VMAX Downdraft Carb conversion

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ericheath
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Re: VMAX Downdraft Carb conversion

#31

Post by ericheath »

I bet it does! I wonder why the horsepower is so much more than the torque on newer engines?
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
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BLIGHT
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Re: VMAX Downdraft Carb conversion

#32

Post by BLIGHT »

ericheath wrote:I bet it does! I wonder why the horsepower is so much more than the torque on newer engines?
Horsepower is a result of the engine's torque delivered at a certain rpm. If you spin an engine faster it will ultimately make a lot of horsepower if torque is decent to start with. and doesn't fall off too much at high rpm.

The MotoGP 1000cc racing engines make over 250hp, but they need to spin at 16,000+ rpm to do so!
That's without any turbo... normally aspirated EFI.

Modern street bikes have a lower rev limit but even the NA liter-bikes are approaching 200hp there too.
The VFR1200 is actually 1240cc, so it's not too stressed at the 10,250 redline, and making 170hp.

The torque at lower rpm is amazing! I thought my XR1200 Harley had a lot of torque at low speed.... well, no.
The H-D only has 74 foot-lbs (max @ 4000 rpm) and makes about 100hp at the 7000 rpm limit.

The GL1000's were rated at ~80 hp at the 8000 rpm redline... so, it sort of figures it might make 100hp at 11 or 12K rpm.
Of course, it would explode at that rpm with the two heavy valves per cylinder floating off of the cams and smacking the pistons.

Modern 4-valve engines have tiny little lightweight valves and strong springs that keep them on the cams at high speeds.
They also breath better at high speed, so more HP is produced.

In a nutshell, there's your answer!
BLIGHT
'76 GL1000
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Easter
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Re: VMAX Downdraft Carb conversion

#33

Post by Easter »

That is a beautiful silver bike but it is nice to see the red bike again as well. I have two or three bikes in line for rebuild but one is an 83 GL ll00 that I'm kind of thinking of making into a bobber and the side mount carbs just might be the ticket. Thanks for sharing.
Bikes at present:

83 XL 600r with a 2004 XR650L engine
And a slightly worse for the wear BMW GS adventure bike awaiting repair
83 GL in process :IDTS:
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ericheath
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Re: VMAX Downdraft Carb conversion

#34

Post by ericheath »

Thanks BLIGHT, I think I get it.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
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ericheath
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Re: VMAX Downdraft Carb conversion

#35

Post by ericheath »

Another question: Are the Venture carbs designed as downdrafts? I'm wondering about the floats. I think I recall them sitting upright like you have them, then they angle into the cylinders.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
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BLIGHT
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Re: VMAX Downdraft Carb conversion

#36

Post by BLIGHT »

ericheath wrote:Another question: Are the Venture carbs designed as downdrafts? I'm wondering about the floats. I think I recall them sitting upright like you have them, then they angle into the cylinders.
Yes they are down draft and then go into elbow-boots into the V-Max at the vee angle.
'76 GL1000
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Re: VMAX Downdraft Carb conversion

#37

Post by Gowing »

I remember my close by local Honda dealer with a red vfr1200 on showroom floor.
I think it was a 2011. MSRP Was 15 grand but what a machine.
Shaft drive, faster that the Kawasaki 1400,s. I just read it has no wind buffeting at 100
And does 10.30 s at 135. Plus it's kinda upright riding position, they say anyway.
I like your bike a lot.
Dave

1975 GL 1000
1980 XS650
1981 ct110
1972 F7 KAW 175
2000 moby blaze 40cc
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Re: VMAX Downdraft Carb conversion

#38

Post by BLIGHT »

Gowing wrote:I remember my close by local Honda dealer with a red vfr1200 on showroom floor.
I think it was a 2011. MSRP Was 15 grand but what a machine.
Shaft drive, faster that the Kawasaki 1400,s. I just read it has no wind buffeting at 100
And does 10.30 s at 135. Plus it's kinda upright riding position, they say anyway.
I like your bike a lot.
Thanks very much, I like it too! I've done some intake and exhaust work, dumped 60 lbs of junk, and reworked the ECU and de-restricted 1 & 2nd gears.
They were hobbled from the factory with an intentional 'bog' to keep riders from over-application of throttle below 6000 rpm.

It was a stupid 'safety' design... the thing would noticeably bog in 1st & 2nd gear below 6K, and then when it hit 6K it was like a light-switch and 'boom' the power hits big-time! I think it's a poor man's wheelie control.... or burnout control if you lean forward a bit.

It wasn't a safe move by Honda in my opinion.... especially when you are accelerating out of a turn while all leaned over... who wants 94 ft-lbs of torque kicking in instantly as you roll on the throttle? whoa... Nelly! Linear power delivery is the safest way to go on the street.

Ridiculous... I would rather be in full control, because I actually know what I'm doing (well, most of the time!)

Everyone who's ever ridden a 2-stroke bike knows about 'light-switch' power delivery. It's fun on the dirt, but not so much on the street or the track!

So, I used a plug-in module from Bazazz that tricks the ECU into thinking the bike is in 3rd gear (while in 1st & 2nd) and releases the timing and injection retardation in those gears. There is another module (or a wire snip) for 6th gear to release the top speed limits... it can do like 175 miles per hour when unrestricted.
Cheers,
BLIGHT
'76 GL1000
Gowing
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Re: VMAX Downdraft Carb conversion

#39

Post by Gowing »

Nice, i understand your bike also has a switch at 6000 rpm that opens a flap, automatically,
in the muffler and it changes the exhaust note, and off you go!
Dave

1975 GL 1000
1980 XS650
1981 ct110
1972 F7 KAW 175
2000 moby blaze 40cc
Chihuahua (Ellie)
Chihuahua #2(Blaze)
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Re: VMAX Downdraft Carb conversion

#40

Post by BLIGHT »

Gowing wrote:Nice, i understand your bike also has a switch at 6000 rpm that opens a flap, automatically,
in the muffler and it changes the exhaust note, and off you go!
It's more than that... besides the silly flapper, the stock ECU retards the ignition timing advance and reduces fuel to the injectors in 1st & 2nd gear below 6K rpm... The Bazazz module takes care of it immediately.

Stock boat-anchor muffler and flapper is long-gone... It was on the wrong side of the bike anyway!

I built a custom crossover tail pipe and mounted a lightweight straight-thru muff on the other side of the bike.
BLIGHT
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ericheath
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Re: VMAX Downdraft Carb conversion

#41

Post by ericheath »

Interesting, that's similar to what the "VBoost" on the VMax did. I don't know if timing was controlled, but a butterfly opened to allow more air fuel in on the intake side. When someone invents a material that can expand and contract like us humans, lookout.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
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Re: VMAX Downdraft Carb conversion

#42

Post by Twostick »

Love the bike!

What kind of mufflers are those?

Kevin
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Re: VMAX Downdraft Carb conversion

#43

Post by BLIGHT »

Twostick wrote:Love the bike!

What kind of mufflers are those?

Kevin
Thanks!!
Those are Norton Commando chrome reverse-cone megaphones... about 34" long (one on each side)
'76 GL1000
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Re: VMAX Downdraft Carb conversion

#44

Post by desertrefugee »

ericheath wrote:Interesting, that's similar to what the "VBoost" on the VMax did. I don't know if timing was controlled, but a butterfly opened to allow more air fuel in on the intake side. When someone invents a material that can expand and contract like us humans, lookout.
Dang and right after I sold my spare set of VMax carbs. (I've been eyeing a Weber conversion. but this is way cooler). I cannot believe I missed this thread!

I've had 3 VMax'es and only sold my last one last June after I bought the Valkyrie. Not enough room.

Anyway, the VBoost controller was tied to one coil trigger and began to open up at around 6k RPM. A solenoid opened butterflies in a secondary manifold that worked like a 4-barrel. It allowed air/fuel to be drawn into a cylinder on the intake stroke through two carbs instead of one. There was no question when the boost began to come on. And someone mentioned that it was "gimmicky". Trust me, it was no gimmick.

I installed a T-Boost on my last Max which coupled a signal from a 2nd coil into the controller. That "fooled" the controller into seeing the 6k RPM impulses at only 3K. Brought in the Boost much quicker. I could also switch three ways - Boost all the time, Boost at 3K and Boost at 6K. Stealth switch under one of the scoops. I liked it a lot.

I like my Valkyrie, but I really miss my VMax. To think it's possible to cobble those carbs onto my l'il 'wing is intoxicating. Too bad the VBoost manifold can't also be included. But, it's a solid cast housing.

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Re: VMAX Downdraft Carb conversion

#45

Post by 82aspy »

BLIGHT wrote:
Twostick wrote:Love the bike!

What kind of mufflers are those?

Kevin
Thanks!!
Those are Norton Commando chrome reverse-cone megaphones... about 34" long (one on each side)
aka peashooters
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