If the service tech says other mods are necessary inform him the rest of the world gets a 45T wheel sprocket.
That said, why bother with a service tech? Download the shop manual and do it yourself. You'll save enough on the 600 mile service to pay for an o-ring chain, which is tied with a new main jet for the greatest need of a North American TW200.
I've been doing some calcs on gear ratios. I want to keep the stock combined primary/trans/final drive ratio in first for dualsporting and the equivalent to a 15/47 with the stock tranmission in 5th for the highway. That means I need a total reduction of 33.571 in 1st and 8.535 in 5th. The XT trans with 15/49 sprockets is really close, with 33.503 in 1st and 8.595 in 5th. That's a +21rpm difference at 21.5mph in 1st, and a +66rpm at 84mph difference in 5th/6th. In 1st at 2.5mph, stock trans will turn 1105rpm, the XT trans 1102rpm. Shouldn't notce the difference.
In practice, maximum rpm shift points are as follows:
15/47 TW...14/50 TW.....XT.....TT-R
24.5............21.5........21.5..........24.3
38.8............34.0........33.3..........37.6
52.7............46.2........46.6..........49.6
66.8............58.6........59.2..........63.1
...................................71.9..........76.6
Note how closely the XT trans with 15/49 sprockets so closely replicates the TW trans with 14/50 sprockets for the first 4 gears. The biggest beef I had with 15/47 sprockets was the wide gap dropping off the cam between 4th and 5th with the TW trans. With the XT trans, 5th would be just a tad lower than 5th on the TW with 14/40 sprockets, and nicely split the gap. 5th with the XT trans and 15/49 sprockets would pretty much yield about the same top end performance as stock, and 6th would be the "overdrive" it seems most everyone is looking for. PERFECT! At least for a dualsport that sees the interstate from time to time. Put a stroker crank and a mild cam in front of the XT trans with 15/49 sprockets and this would be dualsport heaven.
The XT trans with a 15/55 sprocket set would provide a 1st equivalent to the TW trans with 14/56 sprockets for those who are looking for tractor performance, while retaining the highway ability of the TW trans with 14/50 sprockets. Those of you with the ATV tires can run the XT trans with 14/70 sprockets to mach the TW trans with 13/71 sprockets, yet still wind it out to 55mph on the highway.
The speeds shown under the TT-R heading are the maximum shift points for the TT-R trans with 15/46 sprockets. Notice how the 1st is almost identical to the 1st of the TW trans with 15/47 sprockets, allowing better rollout from a dead stop. Notice how the gaps between the first 4 gears close a little with each shift, compared to the TW trans with 15/47 sprockets. The 4-5 gap closes a lot, completely eliminating the dreaded bog from the excessive rpm gap, with slightly better top end potential in 5th than the TW trans with 14/50 sprockets. Redline in 6th would be right at 90mph, which would be possible on a lightweight cafe racer down hill with a tailwind. A big bore kit with pod air filter, fairly radical cam, maybe some port work, and a free-flowing exhaust under the frame would take advantage of the top end potential. Such a cafe bike would be a hoot on roads like Deals Gap.
The TT-R trans with 15/49 sprockets would provide the easy cruising of the TW trans with 15/47 sprockets and tighten up the gaps in all the gears, with first about equal to the TW trans popular 14/47 and 15/50 sprocket sets. This would be the ideal set-up for a commuter or cruiser.
The TT-R trans with 15/52 sprockets would provide the same 1st gear as the TW trans with 14/50 sprockets and slightly taller top end as the TW trans with 15/50 sprockets. This would be ideal for a light diplacement tourer. Put a stroker, mild cam, and pod air filter ahead of this option and you'd have a perfect dependable-as-a-rock bike for slow-down-and-smell-the-roadkill sightseeing coast-to-coast. Run a premium synthetic oil and ride 3000 miles a week for a year with nothing but weekly oil changes and chain lube, twice a month valve adjustments, a full service once a month, 2 sets of brakes, 6 0-ring chain and sprocket sets, and a couple dozen tires. Then slap in new clutch plates and springs, rings, grind the valves, replace the frame and wheel bushings and bearings, and do another 150,000 miles.
I so need to hit the lottery.