Author Topic: Weber carb set-up (Read 151675 times)

scottly · « **Reply #125 on:** July 30, 2012, 07:58:26 PM »

Here is a pic of the MPD; notice the longer runners. The inside is a smooth taper, similar to a velocity stack.

Retro Rocket · « **Reply #126 on:** July 31, 2012, 12:07:22 AM »

Scott, My manifold has a smooth transition from front to back, its that smooth i had to measure either side to make sure they weren't the same ID....

Tintop · « **Reply #127 on:** July 31, 2012, 01:23:18 PM »

One thing I like about the MPD is that it is a single cable, centre pull. Much easier to setup, and balance the carbs.

scottly · « **Reply #128 on:** July 31, 2012, 07:53:03 PM »

Quote from: Retro Rocket on July 31, 2012, 12:07:22 AM

Scott, My manifold has a smooth transition from front to back, its that smooth i had to measure either side to make sure they weren't the same ID....

Pics please!

scottly · « **Reply #129 on:** July 31, 2012, 08:00:25 PM »

Quote from: Tintop on July 31, 2012, 01:23:18 PM

One thing I like about the MPD is that it is a single cable, centre pull. Much easier to setup, and balance the carbs.

Actually, it is a major PITA to sync the carbs; I think the RC would be much easier? The Lynx uses the rubber boots to make the transition from throttle bore to spigot, and looks similar in overall shape to the MPD.
Honestly, it would take back-to-back dyno tests to prove any advantage of one manifold over the other.

Retro Rocket · « **Reply #130 on:** August 01, 2012, 02:10:01 AM »

Quote from: scottly on July 31, 2012, 07:53:03 PM

Quote from: Retro Rocket on July 31, 2012, 12:07:22 AM
Scott, My manifold has a smooth transition from front to back, its that smooth i had to measure either side to make sure they weren't the same ID....
Pics please!

I know, i know....

I took some last night but i can't find the lead that goes from the camera to the puter....

BLUE71TURBO · « **Reply #131 on:** August 01, 2012, 02:33:59 AM »

Quote from: Retro Rocket on August 01, 2012, 02:10:01 AM

Quote from: scottly on July 31, 2012, 07:53:03 PM
Quote from: Retro Rocket on July 31, 2012, 12:07:22 AM
Scott, My manifold has a smooth transition from front to back, its that smooth i had to measure either side to make sure they weren't the same ID....
Pics please!

I know, i know.... I took some last night but i can't find the lead that goes from the camera to the puter....

Some peoples kids.

Old Scrambler · « **Reply #132 on:** August 01, 2012, 02:43:40 PM »

Just so you know...........http://www.ebay.com/itm/Honda-CB750-KO-Weber-Carburetors-Racing-Accessory-1969-1970-1971-1972-rare-etc-/251117331648?pt=LH_DefaultDomain_0&hash=item3a77c264c0

Tintop · « **Reply #133 on:** August 01, 2012, 03:51:55 PM »

Humm.....saved to my watch list. Given that new Weber's are around $380, and Lynx quoted about the same for a new manifold, probably not a bad deal. That said they would need a complete rebuild +++. So you could easily have $1K in them by the time they were on the engine and sorted.

scottly · « **Reply #134 on:** August 01, 2012, 06:31:05 PM »

Thanks Dennis! Now I know why my set-up is such a PITA to synch: I'm missing the proper levers connecting the 2 throttle shafts in the middle. That looks like a 1-piece MPD, and I see it also has sync ports, which mine lacks. I suspect there are no stacks under those filters, just sleeves with a flange at the outer rim. IMHO, these are about as effective as cheap pods at high RPM. Stacks would cost maybe $100? They may be the older made in Italy carbs, but the pics were too low resolution to see any markings at all, much less the fine print.

Tintop · « **Reply #135 on:** August 01, 2012, 07:17:47 PM »

That's the adjustable double linkage in the middle. I've always disconnected it to sync, then reconnect to get both opening at exactly the same time & amount. You can get them from these guys, not expensive. You would want P/N 450048.007 & 450048.005.

http://www.piercemanifolds.com/category_s/181.htm

scottly · « **Reply #136 on:** August 01, 2012, 08:17:35 PM »

Thanks Brian!!! I'll bookmark their website.

754 · « **Reply #137 on:** August 01, 2012, 11:15:25 PM »

the RC manifold could be carved from billet, a piece 2" x $" x 14 inches long.
Or a piece of 1/2 inch plate 4" x 14", then thread in the machined manifold ports made of 2 1/4 ish round bar..

jaguar · « **Reply #138 on:** August 03, 2012, 02:37:56 PM »

Not 100% sure who made this. I like the idea that it uses the stock carb rubbers but the transitions look sharp and I would think it would hurt the performance.

Another unknown for me.
The way the posts go I would think this would offer better flow, but again that might just be me over thinking things.
This also mounts the carbs at a slight angle

Or you could run the "motorcycle" side drafts. They are much smaller/lighter as you can see next to the weber manifolds

Any opinions in the Weber Vs Dellorto Vs Mikuni debate for the 40mm?

Tintop · « **Reply #139 on:** August 03, 2012, 06:56:06 PM »

The 2nd one is the MPD that scotty mentioned. It's also the manifold that is being offered on Ebay with 40DCOE's. Not sure about the 1st one, Lynx?? Agree the sharp bend in 1 & 4 would cause probably tuning issues. Do the holes in the bosses go all the way through? If not, they are probably meant to take rod ends, for a throttle linkage. Those Solex look even smaller than Weber 38's.

754 · « **Reply #140 on:** August 03, 2012, 09:29:12 PM »

The MPD is first version, second one is 2 pce and bolts together in the middle.. My first versionj has been cut, and moves around.
is that first one WEBER pattern or for the smaller Solex Mikunis? Branch sold Solex Mikuni setups.
If that first one is for Webers that makes 6 different types I am aware of..

jaguar · « **Reply #141 on:** August 04, 2012, 06:37:33 AM »

First one is for the 40mm weber carbs
Second is a single piece not a bolt together, I too have normally seen then cut into two pieces.
The last is a branch for the smaller carbs, 32phh

754 · « **Reply #142 on:** August 04, 2012, 09:22:21 AM »

MPD is Jerry Magnussen of MAGNACHARGER fame... for those that were not around back in the day..

jaguar · « **Reply #143 on:** August 04, 2012, 09:27:51 AM »

The smaller solex/mikuni carbs next to 40mm dellortos

754 · « **Reply #144 on:** August 11, 2012, 11:28:30 AM »

I was working on a big bore Honda tracker with webers.. sure is nice to be able to pull out all the jets WITHOUT DRAINING GAS..or making a mess.. Eveything pulls out the topside..

Tintop · « **Reply #145 on:** August 11, 2012, 07:00:51 PM »

Quote from: 754 on August 11, 2012, 11:28:30 AM

I was working on a big bore Honda tracker with webers.. sure is nice to be able to pull out all the jets WITHOUT DRAINING GAS..or making a mess.. Eveything pulls out the topside..

+1, you can change basically everything (jets / float height / chokes) without draining the carb, or even removing it.

johno · « **Reply #146 on:** August 12, 2012, 05:37:49 AM »

Hi guys,
With regard to the manifold pros and cons I went for the RC manifold based on the closest carb centres for a straighter shot at the head ports ( this is achieved by using all ( 4 of) rubber manifolds no's 2 &3 ( no no's 1&4) the manifold also was set up for a simple two cable pull system which is the lightest available.

I have run a set of Dellorto Lynx rubber manifold type on a hot rod roady but was never happy with the pulsing rubbers, I had to use goo to ensure a seal and expected a short life span and I had trouble getting a reliable idle unless I spent time setting it up. The lynx manifolds had the traditional centre adjustment that most Webber manifolds have had for both car and bike systems but RC Eng done away with the centre synch system to get the two carby's closer together. When I purchased the carbs new I had to cut the inside ends off the throttle shafts to get the carbs close enough on the RC Rng manifold.

I can see why RC Eng went to the trouble. The only issue I found out a couple weeks ago was I was mocking the carbs up on a dummy engine in the frame to work out an oil tank clearance when using old stiff rubbers didnt do the hot water , hair dryer trick and while forcing the manifold onto the head snapped the cable adjuster off one side so I will either make up a new manifold from flat bar and tube or make up a linkage system. ( I prefer straight cable pull as the simplest )

You blokes sound like you have it all under control but another tip I use is when setting the carbs up and need to balance them before starting is I remove the progressive jet plug and using a torch, shine in the ram tube , then looking into the progressive jet hole you will see 3 little progression ports and with the light shining in you will see the edge of the butterfly through one of the holes. Adjust both carb butterflys to the same jet hole and they will be almost spot on, then adjust both idle adjusters the same to get desired RPM , recheck butterfly position after you have the idle to your liking.

Looooove those pumps man

ciao Johno

754 · « **Reply #147 on:** August 12, 2012, 07:46:58 AM »

Is that bar at the top of pic, to open the throttles together?

A long time ago at a place called Drag Bike Engineering (think thats the name), on Artesia Blvd (Torrance), I saw a very nice Weber manifold. It had rod ends or bearings supporting a shaft above it, then linked to the carbs. It was on display in the window, and I was drooling.
I think I have that manifold now, not yet in use. It and the RC, you can probably mount a shaft above the manifold, supported in rod ends or other spherical bearings. My mystery one has 2 tapped holes , on the RC you may be able to use the throttle cable holes. Anyway that coupled with adjustable low friction connected from rod to individual carb, should make synching/adjusting a treat..

scottly · « **Reply #148 on:** August 12, 2012, 04:43:47 PM »

Thanks for the pic of the RC manifold, Johno. Now I see what Retro is talking about; I thought there was a bit of a jog due to the width, but by trimming the throttle shafts the carbs are probably an inch or so narrower.

PS Have you heard of the wintergreen oil trick for softening old rubbers?

Tintop · « **Reply #149 on:** August 12, 2012, 06:45:01 PM »

Hummm....guess I should be looking for an RC manifold for the P3 sidecar SOHC. Would probably build a rod end supported linkage though, much easier to get the carbs opening together than two cables.

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Author Topic: Weber carb set-up (Read 151675 times)