Topic: Carb Leak between #2 and #1 - broken "fuel pipe" (plastic fuel connection)

[midnightrider]

Hey guys, I searched for a while and didn't find anything but Im sure that this has been discussed so feel free to direct me to another post.  

My carbs are leaking in between #2 and #1 at the location shown here:


What do I do?

Thanks for any help.

[TwoTired]

There are orings in there.  If they leak, they have to be replaced.
They come with the Honda gasket set.

Gotta separate the carbs, I'm afraid.

[midnightrider]

I was curious what the extra o-rings that came with the gasket kit were.  Now I know! 
Thanks a million.

[bryanj]

Trouble is you only get 1 per set and you need 2

[TwoTired]

Trouble is you only get 1 per set and you need 2

The kits I got from Honda had four of the fuel tee orings, 2 for each fuel tee.  If you get four kits, you end up with extras.

Maybe the kit contents have changed?

[midnightrider]

The kits I got from Honda had four of the fuel tee orings, 2 for each fuel tee.  If you get four kits, you end up with extras.

Maybe the kit contents have changed?

Im pretty sure that I had two extra o-rings in each package - but for some reason I think that they may be different sizes...?  Regardless, I will check when I get home and let you guys know.

[midnightrider]

There are orings in there.  If they leak, they have to be replaced.
They come with the Honda gasket set.

Gotta separate the carbs, I'm afraid.

Dismantled the carbs - and I found some bad news.  My problem is not that the o-rings are bad, my problem is that the connection is broken.  As you can see here:

and here:


I tried to look this piece up in the parts fiche and it is not identified!!! As you can see here:


My bike is running for the first time since I've owned it and I'll have everything else ready to go very soon...now this is going to keep me from riding!  Murphy's Law I guess. 

Any ideas?
Anyone know what this part is even called?
Where I might be able to get one?

Thanks for the help.

[kerryb]

I'm not familiar with your model of carbs pictured, but I know that piece and what it does.  On my carbs those are aluminum.  Yours look black like plastic, is that why it broke? 

Suggestion 1)  Take the parts to a shop and ask to buy one of "these".  The result should be that you learn the proper name for that "fuel line connector thing".  Maybe they can even sell you one.

Suggestion 2)   After learning the proper name of it, post a parts-wanted posting.

Suggestion 3)   Find someone with a small lathe to make you one.  On my carbs they are pretty simple, a tube with grooves for O-rings.  If I had one to copy I think it would take me less than 1/2 hour to make one 'cause I'm slow. 

[midnightrider]

I'm not familiar with your model of carbs pictured, but I know that piece and what it does.  On my carbs those are aluminum.  Yours look black like plastic, is that why it broke? 

Suggestion 1)  Take the parts to a shop and ask to buy one of "these".  The result should be that you learn the proper name for that "fuel line connector thing".  Maybe they can even sell you one.

Suggestion 2)   After learning the proper name of it, post a parts-wanted posting.

Suggestion 3)   Find someone with a small lathe to make you one.  On my carbs they are pretty simple, a tube with grooves for O-rings.  If I had one to copy I think it would take me less than 1/2 hour to make one 'cause I'm slow. 

Thanks for the suggestions.  I will take it to the shop tomorrow; Im not sure that those crotch rocket connoisseurs will be of much help though...

It is plastic, I assume that is why it broke.  It seems as if the PO might have taken the carbs apart and broken it.  It was definitely already broken, when I pulled the carbs apart one piece came off with #1 while the other remained in #2. 

I also have a 73 500/4 and a 76 550/4 at my house since my friend has no place to house his two projects.  I examined the 500 carbs and saw that the connections were aluminum (or some type of metal).  I noticed that the 500 carbs had two connections for the gas line(s), one in between each pair of carbs. So the connections on it were actually tees instead of inline connectors like mine.  My carbs have only one fuel line connection (in between #2 and #3) so it has one tee and two inline connectors in between both pairs of outside carbs. 

You can see on the parts fiche i copied above that the connector is shown but not labeled.  What a #$%*.

Well, Im not sure that I know anyone with a lathe... I will ask around.

How do you think that I should proceed trying to obtain another one of these at this point?
Should I post a new topic with a picture asking folks what it is called?

 

[TwoTired]

Have you tried a Honda dealer?
Or
http://www.motorcyclecarbs.com/
(call them)

[scottly]

Well, Im not sure that I know anyone with a lathe...

You do now! Seriously, if you can't find the part, myself or someone else here might be able to fab one for you.

[midnightrider]

I see that the piece is referred to on motorcyclecarbs.com as a "fuel pipe" but is only available for Kawasaki and Suzuki bike (at what seems to me like a ridiculous price: $39.95).

I will be calling them as well as the Honda dealership shortly.

Well, Im not sure that I know anyone with a lathe...

You do now! Seriously, if you can't find the part, myself or someone else here might be able to fab one for you.

Thanks for the offer, Scottly.  The other one (between #3 and #4) doesn't leak, so I'm assuming it is fine and could be reproduced.  I'll keep you in mind.

[midnightrider]

The Honda dealership had nothing. 

I put in an email to http://www.motorcyclecarbs.com/ and am awaiting their reply, but I am not confidant because I just got off of the phone with a rep from SUDCO ( http://www.sudco.com/ ) who seemed to know exactly what I was talking about and he confidently told me that no one is manufacturing it.  He also told me that he knows of no resource to cross-reference the part (which is definitely commonly referred to as a "fuel pipe") to find out what other bikes it comes on.  I bet that it's only common between the 350F and 400F though. 

So.... I will either need to find a replacement or get it made by someone like scottly.

Know anyone with an extra set of CB350F or CB400F carbs/carb pieces sitting around?

[TwoTired]

Shouldn't be too hard to make one out of brass (or plastic).  It's just a tube with four grooves in it for the o rings.

[kerryb]

OK, I'm up for a challenge just to see if I can do it.  I bought a lathe to learn how to run it, now is my chance.

Post the sizes that define this part and I'll make one out of aluminum.  I'll size the grooves to fit the o-rings I have to the inside diameter of the carbs you give me.  I will also need the total length, the length and diameter of the larger step in the middle, and an approximation of the inside diameter.  Did I miss anything? 

[scottly]

Kerry, kudos for stepping up to the plate. The most critical dimension on a part like this is the o-ring groove. The o-ring needs to be compressed when installed...

[kerryb]

Kerry, kudos for stepping up to the plate. The most critical dimension on a part like this is the o-ring groove. The o-ring needs to be compressed when installed...

...And the o-ring material has to stand up to fuel without swelling.  Can somebody save me the testing time?  Do Harbor Freight o-rings have the right stuff, or do I have to get some other rubber, like Viton, or unobtanium?

[TwoTired]

Kerry, kudos for stepping up to the plate. The most critical dimension on a part like this is the o-ring groove. The o-ring needs to be compressed when installed...

...And the o-ring material has to stand up to fuel without swelling.  Can somebody save me the testing time?  Do Harbor Freight o-rings have the right stuff, or do I have to get some other rubber, like Viton, or unobtanium?

I just gotta say, I'm happy to see you paying attention materials science. More kudos from here.

The one I got from HF were made of Nitrile.

From:   
http://www.industrialrubbergoods.com/nitrile-rubber.html

Nitrile Rubber (NBR)
Nitrile Rubber (NBR)
Nitrile Rubber is a synthetic rubber produced by polymerization of acrylonitrile with butadiene. This rubber is also known as NBR, acrylonitrile-butadiene rubber, acrylonitrile rubber, nitrile-butadiene rubber, and NR. This type of synthetic rubber is widely used in a number of applications. In the year 2005, worldwide consumption of NBR had reached almost 368,000 metric tons annually.

Properties of NBR

    * Nitrile Rubber belongs to the family of unsaturated copolymers of acrylonitrile and butadiene.
    * The physical and chemical properties of this rubber vary depending on the polymer’s composition of acrylonitrile.
    * Different grades are available for this rubber. The higher the acrylonitrile content within the polymer, the higher the oil resistance.
    * It is generally resistant to fuel and other chemicals.
    * It can withstand a range of temperatures.
    * It has inferior strength and flexibility, compared to natural rubber.
    * These rubber is also resistant to aliphatic hydrocarbons.
    * It is less resistant to ozone, aromatic hydrocarbons, ketones, esters and aldehydes.
    * It has high resilience and high wear resistance but only moderate strength.
    * It has limited weathering resistance.
    * It can generally be used down to about -30 degree celcius , but special grades can also operate at lower temperatures.

However, I don't see why you wouldn't use the Honda standard orings for the application and use the old part as a guide for groove shape and size.

[midnightrider]

Kerry, kudos for stepping up to the plate. The most critical dimension on a part like this is the o-ring groove. The o-ring needs to be compressed when installed...

...And the o-ring material has to stand up to fuel without swelling.  Can somebody save me the testing time?  Do Harbor Freight o-rings have the right stuff, or do I have to get some other rubber, like Viton, or unobtanium?

Thank you so much, kerryb.

The dimensions with pictures of the digital caliper making the measurements are here:
http://s1038.photobucket.com/albums/a466/midnightridercb350f/Carb%20Fuel%20Pipe%20Dimensions/
I made notes on each picture.
I can also copy the pictures into the forum if you think that will be better for the thread.
Tell me if you need any other measurements.    

These o-rings come with the Honda carb (gasket/o-ring) kit.  I happen to have some left since I didn't know what they went to when I rebuilt the carbs.  

In the meantime, I am trying to find a way to use a cnc lathe in a lab at the university I graduated from.  A friend of mine worked on it while we were in engineering school (i have an environmental engineering degree - hence no materials or metal lab experience).

Thanks again, brother - and good luck!

[kerryb]

Thanks for the info on the o-rings twotired.  Before I left the house this morning I dropped an o-ring into a cup of fuel.  When I got home from school, I matched it up to another from the same batch.  I guess I won't use HF o-rings on my fuel lines because it had swelled a fair amount. 

If I were trying out this part, I would use Honda o-rings, but come to think of it, I won't be trying out this part.  I don't have those carbs!. 

I looked over the sizes on photobucket (got tired of the pop-up ads) and wondered why the engineers chose those sizes.  They must have been trying to make it tougher to reproduce.  What's wrong with using even mm sizes?  Well this will be a good test of my limited fabricating skills.  I'll let you know how it goes.  Midnightrider watch out for animals crossing the road in the dark and PM me your address so I can send you something that might be useable
wish me luck, kerry

[midnightrider]

kerryb,
I really appreciate your effort regardless of the outcome; no pressure here. 

I am assuming that the measurements that are a few 1/100's mm off of a whole 1/10 mm could be attributed to a combination of digital caliper error ($5 from Harbor Freight), human error, and mishaped specimen (each piece was stuck in it's respective carb).  The total length measurement perplexes me the most though, but you never know what factors may have played into a design - sometimes you just want to get as much overlap of pieces as you can get with what space you have available. 

Thanks again, brother.  PM sent.

 

[kerryb]

Well, here it is.  I hope this works, because as I was finishing it the motor on my lathe quit.  A pop, a bunch of smoke, and a sizzling noise as black goo came out of the capacitor.  Just what I need, something else to repair.

Interesting enough, the diameter is just right to fit my PD carbs from a '78k.  The length is all wrong though so I hope it is correct for yours.  Let me know how well it works, if I need to try again, that is possible.  Maybe I'll get the sizes closer too.

[Kevin400F]

Here's a shot of one I made recently from aluminum, with the proper size O-rings installed.   The center section is a little smaller than OEM, but inconsequential to the function.

[kerryb]

That looks good kevin...better than mine...please tell me, what size are the o-rings.  Are they proportionately beefier in cross-section than the diameter might suggest.  Also a suggestion on finish please.  Should I hit the grooves with 600 grit paper to smooth them out or will the o-rings squish enough to make the seal?   

[midnightrider]

Well, here it is.  I hope this works, because as I was finishing it the motor on my lathe quit.  A pop, a bunch of smoke, and a sizzling noise as black goo came out of the capacitor.  Just what I need, something else to repair.

Interesting enough, the diameter is just right to fit my PD carbs from a '78k.  The length is all wrong though so I hope it is correct for yours.  Let me know how well it works, if I need to try again, that is possible.  Maybe I'll get the sizes closer too.

It looks right to me! Im really sorry to hear about your lathe; I hope that it isn't a big problem.  

That looks good kevin...better than mine...please tell me, what size are the o-rings.  Are they proportionately beefier in cross-section than the diameter might suggest.  Also a suggestion on finish please.  Should I hit the grooves with 600 grit paper to smooth them out or will the o-rings squish enough to make the seal?  

Im not sure the exact size of the o-rings, but I can make measurements if need be.  They come in the OEM Honda carb gasket kits.  I can do the sanding if any needs to be done.

Thanks again, brother. PM sent.