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AMAL R.928/17 pilot jet. #490471
05/16/13 8:00 pm
05/16/13 8:00 pm
Joined: Feb 2007
Posts: 2,231
Atlanta, GA USA
S
Semper Gumby Offline OP
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Semper Gumby  Offline OP
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Joined: Feb 2007
Posts: 2,231
Atlanta, GA USA
In the 1971 Thunderbolt, what was the pilot jet size?

My parts book does not list it.

"I've got the Ethanol Blues"

So I been broken for about two weeks with a mending hand. Today i decide to kick the bikes to life. The BMW cranks up and runs idling just fine. I have a hell of a time starting the Thunderbolt and then even after it gets going it doesn't want to idle. So this gets me thinking (can I put a Bing on the Thunderbolt) what is the difference. Cause the Beemer has been sitting for three weeks and the BSA only for two.

I think the difference is that the Bing jets are sitting down in fluid not getting gummed up while the pilot jet on the AMAL is high up out of the fluid where it gets gummed by drying fuel.

So first chance I get I'm going to drill out that pilot jet and screw in one on the bottom of the carb body. It will still be high up but at least I can get to it to clean it.

Or put an pilot jet in the bottom of the float bowl...hmmmmm.




Last edited by Semper Gumby; 05/16/13 8:03 pm.

Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
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Re: AMAL R.928/17 pilot jet. [Re: Semper Gumby] #490498
05/16/13 11:49 pm
05/16/13 11:49 pm
Joined: Jul 2009
Posts: 3,549
Vic. Australia
P
Pete R - R.I.P. Offline
In Remembrance
Pete R - R.I.P.  Offline
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Joined: Jul 2009
Posts: 3,549
Vic. Australia
If you drill the pressed in pilot jet,you would need a 20cc screw-in pilot jet.The bike would idle better if you don't drill the pilot jet but just clean it with a 0.016" wire,#78 drill,or 0.4 mm drill.
The difference in idling quality isn't huge.

Re: AMAL R.928/17 pilot jet. [Re: Pete R - R.I.P.] #490501
05/17/13 1:04 am
05/17/13 1:04 am
Joined: Feb 2007
Posts: 2,231
Atlanta, GA USA
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Semper Gumby Offline OP
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Semper Gumby  Offline OP
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Joined: Feb 2007
Posts: 2,231
Atlanta, GA USA
I know a place where I can get a #78 drill bit -- tomorrow.

Thanks.

Last edited by Semper Gumby; 05/17/13 1:04 am.

Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
Re: AMAL R.928/17 pilot jet. [Re: Semper Gumby] #490536
05/17/13 6:17 pm
05/17/13 6:17 pm
Joined: Feb 2007
Posts: 2,231
Atlanta, GA USA
S
Semper Gumby Offline OP
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Semper Gumby  Offline OP
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Joined: Feb 2007
Posts: 2,231
Atlanta, GA USA
HA - so I get the #78 drill bit $1.69 and an exacto Pin holder $6.99 and guess what - they don't reach the jet.

Anybody know where I can source a longer #78 drill bit?

Found one!

http://drillsandcutters.com/dwdtl78taperlength-2.aspx

Last edited by Semper Gumby; 05/17/13 6:25 pm.

Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
Re: AMAL R.928/17 pilot jet. [Re: Semper Gumby] #490539
05/17/13 6:35 pm
05/17/13 6:35 pm
Joined: Jan 2007
Posts: 252
Atlanta, Georgia
Atlanta Bonnie Offline
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Posts: 252
Atlanta, Georgia


Bruce


Re: AMAL R.928/17 pilot jet. [Re: Semper Gumby] #490541
05/17/13 6:56 pm
05/17/13 6:56 pm
Joined: Feb 2008
Posts: 4,338
New Jersey USA
Tridentman Offline

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Tridentman  Offline

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New Jersey USA
You dont need a longer drill bit--just stick the normal length drill bit into a piece of the flexible tube supplied with cans of WD40.
Then then you are sure that you have the drill bit through the pilot jet apply a small piece of tape such as masking tape in line with the outside of the carb body. Then next time you will know when you are correctly through the pilot jet----=when the edge of the tape lines up with the outside of the carb body.
HTH

Re: AMAL R.928/17 pilot jet. [Re: Tridentman] #490551
05/17/13 9:01 pm
05/17/13 9:01 pm
Joined: Feb 2007
Posts: 2,231
Atlanta, GA USA
S
Semper Gumby Offline OP
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Semper Gumby  Offline OP
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Joined: Feb 2007
Posts: 2,231
Atlanta, GA USA
SUCCESS!

That is what I ended up doing. Glued the bit into a pipe from my WD40 can...didn't think of the tape part though. With ethanol I'm sure there will be a next time.

The Thunderbolt idles again. The AMAL can stay.

Hi Bruce! Yes that is what I needed but mine is red and almost cost as much in glue gas and bits (oh and a bit of tape). Are you in Blowing Rock or still in Atlanta?

Last edited by Semper Gumby; 05/17/13 9:07 pm.

Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training

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