912S Carb Problem

[mcomeaux53]

Pulled my carbs apart for service & inspection.
Found the pistons galled about 1/3 in circumference at top and as you look
down into the bore about same condition. The actual top where the piston
slides into looks ok. is it required to change both? Engine has 341 Hrs.
And according to a/c logs no service ever performed prior to this.
Any knowledge on this???

Thanks in Advance....

Mike C.

[Paul Z]

I gummed up both my carbs because I tried using auto fuel in my plane. The alcohol stripped mold release from the tanks and it coated the carbs. I pulled both sent them to the Rotax Dealer in Florida, they completely cleaned and rebuilt both carbs for me. They both work well now. I personally didn't think the cost was that bad, something like $300 for both. I figured that was cheaper than the hospital bill if I didn't get it done!

[Av8r3400]

Is it possible to post a photo of what you are seeing?

This has been discussed on the Rotax forum and Rotax says to completely replace the carbs. Personally I think that is unnecessary. I believe that the galling can be cleaned up and the carbs rebuilt for use as long as the pistons slide freely.

Remember the pistons have quite a bit of clearance in their bores, the seal is the rubber vacuum diaphragm on the top.

[Danzer1]

Larry's right. But if there is any possibility of the piston/plunger hanging you really need to go further. You started off here with a rough running engine problem. In my opinion you really need to go through all the systems and perform some serious inspection/maintenance.

On a 2003 with over 300 hrs of service and no maintenance to date, there are many Rotax maintenance items that should be looked at. Such as all the rubber parts every 5 years (includes carb diaphrams). All the 100 hour inspection & service items, etc.

Download the line and heavy maintenance manuals and take a good look (IMHO). Here: http://www.flyrotax.com/customer-ser...lications.aspx

Greg

[mcomeaux53]

I'm going spinner to rudder for sure"......

Is it possible to post a photo of what you are seeing?

This has been discussed on the Rotax forum and Rotax says to completely replace the carbs. Personally I think that is unnecessary. I believe that the galling can be cleaned up and the carbs rebuilt for use as long as the pistons slide freely.

Remember the pistons have quite a bit of clearance in their bores, the seal is the rubber vacuum diaphragm on the top.