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Old 11-16-2003, 10:14 PM   #1
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Default Do I need extra Shims for a Mr-12 when running 30%?

I am going to run 30% nitro in an Mr-12. Do i need any extra shims betwee the button head and the cylinder? The engine is not moded.

Thanks for your help!!

- Dust
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Old 11-16-2003, 10:17 PM   #2
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Default Re: Do I need extra Shims for a Mr-12 when running 30%?

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Originally posted by Dust
I am going to run 30% nitro in an Mr-12. Do i need any extra shims betwee the button head and the cylinder? The engine is not moded.

Thanks for your help!!

- Dust
Try going to the Engine Shim Tuning thread. A quick answer is yes ... add a shim would be good.

Last edited by tIANcI; 11-17-2003 at 12:04 AM.
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Old 11-16-2003, 10:33 PM   #3
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no
use an odonnel 77 or 99 plug
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Old 11-17-2003, 01:08 AM   #4
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Motorman knows what hes talking about. But I'd like to give my little experience from today.

It ran great, but the low end was a little bit funny. Change the glow plug and it would have been fine. Much more power, but I had to richen it up more than I thought I would need to. I too use the Odonnel plug, the 77 worked all day once I got the right setting.
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Old 11-17-2003, 09:09 PM   #5
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Wow! Hawaii. I really want to go surfing there. I run the 77 Odonnel. I have a NTC3. Its quick, too quick for me
Thankyou for you help.
How the weather? I am pretty bumbed out right now since my board broke in half at Laguna Beach hear in California!

Thankx
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Old 11-17-2003, 11:35 PM   #6
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Last week was a bit rainy, but the surf was up. But its been wetter than I would like on race day (sunday), but no rain on the track.
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Old 11-17-2003, 11:49 PM   #7
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Default Re: Do I need extra Shims for a Mr-12 when running 30%?

Quote:
Originally posted by Dust
I am going to run 30% nitro in an Mr-12. Do i need any extra shims betwee the button head and the cylinder? The engine is not moded.

Thanks for your help!!

- Dust
If I were you I would add (0.20 mm.) of shims to run 30%, I add 0.10mm. when I run 25%.
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Old 11-18-2003, 07:31 AM   #8
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Default Re: Do I need extra Shims for a Mr-12 when running 30%?

Quote:
Originally posted by Dust
I am going to run 30% nitro in an Mr-12. Do i need any extra shims betwee the button head and the cylinder? The engine is not moded.

Thanks for your help!!

- Dust
We just put an MR-12 in my friends car and without adding .2mm shims the motor was detonating plugs. After the shims it ran like a dream and we run 30%.
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Old 11-18-2003, 11:05 AM   #9
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I tend to agree blindly with Mr. Dennis Ritchey on anything he says... after all, he is the man. But on this I even have some knowledge and therefore agree with him even more vehemently.

The only thing was that I was quite surprised at how much I needed to richen my needle settings... more than half-a-turn on the top-end setting for it to run right (I forget what I did with my low-end needle settings). I obviously expected this, but not to that degree. Certainly more than just the switch to 30% necessitated this change, but most of the cause undoubtedly was the nitro percentage change.
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