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First time replacing fuel lines on R100RS - questions...

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Mark Malin
(@18720)
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Hi.  I want to change the fuel lines on my 88 R100RS, but it's not clear to me how to get at the connections inside the top engine cover (not sure what it's called).  My bike has 2 petcocks, so the fuel lines go into the cover, then come back out to the carbs.  If I remove the air box, will I be able to access them?  Is it possible to remove the air box without removing the carbs (can they stay attached to the cylinder head)?  This is new territory to me and I don't see any instructions in my Clymers manual.  Any instructions would be most appreciated!
Mark

 
Posted : 11/05/2023 14:40
Richard Whatley
(@wobbly)
Posts: 2498
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• On the older models with the aluminum air box, both halves of the air box must be removed.

• On the newer models with the plastic air box, the entire air box mush be removed.

 

Subject Notes

1. I would HIGHLY suggest using American-made automotive fuel line that is marked with the spec "SAE J30". Otherwise the alcohol will slowly destroy your fuel line, clogging the filters and carbs with tiny bits of rubber from inside the lines.

2. If you have trouble routing the US-sized fuel lines through/under the airbox, then there is a second way to route the lines that is much easier to install and maintain. This involves routing the fuel line in a U-shape around the rear of the engine/airbox. Then cut the U-shape at a point directly over the carb and add the T-connector pointed down, rather than inward. This also leaves more room for fuel filters. Pardon my 3rd grade artwork...

Hope this helps.

[color=blue]Don't hide 'em, Ride 'em !!
#15150[/color]

 
Posted : 11/06/2023 05:19
Mark Malin reacted
Steven Rankin
(@14724)
Posts: 143
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This thread was run at BMWMOA a while back.   I was surprised a couple of guys were able to poke new line through without disassembly.  I have never had such luck.      

 

 

This post was modified 4 months ago by Steven Rankin

Beware! I do not suffer fools gladly! St.

 
Posted : 11/06/2023 06:35
Steven Rankin
(@14724)
Posts: 143
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Well for some reason the Airheads forum won't let me copy and paste the website for the BMWMOA forum post.  The date for that post was Oct 21 23, under airheads "fuel line replacement or something like that.  St.

Beware! I do not suffer fools gladly! St.

 
Posted : 11/06/2023 06:38
Mark Malin reacted
James Strickland
(@8053)
Posts: 411
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Is the OP talking about the top cover, and the fuel shut-offs inside that space? Many motor bikes with carburetors have vacuum operated shut offs that disrupt the fuel flow when intake vacuum stops. (motor not turning) Many Japanese models have this feature incorporated with the fuel tap. I believe these emission control features on airheads in the years they became mandatory were effected with electric solenoids that were located under the top, or starter cover.

I used to own a 1988R100RS, but on my bike, the shut off solenoids were bypassed. That bike's fuel plumbing was arranged like earlier models. Richards depiction of fuel hose routing would work just fine. 

former Airmarshal, IL.

 
Posted : 11/06/2023 07:06
Mark Malin
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Topic starter
 

Thanks for the post, Richard, and for the diagram.  If it comes to that, I can certainly go that route.

Steven, thanks. I'll look that up.  I have the air intake cover and filter off and can kind of see in there, but I think I'll have to remove that top cover.  Not sure how to do that, but I'll figure it out.  I'm assuming the trick is to put the hoses in there with the cover on your workbench, then install it on the bike leaving enough hose to reach the petcocks and carbs then cut those ends to fit? 

 
Posted : 11/06/2023 07:07
James Strickland
(@8053)
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I think you're on to a good procedure there, Mark. The solenoids were already by-passed on my '88 RS when it came to me, so I am kind of stabbing in the dark here. I have never actually seen one of these that was intact with the hoses run in to the top. Also, if you do find fuel shut off solenoids under the top cover, these are enabled by the ignition switch as opposed to motor vacuum. There are 2 cap screws holding the top cover in place. It can be removed with the fuel tank in place, but it is a squeeze to get it out and back in.

former Airmarshal, IL.

 
Posted : 11/06/2023 09:37
Mark Malin reacted
Steven Rankin
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Posts: 143
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Maybe I should have not answered.  I am NOT fully aware of the added EPA "stuff" they added to the bike in question.   Sounds like a more complex job than I thought.  Sorry, St.

Beware! I do not suffer fools gladly! St.

 
Posted : 11/06/2023 11:11
Mark Malin
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Posts: 7
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Topic starter
 

Posted by: @8053

I think you're on to a good procedure there, Mark. The solenoids were already by-passed on my '88 RS when it came to me, so I am kind of stabbing in the dark here. I have never actually seen one of these that was intact with the hoses run in to the top. Also, if you do find fuel shut off solenoids under the top cover, these are enabled by the ignition switch as opposed to motor vacuum. There are 2 cap screws holding the top cover in place. It can be removed with the fuel tank in place, but it is a squeeze to get it out and back in.

Quick update - With the air intake box's top and the filter removed I was able to get in to the back of the cover and pull the hoses off the solenoid (if that's what it is), and with the hoses disconnected from the petcocks I was able to lift the cover off.  FWIW, and this is probably obvious!, you have to disconnect the hoses from the petcocks and carbs (or pull the carb hoses off the solenoid's rear) in order to lift out the cover.  

I think mine may have had the emissions air venting stuff stubbed off (there is a screw in the hose sticking out of the front of the cover!).  

I have 2 questions now - hopefully you guys can walk me through this

1.). I yanked pretty hard on the T connectors at the rear of the solenoid in order to get the fuel hose off.  How do I know that T connector still has a good seal into the solenoid?  The T spins, but maybe by design? Maybe it's like a fuel injector o-ring on a car and I don't have to worry?  I'm thinking, I have this off now, I don't want to get it all back together and have it leak from the junction of the T and the solenoid.  I think it's fine, but how do I know?

2.) I have both braided and non-braided fuel hose handy.  BMW braided hose, and the non braided from The BMW Parts Guy.  Do I use hose clamps on the braided hose?  Do I use hose clamps on the non-braided hose?  Which is better (aesthetics aside)?  

 

Thanks!
Mark

 

 

 
Posted : 11/06/2023 11:27
Steven Rankin
(@14724)
Posts: 143
Estimable Member
 

I have to add, I haven't seen this set up before, LOL, I guess nothing this new has come into my friend's shop so, I can see why there is an issue of replacing lines.

I personally don't like the braided stuff, haven't used it in years as I got sick of it seeping after a short time.  Not to say it hasn't been improved but I went with alcohol proof fuel injector line and have had great luck with it.

I have never needed any sort of clamps.  

Learned something today, maybe if I ever buy a newer than 84 airhead I might have to deal with this.  St.

Beware! I do not suffer fools gladly! St.

 
Posted : 11/06/2023 15:31
Mark Malin reacted
Mark Malin
(@18720)
Posts: 7
Active Member Customer Registered
Topic starter
 

Posted by: @wobbly

2. If you have trouble routing the US-sized fuel lines through/under the airbox, then there is a second way to route the lines that is much easier to install and maintain. This involves routing the fuel line in a U-shape around the rear of the engine/airbox. Then cut the U-shape at a point directly over the carb and add the T-connector pointed down, rather than inward. This also leaves more room for fuel filters. Pardon my 3rd grade artwork...

Hope this helps.

 

I'm going to do something like this, but under the cover.  Like an "H" using 2 T connectors.  Where is a good place to get these T's to be sure I have the right kind?

Mark

 

 
Posted : 11/07/2023 05:04
James Strickland
(@8053)
Posts: 411
Reputable Member
 

Euro Moto Electrics (EME)  offers the fuel line t's you want. Link pasted below. No hose clamps are needed on these, or any fitting on your Airhead. After viewing your picture, I was wrong about the solenoids being electricly activated. That is the first time I have actually seen those parts.

https://www.euromotoelectrics.com/product-p/fp-tpiece083.htm

 

This post was modified 4 months ago 2 times by James Strickland

former Airmarshal, IL.

 
Posted : 11/07/2023 06:16

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