Question about the header on my new (to me) Bandit...

[greg737]

The bike came with an aftermarket header of some sort.  The seller mentioned that there are clearance issues when changing the oil, that you have to drop the header to get the oil filter cover off the bike.

What brand of header is this?  Can anyone tell me about it?  Obviously one of the prior owners was impressed enough with this header to invest the money in buying and installing it (and apparently he liked it enough that he was willing to deal with the oil change clearance difficulty it causes).

(These are just screen-shot images I found on the web of somebody else's bike that has the same header as mine does)





Also, I can't help but notice that it's the oddest 4-2-1 header I've ever seen.  In the sports car world all the 4-2-1 headers I've seen route cylinders 1 & 4 and cylinders 2 & 3 together in the "4 into 2" section before merging the results at the "2 into 1" step.  I understand that this arrangement is supposed to increase/improve scavenging.  

But this pipe merges cylinders 1 & 2 and cylinders 3 & 4 in the "4 into 2" section.  I've never seen that before.  But I guess this header really isn't a true 4-2-1 because the tube lengths are all essentially the same and the junction points of the 4-2-1 are so close together that in the end it probably functions as just a slightly smoothed-out 4-1.

Is there some motorcycle-specific reason for the design of this header?  (please excuse my ignorance, I've never owned a 4 cylinder bike before).

[TJS]

Looks like an old Yosh. You can get the filter cover with patience and busted knuckles....and loosen the exhaust can to allow the mid pipe and header to come down a little.  Just watch out for the oil temp wire on the side.
If you still can't get it; then loosen all header bolts by a few turns and pull header forward.
You couls also completely remove and this would be a good time to apply antiseize to all header bolts.

[andrewsw]

I agree, it looks exactly like my old Yosh 4-2-1. Except mine has these cool "speed dimples" and has been treated with a "aero-crush" streamliner on the bottom pair (cylinders 1 and 2).

As for the merging of 1 & 2 vs 1 & 3, I imagine it has to do with firing sequence.

[greg737]

As for the merging of 1 & 2 vs 1 & 3, I imagine it has to do with firing sequence.

Which leads me to ask, what is the firing order on the Bandit 400?  I can see on the parts fiche picture that the Bandit 400 has a standard flat-plane (180 degree) inline-4 crankshaft. 

Most inline 4 engines fire in 1,3,4,2 order which is the reason why performance headers for them are routed with #1 and #4 joining at one 'Y' and #2 and #3 at the other "Y".  Like the Bandit 250's header does (it gives a 360 degree spread to the pulses in each "Y").  But even if the cylinder firing order was 1,2,4,3 it would still be the same result (i.e. there's only two ways you could configure the firing order of the cylinders with a standard flat plane inline-4 crank).

The way this Yoshimura header is configured, with cylinders #1 and #2 paired together and cylinders #3 and #4 paired together, the exhaust pulses that each of the two "Y"s get are only 180 degrees of crankshshaft rotation apart with a 540 degree period of nothing in between.