can i swap the exhaust port with the intake port?

[Doc Sprocket]

instead of the piston being up at that point in time it would be down.

Which will NOT make it breathe backwards- Just mistimed to the point of being useless.

 

[Russ2251]

Please refer to post #26.

 

[B man]

Please refer to post #26.

i don't feel like pulling one apart. what should happen?

 

[sexyvicta]

Every bike I have torn into uses carb boots because the engine and carb are shoehorned in so tight that carb (or indeed, engine) replacement would be virtually impossible any other way.

if bike makers wanted to solid mount their carbs then they would. They dont want to

i think originaly they started doing it on race bikes so as the float bowl wasnt vibrating with the engine(to the same degree). Before that they used remote float bowls/chambers but that created new problems.

 

[Doc Sprocket]

So... what makes a rubber boot superior, then? Why don't cars use them? Cars vibrate. And you can't tell me a rubber mounted carb doesn't vibrate. In fact, nothing I know of vibrates more than a lawnmower engine, and they all seem to be solidly mounted.

 

[Russ2251]

i don't feel like pulling one apart. what should happen?

Very late port timing, rendering engine unusable. That's all.

 

[sexyvicta]

So... what makes a rubber boot superior, then? Why don't cars use them? Cars vibrate. And you can't tell me a rubber mounted carb doesn't vibrate. In fact, nothing I know of vibrates more than a lawnmower engine, and they all seem to be solidly mounted.

i dont know.

im not an engineer...im just quoting(probably miss quoting) something i read a while back.

it dosnt matter anyway. It is the easiest solution to blue thunders problem however

 

[Russ2251]

One word...Flexing.

 

[JHen]

If you want to reverse the valves you would have to put the cam shaft in backwards. This way, the intake valve is now on exhaust valve timing and the exhaust valve is on intake timing. So, basically, if you want to reverse the gears you would have to make a new cam shaft with the lobes reversed.

 

[JHen]

This picture shows what I mean:

The left is the 'before'. The right is the 'after'. This is the only way to change the valves' purpose.

 

[Bluethunder3320]

wow this thread has taken off.

well im probably gonna go make a manifold, or use a rubber angle piece.

main reason why i havent, is because i dont have a drill bit big enough to make that size of a hole............

so tonight i finished assembling the engine (minus carb) using regular ports. i ground the exhaust valve more because it wasnt nice and grey yet. its good now. well the engine kept locking up at around TDC. i pulled it apart and found that the connecting rod was bumping into the camshaft stopping it.


tomorrow got to pull the engine apart again.....

i need:

more silicone
angle boot or right size drill bit

 

[Bluethunder3320]

JHen, if i move the camshaft 11 teeth, (1/4 turn) wouldnt it do the same thing?

im not sure if i totally understand.

 

[Russ2251]

im not sure if i totally understand.

It will become abundantly clear once you go through the cycles.

 

[shane73]

When the cam turns one lobe will hit the valve lifters first - always. No matter how may teeth you turn it back. When it comes around that same lobe will still hit first. When switching ports - you need the lobe that hitting second now to hit first. If you spin the cam you have now and watch the first lobe hit the lifter - then count how many teeth before the second lobe comes around and contacts the other lifter. You need to reverse this. Second lobe hits first - then that amount of teeth and second hits. If you look at your cam, you notice the lobes are not straight across from each other. They are just offset from each other so far. You need to offset them this same amount but the other way. Then you may need to spin the "whole" cam or flywheel 180 degrees to put it back fireing on the compression stroke. The plastic cams with plastic gears and lobes on metal rod might be best for this because they would be easier to switch the lobes.

 

[Bluethunder3320]

ok..... well i get it more now... thanks!

i havent tried modding a cam yet.... some day when i get an engine with alot of spare cams ill "experiment"

its a plastic gear with metal lobes.

 

[sexyvicta]

One word...Flexing.

i cant see how it would be an issue unless you used a very long piece of pipe. You would only need about an inch or two at the most. I bet it wouldn't flex at all

 

[Russ2251]

I bet it wouldn't flex at all

It does, that is the reason for it.

 

[Bluethunder3320]

wouldnt i need some kind of carb support bracket if i used the rubber piece?

 

[B man]

of corse it flexs. look at most any modern motor bike or other Rv and most will have it.

 

[sexyvicta]

yeh but not much at that length. I mean not enough to cause any issues. A very small amount of flex would be a good thing

edit: you do what you want but its a 2 minute and 2 dollar solution to this problem.


/get a manifold off a horizontal engine.