C90 exhaust heat shield: remove, repair mountings and replace.

The exhaust heat shield on this bike was in very poor condition, rusted through around both mounting points and vibrating badly. A new heat shield is quite reasonable in cost but by the time they've added postage and VAT, a simple £10 item has become £30! This is ridiculous when a new pattern exhaust complete with a heatshield is only £38 inclusive!! My bike has an original Honda exhaust and apart from the heat shield is in good condition. I would therefore like to keep it and remove and repair the existing shield or replace it with a used part. If I have to get a new one then I think a cheaper replacement exhaust would be better value.

First step- remove the old heat shield.
At first sight this looks like a nut- it's a badly rusted cross head screw. I think its more than likely that they will need to be drilled out.

Heatshield mounting screws, hexagonal shaped moulded to underlying structures screw head lacks any discernable screwdriver or key structure.

I didn't need to remove the screws in order to detach the heatshield... it was so corroded it just pulled off!



I will see if I can find a second hand heatshield in due course and in preparation for this I needed to remove the screws... I tried cutting a slit across the screw heads for a screwdriver, and also using a left hand screw extracting bit. No joy so I had to drill off the screw heads to release the remnants of the heatshield. This also meant taking off the exhaust because there's no drill access with it fitted. Its a simple 17mm nut on the swinging arm and 2 10mm nuts on the manifold bracket.

!7mm nut on sw arm

2 10mm nuts on exhaust manifold studs.

Exhaust removed

I drilled the heads off but this left the bodies of the screws in situ.

My attempts to remove it  by drilling them out wandered off centre... Maybe I have a problem with pillar drill so put that on the list! Anyway, I will now need to repair or replace the mounting lugs, drill and retap them to accept the original screws and fit the new heatshield. I repaired the mounting points with weld and ground them back down to match their original shape. This filled in the off-centre holes.

These new pads were then centre punched and drilled to 4mm

...and tapped to M5 using a plug tap to get to the bottom of the hole.

However I couldn't find a used heatshield for this bike and so in the interim I ordered a universal bend-to-fit style from ebay. I don't understand how 2 of these can be supplied from Japan as a pair, with fixing clips, for £11 with free postage when a single item from CMSNL costs more and has postage of £15 applied on top! 

Anyway, illustrated is a single heatshield, its fitted by Jubilee clips threaded through the slits in the structure so it's held slightly above the pipe. Unfortunately the clips need to be undone completely to feed them through the slits and the style supplied don't open right out. Although these would be fine for a simple over the top mounting, I think that will look bad so I used conventional 1" Jubilee clips. 

The shield is folded to match the bends in the pipe and secured with the clips.

This fastening doesn't require the original screws or my laboriously repaired screw thread bosses, but at least these are present if I ever get a replacement Honda shield.

I refitted the exhaust and ran the motor. I found that the screw holes actually penetrated into the exhaust (I don't know if this is a consequence of my drilling) and needed to be sealed. I inserted M5 crosshead screws using Loctite 272 (heat and oil resistant) to make sure that the screws didn't leak exhaust gas or come out again. 

Indicators

Other jobs done while I was at it... Swapped both front indicators for new pattern replacements. They were both cracked and loose. I noted that their wiring was different. My bike had a single wire from the flasher to the headlamp nacelle and a separate earth from the nacelle to the flasher mounting screw. This is shown as such in the C90T parts list, but not in the Haynes manual which shows two wires emerging from the indicator to enter the nacelle and connecting via bullets... black connecting to a live feed and green to an earth. I think this must mean that the indicators used on the C90T and later earthed the bulb internally to the indicator body. My replacements have two wires and so possibly do not work in this way so I connected them as the older style shown in Haynes. I may have to add a separate "good" earth inside the headlamp later if this is a problem. Colours were different though so I kept black for live and used the bl/wh stripe as earth, connecting to green.

Headlamp rim was rusty so I removed it, treated the rust with Jenolite and sprayed it satin black. Please with the effect.