Exhaust issue

[jeff86]

Okay, here's my problem...
I'm installing a sled engine off a '72 suzuki xr400 onto an old yamaha blaster quad frame. The engine is a two cylinder 400cc dual carb 2 stroke. I've modified the frame to allow the engine to fit where a 250cc once resided. The problem is that I have room for everything except the sled exhaust. As big and odd shaped as it is it won't fit the front of the blaster frame. I've been racking my brain and reading up on how to make my own exhaust or modify the existing without losing power or potentially damaging the engine as parts for this rare sled are impossible to find. I need some opinions on what I should do, but keep in mind I'm on very low budget as to not spend an amount I could have purchased an old quad for lol. If all else fails i have an old 340f/a john deere with more suitable exhaust or a 16hp briggs, but the 400 sounds so enticing

Thanks in advance and I have pics I can post from home sometime later!

 

[modelengineer]

I doubt you'll damage the engine if the exhaust is longer than about a foot and a half, but without that pipe or an aftermarket one you won't be making as much power.

 

[Kaptain Krunch]

You could straight pipe it, but you may lose power, also might have to re-jet. Did this thing have an expansion style pipe or just a muffler?

 

[jeff86]

It does have an expansion chamber going into the silencer portion, I'd like to use it and I think I may be able to but the way it's shaped and whatnot I'd have to extend from the headers and I'm just concerned about changing the optimum rpms, but I don't even know how the powerband will be on this frame anyhow haha. I'm pretty new to the 2 strokes but I've done my homework, still unsure on the rejetting though, not sure how it's done. I'll post some pics to kinda give you guys an idea of the situation too. Thanks for the reply!

You can see the fat exhaust in the one pic but not the headers, the headers come together into a flex-pipe that no longer flexes but comes straight forward about 6 or so inches... too far considering the rest of the exhaust comes forward before bending around. The other pic you can see the space constraints lol and the carbs coming out the "back" side with minimal space before hitting the suspension. Engine isn't mounted yet so I can still decide how high to sit it and where as far as front to back.

 

[Kaptain Krunch]

Yea you can cut and re-weld it, thats no problem, just try not to make any very strong bends. Im sure you'll have to jet it for summer use anyways.

 

[anderkart]

Would building your motor mounts to tilt the engine help your stock chambers fit better?

 

[jeff86]

I hadn't thought of mounting at an angle... would that throw off the floats in the carbs or something though?

 

[Kaptain Krunch]

as long as the angle isnt too extreme, it will be fine.

 

[anderkart]

Yep, looks like your carbs are sitting at an angle right now. If your chambers fit with the front of the engine up a couple inches higher your carbs would be sittin level. My old dirt bikes used to have slide carbs like yours and the engines still ran fine whether I was climbing up a long hill almost straight up or going down the same incline.

 

[Kenny_McCormic]

It is entirely possible to run an engine with no exhaust system without any damage besides your hearing, its all in the jetting, gotta go richer.