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Ironhead Sportster Motorcycle Talk (1957-1985) For all those that wanna talk about Ironhead Sportster Motorcycles

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carb, gaskets, idle, spacer, super b

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  #1  
Old 7th August 2019
staniel's Avatar
staniel staniel is offline
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Question S&S Super B installation & setup - did I do this right?

I am experiencing the symptoms of an air leak, yet when I spray the carb all over to check, I can't find any leaks. I have a stock 1971 XLCH. When I got it, it only ran with the enricher on.

Now it will start on the first kick (after priming of course) but it's idling high (~2000rpm) and after a minute or two the rpm starts to ramp up until the bike dies. Then it doesn't start unless I let it sit for like half an hour. If i give it gas when it's idling, it dies. When I check the plugs after it dies, they are dry. This suggests an air leak - right?? It only works with the enricher on.

It has a 70 main jet and a 295 intermediate jet which from what I've read is a pretty good combination. The idle mixture screw is turned 1.5 turns. It has the O-ring manifold which I believe I have installed correctly.

There is a plastic spacer about 1" thick between the manifold and the carb. There are 2 asbestos gaskets on either side of the spacer. Do I need this plastic spacer? I can't find any replacement gaskets for this part. It doesn't appear to be leaking, but if I have an air leak anywhere, it's worth changing all the gaskets.

The O-ring on the carb body appears to be in good condition. The butterfly valve doesn't have any burrs on it that are causing it to hang up. The throttle shaft moves freely. A coworker suggested that since I can't find an air leak, maybe it is leaking at the throttle shaft bushing. Has anyone had that problem before?

I also don't have a support bracket, but the engine does not react when I wiggle the carb when it's idling.

Is my carb installed/setup correctly? I'm confused about that spacer since if you were to buy a carb kit, it doesn't come with any spacers.
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  #2  
Old 7th August 2019
Iron Mike Iron Mike is online now
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Throttle shaft bushing leak is common on a well used B.
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  #3  
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That's good news since I have a carb rebuild kit coming in.

What about the spacer? I've not been able to find any spacer gaskets so I am wondering if I need the spacer in the first place.
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  #4  
Old 7th August 2019
gpydeski gpydeski is offline
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Quote:
Originally Posted by staniel View Post
That's good news since I have a carb rebuild kit coming in.

What about the spacer? I've not been able to find any spacer gaskets so I am wondering if I need the spacer in the first place.
I run a super e. I think you might want to try the s&s spacer between the carb and manifold. Also are you running the s&s manifold or the stock Harley manifold. There is a size difference between the two.
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Old 7th August 2019
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Quote:
Originally Posted by gpydeski View Post
I run a super e. I think you might want to try the s&s spacer between the carb and manifold. Also are you running the s&s manifold or the stock Harley manifold. There is a size difference between the two.
Hmm, I'm not sure. The only markings on the manifold are "27021-71A"

Does the "71A" refer back to the fact that it's a 71 XLCH maybe? Meaning that it is the Harley manifold?
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Old 7th August 2019
gpydeski gpydeski is offline
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Quote:
Originally Posted by staniel View Post
Hmm, I'm not sure. The only markings on the manifold are "27021-71A"

Does the "71A" refer back to the fact that it's a 71 XLCH maybe? Meaning that it is the Harley manifold?
The super e ones have s&s on the manifold where the two sides meet
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when the bike dies, have you pulled the bowl screw to see if there is gas in the bowl?

It seems odd to me that the bike wouldn't run for a half hour if it only was a carb air leak.

Just trying to keep it simple.
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Quote:
Originally Posted by Pickss View Post
when the bike dies, have you pulled the bowl screw to see if there is gas in the bowl?

It seems odd to me that the bike wouldn't run for a half hour if it only was a carb air leak.

Just trying to keep it simple.
There is gas in the bowl after it dies. And the plugs are dry so I've struggled to understand why it doesn't want to start up again.
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Also, I was thinking about the S&S vs. the OEM manifold. It makes sense to me that the OEM would work fine with the S&S carb since I feel like the more critical interface is at the cylinders.

I still don't know what the purpose of the plastic spacer is. I think I read that it's for insulation, but since the manifold and the carb are both aluminum, heat expansion shouldn't be an issue.

Can I ditch the plastic spacer?
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I’m hoping you bought the genuine S&S rebuild kit.
My experience with the aftermarket kits wasn’t good. Especially the idle mix screw.

Yes, I had shaft area leaks and this is what I did...






My carb was 30+ years old and had seen lot of use . I was installing a new S&S kit but decided to do an upgrade.
You counterbore each side a few thou less than the o-ring thickness so it sits a little proud.
These are 1/4 x 3/8 o-rings from a HF&T Kit.
Then use a couple 1/4 I’d SS washers with a good synthetic grease like Super-Lube.
The return spring is on one side and you position the throttle lever on the other side so the washers just pinch the o-rings but still allow proper throttle movement. It solved my leak problems and can be easily maintained.

*Don’t run one of those clear in-line fuel filters. Use a Russell sintered filter instead.
*Check your petcock for proper flow. Maybe one or the other ^ are plugged and that’s your half hour wait.
*Make sure when you have your float bowl upside down that the leading edge of the float is 1/32” in from the bowl surface.
*Check the enrichener for proper assembly and air cleaner port line up.
*Do a propane leak test around your manifold connections.
*Be sure to have a solid carb support bracket.
*I used a 1/4” insulator/spacer between the S&S manifold and carb on mine.

What ignition type are you running? Possibly a bad coil or condenser.

Good luck. This is the right place to get this figured out
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