tim Parker]

Actually, i did recently put a new fuel filter in, effectively a small piece of gauze in the fuel trap bottle.

excuse my ignorance, do you mean check the valve seats for ware? as for adjusting the float do you mean bending the pivot arm?

oh, and Catman2, the 3.5A has no clutch or gears, where as the 3.5AC has neutral and forward. mines a 3.5A

[catman2]

took the advise of adjusting the fuel float level as when the motor dies and had tried to restart I took out the plug it was dry, seems much happier now and didnt cut out at all. the only prob now is restarting when hot it only starts if throttle is open, there are 2 screws on the carb what do they do -1 appears to set the idle on the throttle cable the other? - but what would be a good starting setting for it? thanks Steve

[Tim Parker]

what did you actully do to adjust the float?

[catman2]

there are 3 screws on the float bowl underside of the carb - remove these to gain access to the float - the float is held in place by a pin that should ust slide out so you cab renove the float itself (be careful as there is a small loose dart like object (the needle?) that is held in place by the float (this cuts off the petrol supply when the float is highest) -it could be thta this is just stuck but to increase the fuel height in the bowl you need to adjust the tab on the float that the needle sits on. You need to push it down towards the float to increase the fuel height - hope that makes sense??

[Tim Parker]

hi, adjusted the float, but not much better. did you adjust it a couple of mm or much more?

Runs ok for 10 minutes, but once hot will only run at half throttle, any more and it dies. i've checked float needle and its got no groove or wear on it.

Cheers