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Discussion Starter · #1 ·
I polished my crank case bowl and drilled out the bearing oil channels larger and wanted to know if anyone else has done this?

What kind of gains am I going to get from removing the rough cast and is it worth it....

Also, how do I polish the head? I can't get a Dremel in there or my fingers
 

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should not have done that

If anything this will really hurt the performance.The intake is not smooth because the fuel will now stick to the intake rather than flow freely.Think of it this way if you use a spray bottle and spray water on a window the water beads up and rolls down it, now if take a piece of say 220 grit sandpaper and hold one end and spray water on it the water will just flow right off it.Unfortunatly you have already polished the intake and head ports.If not sure if something is going to hurt or help the bike, in the future put up a post just asking about what you want to do.

NosMan said:
Woops forgot to mention this is my C1 bike
 

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speedjunkieblue said:
If anything this will really hurt the performance.The intake is not smooth because the fuel will now stick to the intake rather than flow freely.Think of it this way if you use a spray bottle and spray water on a window the water beads up and rolls down it, now if take a piece of say 220 grit sandpaper and hold one end and spray water on it the water will just flow right off it.Unfortunatly you have already polished the intake and head ports.If not sure if something is going to hurt or help the bike, in the future put up a post just asking about what you want to do.
Exactly. :thumbsup:
 

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Discussion Starter · #6 ·
DOOH! I can't win. Just when I thought this would improve flow I mess it up. I always ported and polished my heads and stuff for my muscle cars and thought this would be the same idea.

CRAP CRAP CRAP :mad:
 

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Discussion Starter · #8 ·
I do understand what your saying but isn't the air and fuel being forced into the chamber from suction at whatever intervals per second. That's a little different then spraying water an a piece of sandpaper and watching it drip off. There's so much turbulence in there that I can't see how it can hurt it. I've only made the air and fuel flow into the head smoother and less restrictive.

Think of it this way, you just polished and waxed car "A"... then you take a leaf blower and watch the water bead off the car in seconds. Car "B" has no wax, lets just say the paint is oxidized heavily. Do the same thing with the leaf blower and it would take more effort to dry it.

I need you to explain this more to me please, hurting performance is not my objective. Your comments and helpful tips are appreciated, thx guys .


speedjunkieblue said:
If anything this will really hurt the performance.The intake is not smooth because the fuel will now stick to the intake rather than flow freely.Think of it this way if you use a spray bottle and spray water on a window the water beads up and rolls down it, now if take a piece of say 220 grit sandpaper and hold one end and spray water on it the water will just flow right off it.Unfortunatly you have already polished the intake and head ports.If not sure if something is going to hurt or help the bike, in the future put up a post just asking about what you want to do.
 

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NosMan said:
DOOH! I can't win. Just when I thought this would improve flow I mess it up. I always ported and polished my heads and stuff for my muscle cars and thought this would be the same idea.

CRAP CRAP CRAP :mad:
It is the same idea. On cars you don't polish the intake ports on the head. You polish the combustion chamber only and polishing the exhaust ports is ok. You can swirl polish valves but even then it's not shiny smooth even though they say "polish". You are not supposed to polish the intake ports smooth and shiny, nor the intake manifold. You can get away with polishing intake manifolds where the injectors sit at the base of the ports. But if it's carbureted or TBI, polishing is a big no no.
 

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should not have done that

It is as simple as my first post. In a car using a 4 stroke type engine it is totally different the fuel is being forced into heads that distribute fuel above piston assemblie so port and polish benifits performance by causing a smoother flow of fuel and air to piston = hp, by gravity & suction in carb applications if you use fuel injection than same principle but better fuel burn due to forced injection to combustion chambers with smaller carb bore.
In a 2 stroke the fuel is being forced below piston assemblie so if you polish surface it slows the speed of combustion due to beading of fuel on surface from intake vilosity mixed with air below combustion chamber so reducing free flowing.Try the example that I gave you in my first post and it should help you understand, if not pm me and I will try to help you understand best I can hope this helps.
NosMan said:
I do understand what your saying but isn't the air and fuel being forced into the chamber from suction at whatever intervals per second. That's a little different then spraying water an a piece of sandpaper and watching it drip off. There's so much turbulence in there that I can't see how it can hurt it. I've only made the air and fuel flow into the head smoother and less restrictive.

Think of it this way, you just polished and waxed car "A"... then you take a leaf blower and watch the water bead off the car in seconds. Car "B" has no wax, lets just say the paint is oxidized heavily. Do the same thing with the leaf blower and it would take more effort to dry it.

I need you to explain this more to me please, hurting performance is not my objective. Your comments and helpful tips are appreciated, thx guys .
 

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Discussion Starter · #14 ·
Well, whatever you guys think would be good let me know please because I would like to try and return it as best as possible. Thanks all....



zero4 said:
Yeah pretty much, not sure about 80 grit though.
 

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If you are going to try to save it, I would try starting with a lower grit paper like 120, 80 grit is pretty rough and will remove to mutch material to fast, make sure to use a paper rated for metal applications, standard paper will load up to fast and waste alot of paper. If you are going to try to save it be patient go slow and be carefull just want to rough up surface not destroy shape of port design or intake. Once again if you use my spray bottle idea, do some sanding and check to see when water flows NOT beads idea is to get good flow NOT sand until looks rough. GOOD LUCK
NosMan said:
Well, whatever you guys think would be good let me know please because I would like to try and return it as best as possible. Thanks all....
 

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To nosman:
You havent done too much damage to your crank case yet. The edges are cornerd (smooth) prety good, now take 400 grid sand paper and doo some handjob on those surfaces(as the cases are on the first 2 pictures move the sandpaper up and down or square to the air/fuel flow if you understand that better).
It is so that a/f mix is going thru there wery fast but a sandblasted surface of the transfer ports give you more boom thruout the rev range and polished surface is good only for top rev.On your engine you have a lot of port area (small bore and many holes (easyer to understand)), so you are way better of with rough surface of the transfer ports cause it gets you the swirl and beter fuel atomization, therefore you can get some use of that engine in the mid rev aswell. Otherwise it would give power only at top rev and it would be hard to get there under load.
This is spoken generaly for the competition 2 stroke engines (yours is not that far away from it, considering the cc it has and the power it makes).
 

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Discussion Starter · #18 ·
OK guys, just roughed it back up again. Sorry if the pictures are crappy but this should fix my polishing job up. I did the spray bottle thingy and water flows evenly all over again rather then beading in a straight line.

Thanks for all the help to fix this, much appreciated
 

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To Nosman:
That is about it should be. Take care when you put the cases back together and put the cilynder back on, that you port match the cilynder bottom gasket or if you arent gona put any gasket back on (higher compresion) that you aply only small amount of gasket maker (i use red/orange silicone based gasket maker). It should be aplyed on the cranck case with your finger and you have to put it on there realy thin! Then you have to clear the inside edges about 1mm so the gasket maker want go inside the crank case when you tighthen your cilynder on there.
Before you do that you can do the roughening of your transfer ports and polish the exhaust port (make sure your cilynder wals are protected when you do this). Next you adjust the squish to minimum of 0,5mm or maximum 0,7mm by using diferent gasket thicknes. 0,5 is better of course cause it wil give more bottom end and crazy reving engine. I had chinese engines in my hands that had 1,0mm squish! And this is just like you would throw away some power that this engines are capable of anyway.
So good luck by puting it back together and dont forget to break it in properly.
 

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Discussion Starter · #20 ·
Hey thanks buddy, good tips there. I'll let you all know how it went when it's all back together.



r1replica said:
To Nosman:
That is about it should be. Take care when you put the cases back together and put the cilynder back on, that you port match the cilynder bottom gasket or if you arent gona put any gasket back on (higher compresion) that you aply only small amount of gasket maker (i use red/orange silicone based gasket maker). It should be aplyed on the cranck case with your finger and you have to put it on there realy thin! Then you have to clear the inside edges about 1mm so the gasket maker want go inside the crank case when you tighthen your cilynder on there.
Before you do that you can do the roughening of your transfer ports and polish the exhaust port (make sure your cilynder wals are protected when you do this). Next you adjust the squish to minimum of 0,5mm or maximum 0,7mm by using diferent gasket thicknes. 0,5 is better of course cause it wil give more bottom end and crazy reving engine. I had chinese engines in my hands that had 1,0mm squish! And this is just like you would throw away some power that this engines are capable of anyway.
So good luck by puting it back together and dont forget to break it in properly.
 
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