Plastic rear bumpers and pipes

[Matthew Patterson]

OK, I mounted my new plastic bumper, and put my exhaust back on (KT and L3 pipe). The pipe is 1/2" from the bumper. Even worse, the hole in the pipe is about 1.5" from the bumper and pointed straight at it.

So, how do I keep the exhaust from melting a hole in the bumper?

[Wes@NMS]

Simple fix, buy a F200. :-)

Send a pic of what your working with, should have some adjustment on the exhaust positioning.

Wes

[Matthew Patterson]

Why buy one, when I'm going to "own" a few of them next Saturday?:eek:

Seriously, I'd really rather NOT burn a hole in my new bumper. Seems like many people online say that it's inevitable.

http://i119.photobucket.com/albums/o145/mpatterson1410/Kartexhaust3.jpg

http://i119.photobucket.com/albums/o145/mpatterson1410/Kartexhaust2.jpg

http://i119.photobucket.com/albums/o145/mpatterson1410/Kartexhaust1.jpg

You can see how close the pipe is to the bumper. What you can't see is the exhaust outlet. But, to give you an idea of where it is, it's just to the left of the left spring in the 3rd picture, pointed directly at the bumper. Basically, it's right in the middle of the long, straight tube in the exhaust.

I tried turning the whole pipe so that the hole was above the bumper. But, I gotta turn it like 45* or so to get that. It makes for a long, awkward support mount, and then the pipe sticks up 9" into the air. It just looks really odd. And, since my spring tabs on the header are in perfect alignment like this, I think that this is how it's supposed to be.

Another option is to strap/rivet/bolt a metal plate to the bumper to deflect the air. I'd have to put some heat shielding material between the plate and the bumper (else the plate will heat up and melt the bumper itself). That just seems really tacky, too.

The best option, and I don't know if this is legal or if it would affect performance, is to seal off the hole that points backwards (weld a plate over it) and open up a new hole (same dimensions) in the bottom of the exhaust. Would that be legal? Probably not as the rules are written now, but could it be allowed? And, I have no idea what the inside of these things look like. Would that affect performance somehow?

The last option is to put a deflector on the pipe itself. Like an exhaust turndown on a car, strap/weld some curved piece of metal to the pipe that deflects the exhaust away from the bumper.

So, what should I do?

Oh, and I could always put my tubular bumper back on, and weld ears to it to make it full width. But, I kinda like this bumper.

[Bob Beasley]

Matt,

"Why buy one, when I'm going to "own" a few of them next Saturday?"

I'm cataloging these comments for future servings of crow.

[Matthew Patterson]

Between my foot and crow, I don't plan on visiting the NMSP restaurants that much!

[Fast Guys]

Matt, I'd imagine you'll be replacing it regularly due to the Beasley Bump, the Harris Hard Tap and the Donovan Demoralizer. You can forget about vanity...

[Matthew Patterson]

Hahaha - Not so much because I like it's looks, but I like the mounting method of it (I need to remove my rear bumper to put it on both my regular stand and my vertical stand). And, I like the fact that you cannot fit a front bumper between the bumper and the tire, as can happen with metal ones.

[Fast55]

Matt, I'd imagine you'll be replacing it regularly due to the Beasley Bump, the Harris Hard Tap and the Donovan Demoralizer. You can forget about vanity...

That's right, when it comes to karting, I lose my morals

Paul

[Wes@NMS]

That's right, when it comes to karting, I lose my morals

What morals???

[Mitch Wright]

Matt, all you need to do is rotate the pipe up and remount your pipe cradle to the height needed. Feel free to call me and I can talk you through the fix, it is not hard.

[AnthonyHarwin]

To add to Mitch's comment, that will spiral the springs more which keeps the pipe more firmly sealed to the header. Don't change the pipe even if it were legal...it is tuned and who knows what effect would come of it.

Btw...ever heard the saying "Don't let your alligator mouth overload your hummingbird behind?". A joke of course, but I won't be letting Lindsay see the forum...she already has too many scuffs on her kart from "bump drafting", and bodywork is pretty expensive these days!

[Troy V Smith]

Matt - any chance you can run a different header? Not sure which motor you got on there, but a header at different angle might allow you to keep the bumper intact, lift the pipe, and maintain proper alignments? Just a thought...

[Matthew Patterson]

Well, I could run a different header, but that makes 2 problems. First, it jacks the pipe up another 9" in the air. Not bad, but not what I think is ideal. And, I would have to make a pretty long mouning arm, which would bend/break/whatever.

However, I think I've fixed it. I bent a piece of metal and strapped it to the pipe. It directs the airflow down and under the bumper. We'll see if it works.

[AnthonyHarwin]

One of the essential properties of a 2-stroke pipe is the back pressure that makes the expansion chamber work in tune with the motors porting. If the "diverter" that you have created causes the back pressure to change, the motor will behave differently. Make sure it is far enough away from the exhaust outlet that it doesn't change the pressure out.

[Matthew Patterson]

Hmmm - good point Anthony. I hope it doesn't. We'll see.

[Matthew Patterson]

I have made sure that the open area under the "hood" is larger than the exhaust port on the pipe. That should do it, right?

I'm still going to bring my tubular bumper to see if I like it better, and can test the exhaust without modifications.

[darrenmc32]

Is there a straight header available? If so, that could lift the mounting position of the pipe above the bumper. Also, I didn't see a chain on there yet. Could you get away with a few more links to help push the motor forward? It's been years since I raced the KT's so I'm looking forward to seeing you guys run these around this weekend.

Darren

[Matthew Patterson]

We'll see Darren. It's all going to be a big guessing game at first.

I can run another angle header to move the pipe up. But, that raises the pipe something like 9". I have no idea what that does to handling, or rigidity of the mount.

The motor might be a bit far back, I tried to guesstimate since the chain wasn't on. We'll see when I reinstall my chain on Wednesday (it's soaking in oil, getting ready for the weekend).

I'm going to show up with this setup and run a few laps without the bumper at all. Then, I'll bend the shroud away from the pipe and see if I can notice any difference on accelleration curves. If there is no difference, then I'll put it back down and put on my plastic bumper. If there is a difference, then I'll likely put my old tubular bumper back on.

Who knows. It's all a guessing game until I can get some laps.