Hitchcocks Forum

Hi all........... apologies if you get this twice but it never posted the first time. I posted a while back looking for advice on a tinny sounding rattle from the bottom end of my EFI engine, which was only really noticable at high revs and on the come down from those high revs. Well, an update and some further questions....



I had a couple of hours yesterday, so I took the right hand engine casing off to have a look at both the oil, and the cams. The oil was as smooth as glass - given that I was worried about the bottom end, this would suggest nothing majorly wrong there. True, I didn't empty the sump (not enough spare oil in the garage for a refill, and I need to bike for transport) but surely some swarf would be present in the RH case if these was a bearing issue. Cams were also fine and not too much backlash. I didn't have the right spanner to get the rotor off, so I couldn't check their condition, but no need given the clear, smooth oil.



So, on the rebuild I noticed quite a lot of rust on the underside of the silencer... a sbit of a scrape and rubber mallet tapping later and the risty surface was gone, and a rattley sound noticed. It didn't match exactly the noise I hear when riding with high revs and a helmet on... but then again, why would it. The bike was stationary and I wasn't wearing a helmet to check the bike over (safety first eh?!). My questions are... 1: what's inside the exhaust and silencer that might cause a rattle, and would it be tinny. 2: am I right to rule out bearings given the good oil, or do I need to empty the sump before concluding all is well (I will, just not for a day or two until I get iol and a filter). 3: how long would you expect to get out of a silencer and exhaust before NEEDING to change it. 4: is it better to check for a loose exhaust (at the head) when the engine if cold, warm or hot?



Bike ran great on the way in this morning though

Inside the EFI silencer are lots of baffles and a catalytic converter. Any of those could come loose and rattle around in the silencer.
It’s not really possible to say how long a silencer should last before its internals become loose. If it’s a well-made item it should last for many 1000’s of miles. If it's poorly made it could develop a rattle at any time.
I’d have thought the sound from a rattling silencer will be very different from the knocking you’d expect to hear from failed bearings.
(BTW, the EFI silencer costs about £700 to replace!)

hi michael the cat in the exhaust is enormous ,my advice would be this buy an aftermarket silencer off mr h ,bin that ugly heavy silencer i,m sure your bike will be about 10kg,s lighter atb paul.

I saw one of these with the side of the silencer cut out. There are 2 cat units, each about 4 inches long, and a set of baffles that takes the exhuast gas through a maze of pipes and plates.