here's the new and old downpipes - with the CAT




gonna repack the exhaust and all whilst this is off..

question is - do I go in this end ( just screwed on ) with hex bolts?




or drill out the rivets...

Doh!

http://ridersupport.fmfracing.com/RepackingInstructions

seems that I should use the allen keys and do it from that end!!!

well my excuse is that I wanted to get it all set so I can go on a night ride tomorrow...

and been faffing with the brakes most of my freetime today..


what was worrying me also was when I took the old exhaust off the bolts were basically finger tight....

which might explain why my CRM needed a bib?!!!!

I think the best place to start the repacking is here,

http://www.flickr.com/photos/lalootka/2275258340/

Mike

whats the weight difference between the original expansion chamber and the DEP?

yes I'm quite familiar with that type of exhaust mike


I dont have any scales but the old one feels well heavy - an effort to lift - whilst the DEP is light as a feather....


hope that technical explanation helps

I think its going to be noticeable when picking the bike up for instance..

i dont think the DEP is 3 Kg even... I had a few water bottles hanging around and it feels about the same as 1.5 liter bottle of water.. ( 1.5 kg (ish) is my guess )

I had to nip to shop to get a syringe to reverse bleed brakes..

saw they had some cheap scales ( sort of fish ones funnily enough ) so in the interests of science I used mikes wallet widget to squeeze some moths out...

on these scales my old one came in at near 5 kilo

the new ones at just under 2 Kg

Looks good fishy- just like my Procircuit pipe. Use the bolts on the tailpipe- its easier, but don't over tighten! I have repacked mine with stainless steel pot scrubbers fitting around the baffle pipe! -It works brill! Be prepared to have to re-jet. I am going to down-size mine again to a 135 main jet, as it just runs so rich with this pipe.

njhardy wrote: have repacked mine with stainless steel pot scrubbers fitting around the baffle pipe! -It works brill!

surely you mean it works "brillo"


but seriously you mean it works like the fibreglass packing?

actually I'm still not clear to the function of the said packing - whats its actually purpose?

The gases come out of the engine in a series of pulses this makes noise (is noise). The packing in the silencer is to take the energy out of the audible pulses and thus make the exhaust quieter. Fibreglass does this quite well but does breakdown/get gunged with oil in the exhaust over time. That's why you need to repack the exhaust quite regularly.

Steel wool is not quite as good at absorbing the range of frequencies as fiberglass and it breaks down quicker. (As far as steel is concerned - thinner wires absorb more energy but breakdown quicker compared to thicker ones). Seems like a good idea but isn't - why does almost everyone use fiberglass .

Flippin' Eck you're a sound engineer you ought to know this

double post!

a- ha! that I understand - I'm a sound guy by trade..

and I coincidentally just found i t might have some effect on the bikes state of tune as well ? ( just trying to read up a bit so as not to ask so many questions on here! and want to get my bike ready for sunday - when I'm meeting some mates for ride

( waiting for my air filter to dry and procrastinating on work again!!!!!!! )

http://twostrokemotocross.com/2009/12/c ... nd-tuning/


Blown silencer—when the fiberglass packing material blows out of the silencer, excess turbulence forms in the silencer and the turbulence causes a restriction in the exhaust system. This restriction makes the engine run flat at high rpm.



dunno if that has any real world relevance - makes me wonder - cos I just repacked the exhaust then had power problems..

( hard to know cos I changed a few things at once! )

also the exhaust is still blowing a bit... ( worried about snapping bolts - just bought a torque wrench....)

Yes, regular repacking healps keep the engine in tune and performing to its best. In the UK youngsters often take the baffles out of their scooters etc. They feel that they are getting more power. What they are actually doing is losing low/mid range BUT the peak power comes in with more of a 'hit' so they think they have released more . ... they sound horrific ..................

its making sense!

first thing I noticed with a repacked exhaust was that the low down power was quite a bit more..

works getting in the way now - desperate to get out there and see if its better now carbs cleaned and rejetted ( back to standard ) ( and its getting dark

just need to do a bit more work/ then can oil filter - put that in and fingers X'd

and now the missus is after me nipping to the shops cos she got to work late -

hope it blinking starts - I realise I bought the wrong spark plugs... ( they were recommended on here - but they aint standard.. spark pl NGK B9EGV )

( some one said in tuning tips - CRM MK3: Take out stock air snorkel and re-jet carb to pilot 50, stock needle middle clip, main 158. FMF pipe or DEP pipe also drill 3x 12ml holes in left side of air box. Boyesen reeds part No 633 are good for this bike.

You are right about the glass fibre/rockwool, but I actually can't get hold of glass wool packing here, so sainless steel scouring rings wer the best I could do (rather than rinse out the old crap in petrol and dry it out)- I have looped 4 doughnuts of it around the baffle tube and fed it into the tailpipe- it doesn't clog up with oil like the wool does.... However, I will get some from UK and repack then. Not sure what it does to the power curve, but my top-end is less than it was, but low-down and mid is more punchy.