Qingqi (qlink) QM200GY 428 to 520 chain non-conversion!

[forchetto]

We've all heard about the desirability of raising the gearing on the Qinqqi (Qlink) QM200GY to enable first gear to be of some use and reduce the cruising revs and maybe increase the top speed a little in the right circumstances.

This should help engine longevity and cut down some of the vibration that makes its presence felt in the upper reaches of the rev range.

There are several combination of sprockets suggested to achieve this, some prefer changing the countershaft or gearbox sprocket by one tooth, from the standard 15 to 16 teeth, others prefer to change the rear wheel sprocket from the standard 48 to 44 teeth. Both achieve more or less the same gearing ratio change.

The big stumbling block appears to be the use of a 428 size chain by Qingqi, even though the QM200 is apparently based on the Suzuki DR200 range which uses 520 size chain, and alternative sprockets are more widely available, but more of this later.

Apart from the odd aftermarket sprocket not obtainable in all parts of the world, (see posts by volksjagger and his JP Motorsports sprockets), the easiest would be to use suitable Suzuki OEM components available anywhere.

The most popular suggestions centered around wheel sprockets for the Suzuki TS125ERN /ERT /ERZ range. The Suzuki OEM part numbers for various sizes are as follows:

64511-48720 45 teeth
64511-48730 42 teeth
64511-48700 44 teeth

I haven't had any joy in locating the desired 44 tooth one anywhere in Suzuki dealers or major European spares distributors like the excellent "Consolidated Motor Spares" in Holland (EU):http://www.cmsnl.com/
a site, incidentally that list virtually all Japanese bikes, together with spares parts lists and diagrams and an easy to use purchasing procedure.

There's an alternative 44 tooth item for a 428 chain which was used on the Suzuki DS100/125 (1978-1981) and TS100/125 (1978-1979) which appears to be available.

One of our posters (kurt10464), has located some as OEM items for the aforementioned models with Suzuki part number 64511-48001.

I've got one on order from cmsl.com right now.

If, as we suspect, the factory bolts are not strong enough I've also ordered 6 new japanese bolts part number 09100-08094 and 3 dual tab washers 09169-08013.

Why not change to a 520 size chain/sprocket set? I hear you ask. Well, I've tried using the reasoning that if our Qingqi was the same as a Suzuki DR200, we could fit the sprockets from that and have a stronger drive set-up at the same time as raising the gearing.

I started by perusing the DR200 parts lists and it turns out they came with a 15/45 combination of sprockets. Great! I thought, not quite the 15/44 I was looking for, but it'll do.

Without paying too much attention to the illustrations on the parts list, I sent off my order for the items, together with a quality DID 520 chain to go with them.

On receipt, the first thing that struck me was the size of the things. You won't believe the diference in diameter between a 48 tooth 428 sprocket and a 45 tooth 520 one, the latter is enormous!. Although the 520 sprockets are 1 mm thinner than the 428's, and the rollers thinner, the pitch of the chain is 5/8" against 1/2" of the 428. All those extra 1/8" pitches add up and the difference is astonishing. A quick measure up showed that it would only just fit inside the chainguard and would leave the chain rubbing hard against the chain guide fitted to the swing arm.

Undeterred I set about removing the gearbox sprocket cover and found that the new sprocket would hardly fit in there at all. The metal guard fitted to stop a possible chain breakage from damaging the crankcase would have to go for a start, and the chain would rub against the magneto cables which would have to be re-located.

The biggest surprise was that the method of fixing the gearbox sprocket was totally different and not compatible. The Qingqi uses a threaded countershaft that uses a tab washer and counterbored 27 mm nut to hold the flat-faced sprocket but the DR200 has a drilled and tapped countershaft to accept a bolt and washer, its sprocket is not flat faced but has a ridge to accomodate the washer/bolt and a strange nylon ring riveted along with a metal carrier called a "damper" in the service manual.

It appears that Qingqi have chosen to use the countershaft from the TS125 range rather than the one from the DR200. The reason could be that the 428 set-up is evidently a lot lighter or that it's cheaper. I suspect the latter...but, when you have the tooling set-up to make a similar engine to the DR200, why change just one item (the countershaft), complicating production and stockage of parts. If I was doing the production engineering I woud stick with the common DR200 items.

This shows the standard sprocket and the guard. A very good idea incidentaly. I remember wrecking a crankcase on a 1960's CD175 Honda when the chain broke at speed.



Note how close to the magneto wiring loom the standard sprocket is. The DR200 15 tooth would probably touch it due to the extra diameter.



Detail of the 27 mm nut and its tab washer. Note the counterboring that sits on the end of the countershaft. The depth of this counterbore would have been a problem if the DR200 sprocket had fitted. As the 520 sprocket is 1 mm thinner, the depth of the counterbore would have to be increased by a similar amount.



Couldn't find a suitable picture of the DR200's sprocket fixing so I used a very similar one from another vehicle.



Close-up of the DR200 sprocket. Its Diameter is 80 mm against the Qingqi's 65 mm. Note the "damper". No idea what it does, but it's there...why does the Qingqi not need one?.



Rear wheel sprocket for DR200. Size 520/45 teeh. The diameter of the Qinqi's 428/48 teeth is 200 mm and this one is 235 mm. I know it doesn't sound much but the visual difference once it's in your hands, is astonishing.
There's a subtle diference too in the way the rear sprockets are fixed: On the Suzuki 125's and the Qingqi six M8x30 mm class 8.8 bolts with bolt-to-bolt tab washers, whereas in the DR200 the same bolts are used, but they're locked with LOCTITE and no tab washers, just plain washers.