Wednesday, August 20, 2014

Old shock, new shock

In response to queries on the other thread Trevor (Sprint) confirmed the 17 inch wheelers have a longer shock and here's a photo showing the difference. It's not much but the heave onto the main stand is way less now. With the old shock and the 17 inch wheel it was 2.5 inches off the deck when on the stand now it's just over 1.

Can't say I've noticed a huge change in handling or turn in but the ride quality is much better as you'd expect. Overall a happy chap.

This shows the only difficulty in fitment; I had to relieve the top of the drag link (just chamfered the top edge) to allow the bottom shock mount in as it's more chunky than the original.

Friday, August 8, 2014

Six spoke wheels

I'd borrowed the hollow three spoke Brembo wheels from my Daytona, pending a posh polish and paint job on the original six solid spoke SNW Trophy wheels. Meanwhile, Tim decided he had no use for his six spokers so I thought I'd make use of them (cheers Tim) as a way of returning Streaky his wheels. First off, ditch the 20 year old rubber tubeless valves. For a few pounds, it just isn't worth trusting these critical components. I've seen the front tyre of a bike blow out on a motorway. Not pretty.

Tim's wheels were a bit tired but otherwise in decent condition. I decided to give them a simple tidy up with some steel coloured wheel paint I had for years. Literally. I went for a steel colour because I thought it would pick up the graphite stripe on the Trophy bodywork, rather than the aluminium colour these wheels came in.

After a good scrub with a nylon pad, degreaser and CIF, I could see the paint on the rims was very thin and flaking. So a went over the edges with wet and dry. Also, I treated the inner surface of the rims where they had suffered from tyre irons in the past. 

Tyre iron groove ...
... treated to a foam block and wet and dry ...
... until all is smooth again.
I had some grey primer so treated the wheels to a coat of that to start with.

Unfortunately, there was still some flaky paint around the bare ally on the rim and it didn't take very well. So more rubbing back, more primer - still not great but as I was determined not to agonise over the finish, I went on to the wheel paint.

Not bad ... at a distance

Rubbing back Simoniz steel colour wheel paint as it reacts again

Well, more reaction followed, more rubbing back, more wheel paint. I think they are pretty good now.

I installed a new 160/60ZR18 Avon Storm 2 on the rear wheel ... 

... and then noticed how the inner faces of the swingarm had suffered last winter. So more rubbing back - with steel wool this time - but special metals primer this time. Marvellous. Why didn't I use it on the wheels? No idea other than this time I wasn't thinking about a quick job. I was thinking of a sound one.

As a consequence, the paint took beautifully and no futher rubbing back was required so it was actually quicker anyway. When will I ever learn.

Good as new
With the rear wheel reinstalled, I can see that the rear of the bike sits higher now. Tim discovered that there is a difference in the length of the rear shock absorber for bikes with an 18 inch rear wheel and the later 17 inch rear wheel. That figures, with the difference in stance of my bike, back on a wheel it was originally spec'd for.
Better stance with 18 inch rear wheel and original shocker

I have not yet finished the front wheel but Ruby Trophy 12 is blasting around Somerset and Wiltshire again. Soo smoooth on the new chain and new rear tyre.

Ah,  Summer time

Horrible clonking from my gearbox ... no longer

I had noticed a loud clonking banging noise coming from my gearbox at low speed. This was especially going up hill between 10 and 30 mph. It cleared above 30mph and the rate of clanking was the same regardless of the gear (and hence rev rate) the engine was pulling. That meant whatever it was, it was on the output side of the transmission. Needless to say, I was depressed at what it might mean. Google search suggested a whole range of horrors but - wait - also a suggestion that might just save me.

Apparently, some forum posters had diagnosed a similar problem as nothing more sinister than a worn chain. Internet advice was to check for stiff or frozen links that might be causing the chain to ride up on sprocket teeth, then slap down again to create a banging noise. However, my chain looked great. I put the bike on the centre stand and checked every single joint with two pairs of pliers. All moving smoothly. Clean and well lubricated, courtesy of my Scott Oiler, and no hint of any stiff links.

Comparing standard Trophy (left) and modified Daytona (right) sprocket covers

Daytona sprocket cover with 12mm holes for inspecting gearbox sprocket
I had previously modified my Daytona sprocket cover so I could inspect the gearbox sprocket without draining the oil. At my last oil change, I had drilled three 12mm holes at an appropriate radius the gearbox output shaft. The sprockets showed some clear signs of wear but not particularly worrying, I thought. Then I noticed that the Haynes and Factory workshop manuals quoted a maximum wear limit for the chain as 319mm for a 20 link length. It isn't possible to measure this length along the bottom run of the chain because the exhaust and subframe get in the way. So I removed the chain guard and saw 20 lengths of my chain were at 320mm. Let's say, at the wear limit.

I decided to try a new set of chain and sprockets. The chain was on the bike when I bought it and so has lasted at least the 9500 miles I have covered since obtaining the bike. Who knows how many it had covered beforehand. I decided to make another trip to see Trevor. He offers DID and a cheaper (Triple S) chain options. I so rarely need to change a chain, and in my younger days suffered so often with 'bargain' chains, for me it was a no-brainer to spend a bit more for the fantastic quality of genuine DID.

Contents of a DID VX chain and sprocket kit from Sprint Manufacturing
Trevor also sells Sunsstar gearbox sprockets too - again super quality - and includes a gasket for the sprocket cover and locking tab washer in the kit. All for £140. I was happy with that.

Having split the old chain, by first grinding of the rivet heads and then pressing out the old soft link, I was able to measure the wear on the pivot pin. In the picture above, the wear line is visible but it was less than I had imagined - the step is about 0.2 mm so about 5% of the thickness of the pin. The gearbox sprocket was getting to the end of its life. 

I'm guessing the accumulation of wear on the chain 'stretching' the distance between the pins under load, plus the gearbox sprocket, was allowing the riding  up and dropping of the chain at low speed. At higher speed, the centripetal acceleration could have prevented this as the chain was more uniformly pushed out from the rear sprocket, effectively gripping the gearbox sprocket more firmly. 

Locking tab washer in place

I treated the new Sunsstar sprocket to a dousing of paint because it appeared to be in bare metal. It took quite a bit of jiggling to settle on the splines of the output shaft. It was a really satisfying fit when it went home. Beautiful close tolerance for a part that is under huge pressure in operation. 

DID VX Professional, torqued up gearbox sprocket and
tab washer flattened into place. Perfick. 
I have a chain splitter and riveter kit. It was a bit pricey but rewarding to use with a pricey C&S kit. I measured the external width of the fixed links as 20.5mm so clamped up the soft link to the same degree. The gearbox sprocket nut was then torqued down but selecting first gear, turning the rear wheel against engine compression and standing on the rear brake.

And the result?

No more clonking any more. A result indeed.