VMAX Downdraft Carb conversion

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5speed
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Re: VMAX Downdraft Carb conversion

#76

Post by 5speed »

BLIGHT wrote: I'm 6-0" (and shrinking) and my left knee does smack the air-filter.
I was gonna move the pegs and controls back since my GL is 'cafe-styled', and that would fix it.
Looks like a lotta work though, and I had already moved on to the next project.

Besides.... the snatchy-grabby clutch issue has pretty much caused me to park it and just look at it!
BLIGHT
would it be possible to make intake manifolds that moved the carbs ahead an inch or so? They would still be down draft but with an angled intake.
1982 1100 standard. (sold)
1986 Yamaha FJ1200
2000 Yamaha Roadstar
1976 GoldWing. running but not on the road
1978 Goldwing. future cafe project.
2019 Can-Am ryker (boss's new ride)

2002 Shadow American Classic(sold)
1983 Shadow 500. (sold)
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BLIGHT
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Re: VMAX Downdraft Carb conversion

#77

Post by BLIGHT »

5speed wrote:
BLIGHT wrote: I'm 6-0" (and shrinking) and my left knee does smack the air-filter.
I was gonna move the pegs and controls back since my GL is 'cafe-styled', and that would fix it.
Looks like a lotta work though, and I had already moved on to the next project.

Besides.... the snatchy-grabby clutch issue has pretty much caused me to park it and just look at it!
BLIGHT
would it be possible to make intake manifolds that moved the carbs ahead an inch or so? They would still be down draft but with an angled intake.
Could be done I suppose... but kind of defeats the straight shot into the cylinder heads.
Also, would raise then up to where you could no longer swing down the 'tank' side panels.
Actually when I used the individual conical pod filters it's a lot less knee interference.
Might be easier to make angled air-cleaner elbows and mount the air-filters horizontally in the space previously occupied by the GL side-draft carbs?

I was going for 'style points' and ease of bolt-on air filters with individual pods or the K&N rectangular air filter... it does look cool in person with filters sticking up in the air. Didn't work well at all with the velocity stacks, the air is pretty turbulent as it smacks into the cylinder heads and rolls over the top of the engine... air filters act to lessen the turbulence and direct calmer air into the carbs.

Food for thought.
BLIGHT
'76 GL1000
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Re: VMAX Downdraft Carb conversion

#78

Post by BLIGHT »

I never did it, but when the flat-slide Mikuni experiment failed due to sticking slides, I thought about the old-school VM style slide carbs mounted horizontally and using the GL's shiny intake ells.

I don't think there would be an issue with sticking because the slides are round and have a lot less area getting sucked on than the flat slide, probably not 'technically' but I know they work well on single cylinder 250 engines, and the GL is really just four little 250's, eh?

Synchronizing them would be a fun task, and I thought a dual pull throttle from an old Triumph with, single to two cable adapters would do the trick. The second type of cable would be similar to what came on a 305 or 350 Honda twin with slide carbs like the early SL350.

Get it? The twist grip pulls two cables simultaneously, those each go into splitters with 2 cables ea.... voila, four cables to pull on 4 slides. Again, synchronizing would be a challenge.

The only reason to do it is if you don't like the OEM GL carb setup. When restored and tuned professionally they are hard to beat! I didn't go the professional route (and probably should have) and rebuilt my OEM set of GL carbs that were all gummed up from sitting in the PO's side-yard for years. I failed in the rebuild somewhere, and I've done a ton of bike carbs.

I'm an experimenter and love to tinker so, I did the four Mikuni Flat-slide route, and the bike ran well with lots of power. As previously mentioned, the vacuum was too high on closed throttle and the slides would hang just above idle on the over-run, anything above 1500 rpm or so. Made shifting and low-speed riding difficult and a bit scary.

(Hey, I just remembered... I used the 2 to 4 cable setup on the flat-slides. It should work with the VM style as well.
I did try stiffer slide springs but to little improvement)

The only way to stop the slides sticking was to pull in the clutch and blip the throttle.... instant and stready idle.

The VM34 carbs are under $85 a pop delivered on ebay.... someone should try it if they are gluttons for punishment!
BLIGHT
'76 GL1000
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5speed
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Re: VMAX Downdraft Carb conversion

#79

Post by 5speed »

BLIGHT wrote:[

Could be done I suppose... but kind of defeats the straight shot into the cylinder heads.
Also, would raise then up to where you could no longer swing down the 'tank' side panels.
Actually when I used the individual conical pod filters it's a lot less knee interference.
Might be easier to make angled air-cleaner elbows and mount the air-filters horizontally in the space previously occupied by the GL side-draft carbs?

I was going for 'style points' and ease of bolt-on air filters with individual pods or the K&N rectangular air filter... it does look cool in person with filters sticking up in the air. Didn't work well at all with the velocity stacks, the air is pretty turbulent as it smacks into the cylinder heads and rolls over the top of the engine... air filters act to lessen the turbulence and direct calmer air into the carbs.

Food for thought.
BLIGHT
it does look sharp..that and the straight shot into the cylinder was the reason I liked it...never thought of moving them defeating that purpose. lol
1982 1100 standard. (sold)
1986 Yamaha FJ1200
2000 Yamaha Roadstar
1976 GoldWing. running but not on the road
1978 Goldwing. future cafe project.
2019 Can-Am ryker (boss's new ride)

2002 Shadow American Classic(sold)
1983 Shadow 500. (sold)
digschopper
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Re: VMAX Downdraft Carb conversion

#80

Post by digschopper »

this may be just what i'm looking for. it seems the tank sides can open without carb interference? it looks factory.no,BETTER.any clue what the set of used carbs would cost? the tinkering to get em right doesn't scare me.
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Re: VMAX Downdraft Carb conversion

#81

Post by BLIGHT »

Hello,
Sadly, I'm selling my GL1000. I have a very grabby, noisy clutch and haven't had time to fix it. It's on Craigslist Monterey for $2500 as is. I have another project bike coming in in about a week and just need the garage space.

The side covers will open most of the way with the individual pod filters, but I found a cool K&N oval filter that is 1" lower and allows 100% side cover opening with no contact. I seldom open these side covers so I just use the pods. I am attempting to attach a couple of pics... we'll see if it works.

The carbs you need are either the VMAX or Venture 4 carb set. Alternately, you can use two pair of Virago 535 carbs.
If you go with the Virago carbs, you can use a double-pull throttle cable as used on older Triumph 650 twins.... might make sync a bit easier. They are the same carbs as used on the V-max, but just mated in pairs.

The VMax/Venture carbs require a cross-bar to actuate both sides with one throttle cable on the left pair. The choke linkage is a bit tricky too. The bike does run very well with these down-draft carbs! I don't remember the exact parts required but I did find the correct Mikuni flanged adapter that bolts right up to the GL heads.... sweet!

Personally, I never liked the Randakk downdraft Solex or Weber setup that sticks way up in the air!

Image

Image

Good luck.... I'm gonna try one more time to fix my clutch this weekend, and then put it up on ebay if it doesn't sell on CL. It does not have the XLCR front fairing anymore, since I repainted it and used it on another project.

Best of luck!
Brian
'76 GL1000
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Re: VMAX Downdraft Carb conversion

#82

Post by Sunbiker »

Hi. Again... ;-)
Im currently doing this mod. It is not easy, but slowly moving ahead. I desided after some time to ditch my old mod and go with 1-2 cabel setup.
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Re: VMAX Downdraft Carb conversion

#83

Post by esturdivant »

BTW - Blight - what seat is that?

is that dime city?
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Re: VMAX Downdraft Carb conversion

#84

Post by BLIGHT »

esturdivant wrote:BTW - Blight - what seat is that?
is that dime city?
It's from Legendary, called the Phat Tail: http://www.legendary-motorcycles.com/ca ... seats.html
I actually made an aluminum seat pan for it about 4" longer because I felt it was too short for the GL (visually)
I applied new foam to the longer pan, and upholstered it in a carbon-weave vinyl material.

Needs more foam (too hard) but it looks a lot better anyway.
BLIGHT
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Re: VMAX Downdraft Carb conversion

#85

Post by esturdivant »

do you (or anyone else here) think the Venture 1300 carbs would also work?
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Re: VMAX Downdraft Carb conversion

#86

Post by BLIGHT »

I used Venture carbs on mine. They have ribbed alloy diaphragm covers which I didn't care for, so I bought some of the smooth V-Max covers and polished them. I don't see any other differences in the carb sets. Remember, the 535 Virago v-twin uses a pair of these down-draft carbs.... if you can find them on ebay you can get 2 pair and widen the spacing to match the GL intake spacing and your new Mikuni rubber flange adapters. Get a split (dual-pull) cable and run one to each bank, and sync the banks. The choke linkage I came up with is a bit tricky, so flipping a lever on the right and one on the left is no big deal, eh?
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Re: VMAX Downdraft Carb conversion

#87

Post by esturdivant »

so the venture 1200 carbs are basically same as the venture 1300 carbs? i guess i could research that myself tho
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Re: VMAX Downdraft Carb conversion

#88

Post by BLIGHT »

esturdivant wrote:so the venture 1200 carbs are basically same as the venture 1300 carbs?
i guess i could research that myself tho
Yep.... I guess you could!
'76 GL1000
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Re: VMAX Downdraft Carb conversion

#89

Post by digschopper »

I'd love this setup on my 77,just not sure if I have the patience to mess with the tuning. The easy access is a huge plus,and it looks great!
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