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Murnan Modified Motors

Old 12-15-2011, 08:37 AM
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Originally Posted by beebone
Hi,

My MM 35 plus got a strange problem, when idle long then put on throttle, a large pop noise came from exhaust, then the plug was brown.

The 2nd plug works fine, but it's brown again when out of fuel.

The bearings are new, using Odonell99 t, Tornada 25% fuel, any idea. Thx
Make sure the piston does not have any scratches on it. I would use a novarossi c8tgh glowplug. How much fuel has gone through the engine? Is the rod new?
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Old 12-15-2011, 09:25 AM
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Hi Uriah,

Do you recommend picco or nova plugs (are they compatible) for your M21? I will be using the picco 2033 pipe and tornado 25%.

Many thanks,
Brian
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Old 12-15-2011, 10:41 AM
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Originally Posted by Grinder
Make sure the piston does not have any scratches on it. I would use a novarossi c8tgh glowplug. How much fuel has gone through the engine? Is the rod new?
Its only have little scratches, not the deep scratches.
The plug surrounding is slightly wet, proper tune (I think so), good temperature, new rod.
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Old 12-15-2011, 12:21 PM
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Originally Posted by beebone
Its only have little scratches, not the deep scratches.
The plug surrounding is slightly wet, proper tune (I think so), good temperature, new rod.
Sounds like bad plugs. Try a novarossi, or maxpower plug. The tune could be off. Do you think the bottom is too rich, and top lean?
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Old 12-15-2011, 04:08 PM
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Originally Posted by Grinder
Sounds like bad plugs. Try a novarossi, or maxpower plug. The tune could be off. Do you think the bottom is too rich, and top lean?
I guest it's lean on top, There is less smoke when almost 1/4 tank. I did the pinch test, LSN is right about, 4-5 sec to stall and slightly rev abit, so I will try Nova plug, thx!
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Old 12-15-2011, 06:24 PM
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Originally Posted by Sabenza
Hi Uriah,

Do you recommend picco or nova plugs (are they compatible) for your M21? I will be using the picco 2033 pipe and tornado 25%.

Many thanks,
Brian
Brian, broken-in yet?
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Old 12-16-2011, 01:48 AM
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Uriah did the break-in for me. I am going to test it this weekend at the club race but I am not sure what plugs to use. Does it matter if it's a picco based engine? Should I use Picco plugs? Or would nova (or even O'donnell) plugs be a better fit?
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Old 12-16-2011, 03:46 AM
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Originally Posted by Sabenza
Uriah did the break-in for me. I am going to test it this weekend at the club race but I am not sure what plugs to use. Does it matter if it's a picco based engine? Should I use Picco plugs? Or would nova (or even O'donnell) plugs be a better fit?
I heard some Picco users using OS plug
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Old 12-16-2011, 07:22 AM
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Originally Posted by Sabenza
Uriah did the break-in for me. I am going to test it this weekend at the club race but I am not sure what plugs to use. Does it matter if it's a picco based engine? Should I use Picco plugs? Or would nova (or even O'donnell) plugs be a better fit?
I prefer to use the Picco plugs in the Picco engines. I use the Picco P7TC Cold for on road .21. You can also use Novarossi Plugs in the Picco engines. The C8TGH works well too.
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Old 12-16-2011, 09:28 AM
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Originally Posted by beebone
I heard some Picco users using OS plug
odonnell plug(99T) fix too
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Old 12-17-2011, 06:19 AM
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Default Dyno Video

Here is a short video of one of my Novarossi 35+21's on the dyno.

http://www.youtube.com/watch?v=htaW_...qtwPWmdNd9huyq
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Old 12-17-2011, 06:27 AM
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Originally Posted by beebone
I guest it's lean on top, There is less smoke when almost 1/4 tank. I did the pinch test, LSN is right about, 4-5 sec to stall and slightly rev abit, so I will try Nova plug, thx!
Hi Uriah

Found the cause of he pop noise and brown plug, check my pm, thx
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Old 12-17-2011, 04:41 PM
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Default Turbo scoop

I am curious about the function of the turbo scoop on the back of the crank, and the variation one can see among brands.

Any views or opinions?

I saw an old thread with one post saying there is very little performance difference.

Thanks for the education.
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Old 12-18-2011, 07:06 AM
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Originally Posted by HHH
I am curious about the function of the turbo scoop on the back of the crank, and the variation one can see among brands.

Any views or opinions?

I saw an old thread with one post saying there is very little performance difference.

Thanks for the education.
The Turbo Scoop helps the fuel make the turn from the crankshaft bore, into the block. This way all of the fuel does not have to bounce directly off the backplate, and then make a 90 degree turn. There are different variations on this. Single turbo, Biturbo, Triturbo scoops. The turbo scoop does add power.
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Old 12-18-2011, 09:08 AM
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Originally Posted by HHH
I am curious about the function of the turbo scoop on the back of the crank, and the variation one can see among brands.

Any views or opinions?

I saw an old thread with one post saying there is very little performance difference.

Thanks for the education.
The shape and size of the turbo scoop will affect the gasification of fuel. i.e. small size = high flow and will improve gasification but reduce the flow speed.

If the turbo scoop has been cut beyond the sweet point, fuel will be excessive and stay in the lower chamber. That is the case of flooding at low rpm...

The size of the crank hole and scoop is directly related to crankcase volume , size and number of transfer ports, and it will affect positively or negatively the maximization of gas mass flow and speed, from the case through the ports and into the combustion chamber.

So if badly done there will be losses and no gain. If properly done, even minimal gains will be gained.

AFM
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