| Author | Message | ||
     Reepicheep |
OK, stupid question for the day.. My new KZ-400 is a parallel twin, exactly symmetrical, with intake and exhaust paths identical between right and left (just mirrored). The crank appears to be such that it moves both pistons exactly the same. So if one is going up, so is the other. But I just noticed the exhaust has a crossover. Huh? Why? How can that help on a parallel twin with both cylinders moving in the same place at the same time? (Maybe the one cylinder is two strokes off of the other, but the mechanical points don't look complicated enough for that.) | ||
| Nik |
If it's a 360 degree crank like old British twins, it fires both plugs at the same time in a wasted spark arrangement, so you get one power pulse every revolution, with simple points. | ||
| Rohorn |
I used to wonder the same thing about the balance pipe on my EX500 (which has a 180 degree crank, unlike the KZ400's 360 degree crank). I ran the math on the stock header - the length of the header from port to the balance pipe is the ideal length at the engine's peak torque RPM. Which means that both mufflers are more or less needed to flow enough gas and keep the noise down. So, for each exhaust event, the stock pipe is virtually a 1 into 2 system. | ||
| Gregtonn |
If you really want to know which cylinder is on which stroke pull both plugs. You should be able to feel when each cylinder is on the compression stroke by putting your finger over the spark hole as you turn the engine over. G | ||
| Reepicheep |
Good thinking. And it should be obvious if I look at the cam (which is wrapped in a shop rag in a zip lock bag somewere, err, over there somewhere). That would make sense, simple points, wasted spark, use the cams to put them 360 degrees out of phase. Then the intake and exhaust volume can be effectively doubled and you probably get some flow inertia advantages. | ||
| Natexlh1000 |
I think tuners play with the length from the head to the crossover pipe to get whatever midrange hit. I saw a triumph triple with multiple crossovers. I can only assume that someone smarter than me figured out it was useful.  I looked for a picture but I failed to find it. Description: the two outside headers were crossovered behind the middle pipe and then a small amount of distance beyond that, all three went together. | ||
| Fast1075 |
Yes, the pipe is to help midrange torque. You can get the same effect with an X pipe at a larger cost. | ||
| Sifo |
Here's a picture of my wife's Triumph 675 with the radiator pulled away. I happen to be working on it's major maintenance procedure right now, so it's all pulled apart. I've never really understood how it can work the same for all the cylinders. The middle one is connected to two others. The outer one is only connected to one other and will be influenced at different times in it's firing cycle. Or are they all effectively connected to each other through the middle one? I'm assuming that some engineer understands this better than I do though.  | ||
| Guell |
are they actually connected, or is that just bracing? | ||
| Sifo |
I'm sure they are connected. The labor involved in doing it that way would be ridiculously overkill for simple bracing. Mitering tubing and welding completely around the joint is a lot of work. The size is also way overkill for bracing. |
