too much back pressure??

[GTR]

Hi Frank,

The pipe could get a little clogged with carbon but it takes a fair while. If you are concerned plug the end and fill it with ATF leave it 3 days to a week and then drain. The ATF will clean it out.

It is possible that the motor is past it's best days or there is some drag in the drive line taking the edge of the performance - kinked flexshaft, rusting, broken strands.

If the mtoro won't pull the prop try lengthening the piep a bit more and see if it improves. If you don't go too long you won't hurt the RPM you can pull.

Are you certain there is nothing basically wrong with the motor?

Keep trying and I'm sure you'll get it worked out.

GT

 

[zagustin]

Hi Frank,

Just comming along to have a look to your engine. You mentioned new bearings. Does the ball bearing fit in qualitiy to nitro engines ? That means the clearance is specified to C3. Playing around with the flywheel , does the piston move by gravity to the end of the downward stroke ? To perform this check in a right way it is on condition that there is no plug inserted , the motor is clean and oiled with storage oil. Besides the a low friction of piston and bearings a minor clearance of the crank in axial direction should to be felt.

Are you sure to set after reassembly the Zimmermann disk in the right position ? There are two settings possible.

The right posititon is that the timing of inducting in the end of the upward stroke is as large as is to be set. That means the disk is just beginning to close the intake.

Generally the clearance of piston to head insert should be .6 mm for 20% nitro.

A very rare failure to the CMB could be a bypass from combustion area to the cooling line in the head . Where does it come from ? The pin to hold the sleeve in position was too long. The head insert and the shim was not laying smooth on the sleeve . A little gap provides loss of compression. To check that failure, fill oil in the sleeve put the engine upside down an try to move the piston in upward stroke. Hold the piston under pressure for a certain time to see if a loss of oil will happen. In addition it is recommended to dismantle the cooling head cover to check if oil is to be found in there.

Looking foreward hearing from you........................Werner