My First Motorbike Project

[gera229]

Another question here:

You know the head on the big bore kit and it has 1 side of it that is flat?
Can you check one of your engines and tell me which way it faces please? (Toward the exhaust, toward the pullstart/ cgi, toward the clutch, or does it face up?)

Reason I ask this is because I disassembled my engine and did not check which way it was facing. I want you to check 2 of your engines and see if they both have a head that has the flat facing the same direction and which way is it facing?

For your interest, the pull starter outside frame was pushing on the head kit all the time, but when I made it facing the exhaust it was not pushing on it at all.

How I tested this:
Basically the pull start casing interferes with the circular part on the right side, so I took all 4 of the head bolts off, but left the head on.
I made the flat side of the head face up, toward the clutch, and toward the pull start and when I tightened the pull start it seemed to get in contact with the head and I was not able to move/ turn the head.
When I made it face the exhaust and screw the pull start on, I was able to freely move the head and turn it around as if it was loose.
The reason is this: the pull start casing touched the right side of the head where it was circular, but with I turned it to face toward the exhaust the right side was flat and so yes it was not touching it and I was able to move it around.

Now I am asking which is the best position and why?

Another question:
When I disassembled my head.. on the top of the cylinder where it looks like a circle (a circular copper gasket lies on top of it) I saw a lot of scratches. Do you have that? Was it caused by the circular copper gasket? Please check your engine (and take the circular copper gasket off) to understand what I mean.

Will that reduce anything? Will that cause even a slight bit of performance loss?

And another question:
How many circular copper gaskets are inside when you take your head off?
In the big bore stage 2 engine kit pictures it shows 2 of them, but when I opened my head I only saw 1.
Where is the other? Is there even another circular copper gasket? Is there really 2?

Please answer all of these questions that I asked so that I would not end up asking them again later.

 

[happycheapskate]

re: 5/16 all thread.

All thread is like a LOOOOOOOOOONG bolt with no head (no allen head, no hex, nothing). It comes in various lengths and grades of metal.
Usually it is pretty flexible, but does not strip easily. It can be cut to length by tightening two nuts together just short of the area you want to cut, then putting it in a padded vice and hacksawing next to the nut carefully. Use the nuts to chase the threads by just turning them off the shortened piece. If it's hard to put them back on, file it a little at a 45* angle all the way around, just a little to cut off the sharp edge.

 

[lowracer]

Flat side of the head goes towards the magneto so that the side case can close.
Only one circular top head gasket.
The lower 2 copper ones I bought & installed were to replace the paper lower one.
-Lowracer-

 

[gera229]

Ok, to let you know lowracer. I think you should experiment yourself, but the head does not touch the magneto when I turn it.

In fact when the flat part of the head is facing toward the exhaust (down). The right side of the pull start casing no longer interferes, because now the right side is the flat side. And the head moves freely when it has no bolts on.

If you were to put it the head flat side facing toward all other ways, the pull start casing it gets in contact with the head and either pushes it out or pushes it down when it's not bolted on yet.

Take a look at the picture.

 

[lowracer]

They come from the factory the way I described.
You can view the pics @ http://www.bigmotorsport.com/products/Mini-Pocket-Bike-Engine-51CC-With-Upgraded-Carb.html
Go ahead & change things around...hopefully it still works out for you
-Lowracer-

 

[gera229]

Ok, I edited that post and attached a picture for a better description though.

In that website the pictures are not very clear. It does not show all sides of the cylinder on that website so I asked here. And pictures don't always show anything on websites (For example: in pictures all sides could be round without any flat sides.)

But since it comes from the factory that way I guess I should just do it the factory way. The thing is that when I took the head off I did not pay attention which way the flat side was facing and then when putting it back on I got confused. So that is the reason that I am asking.

Thanks.

 

[gera229]

I wanted to ask:
Just below the circular copper gasket on the head of the cylinder, are there any scratches on yours? Does it matter? Will it cause even a slight bit of performance loss?

 

[lowracer]

Gera229,
I am glad you posted a pic of your head. Looks like it fits just fine in that position. I never experimented with the position of the head since both my Cags came shipped flatside inward.
I didnt have any scratches on my cylinder wall. Deep scratches would definitely hamper performance & cause a loss of compression/blowback.
-Lowracer-

 

[gera229]

Not the cylinder wall. The very top of it. Here are some pics.
I circled the biggest scratches I saw (no they were not as deep as they look)

But it has scratches all over. Can that have been caused by the gasket?
Do you have that?

Also a picture to show that the head does not touch the CDI box when it's turned.

 

[lowracer]

I see the imperfections you mentioned. You could lightly sand/file them smooth but make sure not to get any schmutz into the cylinder. I'm not sure I would even bother since the copper head gasket is softer metal & will seat. If you notice any seepage once running, you could remove it again & do some sanding/filing...
Thanks for the pics...A picture says a thousand words
-Lowracer-

 

[gera229]

Lowracer,
Do you have those scratches on your engine?
Before telling me anything, can you please check your engine?

 

[gera229]

Also I did not take a picture toward the direction to which the arrow is facing on the cylinder (exhaust port). Maybe I will a bit later if you don't understand what I say below.

But like there is the exhaust port and just above it it's like a little small port or something. It's a thin rectangular shape thing. Not sure if it's a port (although it looks like a very small one) so I would like to ask:
Do you have that?

 

[lowracer]

Gera229,
I dont remember seeing any scratches like you have when I had both my engines apart replacing them base gaskets. I got both engines running right & loctited tight, so I'm not taking them headbolts out anytime soon, unless something goes wrong. If you didnt remove your piston, then the only way to put the cylinder back on is with the exhaust bib facing down...Capeesh?
-Lowracer-

 

[gera229]

You don't remember seeing scratches? Or did you NOT even look to see if there are scratches?
Just asking.
Anyway I don't think it's a big deal and pretty easy to sand off.

What about the small port right above the exhaust port? Do you have it? Or did you not look at that either?


Hey I'm thinking of getting this exhaust:
Exhaust - Performance, Cag

Can you comment on anything or give suggestions before I buy it?

 

[lowracer]

The pipe looks like the one I got off eBay for the same price (shipping was free).
I like it better than my other pipe (its quieter).
-Lowracer-

 

[gera229]

I guess I'm getting it.
Yeah good thing I haven't ordered all the hardware and gaskets yet. Cuz of the shipping fee.

But even that.. pocketbikeparts only charges 10 for shipping.

 

[gera229]

Hey lowracer, where did you buy your engine from?

Does it have 3 ports or 4 ports?

Is the port on the side of your piston a round oval port (3 ports) or is it 2 triangle shaped ports (4 ports)?

2 triangle shaped ports looks like this:
http://www.ebay.com.au/itm/49cc-BIG...et_Bike_Parts_Accessories&hash=item2c5882e78a

Thanks.

 

[lowracer]

I bought it on eBay from Zero Pulse USA (same seller as Big Motor Sport). It the stage 2 kit (same engine as yours). No piston ports

 

[gera229]

Ok , howcome I have 2 ports and you have no ports? Did you even check?

I bought mines from bigmotorsport.com

 

[gera229]

Hey Lowracer, how can I tell if a spark plug wire is made in China or USA?

Thanks.