Author Topic: Weber carb set-up (Read 151667 times)

voxonda · « **Reply #75 on:** December 29, 2010, 12:14:52 AM »

Quote from: scottly on December 28, 2010, 05:47:17 PM

Rob, you may want to mock up the carbs on the bike, to make sure the 2 1/4" stacks will clear. The OD of the bell end is 64.9 mm.

Blue, that is one serious grenade, I mean, VW motor!!

Thanks, that is what I intend to do. I'll keep you posted.

Cheers.

voxonda · « **Reply #76 on:** December 29, 2010, 06:47:07 AM »

Today adapted the manifold to accept the carb's, rubbers and throttle linkage. Had to remove a small piece af the manifold and remove some material so the linkage runs free. Think it worked out well. Have to mill a small piece to take the throttle cable adjusting bolt and ready. It is a bummer to put on a head when assembled. Have to see if the carbs hit the rails so have to see if the housing can be altered somewhat.

Think it does look neat.

Tintop · « **Reply #77 on:** December 29, 2010, 02:54:05 PM »

Very nice Rob.

Now I really want to try this. Going to have to start looking for a project.

fishhead · « **Reply #78 on:** December 30, 2010, 02:16:23 AM »

Here's a pic of my carbs installed (different carbs, different manifold).

The DCOE's/RC Eng. manifold comes close to the frame rail. In looking at the pics of your carbs, they look to be taller than my DCOE's. The carbs should be/need to have a brace at the carbs/manifold to take the weight off of the rubber manifolds(these carbs are heavy). On my set, I made a brace that bolted to the frame rail and to the center of the manifold. My throttle cable was mounted to the brace I made(my set originally had 2 cables on each end of the carbs).

voxonda · « **Reply #79 on:** December 30, 2010, 05:32:19 AM »

Thanks Fishhead,

Yes am planning to make a brace, using the mountholes for the stack attachment, coupling both carb's and the framerails. Will show when I have it done. The carbs are high, but thinking of reducing that height by milling a few millimetres off, and make new plugs that fall into the top cover. Have to take a closer look after a mock up on frame/engine.

Rob

voxonda · « **Reply #80 on:** December 30, 2010, 07:26:55 AM »

Today I received an article about Webers on a 750 from: Wheel Specialties in Anaheim California. Anyone familiair with that firm? Do not know if they even exist today.

voxonda · « **Reply #81 on:** June 05, 2011, 08:22:56 AM »

Finally came around to mount the Dellorto's on the Japauto replica, to see if I have to change anything. Well since the Dellorto's are even higher than the Weber's I ran into 'trouble'. The housing were the choke is, is way too high. So I milled of a few millimetres to gain some room to have the carb's fitted without having to put stress on the intake rubbers. Now I have enough room, but the choke will not work anymore.

Plan is to shut the choke completely and since this is no daily runner, but a trackbike, will use some plugs with a tiny hole in them to use as a 'choke'. Hope that works, maybe anyone has suggestion?

Still think it looks good.

All this is to eventually switch over to a 'new' cyl. head in order to get rid of this one with the broken rib's.
Thinking of using a 63b cam, lightened rocker arms with Ti nuts, bronze guides and bigger inlet valves.

Rob

scottly · « **Reply #82 on:** June 05, 2011, 09:21:03 AM »

I don't use the "chokes" on the Webers for cold starts; not needed with accelerator pumps. Just feather the throttle a bit until warmed up...

754 · « **Reply #83 on:** June 05, 2011, 09:25:51 AM »

Twist the throttle a couple times, should prime it enough to start.. Will run a bit rough at first, but should stay running with hand on throttle. If its over 50 degrees, You may not miss the chjoke.
Keep track of your jetting please. I have a pair of Dell's that have not been on a bike motor yet

voxonda · « **Reply #84 on:** June 05, 2011, 09:46:02 AM »

Thanks, that is encouraging news. So will lower the second cover also, and put a 'stop' on the choke pistons.

Cheers, Rob

MRieck · « **Reply #85 on:** June 05, 2011, 11:14:44 AM »

Quote from: voxonda on June 05, 2011, 08:22:56 AM

Finally came around to mount the Dellorto's on the Japauto replica, to see if I have to change anything. Well since the Dellorto's are even higher than the Weber's I ran into 'trouble'. The housing were the choke is, is way too high. So I milled of a few millimetres to gain some room to have the carb's fitted without having to put stress on the intake rubbers. Now I have enough room, but the choke will not work anymore.

Plan is to shut the choke completely and since this is no daily runner, but a trackbike, will use some plugs with a tiny hole in them to use as a 'choke'. Hope that works, maybe anyone has suggestion?

Still think it looks good.

All this is to eventually switch over to a 'new' cyl. head in order to get rid of this one with the broken rib's.
Thinking of using a 63b cam, lightened rocker arms with Ti nuts, bronze guides and bigger inlet valves.

Rob

Absolutely. Be sure to bore the intake seat to .9 of the valve OD and blend it into the bowl Rob. It makes a nice difference

voxonda · « **Reply #86 on:** June 05, 2011, 12:22:46 PM »

Hey Mike,

Such a shame I cant bring the head your way. Could use your 'magic-touch' on the head.

Cheers, Rob

PS. Your Ti-nuts are shipped last Friday. Hoping they will arrive within a few days.

Tintop · « **Reply #87 on:** June 05, 2011, 03:48:16 PM »

Rob, I've never used the chokes in Webers, usually removed everything. As 754 mentioned, with the accel pump they aren't really needed. Even at 40F, the Lotus would fire with 3 full presses on the accelerator.

MRieck · « **Reply #88 on:** June 05, 2011, 04:57:08 PM »

Quote from: voxonda on June 05, 2011, 12:22:46 PM

Hey Mike,

Such a shame I cant bring the head your way. Could use your 'magic-touch' on the head.

Cheers, Rob

PS. Your Ti-nuts are shipped last Friday. Hoping they will arrive within a few days.

I have heads here Rob.

voxonda · « **Reply #89 on:** June 06, 2011, 09:25:55 AM »

[/quote]
I have heads here Rob.

[/quote]

PM to you, Mike.

scottly · « **Reply #90 on:** May 31, 2012, 11:41:24 PM »

Bumping this thread for shiny.

Lostboy Steve · « **Reply #91 on:** June 01, 2012, 10:13:39 AM »

lol I love it. How is tuning these things? Big improvement in power? Also, isnt that a lot of weight on those rubbers?

Tintop · « **Reply #92 on:** June 03, 2012, 06:33:30 PM »

Finally got to run the XS (with Weber, and 750 kit) powered sidecar. So I thought I would post the initial jetting. Keep in mind its a full race engine, so being able to idle at a stop light is not a consideration. This is preliminary, hoping to get it on a dyno before the next race weekend.

Venturi - 4.5
Chokes - 34
Idles - 45F9
Airs - 175
Mains - 140
Tubes - F9
Accel - 50
Bypass - .50
Needle - 175

scottly · « **Reply #93 on:** June 06, 2012, 05:34:06 PM »

Quote from: twistedengineering on June 01, 2012, 10:13:39 AM

Also, isnt that a lot of weight on those rubbers?

The rear of the carbs should be supported, and should not just hang off the rubbers. (Even stock carbs with pods should have supports added; the airbox served as the rear support.

)

scottly · « **Reply #94 on:** June 06, 2012, 05:40:23 PM »

Quote from: Tintop on June 03, 2012, 06:33:30 PM

Finally got to run the XS (with Weber, and 750 kit) powered sidecar. So I thought I would post the initial jetting.

So just how close do you think you are? Any major issues, or are you pretty much in the ball-park?

Tintop · « **Reply #95 on:** June 06, 2012, 06:55:50 PM »

I think I'm in the ballpark. Top end seemed very close. Did a high end plug chop & the insulators were tan from bottom to about half way up. The chokes may be a bit big though. Hard to get any kind of decent idle, even with the stacks on it. I'm going to recheck the ignition timing, then rebalance the carb. I did try going up on the mains, but think I should have gone the other way. Also have F16 & F11 emulsions to try. If possible I'd like to get it on a dyno before the next race, that would sort everything out.

Tintop · « **Reply #96 on:** June 07, 2012, 01:46:03 PM »

Just a FYI regarding Weber books. I've had these two for over 20+ years. The John Passini (small green one) is excellent. It covers theory / tuning / maintenance. The Haynes one is also good as it covers all the Weber versions. I used the two to come up with my initial jetting for the sidecar. I'm not sure if either is still in print, the Passini book was last published in 1992.

scottly · « **Reply #97 on:** June 07, 2012, 05:39:48 PM »

Quote from: Tintop on June 06, 2012, 06:55:50 PM

The chokes may be a bit big though. Hard to get any kind of decent idle, even with the stacks on it.

The chokes shouldn't affect the idle much. How far out are your idle mixture screws?

I have the same Haynes book, but have never seen the Passini one. I would be interested to read the tuning section; any chance you can scan those pages and post them?

Bill/BentON Racing · « **Reply #98 on:** June 07, 2012, 06:12:27 PM »

Quote from: scottly on June 06, 2012, 05:34:06 PM

Quote from: twistedengineering on June 01, 2012, 10:13:39 AM
Also, isnt that a lot of weight on those rubbers?
The rear of the carbs should be supported, and should not just hang off the rubbers. (Even stock carbs with pods should have supports added; the airbox served as the rear support. )

As Scottly said,use the the airbox tabs for rear support,little rubbers with 6mm studs.Them carbs not ltwt!!!
Vox,you bringing back old memories! Thanks,Bill

754 · « **Reply #99 on:** June 07, 2012, 06:35:41 PM »

Found some nice info online by I think Micky Lauria of Inglese..
Stuff like if you got to go bigger than this to clear up the *** jet needs bigger.
I at one time played a lot with them up at outr1/8 mile strip.. think I gained 3/10 or so, on a bike that ran fine already.. that would be 4 tenths or so in the 1/4..

Although there are more circuits, it seemed easy, and wwwwAAAAYYYYYYYYYYY faster to jet than the stock ones..

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Author Topic: Weber carb set-up (Read 151667 times)