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Stupid Question - Carb Throttle Disk

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steve_wood
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Stupid Question - Carb Throttle Disk

#1

Post by steve_wood » Sat Oct 18, 2008 2:15 pm

Bike won't idle down. I'm checking everything.

Is this throttle disk installed directly?
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Re: Stupid Question - Carb Throttle Disk

#2

Post by Cotten » Sat Oct 18, 2008 2:38 pm

Yes.

Is the daylight around it excessive when fully closed?

If that's a modern repop disc, we may have to suspect something about it.

....Cotten

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Re: Stupid Question - Carb Throttle Disk

#3

Post by steve_wood » Sat Oct 18, 2008 4:11 pm

I would say that the clearance between the disk and the barrel is 0 in some spots and maybe .001 to .002 in others. It is a repop, but it's better than the old disk that was on there before.

I did find a vacuum leak. What I thought was a pinhole leak was actually a cluster of about 5 pinhole leaks. I suspect that is the reason for poor idle, but I wanted to check the carb while it was off the machine. The idle tubes were clear, the liberty float was free and and at about .270 clearance.

Thoughts?

steve

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Re: Stupid Question - Carb Throttle Disk

#4

Post by john HD » Sat Oct 18, 2008 8:30 pm

is the washer under the spring on the idle needle present?

john

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Re: Stupid Question - Carb Throttle Disk

#5

Post by steve_wood » Sat Oct 18, 2008 10:03 pm

You mean that special washer with a raised middle part? 27345-41? If that's what you mean, then yes.

steve

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Re: Stupid Question - Carb Throttle Disk

#6

Post by john HD » Sat Oct 18, 2008 11:37 pm

yes that is the one i was thinking of.

any chance your bike's ignition is way too advanced?

john

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Re: Stupid Question - Carb Throttle Disk

#7

Post by steve_wood » Sat Oct 18, 2008 11:58 pm

Hmmmmm... I suppose anything is possible. But, I retard it to start, and when it catches, it runs a little roughly until I advance the timing. Kinda seems like the timing is correct. I haven't had a chance to strobe it to check.

steve

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Re: Stupid Question - Carb Throttle Disk

#8

Post by Cotten » Sun Oct 19, 2008 3:19 am

Steve!

Did you seal those pinhole leaks?

No leaks are acceptible.

....Cotten

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Re: Stupid Question - Carb Throttle Disk

#9

Post by steve_wood » Sun Oct 19, 2008 4:13 am

Yes, I sealed them, but only as a troubleshooting temporary fix. Although J Precision did exactly what I told them to do, these pinholes leaks were unknown to both me and him. And the other head has developed an oil leak that is new. I have another set of much better heads currently being worked on by head hog. I'm just trying to get the rest of the bike dialed in while i wait. In any case, the patch will hold enough to start the bike and see if it fixes the idle problem, but this engine configuration will never leave the shop.

steve

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Re: Stupid Question - Carb Throttle Disk

#10

Post by steve_wood » Sun Oct 26, 2008 2:33 pm

The bike now idles down. It was the pin hole leaks.

Just goes to show; the experts keep emphasizing the importance of eliminating vacuum leaks and us neophytes would best take notice.

Thanks to all!

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Re: Stupid Question - Carb Throttle Disk

#11

Post by 108 » Thu Oct 30, 2008 9:07 pm

Steve Wood, Where were the pin holes you found located ?

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Re: Stupid Question - Carb Throttle Disk

#12

Post by steve_wood » Thu Oct 30, 2008 9:26 pm

This is another head, not the one in question, but useful for showing where they were:
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Re: Stupid Question - Carb Throttle Disk

#13

Post by 108 » Fri Oct 31, 2008 4:51 am

Steve Wood, Thanks for the pic. Do you think they were holes caused by corrosion or casting porosities that have always been there ?

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Re: Stupid Question - Carb Throttle Disk

#14

Post by steve_wood » Fri Oct 31, 2008 9:10 am

Porosities.

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Re: Stupid Question - Carb Throttle Disk

#15

Post by Cotten » Fri Oct 31, 2008 12:13 pm

That is also an area that is heavily stressed when hardened seats are installed. Proximity to the headbolt insert stresses it in yet another direction when torqued.

The worst possible scenario would be if it also leaks beneath a seat insert into the combustion chamber.

....Cotten

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