Yamaha 40 hp, 2 stroke, 3 cyl - 1987 40ELH

[latter88]

Hello. This is my first post on this forum.
I am a 28 yr old guy from Denmark, having trouble with my Yamaha 40 hp, 2 stroke, 3 cyl - 1987 40ELH

I simply cannot get the engine proper tuned.

Story made short, everything has been taken apart.

Replaced parts:
- Complete new powerhead gaskets
- Reeds (carbon 0,3mm 'are these thick enough compared to original steel??')
- Piston rings (all repair manual wear limits are within spec)
- Lightning coil (the old one red 0,7 ohm - so broken)
- Upper and lower crank bearing
- Sparkplugs
- Fuel lines
- Sparkplug caps

So the sad part of the story is that after assembling the engine back together, I am just back to where I started.
Engine impossible to tune up.

I have setup everything by the repair manual specifications.

All OHM readings are within spec.

Timing:
Idle: 4-6 ATDC
Carb pickup: 0-2 ATDC
Full Advance: 24-26 BTDC

Carbs:
Pilot screw: 1 3/8 - 1 7/8
Float drop setting in mm. 12-16 (This one I am wondering if I am doing correct - someone please describe this in detail - how can it vary 4 mm??)


Symptoms are: Rough idle, sneezing, stalls when increasing RPM, fuel running out #1 and #2 carb (not spitting - which indicates float problem, correct?), alot of smoke.


I have already tried the following:

Cleaned tank, replaced fuel, precise oil mixture, carburetors cleaned with several products (carbcleaner, ultrasound etc.) tried to follow the link&sync as best I can.

My main suspicion are with the carburetors! And here I have a few questions. Can you take the jets apart in the 6H4-14301-06-00 carburetor? Someone told me they are 'heated?' in? Dont know the english term for this. Also, how can you balance these carburetors, when there is no where to hook up a gauge?
And as mentioned above, how do you set a float drop to 12-16 mm ??? Does that mean just somewhere in between?



I really hope some of you can help me.


Sorry for the bad spelling.


Thomas

 

[99yam40]

fuel running out of carbs and sneezing are way different
one floods cylinders and the other is what I think is a lean sneeze

needle and seat are not closing off the fuel into the carbs if it is over flowing and a lean sneeze would be jets/passages plugged

 

[latter88]

Thank you for helping. Do you know if the jets are removeable in this carburetor?

 

[99yam40]

If they are sold as a separate item in the parts, then they should come out for replacement.

sometimes a heated ultrasonic bath is needed to clean them properly
once clean , setting a factory spec should make the motor run well.
no need to try to hook up gauges to tune
Just make sure you follow the link and sync procedure in manual to make sure the carbs are all opening and closing exactly the same. This is needed everytime you put the carbs back on

 

[latter88]

One of the parts I cannot find thuogh. It isnt sold anymore. So its dangerous to remove these jets as they are very stuck. Is it possible to maybe heat up the surrounding aluminum carefully and then try an impact driver? Or do you think they will snap?

 

[99yam40]

brass is soft and can break