How to knock up a chrome race baffle for a Harris...

For less than a fiver

Words by Webmaster Taff,
pictures & video by Jason Webb (cheers mate)   

This Saturday (29th March) we successfully performed the operation described below on the Harris of Minxy's GSX 1100 chop - with my mate & his digital camera present, so this now has full "How To" pictures!

 NB "for idiots" Disclaimer bit:

  • This info is provided as a "how to" ONLY, and was done outside someone's garage with minimal tools & equipment to show how easy it is to accomplish (and also 'cos that's the only place we could find to do it at the time...)

  • The photos below show persons handling sharp bits of metal and power tools in a non-workshop environment, NOT wearing safety footwear, chain mail gloves and, come to think of it, not wearing a full suit of armour with a bubble-wrap oversuit either. This was my choice and if I got hurt (which I didn't), I only had myself to blame...

  • Only you know how competent you are with tools, what you need to wear to protect yourself while using them and where you should be using them. If you injure yourself in ANY WAY while doing this project - IT'S NOT MY FAULT! So don't bother sending your lawyer round on the double for 1 million compensation when you get a bit of swarf in yer thumb...

  • In fact, if you are that way inclined, just buy a race baffle from Harris and save yourself the legal & medical bills!

  • This info is provided as a "how to" for your exhaust ONLY - it's then up to you to sort the carburation out; you WILL need to upjet from stock. So don't go mailing me with tales of huge midrange flat spots or melted pistons! If you can't / aren't going to sort the carbs out, leave the street baffle where it is or buy a Motad!

  • And of course, once your Harris is modified in this way it will be Very Loud Indeed and hence illegal for the vast majority of road applications - so if you get nicked, that's not my fault either...

  • by scrolling further down this page you hereby agree, if you have a go at it, not to send your Mum (or your lawyer either) round my house to throw things at me if you do hurt yourself. Shall we continue now?

     Harris works systems. Great aren't they? For your 70's / 80's superbike they still are the cheapest option for a performance 4-1. Vance & Hines give you better mid range but less top end and are twice the price, and Marshall Deeptones just don't come close.

   But they all come with horrid nasty street baffles which are nice and quiet as they strangle your performance to b*ggery. Race baffle! Aaargh another 30+ quid, and they come in bare metal only - you have to (constantly) paint them or else pay more for chroming. Boo!   

   For those of you with no curiosity who have never had one out, here is a crude schematic of a Harris street baffle showing gas flow route:

  As you can see, the gas come in, hits a big plate which is in the way, has to divert round two tubes then back round again to exit. Very good for noise but crap beyond belief for performance.

   There is a cheap solution! As with the "GSXR" tailpiece scam it again can be accomplished cheaply using common or garden tools. Well no perhaps not with the garden tools (more of that later!)... you'll need at least an angle grinder, drill and pop riveter.

[ Click on Images for full size image in new window ]

1. Firstly, remove street baffle - you don't even have to take the pipe off the bike. Before you do though, you will need to drill at least one extra hole. A new / stock Harris will have just one pop rivet holding it in place, at the bottom of the collector at the very back. Firmly centre punch the proposed site for your extra hole(s), or the drill will skitter all over the place - i.e. all over your nice new chrome!

2. Drill at least one more hole through the side of the pipe and the end plate for extra rivets - a total of three at one-third circumference from each other is ideal (but you may not be able to manage this if you still have the pipe on the bike). If you leave just the one, the whole plot will blow out for sure!

Once you have done this, drill the bottom (factory fitted) rivet (already drilled and re-secured temporarily with a big self tapping screw in the photo here) and then it's baffle extraction time...

3. Extract the street baffle - you may have to resort to crowbar / slide hammer tactics as they are a snug fit. If you bend the internals, don't worry - you won't be needing them again! Here, a set of 99p water pump pliers have been opened to full stretch, one jaw wedged in the hole and then opened as far as they can go to enable the baffle to be tapped out with a hammer.

Once the middle plate is clear it will come out by hand...

Congratulations! You have won the 'Most Restrictive Baffle' Trophy!!!

4. And here's t' big 'ole... now... due to drilling you will have swarf in your collector can. If you have the pipe off the bike - no problem. If the pipe is still on the bike, you could fire it up now and rev it a bit to shift the swarf - as long as nothing / nobody is behind it at the time! Otherwise, don't worry too much as it will come out in due course, just be aware when firing it up for the first time that bits of swarf will be flying out at some point...

And now my favourite part - the angle grinder bit (Minxy couldn't watch at this point!)

5. Now cut, as close to the end plate as you can, through the tube. You can go all the way through if you want, but you only really need to cut the metal of the outer sleeve, all the way around...

...which, once cut, will allow you to remove the end plate from the rest of the baffle.

7. You should now be left with a chrome / black chrome / bare metal end plate according to what system you bought. You can put this back on and run a completely empty collector but again not recommended, what you gain in top end, police attention and tinnitus you lose in midrange and friends willing to ride with you.

8. Measuring time. Take your hacked about end plate, place it in the end of the Harris and measure from the end of the plate to an inch past where the end can starts to taper in towards the collector. (This should be just over the 11 inch mark usually)
9. Now go to a metal dealers - err if your only transport is your bike and you're reading this while you're working through it you're in trouble... you will need some big pop rivets (about the size of the one you took out of it) and an offcut of some mild steel thin perforated sheet. This stuff is basically sheet metal with loads of holes drilled in it. You will need at least a 12 x 10 inch piece to accomplish your mission - my last bit cost me £2.10 - you should be able to bend it by hand but obviously don't buy fag paper guage!

10. Now cut a bit of thin cardboard to length (the one you measured in 8. above = 11 inches or so), then roll it into a tube so that it locates on the INSIDE of the end plate, OUTSIDE the hole. Cut it to width, then unroll it.

11. Now you have a piece of cardboard of the correct length & width, place this on your sheet of metal and mark it out accordingly.

12. Cutting time again - so that the sheet of metal is the same size as the cardboard template. Cut your perforated sheet slightly longer than the measured length - it's easier to cut more off than to weld more back on!

13. Bending - get it in a 'U'shape to start with...

... then you will need something long & circular to shape it. Remember the bit at the top about the 'Common or Garden tools'? Well after casting around and panicking a bit we found that the shaft of a garden fork did just nice!

... final precision shaping with club hammer and...

Voila! One baffle tube. Don't worry about it not being a perfect circle or welding the gap up - not necessary unless you really want to; just secure it with some bare wire along the "seam" if you want to, but it should hold itself in shape / place without any of that.

14. Nearly done now - insert the tube into the pipe until it jams in the tapering bit. Locate the end plate on the other end and push the end can home.

If you can't seat it without major hammering then this means you need to cut a bit more off until it is a snug fit...

...a few light taps to seat it with the rubber mallet is about right. If it is too short then it will rattle like b*ggery and you have arsed it and need to start again, measure it right this time! Secure with pop rivets, finished.

   15. Bonus options / finishing: If you are handy with a welder you can weld it on to the inside of the end plate, also an option if it is too short - but you risk scorching the chrome!

   A near-essential (& neighbour-friendly) finishing touch; wrap the tube in baffle wadding (available from all good bike dealers) and secure with some wire. This makes surprisingly little difference to top end performance, BOOSTS the midrange and makes a huge difference in the harshness of the noise, but you do have to renew it every so often as it does eventually blow out.


So woss it like? Big thumbs up from Minxy... click HERE for a video clip of how it sounds!

(This is an .avi file - I am trying to get it changed to Mpeg...)