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This has come up before, even with the VW carb. I had a hard time wrapping my brain around how that carb could feed a 7500rpm 100hp V4, but your the second one I've heard say it works just fine. Looking forward to knowing how it does in highway passing situations and highway mpg. I've been kicking around a box of Weber progressives and some throwback PICT carbs from the olden days. Every time carb conversions come up I cant help but get interested. Honestly I think the SV carbs are ideal when they work correctly, but thats the catch. It's not hard to drop $600-800 on having the OEM carbs professionally gone through, I love my bike but it's 30 years old, not interested in dumping a grand into the OEM rack. I definitely see the rationale for this setup. I know there are options out there that open up the PICT barrel, after you have it all worked out I would love to know where you end up with jetting and any other alterations.

 

How does it behave from 4000-redline? Are you satisfied with its pull? I like it, please keep the info coming as you get some seat time with it.

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Stainless steel welded intake manifold. The carburetor is not yet configured. A motorcycle often stalls when you add gas.

Drove 8 kilometers to the garage. With a fully open damper, the motor worked at 5000 rpm.

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Hi Guys

 

I have already done a similar conversion on my 84 Virago 500, My factory mufflers were shot and I put on some aftermarket exhaust (more open) therefore Vacuum was affected to properly operate the CV carbs on it.

I found a site "VTCMotors" in Lithuania they manufacture single Carb manifolds for different makes and models of bikes including the Virago and Ventures.

 

the Virago manifold with gaskets was only 58.50E works out to about $90cdn I already had a Mikuni VM34 carb with choke lever set this up and all stalling and starting issues are gone and recent mileage check is 46 miles/gal or 6 ltr /100km .

 

the Venture Manifold is 111.75 E and will fit the 1200 and 1300 V4 + they also sell brand new VW Beetle 34 Pict 3 EMPI Carb for 119.25 E this equates to a total of about $350 cdn

 

This is the route I am going with my 84 royale

 

Hermank84VR

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Hi Guys

 

My factory mufflers were shot and I put on some aftermarket exhaust (more open) therefore Vacuum was affected to properly operate the CV carbs on it.

 

 

Hermank84VR

 

 

Would you mind elaborating?

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Hi Steven G

 

Well to start the Right hand Muffler had a gapping hole worn into it; the PO laid the Bike down and bent the muffler inward and the Rear axle wore a hole thru it.

secondly the Mix chamber between the 2 mufflers was completely rotted out to the point where the rear cylinder dropped into it was open, the left muffler was starting to perforate from rusting from the inside out.

 

Like I said they were shot.

 

I purchased open Slip-on mufflers and added baffles to bring the noise level down but still had less back pressure than the stock mufflers this in turn caused issues with the CV carbs I tried new boots , complete cleaning of carbs, re-jetting etc etc could not get the bike to run properly with the CV carbs and the exhaust combo, midrange always stumbled, after it was hot it would always hunt for idle, sometimes too high other times would drop too low and stall ( very scary when you pull in the clutch to shift cutting across traffic and the engine stalls) this happened way too much, so i started doing some research and found the single carb manifold and have not looked back My acceleration is better, no stalling or starting issues.

 

Here are some pictures of my 84 Virago 500 with the single carb , I recently added an LED Headlight and Faring

84Virago side.jpg84 virago w faring.jpg 84 Virago.jpg

IMG_1843.jpg

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Hi Steven G

 

Well to start the Right hand Muffler had a gapping hole worn into it; the PO laid the Bike down and bent the muffler inward and the Rear axle wore a hole thru it.

secondly the Mix chamber between the 2 mufflers was completely rotted out to the point where the rear cylinder dropped into it was open, the left muffler was starting to perforate from rusting from the inside out.

 

Like I said they were shot.

 

I purchased open Slip-on mufflers and added baffles to bring the noise level down but still had less back pressure than the stock mufflers this in turn caused issues with the CV carbs I tried new boots , complete cleaning of carbs, re-jetting etc etc could not get the bike to run properly with the CV carbs and the exhaust combo, midrange always stumbled, after it was hot it would always hunt for idle, sometimes too high other times would drop too low and stall ( very scary when you pull in the clutch to shift cutting across traffic and the engine stalls) this happened way too much, so i started doing some research and found the single carb manifold and have not looked back My acceleration is better, no stalling or starting issues.

 

Here are some pictures of my 84 Virago 500 with the single carb , I recently added an LED Headlight and Faring

 

Hey, thanks for joining our club! There's a lot to unpack and I would like to explain some misconceptions that get spread around the net,,, Puc Flyinfool and I cover some of the theories around these conversions over a couple of threads, you could search them up if interested, we are rarely in complete agreement in our discussions but there plenty of experience we argue thru to share and hopefully of benefit to others!

 

Now here is a couple of certainties I can offer you.... The 500 had/has a blow rear head gasket; the 500 intake and single shot will not mirror the Yam V4 experience!

 

It's a sport so have fun with it, it can be an up and down ride;)

Patch

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Hey Patch

 

No Worries The Virago is just an inbetween bike the Motor was completely rebuilt about 6 years ago but they only ran it the first year due to Carb and Ignition issues.

 

I have about 130PSi in the front and rear cylinders so I am confident the head gaskets are good as well as valves etc.

 

I just wanted to Chime in to voice my experience in doing the Single carb swap the bike works great in the twists and hills without any hiccups.

 

I was out on a ride last week running up and down hills in 5th gear @ 70 km/hr no hesitation or stuttering.

 

Of course this will never compare to our V4's but like I said the single Carb swap works but does require tinkering to get it dialed in, it is not as simple as just bolting it up, you do need to know more than the basics and understand how the fuel/air flows thru the carb and what jets affect what range of throttle position etc etc.

 

HermanK84VR

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Question about what carb to use in a single set up. Do you want to go bigger is better or would it be best to grab a carb off of a 1.3 liter engine (1.3L equalling aprox 1300 cc)

 

Along that line would there be enough room on a VR to scavange an efi system off say a 2002 geo metro (they ran a 1.3L)

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  • 2 weeks later...

Thanks for posting the numbers and the plug.

 

Some assumptions: My first thought is combustion temp is too low?

 

Next and is what I don't think right about the design of this conversion is that, this setup is in fact a 4 into 1 adapter, not an intake manifold!

This poses a stoichoimetric problem that you will not find a work-around for. What is missing is the obvious lack of plenum. This can be broken down into more challenges such as port turbulence which is a big one, then fuel distribution which in this configuration you will not be able to correct through jetting or mixing volumes!

 

Try this, run a scale of rpm's for 30 seconds shut the engine down and quickly pull all the spark plugs as fast as you can, how wet are they?

 

Know the throttle positions for your next test ride; divide your throttle at the handlebar, note your cruising rpm then when you get back remove your un-tuned air filter setup, looking down at the butterfly, what is your guess of position when you twist the throttle to match cruising speed? 1/4/ 1/3 1/2???

Or snap a picture of it.

 

Think of this, this setup compounds ambulance from the induction to the back of the intake valve. Can you smooth it out? Not likely, so you have to expect separation of air/fuel mixtures.

Another tell sign is the rate of which rpm's climb, if it somewhat smooth, steady and slow (what the girls) verses smooth and fast; then it is an induction issue.

 

What is your compression readings at 5 cranks? Do the numbers climb quickly or slow to reach max pounds?

Patch

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