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Last of the Minoans
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Discussion Starter #1
Ah, it looks like it's one of those times where the expense never stops. No sooner than I get a new tyre (and brake pad set), than I notice that familiar metallic clanging that signifies a new chain is required is here (I think after 22,000 miles this time - not as good as the last chain and sprocket set). I've noticed that on these bikes (TA and AT) the chain signals its retirement by making this noise and sending vibes out, mostly through the nearside foot rest. It seems the clanging occurs when one of the links develops significantly more side play than the others - as it hits the output sprocket (?) it 'knocks'. One chain snapped on me because I ignored it too long, and I don't want that to happen again!

So, my question is, does anyone know if there is a 15 tooth front available? I'm running an extra tooth at the rear, but would like to try a set up that's lower still; standard (45 tooth) on the rear and one down (15 tooth) on the front. Wemoto do the 46 tooth rear sprockets, but not a 15 tooth front. I know the output spline configuration on the 600 and 650 Transalps is different, although the sprocket is a 15 tooth-er, but there must be another out there that fits. If not, I'll just go back to the 46 tooth rear - I would rather not return to standard gearing; the engine just isn't happy in top at 40 mph. Lowering top speed is not a problem. I don't spend that much time over 100, and would rather have more oomph getting there anyway. I know lots of people raise their gearing to try to lessen the vibes, but this just seems to put them in a different place, and makes that around town chuggy-ness worse. And it makes the AT worse off road......

Any thoughts out there?

Stig
 

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Last of the Minoans
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Discussion Starter #3
Yep, they appear to list one. I'll give them a ring to make sure it's the right one - cheers for that.

Stig
 

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Last of the Minoans
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Discussion Starter #6
Thanks for that - I've ended up ordering from T.E. Spares (nice chap) both a 15 and a 16 tooth front with a standard rear - that way I can try both with a 124 link chain. Going one further tooth up on the back would have meant a longer chain. In truth, I think the 15 tooth front will be too low. I did a calculation at http://www.ozsportsbikes.com/wrap.php?file=tools.htm#gearing3 for an RD04 (the only model I could get primary gearing specs for at the time), and that set up would give 99.5 mph in top at 7,500 rpm (the standard 16 front/45 rear RD07 set up gives 106 mph at the same point). It's more than possible I've miscalculated the rear tyre circumference, but not by much, and I have a feeling the RD04 had some slightly different primary cogs, but not sure. I figure I can try the 15 tooth and change to the standard gearing if it turns out to be just too low. I can live with the slightly too tall fifth gear in town when it comes to it. Will I have a mad wheelie machine that won't crack the ton? It'll be interesting to find out.....

Yet more expense: the nylon worm gear in my speedo drive is kapput again (on the way home last night) - only 17,000 miles this time, replaced earlier this year. I've ordered some 'red rubber grease' to try this time. Apparently it's for brakes and is formulated not to attack the rubber. If it really is true that standard grease attacks the nylon (surely not?) this might be better as a lubricant. Yen - I noticed that the base of the nylon gear recesses into the drive housing over time, so what you heard about being able to get a bit more life from a dead gear by spacing it out might well be true. I couldn't find a washer that would fit without fouling the metal worm gear that meshes with the nylon and outputs to the cable. At this rate I could afford a proper IMO set up with the money used to fund the Japanese nylon industry. Oh, and David Silver haven't got one on the shelf. Sold out perhaps?

Thanks for the help all of you!

Stig
 

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Last of the Minoans
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Discussion Starter #7
Thought I'd post an update. I finally got the sprockets and chain, although I had to run with the worn output sprocket for a while because the standard and 15-tooth ones were out of stock, so the chain won't last as long as it would have....

I also finally got a new speedo drive gear yesterday (on order from David Silver for three weeks), so now I can tell what difference the lower gearing makes.

On the subject of the nylon speedo gear, I noticed that the gear actually sits on two washers that act as something like bearings. They aren't noticeable to start with, especially if they have already stuck to the gearbox allow. Mine are very thin and one has pinholes all over it from where the corrosion has got it. I made sure they were well greased (with the red rubber grease) on all surfaces, but I need to try to source new ones. I'm fairly sure now that the reason the gear often fails is that these washers either wear out or seize, leading to the base of the speedo gearbox recessing itself into the bottom of the nylon drive (both of my other worn out ones had this). As the drive sinks in the gearbox it is no longer in proper contact with the bevel gear, and eventually the two gears start to skip. The result is that the teeth of the nylon gear are worn away, and that's when the thing fails. This would explain why (as Yen heard) packing out the base can give the gear a little more life. This problem affects the TA as well. Next time you have the front wheel off, take a look at the condition of the bearing surface of the nylon gear and the gearbox.

Now, on to the final drive. The lower gearing isn't as extreme as I expected, although (for reference) 4000 rpm = an indicated 50 mph, and 70 is at 6200 rpm. It obviously red lines very easily in top now (headwinds are less of a factor!), and the acceleration to the red line in top is much better. Wheelies are probably easier. In fact, for £11 you get the cheapest bit of bolt on acceleration boost possible! It seems much better in the bends and around town (peak torque seems a little more useable for these situations). Top speed is over an indicated 100 mph, but my calculations suggest it's just scratching the ton in reality. Yesterday I did my usual 150 miles on £11 worth of fuel as usual, but without a working speedo I've been keeping it under 6000 rpm. Obviously I was actually travelling faster with the original gearing! That said, I had a protracted race with a van that had the poor machine sitting just short of the red line for five minutes or so. That can't have done much for mpg (and engine life). I'll have to see how the economy is affected at the end of today.

All in all I'm pretty pleased with the change, but I might swap back to the standard 16-tooth cog tonight, as my commute is largely dual carriage way. The standard reduction is not a bad compromise, but for me an extra tooth on the back (taking it to the same reduction as an RD04) is about perfect.

Stig
 

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Last of the Minoans
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Discussion Starter #8
Ah - mistake there, that should have read 70 mph at 5600 rpm. Sorry about that.

Stig
 

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Premium Member
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1,015 Posts
Perhaps someone techie can write a simple javascript page which can work all this stuff out so you could experiment with changing gearing before you go out and buy the bits..?!?
 
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