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2002 50 TLRA will not rev under load

B

bigyoung

Member
My 2002? Yamaha 2 stroke 50 TLRA will not rev over 2800 rpm underload.
Problem occurred after 6 mo. Period of non use. Prior to running, I drained old treated fuelfrom tank and refilled with new 91 octane and topped off oil tank. Cranked up in driveway on hose, thenlaunched, warmed up and ran at 4400 rpms for approx 20 minutes. Returning to launch at 4400 rpm and openthrottle to 5200 for 30 seconds and engine lost power/dropped rpms to approx2800. Will only rev to 2800-3000 under load, but will rev higher in nuetral or reverse.
So far, I have conducted basic checks to include:
· Checked compression cold – 110 all cylinders;
· Installed new NGK plugs – some oil on old plugsbut not fouled;
· Checked fuel filter on engine – no water;
· Changed spin on water sep. canister filter;
· Checked/siphoned 6 gallon tank for water – no wateror trash;
· Ran in slip in forward – opened throttle butmotor only revs to 2800; even stopped and started disconnecting plugs and couldnot tell a bad plug/ignition coil;
· Check throttle linkage for full range of motionwith full throttle;
· Checked spark with inline spark checker-crankedand lighted bulb all 3 plugs.
I was relieved to see good compression, motor starts andrestarts quickly. Revs past 2800 in neutraland reverse.
I have not pulled carbs down since condition as filters wereclean but have cleaned carbs within last year. Also use non ethanol treated fuel. Any suggestions? I’m thinking abad coil not firing under load?

 
aliboy said:
Have you checked the fuel pump?
Click to expand...

Fuel Pump is original 2002 pump. Prior owner ran ethanol fuel. How do I check the pump?

Also have changed small oil injection intake manifold hoses and would like to change the hoses between the tank and oil pump while I have the carbs off. Will I have to bleed the oil pump if I only remove/change the supply hose from tank?

Thank you aliboy.
 
Found sawdust looking crap in carb bowls; and disassembled fuel pump. FP diaphrams stiff but not torn.

Jets and needles are getting brite & shiney in Berrymans Carb Soak.

What about bleeding oil pump with new supply hose? Will run and udate post.

Thanks
 
Not sure about the 50, but on the larger yamahas I run premix in the tank when first firing them up after playing with the oil system and then pull the oil tubes at the intake end to see if they are letting oil through with the engine running. The larger engines also have some type of check valves in the oil lines and don't easily self bleed until you pull the hose off the intake. Probably would be OK if run for a while on pre-mix, but I just pull the hoses and check each one to be sure.
 
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