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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: frankenduck on February 19, 2012, 07:00:38 PM

Title: K75 Fuel Cooler
Post by: frankenduck on February 19, 2012, 07:00:38 PM: One of the reasons that the fuel tanks heat up much on K75s and K100s is that the return line from the fuel pressure regulator is routed right behind the left side of the radiator. This heats up the fuel. Here's a local guy's K75RT where a previous owner installed a fuel cooler on the return line to keep that from happening.

(http://i1221.photobucket.com/albums/dd470/Motobrick/k75_fuel_system/k75_fuel_cooler2.jpg)

(http://i1221.photobucket.com/albums/dd470/Motobrick/k75_fuel_system/k75_fuel_cooler.jpg)

Another option for mitigating this is to install insulation around the return line like BMW did on some Ks. The BMW part number for this insulation is 13531460584. About $15 from a dealer.

(http://i82.photobucket.com/albums/j246/smithduck/k75f/k75f_017.jpg)
Title: Re: K75 Fuel Cooler
Post by: Lawrence on February 20, 2012, 01:31:48 PM: Interesting mod! It will reduce the temp of fuel in the tank, no doubt a very good thing during the summer. I'm not sure I understand the reason for the brass bits. It appears the lines to the cooler are connected and valves plumbed into them to bypass the cooler. Is this correct?
Title: Re: K75 Fuel Cooler
Post by: frankenduck on February 20, 2012, 02:28:34 PM: Quote from: Lawrence on February 20, 2012, 01:31:48 PM
Interesting mod! It will reduce the temp of fuel in the tank, no doubt a very good thing during the summer. I'm not sure I understand the reason for the brass bits. It appears the lines to the cooler are connected and valves plumbed into them to bypass the cooler. Is this correct?

I think you're right - so it can be bypassed in the winter months I suppose.
Title: Re: K75 Fuel Cooler
Post by: rbm on February 21, 2012, 05:55:29 AM: This plumbing seems unnecessarily complex IMO. I've seen other fuel cooling suggestions on other K-bike sites (Ref: Heat Exchanger (http://k100rt.aforumfree.com/t2806-fuel-heat-exchanger), Fuel Cooler (http://k100rt.aforumfree.com/t2837-fuel-pressure-reg-relocation-now-with-fuel-cooler-added)). Most use small coolers designed as oil or fuel coolers for go-karts. The favourite place to tuck these small in-line coolers into is the air scoop on the RT's radiator surround. I've been contemplating a finned cooler (below) to install on my RT but haven't gotten so far as to think of a good location that facilitates efficient cooling and simple plumbing.

(http://www.dana.com/wps/wcm/connect/7c8f6c0041f3cfae9a33be1c9e250a89/dext-Fuelcooler.jpg?MOD=AJPERES)

Who knows, I might just end up using a small oil cooler like the others in the end.
Title: Re: K75 Fuel Cooler
Post by: BrickFlyer on February 21, 2012, 08:00:24 PM: I'm not sure I'd like that mod. I'm picturing a rock ripping through the fuel cooler fins, fuel spraying everywhere and eventually a disaster. On top of that you also introduce so many additional fuel connection points that can be future leak spots. I agree with the other poster that suggested you tuck that baby away into an air scoop or something for that application.

I'd go with the extra insulation. Simple, cheap and lower risk.
Title: Re: K75 Fuel Cooler
Post by: frankenduck on February 21, 2012, 08:30:57 PM: Personally I just go the insulation route. I just posted that up because I thought it was an interesting mod.
Title: Re: K75 Fuel Cooler
Post by: TimTyler on August 16, 2012, 11:30:51 AM: (sorry to resurrect this old thread)

I'm replacing old fuel lines and finding it impossible to slip the insulation tubes onto the lines. I've tried dish soap and rubber/vinyl conditioner without success. What's the trick?

Considering slicing the insulation and attaching with zip-ties.
Title: Re: K75 Fuel Cooler
Post by: Lawrence on August 17, 2012, 10:57:30 AM: I found the insulated sleeves slipped on easily when I did this mod. Perhaps you just bought the improper size.
The material I used was sourced on EBay for a reasonable price.
Title: Re: K75 Fuel Cooler
Post by: frankenduck on August 17, 2012, 04:04:56 PM: The OEM insulation should fit on the fuel lines easily. Part 13311461507
Title: Re: K75 Fuel Cooler
Post by: TimTyler on August 17, 2012, 04:12:51 PM: I was only able to slip it on an inch or so.

Sliced and zip ties was the solution.
Title: Re: K75 Fuel Cooler
Post by: jsb on November 19, 2012, 01:47:33 PM: Quote from: frankenduck on August 17, 2012, 04:04:56 PM
The OEM insulation should fit on the fuel lines easily. Part 13311461507
I have not been able to find this yet, it seems it is unavailable. Do you know of a supplier that still has some, or is there something else I can use that will do the same thing? Not having seen the stuff in person, I have no idea what it is made of.

jb
Title: Re: K75 Fuel Cooler
Post by: frankenduck on November 19, 2012, 02:26:17 PM: Have you tried calling a dealer? It may not show up online but maybe they can get it from The Fatherland.

If you Google fuel line insulation you can probably find some generic stuff online.
Title: Re: K75 Fuel Cooler
Post by: jsb on November 19, 2012, 02:50:14 PM: Quote from: frankenduck on November 19, 2012, 02:26:17 PM
Have you tried calling a dealer? It may not show up online but maybe they can get it from The Fatherland.

If you Google fuel line insulation you can probably find some generic stuff online.

Hmm, noooo, I had not. :embarass:

I honestly hadn't even thought about something actually called fuel line insulator that would be generally available, had chalked this up to some Teutonic thing. I see some stuff out there that could be even better than stock, so I'll go that route, and put the Johnny blanket on the bike while I'm at it. It does get mighty hot here in Texas on the commute home each summer. :yow
Title: Re: K75 Fuel Cooler
Post by: frankenduck on November 19, 2012, 03:09:42 PM: This stuff looks interesting: http://store.newlevelmotorsports.com/hea204009.html (http://store.newlevelmotorsports.com/hea204009.html)

You need a bit less than three feet to do all of the fuel lines on a K75. The aftermarket fuel line I have is just over 1/2" OD so it might be possible to get two layers of it on.
Title: Re: K75 Fuel Cooler
Post by: jsb on November 19, 2012, 03:22:49 PM: I had my eye on this: http://store.newlevelmotorsports.com/reheshsl1x3f.html (http://store.newlevelmotorsports.com/reheshsl1x3f.html). If that stuff lives up to their claims, it would be great. Plus, it wouldn't add any bulk.
Title: Re: K75 Fuel Cooler
Post by: rbm on November 20, 2012, 02:32:44 AM: Reflective tape insulation been used by Oldgoat on his 85 K100 restoration project (http://k100rt.aforumfree.com/t1941p50-85-rs-restoration-part-1#14912) and apparently works well.
Title: Re: K75 Fuel Cooler
Post by: frankenduck on November 20, 2012, 04:53:33 PM: Check out product 4463K123 at McMaster-Carr. $2.66 for 6 feet of it. :eek2:
Title: Re: K75 Fuel Cooler
Post by: billday on December 30, 2012, 09:17:58 AM: Quote from: frankenduck on August 17, 2012, 04:04:56 PM
The OEM insulation should fit on the fuel lines easily. Part 13311461507
Max's fiche says that this p/n is not available, and superseded by 13317666005; but a search for 13317666005 gets no hits....
Title: Re: K75 Fuel Cooler
Post by: Lawrence on December 30, 2012, 01:30:06 PM: If the aftermarket material works, and it certainly has on my K100RS, why obsess over the OEM product? You've lots of options out there....
Title: Re: K75 Fuel Cooler
Post by: frankenduck on December 30, 2012, 01:45:18 PM: Quote from: frankenduck on November 20, 2012, 04:53:33 PM
Check out product 4463K123 at McMaster-Carr. $2.66 for 6 feet of it. :eek2:

I just replaced and insulated all of the lines on my K75. This stuff works for the part of the line that goes behind the radiator (the top 2/3s of it) and the line from the tank to the fuel rail. I used the OEM stuff on the line from the fuel rail to the FPR.
Title: Re: K75 Fuel Cooler
Post by: billday on December 31, 2012, 06:20:48 PM: I just ordered the McMaster-Carr item too. Looking forward to making some progress on my air/fuel intake refurb.
Title: Re: K75 Fuel Cooler
Post by: billday on January 03, 2013, 05:36:19 PM: Quote from: frankenduck on November 20, 2012, 04:53:33 PM
Check out product 4463K123 at McMaster-Carr. $2.66 for 6 feet of it. :eek2:
Heads up, people: I ordered that item plus a box of hose clamps.... total for merchandise, $11.66 -- total shipping, $17.66! Yikes.... I had no idea from the shopping cart....
Title: Re: K75 Fuel Cooler
Post by: frankenduck on January 03, 2013, 05:50:27 PM: Yeah, MaMaster-Carr calculates shipping when they ship, after you've paid. Mine usually isn't that bad since I'm in Seattle but NY is all of the way across the country from LA.