vaccume advance question

[GLoweVA]

I don't think going too deep is so much the issue as long as the butterfly is turned out of the way. All that's required there is to rotate the throttle a little and hold it open some how.
Slow and steady wins the race here.
Like Nate says, a small pilot hole first then find the right insert you're going to use and then drill out the hole to match the size of the insert.
Once you get the pilot hole drilled, you'll know how thick the carb body is and then you can go shopping for an insert that won't go too deep. (too deep interferes with the butterfly)
(I'd have to look again at my carbs, but I think #2 carb body has a small recess at that location or the butterfly has a small notch. I can't remember exactly, but I do remember #2 being a little different than the other 3)
I would think a threaded insert would be better than a press in one. (more secure, but you'd have to tap the hole of course)
I'll pull my carbs off my SG and snap a pic late this afternoon. (unless someone else beats me to it. )

Edit: I found a crappy pic in the tech forum:

Notice the notch in the butterfly. I suppose it's there so the insert doesn't get 'restricted' by the butterfly when it's fully shut.

Alright, time for some of you gurus to chime in here. He's got XJ carbs, so they probably don't have the same #2 butterfly, so If he does insert a vac port, do you think it'll still work? or should he maybe try to position the hole a little more forward towards the intake to avoid this possible issue?

[natemoen]

My point about going to deep was so that you don't drill the large hole all the way through the body. Just deep enough so you have enough for tge nipple to engage but still deep enough so that there is enough meat in the small home to adequately restrict the vacuum.

[motoman]

Originally Posted by natemoen

My point about going to deep was so that you don't drill the large hole all the way through the body. Just deep enough so you have enough for tge nipple to engage but still deep enough so that there is enough meat in the small home to adequately restrict the vacuum.

Have to use an inline restricter either way Nate, and hopefully it will be ported vacuum, not manifold vacuum. Restriction doesn't change vacuum, just restricts impulses from cyls. Vacuum is constant.

[Nightengale]

Originally Posted by motoman

Have to use an inline restricter either way Nate, and hopefully it will be ported vacuum, not manifold vacuum. Restriction doesn't change vacuum, just restricts impulses from cyls. Vacuum is constant.

tc had suggested that i put a piolt jet in the line.

[natemoen]

The tiny hole in the carb body is all that is used in the OEM carbs, there is nothing else in line. So if you can measure the depth of the small hole in the original carbs and then recreate that in the other carbs, you should be pretty close.

The placement of the hole is what makes it ported/metered vacuum, the size of the hole is what restricts impulses.

[motoman]

Originally Posted by Nightengale

tc had suggested that i put a piolt jet in the line.

That'll work, or if that is too small for the inside hose size use a Kihen carb jet, any size.

[Nightengale]

does anyone have a pic of the exact location of the hole in relation to the butterfly valve

[GLoweVA]

John, here's some pics I snapped while over at TC's.

Here you can see the hole just by the butterfly where the notch is.
Note that the hole size is very small. Like the same size as the pilot holes.
Thus the restriction that others are talking about.



Here you can see the hose nipple on the outside, so like someone said, if you do drill it out, make sure you don't go too deep with the larger diameter bit.

[Nightengale]

[quote=GLoweVA;371791]John, here's some pics I snapped while over at TC's.

Here you can see the hole just by the butterfly where the notch is.
Note that the hole size is very small. Like the same size as the pilot holes.
Thus the restriction that others are talking about.


thanks george, i havent had any time to mess with the bike lately, my father passed and i have not been too motivated to do any thing.

[Rasputin]

My Condolences on your loss John. At this time everyone understands how you feel to a point. You will work on the bike again when the time is right for you. Take care.

[GLoweVA]

John, sorry for your loss, When you're ready, the bike will be waiting for you.
(oh, and we'll be here for you too.)

[DGXSER]

John, Sorry to hear of your loss. Its been 15 years since I lost my father, and I still recall the minute I got the call. It gets better with time, the bike has been here 30 years, it will wait till your ready.

[Nightengale]

i am going to try and get back on working on the bike, to try to get my mind off things, because when i am working on the bike the bike is all i think of.
thanks again guys. i will update once i get back into it.