Repacking your dirtbike end can – The easy way
The end can on your dirt bike’s exhaust system has a miserable life. It gets bashed, scraped, scratched, clouted and generally abused every time you go out on the trails. But that length of alloy is a precision designed item, carefully crafted to get the best performance out of your motor. And as time goes by, the packing inside will degrade with the rigours of use. In two strokes will become thick with unburnt oil, in for strokes it will become brittle and loses it’s ability to absorb sound – neither are good news It’s time to learn about repacking your dirtbike end can.
Now when we mentioned doing this to a fellow trail rider, the reaction was quite surprising. We mentioned we were going to repack the exhaust on the trusty KTM EXC250 and he literally had no idea that this was something that he might ever need to do. And if you come from a background of road bikes and cars then that’s perhaps understandable – this is not something you’ll ever consider on your CB600F or Ford Mondeo.
But on dirt bikes it’s different and regularly spending some time replacing the packing on the end can will pay dividends. The bike will run smoother, it will be noticeably quieter and generally the bike will feel refreshed. And all this for less than £20 and half an hour in the garage.
What’s not to like there? It’s workshop heaven and you can do it with even the vaguest of mechanical aptitude. We bought our packing through an eBay retailer but you could just as easily go to your local bike shop and pick up a pack for much the same money.
STEP #1 PREPARATION
First off, clean the bike. This might sound daft but beginning mechanics on a filthy bike caked in mud from the last ride is not smart – it’s like going to the dentist seconds after finishing your lunch …
If you are looking for tips on bike cleaning, then check out our blog right here – starting any mechanics is always better and easier when everything is clean and dry.
STEP #2 REMOVING THE END CAN
With the bike clean, you need to remove the end can. How this is done will vary as to which make and model you have, but for most it’s not a difficult task. On the KTM it’s just two bolts, one of which is accessed through a convenient hole in the number board and one at the rear of the seat.
The can should just slide back out easily, but if the fit is tight, you might need a bit of wiggling of maybe a gentle few taps with a hide mallet. Either way don’t rush it and the can will be off and ready to go.
So before you take the end can apart, finish cleaning the exterior in the areas that the jetwash didn’t reach. On two strokes there is likely to be a residue of unburnt two stroke at the end so wipe this off and use a bit of WD40 to totally clean the outside metal. You’re ready to remove the old packing now.
STEP #3 REMOVING THE PACKING
OK so now the pipe is off then it’s time to dismantle it and remove the old stuff. We’re changing ours on the KTM because we had a head gasket go and the bike was running roughly 50/50 coolant to petroil mix, so we’re expecting a bit of a mess in there. For this reason you should be wearing latex gloves to protect your hands and keep your pinkies from turning black and oily.
Lay out the can on some cardboard or newspaper, undo the retaining bolts at the rear end and slide out the central core with the packaging on. The packing may stay inside the outer sleeve, but once the core is out will simply slide out. Put the central core to one side and put the packing into a plastic bag. The packing and bag should then be disposed of in a suitably environmentally effective way.
STEP #4 CLEAN AND PREPARE
So now you need to clean up the central core and the outer tube. Both are likely to be very dirty so start with wiping down with rags and then either use a proper parts washer, or use some suitable solvent to remove the combustion deposits , remembering to do this in a well ventilated area away from any naked flame.
When both are suitably sparkly and dry you are ready to repack and rebuild.
STEP #5 REPACKING THE CAN
With the end core on a clean surface – again we’re using the cardboard – and with fresh gloves on to protect from the fibres of the packing, we’re ready to repack. You should be aiming for a tightish layer round the central core to the correct outer diameter, so first do a test roll to work out how much you are going to need and cut the packing accordingly with household scissors or a craft knife. Our end can is oval in profile, but we are going to roll as if it is circular and as the packing is compressible it will sort itself on refitting.
Now you are ready to fit the packing, but you are going to need to keep it rolled and in place. We use a loop of light twine to start with and then wind it loosely around the packing to hold it in place. You can use wire but it’s not really necessary as once the silencer is repacked, it’s not going anywhere. Tie off the twine and it’s ready to fit into the outer sleeve.
Slide the repacked inner core into the outer sleeve, moving slowly to ensure the packing stays in place. You might need to push a bit on the final section if the end of your end can has a taper at the end. Some people use a high temperature silicone sealant on the join, but ours is tight so we do not bother. One done, apply some thread lock to the bolts, refit and tighten. Job done
STEP #6 REFITTING THE END CAN
Last up, we need to refit the can to the bike. Unless there was a problem with the original seal, we shouldn’t need to replace it, so it’s just a question of lining up the can and sliding the link pipe into place.
Once correctly positioned, replace the mounting bolts and tighten to the appropriate torque setting, which will be listed in your service manual. Start the bike, allow to run to check for leaks and allow any cleaning products to evaporate. If you are in the garage, you might want to open that door!
And that’s the task completed. You bike should be sounding better and running crisper than before. Time to get out on the trails then ….
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