Well, that's pretty much the question. I haven't run this engine in quite awhile and can't remember what pipe length I was using. Any suggestions?

Thanks, Wayne.

Brad,

I finally found my notes on the plane I ran this engine on with a pipe. Seems I started out with a 17.5" pipe length and ended up with 18.25". I'll probably start there.

Thanks, Randy

17.5 is what Richard suggested I start with on my 51. Since majority of RoJetts(40-65) have same timing, I'd start there with the 65 as well. It runs in very comfortable constant 4.

Hi Steven

I am curious ,What makes you think that the  Jetts all have the same timing?

Regards

Randy

and report back.

Quick search on SSWF brought this:

http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=232053&mesg_id=232053&listing_type=search#232061

It looks like at least 61 and 65s are timed the same.

From your  quoted  thread.  So  there maybe could be multiple  timings  on the RO Jett  65 that  Randy asked  about.

I believe in the quote you to refer to, Rich was talking about the first 61 engine. 65 came later and used CNC program already setup for the 61 sleeves. He also wrote about having just the first 61 motor with odd timing.

That was my only point, check it then you will  know. Other  people have and were surprised.

Is there a HOWTO on how to get engine timing measured? You peaked my interest and I'd like to try checking timing on my motors.

I understand that there are also different PA75's configurations out there. I own two and am very curious as to which setup they are.

Steve

There are  no  PA 75s out there  with differant timing.

I just wrote that there are two different configurations, not necessarily timing configurations. Something to do with booster ports...


P.S. Randy, I hope you don't think I am trying to boo your products. I'm a happy owner of several PA's. As a matter of fact, next year I will have three new ships; all powered by your stuff(PA75, PA40Lite and AT36).

""I got curious about the timing differences between a 51 and a 65 RoJetts. Since I don't know how to check the timing with a wheel, I just unbolted the header from the 51, bolted it onto 65 and stuck it back in my current ship. At 17.5", it 4-cycled very nicely at 9800 with only a hint of 2-cycle. Same type of run as with the 51! I know is NOT scientific but it does indicate that 65 and 51 have similar type of timing and run characteristics! Cool.""


HI Steven

That doesn't really indicate anything about the timing. I can make most any stunt engine run in a 4 cycle 2 cycle at most any pipe lenght. And I have ran several engines from 14 inches to 21 inches all in a nice 4 cycle. What is missing was the governing-holdback in the wind, also some would hit harder or softer at differant lenght.
You really have to time the motors to find out the info you want.
Timing engines is not difficult, You can buy a Inexpensive round plastic 360 degree compass many places, Just drill a hole in the middle of it, Install it on your motor like you would a prop, and you are set to check the timing. It is easiest most times if you remove the head. A good technique to use is to make a pointer from a small piece of piano wire with a loop in it. use a head bolt to hold it in place to the top of the case and use another head bolt in front of it to make sure it doesn't move. You can then read where the pointer is in relationship to the compass, and for exhaust turn the motor over the entire range that the ex. ports are open for. read the compass and do the math for how many degrees it stays open.
The intakes are done the same way, just turn the engine over and read where you start and where you stop on the compass.
Many people will try to set the compass a  zero degrees to make it easy to read, this is fine but not necessary, you can read where the ports open and then read where they close and figure from there.

Regards
Randy