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Old 07-02-2008, 06:52 AM   #16
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This has been helpful thanks guys.
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Old 07-02-2008, 10:20 PM   #17
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Nice mod! I did one like that on a RB C5 about 4 years ago and have been refining the mods ever since with the new RB's.

Heres a pic of the crank I worked on from the fastest motor I ever had. This motor was also re-timed, ported, polished like the ones I do now. I cant even explain the power. Band was twitchy, perfect for a truggy.



You can also find a video on how to port and polish the sleeve at UndergroundRC.com. But I think you might have to be a member...?
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Old 07-05-2008, 07:42 PM   #18
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Nice mod! I did one like that on a RB C5 about 4 years ago and have been refining the mods ever since with the new RB's.

Heres a pic of the crank I worked on from the fastest motor I ever had. This motor was also re-timed, ported, polished like the ones I do now. I cant even explain the power. Band was twitchy, perfect for a truggy.



You can also find a video on how to port and polish the sleeve at UndergroundRC.com. But I think you might have to be a member...?
carcrazy thanks for the pic looks nice what engine is that crank out of just wandering it looks great.
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Old 07-06-2008, 02:09 PM   #19
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I think this this crank was from a RB C5BB. Also you cant see it in the pics, but the back of the crank was trimmed for weight reduction also. Be cautious when reducing the weight off the back of the crank... if you go too far it wont idle well.
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Old 07-06-2008, 05:36 PM   #20
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Thanks again i have not done anything with the back of my crank but i will try it little won't hurt i went this far let you know how it works out.
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Old 07-06-2008, 07:15 PM   #21
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just a freindly word of advise... polishing the internals of any of these motor really doesnt help. the object if to keep the fuel addimized till it reaches the chamber. when something is polished it doesnt addimize and you just wasted time making it pretty. polishing works really well on full size cars but not so much on these. I have made the same assumption about it too but until i pretty much got hounded by a bunch of people about it i didnt believe it. there is nothing wrong with polishing it your just making it look pretty that it.

just something friendly i know.

good luck and everything looks great.
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Old 07-06-2008, 07:37 PM   #22
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Haha, I seem to recall having a bit of an argument with you before Deisel but on this we agree.
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Old 07-06-2008, 08:25 PM   #23
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Originally Posted by dieseldog20 View Post
just a freindly word of advise... polishing the internals of any of these motor really doesnt help. the object if to keep the fuel addimized till it reaches the chamber. when something is polished it doesnt addimize and you just wasted time making it pretty. polishing works really well on full size cars but not so much on these. I have made the same assumption about it too but until i pretty much got hounded by a bunch of people about it i didnt believe it. there is nothing wrong with polishing it your just making it look pretty that it.

just something friendly i know.

good luck and everything looks great.
thanks for the help i did polish the crank bell and left the inside of the crank bumppie to keep the mix bouncing around Thanks again
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Old 07-06-2008, 10:44 PM   #24
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just remember: smooth entry and exit lines and maintain a course but symetrical surface. Also, be careful about velocity placement with motors with a higher port count. If you accellerate and decellerate the flow in the wrong areas, the motor will short circuit and will not properly loop scavage.
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Old 07-07-2008, 12:25 AM   #25
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No single cylinder engine is "balanced". All you can do is change the plane that the imbalance is in. In fact, you can't truly balance any engine with less then four cylinders.
This is halfway true. You cant fully balance a single cylinder engine. A Multi Cylinder engine you can. Basically in what is called balancing on these engines is taking vibration out. It can only be done at certain RPM windows and its not a very big window at that. Almost all Multi Cylinder engines can be fully balanced though
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Modding is trial and error. I own and engine modding biz. We started out by modelling an OS V-Spec on high-end computers used in the Aerospace industry. But that was only part of it. Real-life testing was the next part. We learned alot...

Cutting the scoop will help some with packing. The flywheel (crank) is now lightened. Part of the affect of this is less low-end torque. If you are doing it to an engine like an RB, which IMO are already weak on the bottom it makes it more noticable... It will also spin more RPMs faster. We've seen con-rods go easily with this mod...

As you mod you may make the engine much for finicky when it comes to tuning. You make the tuning window much more narrow. Again, not good. There is a balance...

And as mentioned in one of the above posts, we is it you are looking to achieve? What is wrong with the current engine now that you don't like? Did you already try other methods to improve the performance such as different clutch shoes, pipe/header combos, plugs, shims?

Again, there is alot of work in modding an engine correctly. We've got a stack of destroyed motors from when we first started out...
Ive ran more modded engines that i care to think about and the tune never gets anymore finicky.

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Originally Posted by CarCrazy View Post
Nice mod! I did one like that on a RB C5 about 4 years ago and have been refining the mods ever since with the new RB's.

Heres a pic of the crank I worked on from the fastest motor I ever had. This motor was also re-timed, ported, polished like the ones I do now. I cant even explain the power. Band was twitchy, perfect for a truggy.



You can also find a video on how to port and polish the sleeve at UndergroundRC.com. But I think you might have to be a member...?
Not to sound negative but all that cutting did alot more bad than anything. You totally threw the factory spec harmonics out the window. All but one of those cuts to nothing and i bet it vibrates really bad once it hits the harmonic threshold of the pipe and vibration wears stuff out alot quicker.

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Originally Posted by dieseldog20 View Post
just a freindly word of advise... polishing the internals of any of these motor really doesnt help. the object if to keep the fuel addimized till it reaches the chamber. when something is polished it doesnt addimize and you just wasted time making it pretty. polishing works really well on full size cars but not so much on these. I have made the same assumption about it too but until i pretty much got hounded by a bunch of people about it i didnt believe it. there is nothing wrong with polishing it your just making it look pretty that it.

just something friendly i know.

good luck and everything looks great.
Most of the time you can polish the sleeve lightly to get it to shine and smooth out some of the roughness after modding. After it is heated and cooled a few times and fuel ran through it then the surface will dull and atomize the fuel mixture a little better. Polishing doesnt hurt anything as the engines come from the factory CNC Machined which is really close to a polish finish.
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Old 07-07-2008, 06:20 AM   #26
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mfroot- You can post picks using photobucket by right clicking on the img code and pasting that code in your post. On Photobucket, when you right click the img code, it will copy automaticly.
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Old 07-07-2008, 07:15 AM   #27
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mfroot- You can post picks using photobucket by right clicking on the img code and pasting that code in your post. On Photobucket, when you right click the img code, it will copy automaticly.
Thanks so by doing it that way the pic will show up not the link.
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Old 07-07-2008, 07:34 AM   #28
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All I can say is I polish all of the engines I modify, especially the crank barrel... I am well aware that a rough textured surface flows better then a polished surface, but that applies to a stationary surface, the crankshaft is spinning anywhere from 15 000 RPM all the way to 40 000 plus RPM. that changes everything, as the surface is moving at a very high rate of speed and i dont feel there is any risk whatsoever of fuel puddling or being impeded by a polished surface..... As for polishing the sleeve, well first and foremost is the polished finish only lasts for several tanks of fuel before it becomes stained and "oxidized" from the fuel flowing over it... As well more fuel travels along the back of the case channels then flows up the sleeve face anyways , so having either a smooth or textured surface on the sleeve surface is going to have absolutely zero effect on engine output one way or the other..........
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Old 07-07-2008, 07:41 AM   #29
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All I can say is I polish all of the engines I modify, especially the crank barrel... I am well aware that a rough textured surface flows better then a polished surface, but that applies to a stationary surface, the crankshaft is spinning anywhere from 15 000 RPM all the way to 40 000 plus RPM. that changes everything, as the surface is moving at a very high rate of speed and i dont feel there is any risk whatsoever of fuel puddling or being impeded by a polished surface..... As for polishing the sleeve, well first and foremost is the polished finish only lasts for several tanks of fuel before it becomes stained and "oxidized" from the fuel flowing over it... As well more fuel travels along the back of the case channels then flows up the sleeve face anyways , so having either a smooth or textured surface on the sleeve surface is going to have absolutely zero effect on engine output one way or the other..........
Maximo That is a really good point. As I was thinking of polishing the inside of the barrel, but didn't. Like the point you make the barrel is spinning, there is absolutely no way for the fuel to puddle as it could if it was flowing over a stationary surface, like a motorcycle head. I give you a plus 10,000 points for you idea. I do have a question, do you or any of the pro modders modify the crankcase? Like polishing the exhaust port of the case? Thanks, Froot
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Old 07-07-2008, 08:33 AM   #30
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Haha, I seem to recall having a bit of an argument with you before Deisel but on this we agree.
i think i do recall that awhile ago. that was when i wasnt to bright about the stuff, but i have come along way from a couple months ago. being deployed were i am at helps me research into things and talk to people and stuff you know. but its all good
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