Yamaha 40H 2T 1994 lost

[tinker]

Interesting, which ultrasonic cleaner did you go for? I'm seriously considering adding to my collection of gadgets/tools....

[nw04jen]

went for 2l one off ebay - want to do them individually as im no engineer so prefer to dismantle and reassemble one at a time

AIPOI ultrasonic cleaner

[nw04jen]

Got this one. Would suggest 3L altho this took the carb. Cleaned all 3. Put back together. Sneeze / cough gone ...almost revved via linkage without cutting out but still happening. Lift choke lever and revs to hearts content so it's fuel...all floats seemed correct to me - parallel lining up
Spray easy start in 3 will rev ...just at a loss now - all fuel lines clear too..
Ultrasonic cleaner decent tho

[tinker]

Cheers , looks good l'm tempted. You say choke lever.....mines a switch under the key, the lever is to rev the engine in neutral.

Have you replaced anything on the carbs, jets or float valve. Could be related to one of those.

When I start mine it high revs for about 10 seconds and then slows down, apparently it's based on the Thermostat and controlled by the cdi, does your do that?

[nw04jen]

Yes mine revs high and if push linkage then she will rev ..but when she settles, push linkage and she cuts out. Spray easy start and fine. Somewhere somehow she isn't getting enough fuel is all I can think. Floats look okay to me. Float needles replaced. I meant the lever by throttle. So basically if I increase rpm with lever then she doesn't cut out when push linkage but obviously when on water with that up she won't go into gear.
It must be the float level is all I can think but they all equal and parallel to bowl line. Idles perfectly..good strong jet ..wondering about lowering floats so make them closer to the bowl

[A1an]

Did you remove the mixture screw when you stuck them through the bath?

[User name]

Originally Posted by nw04jen

Yes mine revs high and if push linkage then she will rev ..but when she settles, push linkage and she cuts out. Spray easy start and fine. Somewhere somehow she isn't getting enough fuel is all I can think. Floats look okay to me. Float needles replaced. I meant the lever by throttle. So basically if I increase rpm with lever then she doesn't cut out when push linkage but obviously when on water with that up she won't go into gear.
It must be the float level is all I can think but they all equal and parallel to bowl line. Idles perfectly..good strong jet ..wondering about lowering floats so make them closer to the bowl

I'm not sure if I'm following along correctly, but are you saying you can throttle it directly from the linkage and it runs fine every time?

Or are you throttling it from the linkage once and then the following attempt it bogs down as if starving for fuel?

When you say you reset the floats, was that setting the height using the info in the service manual? or just eyeballing it to what looks right?

[nw04jen]

Mixture screed remained.

So after she starts she will idle fine.
If I press linkage to increase rpm she dies unless I spray easy start in the carbs. After ultra sonic she is slightly better when increase rpm via linkage and sometimes stalls sometimes revs
If I lift lever at throttle I can press linkage without stalling. So somehow / somewhere she is not getting quite enough fuel.
Floats I set by making line on plastic parallel to bowl line. I did not set an exact height of that line but I would say it's about 5mm above bowl - not sure there is a manual out there for a 94 40H

[beamishken]

Have you tried pulling the plug caps at idle recently? A few posts ago you said nothing changed when pulling no2 plug cap, is that still the case?

[nw04jen]

Originally Posted by tinker

Cheers , looks good l'm tempted. You say choke lever.....mines a switch under the key, the lever is to rev the engine in neutral.

Have you replaced anything on the carbs, jets or float valve. Could be related to one of those.

When I start mine it high revs for about 10 seconds and then slows down, apparently it's based on the Thermostat and controlled by the cdi, does your do that?

Mine does the same and is now idling really well - its just when i 'call' for more revs she cuts out - IM wondering if main jet isnt protruding high enough from carb or something odd as easy start cures it - fuel lines all clear, pump new altho im going to check today that it is pumping and will bypass new filter to see if thats an issue - all carbs have fuel in them when i open drain screw

[tinker]

Have you tried pumping the primer bulb when you rev it?

[nw04jen]

Yes done that. That's not the fault. Bulb stays firm.
Have cleaned again. Air pressure all lines and needles etc and reassembled. One drain screw broke off so waiting on that and will try one more time. Altho link Rd so snapped so waiting on that too!

[nw04jen]

So she is running slightly better but still getting this squeal - every time slightly causes the engine to slow - have greased drive shaft - not that - also puff of smoke from under cowling on each squeal and a slight puff of fuel leaks out the top of carb 1 fuel pipe entry ...could it be gasket on crankcase?> at a loss

squeal is not a cough / sneeze as we have altered mixture both ways - and noticeable puff under cowling

https://drive.google.com/file/d/1EHh...p=sharing&t=12

[tinker]

Doesn't sound related to the crank but maybe the oil injection pump. The fuel leak, has to be carb related.....I think, float or the valve, there's a spec for the distance from the top of the float to the top of jet mount. Have you got a manual?

[nw04jen]

Thanks. Don't think carbs - as been cleaned x 3 and can see fuel happily coming out of main Jersey. The squeal sounds as though coming out from just under the cowl where there is a gap in video and each time she squeals there's a puff of smoke. Not sure where the oil pump is or why a fault would make that awful noise. Fuel delivery now seems fine - I've booked her in with engineer in couple weeks but wondered if any Yamaha gurus might come up with a definitive answer ...checked compression, spark, replaced fuel pump, plugs, fuel line, coils, filter ...now just this awful squeal / hiccup ( but have altered mixture screws both ways ..and squeal still exists -could it be air related somewhere?

[User name]

Have you done any other work besides the carb cleaning? Have you confirmed the ignition timing is correct?

The squeak could be from over-pressuring of the crank case if the ignition timing is off.

[nw04jen]

No other work no - wouldn't know how to correct ignition timing unfortunately.

[User name]

Originally Posted by nw04jen

No other work no - wouldn't know how to correct ignition timing unfortunately.

Not sure if you already mentioned it, but can you post the exact model number/serial plate? I might have a workshop manual that will explain the procedure for checking/setting the timing.

[nw04jen]

Thank you that's very kind but I'm not going g to attempt that. Done all I can within my capabilities.
Was hoping someone may know definitively what that squeal was ...next stop dealer !

[User name]

Originally Posted by nw04jen

Thank you that's very kind but I'm not going g to attempt that. Done all I can within my capabilities.
Was hoping someone may know definitively what that squeal was ...next stop dealer !

Defo take it to someone experienced if you don't fancy it, but the process is actually fairly simple. You've obviously got some technical skills if you're rebuilding the carb so I wouldn't be too intimidated by it. Don't confuse it with timing a 4 stroke engine engine also. That is actually more complicated.