Curing my rattling throttle bodies
Posted: Mon Feb 11, 2019 8:51 pm
With my bike approaching 80k miles my throttle bodies have developed an embarrassingly loud rattle. I was aware that it's a common complaint and also aware of the 'ticker killer' fitting that's supposed to shut them up but I don't like the idea of pre-loading the throttle shaft axially nor the fact that it basically prevents the symptoms rather than curing the problem plus that thing only works on the right hand throttle body and my left hand one is just as noisy as the right.
This week one of my stick coils has failed (which of course has made the bike run rough, and rattle more) so whilst I wait for the replacement coil to turn up I thought I would take a look at the reason why the throttle bodies were so noisy, so I remove the left hand one and stripped it down.
It turns out that the cause is a worn out bearing bush. Each end of the shaft runs on a split oilite bush 8mm Id and 10mm OD. One is 12mm long the other 8.6mm, the shorter one being the TPS sensor end. I pulled out both of them by screwing in a M9 taper tap and drifting it out with a thin rod and small hammer.
I measured the throttle shaft and found between 0.1 and 0.15mm wear in it - not a lot. The bushes however were much more worn. Actually the short one wasn't bad at all but the long one at the quadrant end was worse and a bit oval too. Removing the bushes essentially trashed them so I turned a couple of new ones from Acetal. This engineering plastic is very chemically inert and doesn't absorb moisture like for instance nylon. I turned the OD and reamed the ID, but I had to ream it again after I pressed in the bushes because the thin walls were too flexible.
After that I re-assembled the throttle body and there's no discernible radial play plus the action is very smooth.
After this I had my dinner and got to thinking that the bushes might be available as a standard part - and they are (at least the 12mm long one is). Cheap too so I have ordered some. I was intending to do the right hand throttle body with the same bushes but now I have found these off-the shelf parts I'm going to wait and use those instead.
https://www.bearingboys.co.uk/Split-Bea ... hes-1024-c
I'll report back when I have fitted the new bushes.
Pete.
This week one of my stick coils has failed (which of course has made the bike run rough, and rattle more) so whilst I wait for the replacement coil to turn up I thought I would take a look at the reason why the throttle bodies were so noisy, so I remove the left hand one and stripped it down.
It turns out that the cause is a worn out bearing bush. Each end of the shaft runs on a split oilite bush 8mm Id and 10mm OD. One is 12mm long the other 8.6mm, the shorter one being the TPS sensor end. I pulled out both of them by screwing in a M9 taper tap and drifting it out with a thin rod and small hammer.
I measured the throttle shaft and found between 0.1 and 0.15mm wear in it - not a lot. The bushes however were much more worn. Actually the short one wasn't bad at all but the long one at the quadrant end was worse and a bit oval too. Removing the bushes essentially trashed them so I turned a couple of new ones from Acetal. This engineering plastic is very chemically inert and doesn't absorb moisture like for instance nylon. I turned the OD and reamed the ID, but I had to ream it again after I pressed in the bushes because the thin walls were too flexible.
After that I re-assembled the throttle body and there's no discernible radial play plus the action is very smooth.
After this I had my dinner and got to thinking that the bushes might be available as a standard part - and they are (at least the 12mm long one is). Cheap too so I have ordered some. I was intending to do the right hand throttle body with the same bushes but now I have found these off-the shelf parts I'm going to wait and use those instead.
https://www.bearingboys.co.uk/Split-Bea ... hes-1024-c
I'll report back when I have fitted the new bushes.
Pete.