Fuel Tank Swap 85 to newer - K-Bikes.com - Excellence in Motion
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post #1 of 11 (permalink) Old Sep 30th, 2013, 11:10 am Thread Starter
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Fuel Tank Swap 85 to newer

I am needing a new fuel tank for my 85 K100RS. I have read that after 85 the tanks switched from a single hole at that back mount to something with two holes that mounts to the frame. Does anybody have a diagram or picture of the two hole mount?

Because the newer tanks are easier to find, I am considering trying to modify my bike to fit one on. An added bonus for me would be the switch to a float type fuel level sensor that the newer tanks use.

Is there anything else that would need to be considered besides the rear mount?

One tank i am considering does not have a fuel level sensor or fuel pump. Could I use my current fuel pump?

How about the electrical connector beneath the tank? On mine there is a three wire cylinder shaped connector that plugs into the female connector on the front left lower corner of the tank.

How about the top "door"? Is this fit the same for both.

thanks for any advice you can offer.
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post #2 of 11 (permalink) Old Oct 1st, 2013, 7:00 pm
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Another issue is whether the 85 seat will fit with a later tank. This is an issue because if you need to change the seat you will also need to change the rear cowl. On the 85 the tank, seat and cowl are orphan parts.
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post #3 of 11 (permalink) Old Oct 1st, 2013, 7:05 pm
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Quote:
Originally Posted by 97tiger885
Another issue is whether the 85 seat will fit with a later tank. This is an issue because if you need to change the seat you will also need to change the rear cowl. On the 85 the tank, seat and cowl are orphan parts.
Non-issue in the front of the seat. 85 and 86+ tank shapes are identical - only the rear mounting of the tank varies.
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post #4 of 11 (permalink) Old Oct 3rd, 2013, 2:19 pm Thread Starter
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That's good to know that at least the seat is not an issue.

I found this image online that answers a lot of my questions.

I can see the electrical connection is different so would need to modify that. that is probably the easiest part.

I assume that the fuel pump is the same.

So it really is just the rear mount. In the image you can see the two posts at the rear of the tank. Maybe the easiest solution would be to create a bracket the connects to the two posts and which also extends out behind the tank with a hole to bolt onot my current mount.

Whether there would be enough space to accommodate this bracket is a question. Since the tank shapes are otherwise the same i should be able to check for clearance tonight and see if I can tell anything.
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post #5 of 11 (permalink) Old Oct 3rd, 2013, 2:27 pm
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Fuel pump is the same - non-issue.

However the fuel level sender circuitry is different so you may have to rely upon your trip odometer to know when to fill up.
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post #6 of 11 (permalink) Old Oct 3rd, 2013, 2:28 pm Thread Starter
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Another question,

What are the differences between the k100 and k75 tanks?

thanks
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post #7 of 11 (permalink) Old Oct 3rd, 2013, 2:30 pm Thread Starter
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I have an acewell speedometer. I use the odometer for fill up because the acewell will not work with the thermistor readings. It should work with the float sender circuitry. that is the added motivation for me.
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post #8 of 11 (permalink) Old Oct 3rd, 2013, 2:50 pm
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Quote:
Originally Posted by kringb
Another question,

What are the differences between the k100 and k75 tanks?

thanks
K75 tank has a slightly lower volume and different shape. The inner fairing knee panels won't hug the tank perfectly like they do on an RS with a K100 tank.

Unless it's a K75RT tank as those use the same tank as K100s.
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post #9 of 11 (permalink) Old Oct 3rd, 2013, 5:47 pm Thread Starter
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Thanks Flying Duck. I knew I could count on you for the details.
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post #10 of 11 (permalink) Old Oct 7th, 2013, 2:34 pm
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I'll going to hijack this thread slightly. I have an 86 K75, (haven't referenced the VIN, I think its just a K75, not much for front end bits, just a round headlight) the current tank has the little nubs at the front which I presume are for the rad surround, correct?

If using a different K tank, how critical are the nubs to that rad surround? is it mounted elsewhere?

TIA.
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