97 speedster 2x717 rotax, carb backfires-rebuilt engine

[mkmk123]

i got a new rebuilt engine after for the port side.
my old one was done for after a bad bearing.

the old engine jumped between 4500 to 6500 rpm back and forward

got the rebuilt engine.

-swaped the carb from old to the new engine
-swaped stator but used the new flywheel whichh came with the rebuilt one
-and the timing of the rv is set as factory. and doubles checked it with the working starbaurd engine.


now it back fires from carb even in ideal


-switched the carb from the working enine to the port side
-rechecked the rv valv
-cut 1/4 of an inch of each spark wires
-new spark plugs


still same problem.
the carb i swaped from port side to starboard works fine.


tomorrow i will check the flywheel is in right place
and swap the egnition coils.


any other suggestions????



thx for any help or ideas any one can give me

 

[timmyboy76]

make sure the RV isn't installed, 180* the other way. With mag piston at TDC, the "pto" cylinder port hole, should be closed.

Cant see the flywheel being outta whack, since its aligned with the woodruff key. Maybe the stator isnt correctly installed.

 

[mkmk123]

the stator has e marking which lines up with another marking on the engine were the stator is mounted.

mag cyl is at tdc and rv valve is correct adjusted as you say and compared with the working engine

 

[mkmk123]

ok. i got it solved.

the spark plugs were 1 month old. they ran max 1 hour.

and one of them gave up.

new spark plugs.

now it runs fine and no backfire through carb.



NEW PROBLEM.

the engine cant hold a high rpm??

drops from 6500 to 4000 back and forward

and some times drops to 2000 and engine stalls??


any ideas?

tomorrow i will rebuild the carb

 

[timmyboy76]

locate the rectifier/s, and unplug the red wire..if problems gone, replace the rectifier.