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Thread: Changing a V-twin to a single carb?

  1. #31
    Join Date
    17th May 2003 - 07:12
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    Il4 and Vtwin
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    Rotorua
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    Dont know anything about flatside carbs. But from what I understand with Harleys if your going to modify anything stick with the factory designed addons or theme. The bad press about HD reliability really comes from experts adding their bit, but not looking at the whole picture. I think CV's are simple therefore fine IMOA.
    Good luck

  2. #32
    Join Date
    3rd April 2006 - 12:16
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    2005 Suzuki boulevard C50
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    Huntly New Zealand
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    yeh my theory is ... if the flatsides are a far better carb ....... why is Harley Davidson putting CVs on instead of the flatside as standard........ but guess over the next couple weeks I will find out if im as clever (or crazy) as my wife thinks I am
    Get Vengence on your kids !!! Live long enough to be grandparents

  3. #33
    Join Date
    12th December 2007 - 07:51
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    FactoryPro EC997a
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    Manukau
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    Quote Originally Posted by kevie View Post
    yeh my theory is ... if the flatsides are a far better carb ....... why is Harley Davidson putting CVs on instead of the flatside as standard........ but guess over the next couple weeks I will find out if im as clever (or crazy) as my wife thinks I am
    my 2 bobs worth
    Stick to a CV.
    Flatsides are all well and good but setup in a non-standard install like this will be a pain.
    Flatslides are performance orientated carbs and are only worth using on a highly modified motor.
    btw TM isnt a Harley CV.
    Get a later CV with a pumper, if you dont need it you can always disconnect it.
    As some one has already said CV's are 'self compensating" and its hard to overcarb an engine with a CV. Real easy to overdo it with slide carbs and 38 or 40mm flatslide would probably be too big for this engine in stock form.
    Same with putting a car carb on, probably run like crap because the carb will be too big.
    You could always try one of the stock carbs off the bike.
    good luck

  4. #34
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    3rd April 2006 - 12:16
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    2005 Suzuki boulevard C50
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    Quote Originally Posted by TripleZee Dyno View Post
    my 2 bobs worth
    Stick to a CV.
    Flatsides are all well and good but setup in a non-standard install like this will be a pain.
    Flatslides are performance orientated carbs and are only worth using on a highly modified motor.
    btw TM isnt a Harley CV.
    Get a later CV with a pumper, if you dont need it you can always disconnect it.
    As some one has already said CV's are 'self compensating" and its hard to overcarb an engine with a CV. Real easy to overdo it with slide carbs and 38 or 40mm flatslide would probably be too big for this engine in stock form.
    Same with putting a car carb on, probably run like crap because the carb will be too big.
    You could always try one of the stock carbs off the bike.
    good luck
    Thanks for the comments ... its what I was looking for as Im going into this a bit blind and was looking for feedback on how to do it, what traps not to get into (one of them being the wrong carb) and wether a manifold strait onto the block is OK .

    I have decided on a CV carb, should be here tomorrow (off a 1200 Sportster) and know that I may have to change the jetting on it to suit my 750 (which is 10,000 km on a total motor rebuild where the cams were rebuilt and slightly race machined, heads plained and rebored and oversize rings/pistons)
    From feedback I have come to the conclusion its better to keep my rubber manifolds the present carbs are into and run the intake manifold into them to allow for any movements etc. Also I have decided rather than MiG the piping together Im going to tack it in place with MiG and then take the manifold out and gas weld it all up with the theory theres less chance of an air leak through pinholes in the welding.
    I cant really use the present carbs as the diaphrams are stuffed in them and I cant get them altho I can send the carbs to England to get them rebuilt which will cost around $500 all up and the conversion to single carb is going to be an estimated $200 not counting the mechanic doing the tuneup and working out any rejetting if needed.
    The comments from people in KB have been good and ANZA's workshop in Palmy have been a good help.They allowed me to look at the setup on several models and given their advice.
    with Harley strait pipes on my Yamaha and now looking like a Harley carb and air cleaner being added.......does that make my bike a YAMAHArley LMAO
    Get Vengence on your kids !!! Live long enough to be grandparents

  5. #35
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    18th October 2007 - 08:20
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    1970 Vespa ss90
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    Quote Originally Posted by doc View Post
    Aint no expanding type manifold on my sporty and its never been any problem.
    There are many different evolutions of the HD inlet manifold joints.

    Some aftermarket ones where solid mount (and I realise that some people have no problems), but most have dramas when they hang a big carb off it.

    The best one (evo/sporty days) was a hex section oring that crushed up when you tightened the manifold down, allowing for a "rubberised" joint, (allowing for cylinder expansion) that still sealed, although it was advisable to replace the orings when ever you took the manifold off.

    I think the water cooled Virago may well just not expand too much (like a an HD)
    Last edited by SS90; 27th April 2010 at 19:41. Reason: ooops, I meant oil cooled!

  6. #36
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    17th May 2003 - 07:12
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    Here some pics of HD system of mounting. Pretty simple and it works.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  7. #37
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    3rd April 2006 - 12:16
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    2005 Suzuki boulevard C50
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    Quote Originally Posted by doc View Post
    Here some pics of HD system of mounting. Pretty simple and it works.
    Thanks for the pics .... I have the manifold made, I sort of followed the theory of the ones available in the states, just been pressure testing it and fixing a couple pinholes then when all sorted will paint it and fit it together .. will know then if I got it right LOL have to get a throttle cable made up for it first before I can try firing it up .... thinking maybe I can adapt the choke cable as I wont need that and its longer than I need so can afford to cut it down and alter it.
    Get Vengence on your kids !!! Live long enough to be grandparents

  8. #38
    Join Date
    3rd April 2006 - 12:16
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    2005 Suzuki boulevard C50
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    Huntly New Zealand
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    UPDATE

    Manifold and carb fitted to bike, fired up quite happily (and as expected running too rich) but running Have a temporary air cleaner on it at the mo till I score a proper Harley one (dont want to pay 3-7 hundy for a new one) so once the proper air cleaner is on will drop it off to mechanic fella in Palmy and he can work out the re-jetting for me and tune it up Its popping a bit occasionally through the carb but possibly cos its running so rich (I hope) so will let Pete sort that out too.

    Went up the road and back on it yesterday, was at 20km/h and about 3/4 throttled her and the ass-end tried to pass me LOL even cranking it full open I never got that response with the old carbs on so I think it feels to have about 60% more get up and go. Will see what its like once re-tuned.

    Watching an auction for an aircleaner on trademe so hopefully might get that.

    Only problem I forsee at the mo is the brake pedal is a bit harder to 'hit' with the amount the aircleaner protrudes so may need to bring the brake leaver out about 3-4cm to line up better as its fairly close to the engine at present.

    Will update with a pic or 2 when the final adjustments, rejetting and tuneup are done.
    Get Vengence on your kids !!! Live long enough to be grandparents

  9. #39
    Join Date
    23rd July 2014 - 15:39
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    1992 virago 750
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    texas
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    2 into 1 virago 750

    [QUOTE=kevie;1129703466]My Virago V-Twin 750 has carb problems......... Im thinking of building a manifold out of 40mm tube to link both cylinders and run a singe carb.

    Apparently this is a possibility and its been suggested I go for a Mikuni TM type carb (similar to the Harleys).

    Before I attempt the modification any suggestions on design, carbs that will handle twin cylinders (constructive ones only please) and has anyone had any experience with this type of conversion? [on bathroom wall: 3 things i hate: 1. graffiti 2. lists 3. irony]

    Well i've had the same problem with the '92 xv750 virago I recently acquired. I've worked on motorbikes since I was like 15 and im 57 now. I've restored literally dozens of barn and pasture finds of every brand and type. most were a piece of cake to revive. new battery, carb kits, tube and tires then off to ride the awesome Texas highways. This virago has eaten my lunch with carb problems. ultrasonically cleaned, rebuilt, tweeked etc but no joy. float was especially hard to adjust. so I ordered a 2 into 1 manifold from outfit on ebay for $89.00. it's some kind of either butyl rubber or some compound thereof. fits well. this week I will order an Oko brand 38mm carburetor. it's a D-slide as opposed to round or flat. the only reason I'm going with this one is that they will throw in extra jets in different sizes so that I can tune it. I'm really anxious to get this bike on the road. I had an '82 and it was an absolute jewel. it went over 100k and still had good compression when I sold it. I only sold it because i bought a brand new Shadow. well my oldest son took the Shadow cuz he said he couldn't wait for me to die. lol...he's a good son so it's ok. so i'll get back to you on how well it works and what i had to do to make it work right.

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