Saturday, November 9, 2013

JT Sprockets review

Below you can read our on-going evaluation of JT Sprockets and JT Chains, or you can go straight to the JT Sprockets website by clicking on the JT logo on the left.

We have installed JT Sprockets and chain. Read below how that came about and what our real-life test results are.

I must admit I had never heard of JT Sprockets. Sprockets are one of those things you buy at the shop without paying too much attention to them. Well, I did anyway. Strange as poor quality sprockets ruin a chain. We came into contact with JT Sprockets because we could not find any sprockets in Canada or the USA for Mike's XT660R. The front sprocket seems unique to that particular model. I contacted JT Sprocket as, by pure chance, I found it listed on their website! They didn't have one in stock, which is understandable as there is no demand for it in the USA of course but organised it in a couple of days and sent it out to us. As chains and sprockets go together we also fitted their Z1R X-ring chain, and did the same for the Bonnevilles.

The Bonneville OEM sprockets were available in the USA but I wasn't too impressed by the so called Very Heavy Duty RK chain, with a matching very heavy price tag, that was fitted on My T100 at the time and that couldn't match Triumph's original chain in durability. Remember that we have two Triumph Bonnevilles, one fitted with the original chain, the other with the 'better' quality RK. Both did the same trip, the same distance and received exactly the same lubrication and by the same guy (me). The RK failed miserably. As the original chain and sprockets on Jeanette's T100 began to show serious signs of wear as well, and as Triumph's original sprockets were hardly perfectly round, I decided to try JT chains and sprockets on our Bonnevilles as well. 

First thing I noticed was the perfect fit over both splines and hub. Second thing was that the sprockets are so perfectly round that I measured the same chain slack all the way round. Usually after 800-1000km the new chain and sprockets have bedded in and the first re-adjustment is necessary. Not so with these… After 2.000 km Mike's XT could do with it's first adjustment, that big singles are hard on chains and sprockets was evident as the Bonnevilles needed a first adjustment after almost 4.000 km. In 30 years of riding motorcycles I had never seen this! They all have 10.000 km behind them now and no further adjustment has been necessary, despite lots of dirt roads. The original DID chain had stretched 1,5 links when we replaced them after 24.000 km and the sprockets looked like saw blades.
Time will tell if JT Sprockets and chain can match that or improve on it.

Update 18-06-2014: The first set of JT Chains and sprockets needed replacing. Read below how they fared.
Fresh chain and sprockets! Chain tension is per Yamaha specs
Single cylinder motorcycles are traditionally hard on chains and sprockets. Years ago I saw a movie that showed a motorcycle chain in slow motion on a big single which showed it wasn't rotating round smoothly but in a jerky fashion. Each firing stroke hammering the chain and sprockets. It's no wonder then that the chain on the Yamaha XT660 was first up for replacement. In Montana we fitted a new set of JT Sprockets and a JT chain, and now you want to know how long they lasted…!

JT Sprockets suggested a set of their chain and sprockets should last about 20.000 km when used on asphalt. But we didn't just used them on asphalt… we took quite a lot of dirt roads too :-) I also don't use aerosol type chain lube but lube them with gearbox oil and a brush. So how did that all work out in practice? Quite honestly? Very good! Both the sprockets and chain from JT outlasted the ones fitted by Yamaha (DID) comfortably despite all the sand and gravel. 

We all know that we should replace chain and sprockets as a set. Yet Pro Oiler suggest, when using their automatic chain oiler, to replace the front sprocket at 20.000-25.000 km intervals and expect 75.000-90.000 km out of the chain and rear sprocket that way. That kind of makes sense to me as the front sprocket wear is roughly 3 times higher than the rear. To test the theory I decided to lay all the parts on the work bench, old and new, side by side and do some measurements.

Old and new, the old chain had stretched half a link in 24.000km
which is 3x better than the previous fitted DID
As you can read above, the original DID chain had stretched 1,5 links by the time we replaced it. The JT chain not even half a link, see photo. Of course chains don't stretch, they wear at the pins and that makes them appear to stretch. From this we may conclude that the chain wear of the DID chain was 3 times higher than the JT version…! The rear sprocket showed signs of wear but nothing serious. The 'pull the chain from the rear sprocket' test showed no wear between the two, which makes sense as we only adjusted the chain once after the initial bedding-in period. The front sprocket however needed replacing, see photo. Quite frankly, under normal circumstances I would have tried to replace the front only and see what happens. As we have a pretty long trip still ahead of us, and as we are close to JT Sprockets warehouse now, we decided it was better to start with a fresh set.

Shortening the new chain
So how long did they last? The front sprocket 24.000 km (23.400 if you want to be exact), but the rear sprocket and the chain? The wear of half a link in 110 links is well within wear limits and the rear sprocket was nowhere near the end of it's life. Don't forget, we do ride a lot of dirt roads too and this particular chain and sprockets came off a big 660 single. The ones fitted to our Bonneville T100s have covered the same distance under the same conditions and do not need replacing yet. In fact they haven't even needed any readjustment after the bedding-in period.

JT Chains and Sprockets come highly recommended!

The JT website has an easy to use product finder and cross reference for sprockets. Click on the JT Sprockets logo on the right to find yours.
Extract from our post 'All our gear after two years on the road: JT Chains and Sprockets The second set:
Just like the first set we tried from them, the second also took a long time to bed-in, which is a good sign. First adjustment was around 4,500 km. We seemed to be heading for even higher mileage than the first set, but the weather had other plans. As anyone who lubricates his chain manually will know, riding in the rain will wash the lubricant from the chain, and we've had lots of rain. In northern Norway we saw amazing landscapes and rode long dirt roads to get there. The mixture of lubricant, fine gravel, lots of rain and simply not being able to keep it all clean and lubricated as it should, gave the chains and sprockets a very hard life. On top of that the XTs cush drive rubbers, a notorious weak point on any XT660, started to disintegrate, hammering the chains and sprockets even further. They still lasted 23,000 km, which anyone with a big single will tell you is nothing short of fantastic even in good conditions. To be honest the sprockets weren't that worn at all and the chain had only stretched to the wear mark given by Yamaha. We were pretty pleased with how long they lasted, especially considering the conditions they had to operate in, but did realise we had to make a few changes. The XT needed new cush drive rubbers, which we have fitted now with a fresh set of chains and sprockets, and we went looking for a proper chain oiler so that they can operate under better circumstances! Keep you posted.