Rotax 185s

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Postby ger » Tue Sep 16, 2008 9:09 pm

Hi,

I have replaced the JPXs that I sold to Tyler with the 185s that I bought from Frank Doolittle. I was worried that the CofG would be way out, but it wasn't. Removing the out-of-date BRS brought the CofG back into line. (My apologies to Richard E.)

The top revs we can get out of the engines is one at 4200 and the other at 4800. What is the max rpm one should get while static?

What should we be looking at first? I installed new plugs and we have set the 2 jets by the manual. We are at 2200 ft el. Using the double props.

Will appreciate any help you can give.

Gerald
ger
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Postby 89 CHARLIE » Wed Sep 17, 2008 9:12 am

We get about 5500 with our 185s and the two bladed props at 540 ft el. Do you have good compression?
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Postby ger » Wed Sep 17, 2008 2:35 pm

Yes there is good compression.
ger
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Postby huronflyer » Wed Sep 17, 2008 4:24 pm

Gerald,

I never flew Frank's plane with those engines, I did fly his other plane.
He never had a tach on either plane...
that is a thousand rpms too low if your tach is accurate.

do you have an optical tach handy/
you can also hook up a GA tach for comparison

I used to get 5500 low side and more like 5600 - 5700 with my 185s and bi-props

I now get 4600 - 4800 static with P-tips and 5000 - 5100 in air.

Did you check the pistons and rings on those engines?

Dave
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Postby ger » Wed Sep 17, 2008 10:34 pm

huronflyer @ Sep 17 2008, 04:24 PM wrote:Gerald,

I never flew Frank's plane with those engines, I did fly his other plane.
He never had a tach on either plane...
that is a thousand rpms too low if your tach is accurate.

do you have an optical tach handy/
you can also hook up a GA tach for comparison

I used to get 5500 low side and more like 5600 - 5700 with my 185s and bi-props

I now get 4600 - 4800 static with P-tips and 5000 - 5100 in air.

Did you check the pistons and rings on those engines?

Dave
CYEL


It's the Tiny Tach, I believe. You wind the sensor wire 4 times around the sparkplug wire. I will try to get hold of a GA tach. I don't have an optical tach.

I have not checked the pistons and rings. I assumed they were pretty good based on what Frank told me.

Gerald
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Postby lazairiii » Thu Sep 18, 2008 1:17 pm

Dave is correct. 5500-5700 with Bi-props, and you should get 4900-5100 with P-tips. I'd look at carb kits and make sure they are set up correctly and then possibly rings if you are 1000rpm's low.

George
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Postby russell » Thu Sep 18, 2008 1:56 pm

Crankshaft seals are critical to the performance of any two stroke engine. Through normal wear or drying out due to not being ran in a while, a pressure/vaccum test would be an important check. Ignition timing?

Russell
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Postby ger » Mon Sep 22, 2008 1:29 pm

Thanks for your help, you guys. I don't always have a shop to work in and don't feel I have the expertise to check and overhaul a 185 engine properly. Do you know where, in western Canada I could get this done?

Thanks again, guys.
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