Thumper Club Forum
Technical => Bike Problems/Questions => Topic started by: SteveC#222 on May 30, 2016, 09:51:00 PM
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Leading from the last question
The XBR has a damn great chunky 525 chain - probably to try and make it last a bit longer ( a 520 would probably be enough for the power).
Now because of this the chain is usually rivited which a PITA to get done and makes some maintainance jobs hard work.
Question - given that the XBR only produces about 36bhp at the rear wheel does it really need to be rivited? surely a simple split link would be enough for the modest power of the XBR? what do we think?
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having had split links go on me twice in the past, id say always always rivet. id imagine that on the xbr its not the power it puts down, its the torque and the way it delivers it that would chew through chains, thumpers have always hammered their chains so id go for rivet every time, but, its your bike, so your choice.
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My XBR came with split link.
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I use a non O ring chain with a split link, You cant imagine it amount of horsepower an O or X ringed chain absorbes, especially when you may have only 40-50 Hp to play with
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I have never had a split link break in nearly 50 years including 20 years and 50,000 miles on my Norton Commando which is probably similar power to the XBR. I did however change the link regularly.
I do think riveted links are probably necessary on higher powered bikes though.
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Dunno the exact reason for the heavy duty chain but consider the following:
Imagine a 500 single and a 500 four. Say both gave the same max power at the same max rpm. Then the max torque at the rear wheel might be the same, assuming the same gear ratios. But look at what the torque figure given actually is. It's an average, taken over two revs (the four stroke cycle) for each cylinder. So in the case of the single the peak torque ** will be miles higher than the four.
What a chain "feels" is a pull in proportion to the pulses of torque. You can work out the pull from taking the torque applied at the relevant sprocket and divide it by the radius to the centre of each roller. The pitch circle radius.
I'd expect a single cylinder machine to have generally chunkier transmission components than an a four of equivalent power.
Possibly they are also trying to keep the inertia in the chain highish? Less likely to have immediate response to each on/off pulses of force?
**edit: I mean peak transient torque.
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This is an old topic and usually polarises opinion. I'm in the split link camp, and would point out that a lot of drag racers use split link chains on their 200bhp drag bikes. If it's good enough for them, it's good enough for me, and I've never used anything other than split link chains in my 30 odd years behind bars.
The secret, as with most mechanical things, is good maintenance....
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might need a big top box if you plan to emulate the drag boys and swap the link every half a dozen quarter miles. whilst drag bikes put some serious power down, i hardly think the two are comparable situations, unless you stop and inspect 4 times a mile too...... ;D
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All it takes to break a chain is a bit of gravel twixt sprocket and chain, and the chain will then part at the weakest link, which in a split link chain is inevitably the split link. This leads to the false assumption that the failure of this link lead to the chain breaking.
This is one of the reasons I like MZ's. ;)
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Interesting thread this one. I have a split link chain on my Dommie 650, which is torquey as fk, and no probs, but my local bike mechanic fella, who has raced motocross for forty years, reckons they aren't as strong. I think I'll just keep well oiled ;)
On the MZ topic, I'm stripping Minnie the Minsk at the mo, and on removing the fully enclosed chain case, have discovered, a practically new looking chain!
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Interesting thread this one. I have a split link chain on my Dommie 650, which is torquey as fk, .....
It would be interesting to look at the dommie first gear, rear wheel torque versus something like a zx6 first gear, rear wheel torque. Most people (except me ;D) would probably not refer to the zx6 as torquey.
Then it would be interesting to know (I don't see how we could know though) the peak transient torque of both machines.
It wouldn't surprise me to find the zx6 way more torquey at the rear wheel (it has way more power), but with a much less transient torque figure.
Any thoughts?