Author Topic: Carb boots/joints  (Read 3659 times)

fret not

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Re: Carb boots/joints
« Reply #20 on: July 20, 2019, 08:30:33 PM »
POD, so what material would you suggest the 'new' parts be molded from? 

One thought I have is regarding the removal of all the old molded material from the base usable parts.  Either a chemical solvent, which would be really nasty toxic stuff, or heat and a wire brush (on a motorized spindle of course).

My first thought is to take a new set and make molds from them, THEN remove all the 'rubber' from the hard parts of an old leaky set and bolt the hard parts into the molds in preparation for casting the new set.  The new material needs to be fuel proof, and remain somewhat flexible through many heat cycles.  Would that silicone tape previously mentioned be a good material?  Does it remain flexible?
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injuhneer

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Re: Carb boots/joints
« Reply #21 on: July 21, 2019, 12:17:26 AM »
The original parts were BUNA-N. Most replacements would be EPDM or Viton. You might get away with a castable urethane for a while.

Silicone in tape or sheet form that I have used doesn't like gasoline.

Also note in my comment that there is a link to parts on ebay. Someone is already remolding these. Clearly injection molded with investment parts.
« Last Edit: July 21, 2019, 12:52:19 AM by injuhneer »
- Mike O
injuhneer
1982 Yamaha XZ550RJ
--------------------------------------------
1975 Honda ST-90 (164cc stroker)
1972 Kaw GT4R
1978 Kaw KM100
2008 KTM 450 SXF

Prophet Of Doom

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Re: Carb boots/joints
« Reply #22 on: July 21, 2019, 02:21:37 AM »
POD, so what material would you suggest the 'new' parts be molded from? 

One thought I have is regarding the removal of all the old molded material from the base usable parts.  Either a chemical solvent, which would be really nasty toxic stuff, or heat and a wire brush (on a motorized spindle of course).

My first thought is to take a new set and make molds from them, THEN remove all the 'rubber' from the hard parts of an old leaky set and bolt the hard parts into the molds in preparation for casting the new set.  The new material needs to be fuel proof, and remain somewhat flexible through many heat cycles.  Would that silicone tape previously mentioned be a good material?  Does it remain flexible?
I really don't know about suitable materials Fret (which is why I'd love someone else to do the hard work). 


Injuneer mentioned Buna-N - that's the same as Nitrile - you can't buy liquid castable nitrile here so that's out.


I think you are bang on about the method.  Perhaps a casting silicone for the mould, as there are a few ridges in there and you'll need some flexibility to get it out.  As for the material itself , perhaps a medium-hard eurethane or casting rubber.  Neither are fully resistant to petroleum, but then again the stock ones aren't either so perhaps a shitty version of nitrile - I don't know.

As for cleaning up the hard parts - perhaps cut off the soft bits with a craft knife, then clean up with a wire wheel.  Just guessing on this.

Where's the fun in buying parts if you can make them?





fret not

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Re: Carb boots/joints
« Reply #23 on: July 21, 2019, 02:34:30 PM »
So far this sounds like an industrial process, not to be done at 'home'.  Besides, since the company in Germany offers a refurbished set including shipping for about $58US who would want to go to the trouble of making them at home?  At least they are available!  I wonder if these parts were used by the factory on any other models.
« Last Edit: July 21, 2019, 02:37:49 PM by fret not »
Retired, on the downhill slide. . . . . . . . still feels like going uphill!

injuhneer

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Re: Carb boots/joints
« Reply #24 on: July 21, 2019, 04:19:08 PM »
So far this sounds like an industrial process, not to be done at 'home'.  Besides, since the company in Germany offers a refurbished set including shipping for about $58US who would want to go to the trouble of making them at home?  At least they are available!  I wonder if these parts were used by the factory on any other models.

Well in a word; yes. Injection molding takes a little doing. I suspect that the components could be cast but the original manufacturing and the current re-manufacturing are injection molded.

I suppose one could make a batch molding system or acquire a small lab extruder and mold. This little Engel looks like it might do the job:

http://www.stopoles.com/used-molding-machines/2006-100-ton-engel-6-5-oz-tiebar-less-injection-molding-machine/113668

One of the problems we would have here in the USA with cast urethane is the presence of ethanol in fuel. Urethane(s) resist gasoline but only conditionally resist ethanol. I'd have to do a bit  more research to determine the efficacy of cast urethane.



- Mike O
injuhneer
1982 Yamaha XZ550RJ
--------------------------------------------
1975 Honda ST-90 (164cc stroker)
1972 Kaw GT4R
1978 Kaw KM100
2008 KTM 450 SXF

injuhneer

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Re: Carb boots/joints
« Reply #25 on: August 03, 2019, 11:08:03 PM »
So far this sounds like an industrial process, not to be done at 'home'.  Besides, since the company in Germany offers a refurbished set including shipping for about $58US who would want to go to the trouble of making them at home?  At least they are available!  I wonder if these parts were used by the factory on any other models.

I ordered a set of these carb mounts. I will report back when they arrive and after they are installed.
- Mike O
injuhneer
1982 Yamaha XZ550RJ
--------------------------------------------
1975 Honda ST-90 (164cc stroker)
1972 Kaw GT4R
1978 Kaw KM100
2008 KTM 450 SXF

injuhneer

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Re: Carb boots/joints
« Reply #26 on: November 10, 2019, 09:34:03 PM »
The carb boots/mounts arrived. Finally a little spare time came my way so I started into the carbs on the XZ yesterday.

First the removal of the carbs and intake -


Mount the new boots -


Give the carbs a thorough cleaning -




And of course made sure all secondaries and progressions are clean -


« Last Edit: November 10, 2019, 09:38:51 PM by injuhneer »
- Mike O
injuhneer
1982 Yamaha XZ550RJ
--------------------------------------------
1975 Honda ST-90 (164cc stroker)
1972 Kaw GT4R
1978 Kaw KM100
2008 KTM 450 SXF

motoracer8

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Re: Carb boots/joints
« Reply #27 on: February 16, 2020, 02:26:58 PM »
 The front carb boot is still available from Yamaha as they use it on something else. It can also be used on the rear cyl.
83 Vision and 11 others, Japanese, German and British

injuhneer

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Re: Carb boots/joints
« Reply #28 on: February 18, 2020, 10:42:36 AM »
Thus far I am pleased with the quality and fit of these replacement items.

I have them installed and have operated with them for about 12 hours of running time. That isn't much but it is a start.

- Mike O
injuhneer
1982 Yamaha XZ550RJ
--------------------------------------------
1975 Honda ST-90 (164cc stroker)
1972 Kaw GT4R
1978 Kaw KM100
2008 KTM 450 SXF