RS & LT engine differences

4516 Views 7 Replies 6 Participants Last post by K100Dennis, Mar 6, 2012

K100Dennis

Discussion Starter · Mar 6, 2012

My mate has a K1200RS (2003). I wonder what the logic is for using the oil cooler on the RS but not the LT ? Also I think the RS is around the 130 HP mark ?? Physically the same engine as the LT but possibly different cams and computer/fuel mapping etc. I thought the oil cooler could only be a good thing on the LT due to its weight and heavy loading, the extra engine output would also be a bonus, maybe a slight increase in fuel consumption. Thoughts ?

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New2rt

· #2 · Mar 6, 2012

I haven't looked at the torque curve but I would think the LT comes on earlier and is flatter which is what you would want in a touring bike. The RS later requiring you to run in a higher RPM range, looked for in a sport bike. It would explain the higher peak HP, easily done with different cam profile and timing.
.02 worth.

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Rocketsled

· #3 · Mar 6, 2012

See, this is why I like this place. This question has been forming in my head for a few days...now I don't have to ask it.

(Specifically, why are there power differences between two nearly identical motors)

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meese

· #4 · Mar 6, 2012

You can't look at pure max numbers here, you have to also look at the character of how the power is delivered.

The RS motor is tuned for more horsepower at higher rpms, as befits a "sportier" ride on a "lighter" bike.

The LT motor is tuned for more torque at lower rpms, as befits a larger, heavier touring bike.

There was a guy who swapped an RS motor into an LT many years back. I spoke with the mechanic who did the job, and he said it was a lot of time and expense for a very negligible benefit. The power curve of the RS motor just didn't suit the LT.

You can get a similar benefit much cheaper by just swapping the cams in the LT motor, or better yet by going with an '05 or later LT, which has some useful motor mods over the '04 and earlier bikes.

And for the ultimate power upgrade, look at the Slant/6 GTL. 160 horsepower and 130 lb-ft of torque will flat blow you away . . . :bmw:

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zippy_gg

· #5 · Mar 6, 2012

I am not sure if the RS came with a 5 or 6 speed transmission, but the LT only has 5 and has a very tall 1st gear so I would think that coupling a motor with high HP at high RPMs would not be a good thing. Add to this the heavier weight of the LT and you'd probably burn your first clutch very quickly.

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meese

· #6 · Mar 6, 2012

The RS has six speeds. The LT was reworked to 5 speeds to make room for reverse.

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jzeiler

· #7 · Mar 6, 2012

The 05 and up LT uses RS pistons and larger throttle bodies and different cams than the earlier LTs but they are not RS cams.

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K100Dennis

Discussion Starter · #8 · Mar 6, 2012

The oil cooler took my eye (spacer in the oil pump assy to accomodate offtake), and on the tall first gear, my opinion is that if it were slightly lower then clutches wouldn't suffer nearly as much. First and second are very close ratios, it would have meant just a slightly larger difference between the 2. My K100RT was great in that regard, and clutches were never an issue, keeping in mind the FD was also larger ratio (lower geared). As for the engine output, the difference between an '03 and my '05 is noticeable if you ride 1 then the other as I have done.

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