Bobbers are cool, and one of their standout features is definitely the exhaust system. Discover the different types of motorcycle exhausts that can give your bike that killer custom look.
The humble bobber may not be as showy as a chop, but they can, of course, be chromed up and tricked out. However, the emphasis for the street is usually one of cool useable custom.
Origins of the Bobber Exhaust
Some sources maintain that you can trace the roots of the bobber in the USA all the way back to the 1920’s, but I think that’s pushing it a bit. Fast forward a decade though, and one look at the bikes that raced across the dirt tracks of the USA will convince you you’ve arrived at the right era.
The Flathead Harleys and Indian Scouts that competed in the early 1930’s Class C AMA dirt track races, were Bobbers through and through.
And what did the racers of the day, competing on a shoestring budget do to their heavily fendered cruisers? Yup, they bobbed the hell out of them. But what did that mean for the bobber exhaust?
The V-Twins of that period all carried crude versions of a 2-1 system, so all they did was cut a couple of inches past the rear downpipe and dump the silencer. This trend continues today, the first thing to go on any bobber is always the stock can.
Over the following years, the Brits invaded the USA, and before long, bobber exhausts quite literally took a whole new turn.
But what did the Brit bikes bring to the table? Well, those early competitors were all on single cylinder machines. Meaning, that high level swept back exhausts became yet another bobber staple. Once again this style is still popular today.
This continuity with the past is why bobbers look so right, and except the more creative header designs, the majority of bobber exhausts can trace their lineage right back to the dirt track.
Cost Effective Change
It’s no wonder that the bobber has taken over from the chopper as the most popular style of custom bike. With a few subtle improvements a motorcycle can go from stock snoozer to cool custom with very little outlay. One of the easiest and most cost effective changes can be made to the exhaust system.
Have you ever heard a quiet bobber? Probably not, which is why the end can is always the first to be jettisoned. If you’re bobbing a Japanese multi, you can of course just run the header pipes with bolt in baffles. If the system runs into a 4-1 or 4-2 system, then you’re looking at a slip-on muffler.
The choice is almost endless, from slash cut, turn out, chopper pot, reverse cone megaphone or the ultimate in cool, the trumpet. The last two are probably more commonly seen on twin cylinder bikes, but when it comes to bobbing an exhaust system, there are only two rules.
Is it minimal? Does it look cool? Check those two boxes, and you’re well on the way. If you like a little more go with your show, then there’s also a range of performance mufflers that will do the job and still look the part.
Supertrapp with their tunable multi-disc system has been around since the early 70’s, and the latest slip-ons also have built in spark arrestors. Slovenian exhaust specialists, Akrapovic also do a huge range of Slip-ons too.
You should also check out Vance and Hines and Japanese tuning wizards Yoshimura. Not forgetting that bike manufacturers such as Harley, Triumph and Ducati have been offering louder versions of their stock silencers for years.
These days, regardless of what exhaust system you go for, the go-to accessory seems to be an exhaust wrap.
The muscle car-racing crowd of the 1970’s with crammed engine bays first used this. They would bind fiberglass wrap on the headers as a quick fix for keeping the heat away from brake, fuel and oil lines.
So in reality, wrapping an exhaust pipe exposed to the air with fiberglass, titanium or crushed volcanic rock, is more for cosmetic reasons. But there’s nothing wrong with that, it looks old school, even if the old school bobbers never actually used it.
You may also notice some wrap manufacturers claiming that it enhances performance. Technically it can, but unless you’ve got an engine so highly tuned that fractions of a second are crucial, then we’re back to cosmetics.
Beware of the Burn
But, and there’s always a but, if you’ve got an exhaust system on your bobber that comes close to the inside of your leg, then, by all means, wrap away. If there were a market for used waterproofs with a hole burnt in the right inside leg, I’d be the king of it.
And talking of pipe burns, bobbers by their very nature are short and sweet. Cut down bikes, with all the stock crap removed and the same goes for their exhaust systems.
If you’re looking at building a bike from the ground up or bobbing your stocker, it’s worth mentioning a couple of basics.
- Firstly, exhaust gases exit the cylinder head in pulses and the larger diameter the exhaust pipe, the less effective you make it because you’re lowering the velocity. In other words, you’ll be all show and no go.
- Do the opposite and make the pipe too narrow, or too complicated in shape and you run the risk of creating excessive back pressure, which can result in a worst case scenario, sends exhaust flow back up towards the heads.
If it Blows It Sucks
When you bob your exhaust, remember that you’re letting the gasses escape quicker. To take advantage of this, you will need to let the engine suck air in faster. So make the equivalent alterations to the air filter and perhaps even alter the carb jets.
Finally, pay attention to where you route the new exhaust pipes and where they exit. It’s very easy to forget when you’re bolting them on in a cold garage that they’ll be reaching temperatures anywhere from 400-1000 degrees F. Rubber as in fuel and oil pipes will melt at around 300F, just a thought.
An exhaust system can make or break the look of your ride so choose your pipes carefully before deciding which is the ultimate exhaust system for your bobber.