Or rather, more to the point, what are bobbins? I thought I would do a quick bit of blurb about floating brake discs as so many bikes we see have a vital point of maintenance missed.
Many bikes these days have floating discs – these can readily be identified as the inner and outer pieces are separate, they are joined with round button like things called bobbins. The idea is that the inner can not rotate around the inner but it is able to move from side to side – not by much but enough to ensure the disc is always absolutely in line with the brake pads and presenting the maximum surface area. They are also less prone to warping due to the way heat is better dispersed. They work really well when they are working but not so well when they become contaminated and chogged up with corrosion and brake dust.
What I like to do as part of my regular maintenance is to go through each bobbin and make sure it is free. They are made to quite a tight tolerance so they will never be so loose that the outer part is allowed to flop about but they should be able to move with slight resistance.
What I do is use a nut and bolt to go through the bobbin – they usually have a hole in the middle. I then tighten up the nut and bolt until they are gripping the bobbin tight enough to turn it. I then use brake cleaner to clean out the bobbin while I continue to rotate it, you can feel when it starts to turn with only slight resistance. Repeat the process with all the other ones and that’s job done.
Do not be tempted to use WD40 or similar products – there is too much risk of contaminating your brake pads if you do. Brake cleaner evaporates really quickly without leaving any residue so that’s the right stuff and the only stuff to use for this job. Disclaimer – if you are a dick head, or think you may be a dick head, don’t piss about with your brakes – get somebody that isn’t a dick head to do it for you. There, that should satisfy the health and safety brigade.
Now, back to the RG250 I introduced you to in last week’s exciting episode. You may remember that I said it had no airbox and was running cone filters. I suspect it is on standard jetting and seemed to be a bit languid in the way the revs rise when the right grip is twisted – it just seems a bit less crisp and lively than a performance two stroke should be. Scottie dropped me a message to say that he knew somebody that had a complete filter assembly with the inlet tracts – would I like it? As parts for these are getting hard to find and his mate only wanted a paltry twenty five of yer finest British pounds (no it wasn’t Henry Cole) I had no choice but to agree without putting too much thought in to it. I shall pick it up at the weekend. I might not fit it as I need to check the jet sizes first and put them back to standard if they have been changed. I will keep the parts with the bike regardless as one day it will be sold on and the next owner can then choose which way they want to go.
I tried dealing with the crazed paint – I worked on a patch by the seat. I rubbed it down with 1500 grit until the crazing looked like it had gone and then tried spraying on some fresh lacquer. The results were not what I hoped for – the new lacquer crazed even worse than the old stuff!! I am going to have to seek advice on this. A chap from one of the forums has a new old stock tank at a pretty reasonable £350 but that would still leave me with the rest of the bike to sort and I know the blue stripes are non original shades so I need to have a better think about that. I may farm the entire job out to somebody that knows what they are doing.
Still looks alright from a distance but things get a bit disappointing when you get up close aand personal
I asked about the paint on a couple of forums and it looks like I have to take the tank etc right back to clean metal – if I try anything else it will just crack and craze again. As the bike is a valuable one I shall most likely go with my initial thought and farm the job out to make sure I don’t devalue it with one of my mediocre paint jobs. It will have to wait a while now as I have more pressing stuff to get on with and I am in no hurry to sell it.
Article provided by David Powell of Boston Bike Bits.