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Old 04-04-2010, 01:23 AM   #1
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Questions?? Need some advice.....

I have an OFNA red dot JL .12

I purchased it from a fellow member. I finally ran it today and when I got home and stripped it down to clean it and noticed it has 4 shims. Two appear to be the same thickness, one is thinner and the last one is even thinner.

Question is how many should be on this motor since I am running 20% nitro.

This is my first "good" motor and I want to get the most out of it while not pushing it to far so it will last.

Any help would be much appreciated.

Thanks.
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Old 04-04-2010, 02:19 AM   #2
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Originally Posted by DK9mm View Post
I have an OFNA red dot JL .12

I purchased it from a fellow member. I finally ran it today and when I got home and stripped it down to clean it and noticed it has 4 shims. Two appear to be the same thickness, one is thinner and the last one is even thinner.

Question is how many should be on this motor since I am running 20% nitro.

This is my first "good" motor and I want to get the most out of it while not pushing it to far so it will last.

Any help would be much appreciated.

Thanks.
That motor normally comes shimmed at .50mm, for 30% nitro. So you can remove the thinner one to start. If you need alittle more then take another one out. But dont go smaller then .40mm.

Is this the JL Tuned version? If so the head is shimmed differently.


Shawn.
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Old 04-04-2010, 12:35 PM   #3
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Originally Posted by Shawn68z View Post
That motor normally comes shimmed at .50mm, for 30% nitro. So you can remove the thinner one to start. If you need alittle more then take another one out. But dont go smaller then .40mm.

Is this the JL Tuned version? If so the head is shimmed differently.


Shawn.
Here is what I got.....
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Old 04-05-2010, 06:18 PM   #4
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Quote:
Originally Posted by DK9mm View Post
I have an OFNA red dot JL .12

I purchased it from a fellow member. I finally ran it today and when I got home and stripped it down to clean it and noticed it has 4 shims. Two appear to be the same thickness, one is thinner and the last one is even thinner.

Question is how many should be on this motor since I am running 20% nitro.

This is my first "good" motor and I want to get the most out of it while not pushing it to far so it will last.

Any help would be much appreciated.

Thanks.
HEAD CLEARANCE

We recommend a real head clearance between piston and burn room of about 0.45mm (0.018inch.
Or more, when the piston is at Top Dead Center. The real head clearance can be calculated as follows:

Real head clearance = Thickness of head shims + 0.05mm*
* (that‘s due to the internal construction of the engine and the compression of the head shims, when the cooling head is mounted)

You may need to adjust the shims depending on nitro-content (see table below).

Also, depending on track layout you may wan´t to adjust shims.
Large tracks may require an extra 0.10mm (0.004“) shim to reach higher top speed and improved fuel consumption, but this will decrease acceleration slightly.

Nitro content:
16% Real head clearance 0.45mm(0.018") Head shims 0.40mm(0.016")
20% Real head clearance 0.45mm(0.018") Head shims 0.40mm(0.016") 25% Real head clearance 0.45mm(0.022") Head shims 0.50mm(0.020")
30% Real head clearance 0.65mm(0.026") Head shims 0.60mm(0.024")


hope this helps
AFM
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