FJowners.com

General Category => Maintenance => Topic started by: Dads_FJ on October 28, 2016, 05:13:52 PM

Title: Diaphragm hole diameter question
Post by: Dads_FJ on October 28, 2016, 05:13:52 PM
Quick question... Does anybody know the correct factory size of this hole?  Mine measures .140" or 9/64" but I believe it was drilled out as part of a 'jet-kit' installation by the PO.  I've struggled with cold bloodlessness and a flat spot/hiccup off idle for the entire time I've owned it, almost 20 years...  I've replaced all the jets to factory but went with a larger pilot (I forget what the value).  It deserves better...

(http://fjowners.com/gallery/10/2200_28_10_16_4_06_01.jpeg)
Title: Re: Diaphragm hole diameter question
Post by: Flynt on October 28, 2016, 05:21:28 PM
Mine are about the same size as the hole in the backing plate (that retains the little spring and needle assy)...  Not precise I know, but should be close enough unless the backing plate has been drilled out as well?

Frank
Title: Re: Diaphragm hole diameter question
Post by: racerrad8 on October 28, 2016, 05:34:27 PM
Those have definitely been drilled out the stock hole I measured is  0.085" (for the flat slide)

Robert
Title: Re: Diaphragm hole diameter question
Post by: Dads_FJ on October 28, 2016, 10:11:44 PM
Thanks Randy, much appreciated.   :drinks:
Title: Re: Diaphragm hole diameter question
Post by: racerrad8 on October 28, 2016, 10:16:13 PM
Quote from: Dads_FJ on October 28, 2016, 10:11:44 PM
Thanks Randy, much appreciated.   :drinks:

John, I can't take the credit for that info, I'm away from the shop until next week.

That's all Robert.

Randy - RPM
Title: Re: Diaphragm hole diameter question
Post by: Dads_FJ on October 28, 2016, 10:18:53 PM
Duh, thanks and cudos to Robert!  :drinks:
Title: Re: Diaphragm hole diameter question
Post by: racerrad8 on November 01, 2016, 12:54:09 PM
John,

Robert and I were talking this morning and he recalled one other thing. You used those JBM(?) replacement diaphragms on your carbs. If the needle is not in the design position for the RPM/fuel range that might be the cause of the stumble.

Randy - RPM
Title: Re: Diaphragm hole diameter question
Post by: Dads_FJ on November 01, 2016, 01:09:54 PM
Quote from: racerrad8 on November 01, 2016, 12:54:09 PM
John,

Robert and I were talking this morning and he recalled one other thing. You used those JBM(?) replacement diaphragms on your carbs. If the needle is not in the design position for the RPM/fuel range that might be the cause of the stumble.

Randy - RPM

Thanks for the info Randy - I do use the JBM diaphragms and did secure them in place on the slide.  I verified they did not rotate and the hole is facing toward the engine.

With that:  I'm in the market for a set of four slides - even if the rubber diaphragms are worn and have holes etc...

Thanks - John

Title: Re: Diaphragm hole diameter question
Post by: racerrad8 on November 01, 2016, 01:54:13 PM
Quote from: Dads_FJ on November 01, 2016, 01:09:54 PM
Quote from: racerrad8 on November 01, 2016, 12:54:09 PM
John,

Robert and I were talking this morning and he recalled one other thing. You used those JBM(?) replacement diaphragms on your carbs. If the needle is not in the design position for the RPM/fuel range that might be the cause of the stumble.

Randy - RPM

Thanks for the info Randy - I do use the JBM diaphragms and did secure them in place on the slide.  I verified they did not rotate and the hole is facing toward the engine.

With that:  I'm in the market for a set of four slides - even if the rubber diaphragms are worn and have holes etc...

Thanks - John

John,

We need to get your carbs changed over to curved slides and shrouded e-tubes.

Randy - RPM
Title: Re: Diaphragm hole diameter question
Post by: Dads_FJ on November 01, 2016, 02:42:26 PM
Quote from: racerrad8 on November 01, 2016, 01:54:13 PM
Quote from: Dads_FJ on November 01, 2016, 01:09:54 PM
Quote from: racerrad8 on November 01, 2016, 12:54:09 PM
John,

Robert and I were talking this morning and he recalled one other thing. You used those JBM(?) replacement diaphragms on your carbs. If the needle is not in the design position for the RPM/fuel range that might be the cause of the stumble.

Randy - RPM

Thanks for the info Randy - I do use the JBM diaphragms and did secure them in place on the slide.  I verified they did not rotate and the hole is facing toward the engine.

With that:  I'm in the market for a set of four slides - even if the rubber diaphragms are worn and have holes etc...

Thanks - John

John,

We need to get your carbs changed over to curved slides and shrouded e-tubes.

Randy - RPM


You lost me I'm afraid.  The slides are factory OEM and I've replaced all the jets and emulsion tubes which I believe were purchased from RPM.  If I sink any more $$ in these carbs I might consider sending my bike to Kansas for an EFI upgrade :)
Title: Re: Diaphragm hole diameter question
Post by: FJmonkey on November 01, 2016, 03:38:13 PM
Quote from: Dads_FJ on November 01, 2016, 02:42:26 PM
You lost me I'm afraid.  The slides are factory OEM and I've replaced all the jets and emulsion tubes which I believe were purchased from RPM.  If I sink any more $$ in these carbs I might consider sending my bike to Kansas for an EFI upgrade :)

If you are getting new slides anyway then get the modern round bottom slides with shrouded e-tubes. They will work with your carb bodies.
Title: Re: Diaphragm hole diameter question
Post by: Dads_FJ on November 01, 2016, 06:23:08 PM
I have these e-tubes.

http://rpmracingca.com/proddetail.asp?prod=Carb%3A50H-14941-92-00&cat=24 (http://rpmracingca.com/proddetail.asp?prod=Carb%3A50H-14941-92-00&cat=24)

Are these the shrouded type?
Title: Re: Diaphragm hole diameter question
Post by: racerrad8 on November 01, 2016, 07:02:10 PM
Not according to my records.

The carb kits you purchased will have the non-shrouded e-tubes.

Randy - RPM