Exhaust manifold

No

Concise, correct, good answer.

Searching most any of the motorcycle websites/forums will provide several options for repairing the damage.

Realistically, on a stock (or near-stock) motorcycle, you shouldn't notice any problem under average use. Now, if you're pushing redline on track-days, then yeah, the dent is going to make a difference.

Thanks men, I am a bit older so rarely approach the redline and have not noticed a bit of difference from the dent and could not yet find any aftermarket parts except a "slipover" for the rear end of the pipes (whatever that adds to performance I do not know).

jimray50,

An old trick for estimating length of header pipes was to draw a line using chalk length wise along the pipe then where the chalk burned cut for a combined collector. Though this was for performance conditions you may experiment or not.

Intersting idea, have to try it some time... where are my ear plugs?

But isn't this ideal for a specific rev range? where your trying to tune to a certain standing wave where the collector is positioned?

Pity you cannot use this idea as easily with intake systems...

Your bikes engine has a specific revv range in which the characteristic of performance (power band) is and your engine is built for demonstrating it and like all scooters you muffle not muzzle them.

Yes the tubing expander would fix the dent so the header life isn't shortened because of the xtra heat at that specific spot causing failure of the tube or protective coating and of course then corrosion. But the damage is done already eh?

Was a bike header shop near the junction of Ca hwy 101 & I-405 named Racer's Edge with superb performance available for a streeter or touring just specify your desired level of romp and excellent chrome.

Any performance loss will depend on the diameter of the exhaust and the RPMs you are planning to achieve. Obviously a dent in a 2" dia tube isnt going to be as dramatic as a dent in a 1" tube. Denting tubes is quite often done intentionally on automotive headers when there is limited clearance for spark plugs or steering columns. If your exhaust is in otherwise good shape, there is a tool out there that pushes the dent back out. It has an expanding "ball" on one end, and a hand operated hydraulic pump on the other. Might be cheaper to rent or borrow this tool then to buy a new exhaust. I used them when I worked on aircraft engine tubing years ago.

Avery Montembeault

Some people say that the wind produced by a flying bird can cause a Tornado on the other side of the earth. Your 25% dent is small, I believe Shumacher would complain if he had to race with this damage, but with normal use you or your engine will not find any difference. Normally one is not running a bike at 100% power output for hours but even if so the cooling system should also have a buffer to cool down the engine anyway, but theoreticaly this does make a difference, higer pressure on the exhaust side = redused performance in highest rev. and if you bend a little more or all the way (100%) you will not be able to start the motor or you will blow the exhaust gasget out...But a 25% restriction ..practically..no... I would not let this disturb me from dreamland.

Pumping losses increase dramatically after about 70 metres per second, which is usually the maximum velocity through the exhaust valve heads at a maximum continuous rated speed ie as in marine engines and generators. But bikes rarily run at maximum speed, 70% of maximum probably, so valves are smaller and velocities are therefore higher (maybe 120 metres per second) at maximum speed. So, dont worry. I guess you can still achieve 60 mph

The spark plug is the window into the combustion chamber.

If you have done any recent work, specifically a tune-up, you may have noticed the condition and color of the four different spark plugs. The difference in exhaust scavenging, if there is a difference after the dent has made it's mark, may show a slightly different color on the affected cylinder. The spark plug tip and center insulator as you look down into the spark plug should have a light tan color if operating in the ideal fuel ratio zone, this does vary with different rpm loading though. Your model does come from the factory set towards the lean side of the fuel ratio to meet emission standards and the insulator may be almost white in appearance.

If there ends up being a difference in power produced by the affected cylinder, you may need to have a synchronization of your injection system to bring everything back into balance. The affected cylinder may in fact have a difference in intake vacuum that may disrupt the balance of the four cylinders. This may also be indicated by additional engine vibration.

I ride a 1200 Bandit with stage one jetting and know that the bike already has more than enough grunt to move out of it's own way.

And if all else fails, replacement headers can be purchased from Holeshot. Holeshot is a small company out in the land of California that sells aftermarket products for the Bandit and a few other models of motorcycles. And then there is always Ebay.

If you have not given that Bandit a good wringing out, now is the time. Be sure you have a good grip on the bars and don't twist it too much in the lower two gears. :) Mine usually lifts the front end in first and second with no effort. The larger Bandit requires a fair amount of respect above 5k rpms.

If you are low in the mileage and still close to your 'break in', the bursts into the upper end of the powerband will help seat your rings for better long range performance. Piston rings contacting cylinder wall wear is a valid issue in high mileage engines, but a 1250 should still be relatively fresh.

Be sure not to shift to synthetic oil until after your full break in. A premature shift will shorten the break-in schedule. Premature tends to be a bad word in most instances.

If for no other reason I would repair it for the cosmetic effects on the bike.

If the pipe can be removed with out to much difficulty take it off and fix it.

If you have a chest freezer use it to pop the dent back out.

To do this, add enough water to the pipe that has the dent. Just enough to so that when the dent is positioned at the lowest point, the water level is slightly above it. Set the whole thing in a freezer over night. Pull it out in the morning and see what happens.

The exposed surface of the water will freeze first and create a trapped volume of liquid. As the rest of the water freezes it will expand and put pressure on the dent, slowly pushing it back out. It may take more than one application, but trust me it works.

I have used this trick on two stroke pipes off of bike and snowmobiles with great results. Also did the to the header pipe on a DRZ400S. By far the cheapest way to fix a dent, assuming you have a chest freezer.

i think itwould effect although it would depend on pipe size.constriction losses apart it will effect the dynamics of fluid flowiong out cretiong eddies,temp.variations would cause reflection of fluid wave.i cant say how much the loss will be given no info. calculations cannot be done but personally i coulgnt live knowing something was wrong with my ride no matter how measly.get it fixed at least to protect ahainst corrosion and collection of exhaust matter at the point.tke care.