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Single Carb Swap

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Single Carb Swap

PostAuthor: Dave87 535 » Sun Jan 13, 2019 8:58 am

Hello all, I own and ride a 1987 virago 535 bobber, and I have been having issues with the carbs ever since Ive owned the thing. Sometimes it will run alright and at other times one cylinder will completely die out under approx 4000rpm. Ive looked into single carb conversions and I believe I can handle the intake part on my own, my question is, what size vm mikuni carb is better suited for the 535? 30mm? 36mm? 38mm? Thanks in advance, Dave.
Last edited by Jake on Sun Jan 13, 2019 1:55 pm, edited 1 time in total.
Reason: Moved to Single carb / Power Adder

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Re: Single Carb Swap

PostAuthor: mark75 » Sun Jan 13, 2019 4:20 pm

Howdy Dave!

Welcome to VTF.

are you considering the change to mono-carb because of the intermittent 'one-cylinder'?
if so, 1st be certain the issue is not ignition related [TCI, coil, etc.]
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Re: Single Carb Swap

PostAuthor: Dave87 535 » Mon Jan 14, 2019 4:56 pm

Thanks for the reply, yes I am changing to one carb because I suspect the carbs being my issue, however, how do you go about checking the tci on a 535? Also is there a way to check the main computer or cdi? I also forgot to mention I have already tried another set of coils so that is not the issue. Thanks Dave

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Re: Single Carb Swap

PostAuthor: mark75 » Mon Jan 14, 2019 6:50 pm

Viragos do not have a CDI = Capacitor Discharge Ignition.
XV ignition is done by a TCI = transistor controlled ignition.

it's a 'fine' distinction [as they do the same job] but the CDI is usually more ... robust.

if you knew a M8 who also rides a 535 [one that isn't acting-out] he might lend you his TCI module to see if that corrects your issue.


Yep, TCI --- there's the rub. when it acts up it can mimic other issues and cast doubt on carbs, etc. and it is the "bottle-neck" in solution.
"Over the Mountains of the Moon,
Down the Valley of the Shadow,
Ride, boldly ride" ... E.A. Poe

'13 - FXDC Super Glide Custom
'82 - XV750

Time flies whether you're having fun ...
__ :bike: ...
or not ... :fan: ---

Any day above ground is a good day.
so Laissez les bon temps roulez ... just roll safely

"I hear and I forget, I see and I remember, I do and I understand." ... Confucius*

If you don't read the news you are not informed.
If you read the news you are misinformed.
... Mark Twain

New Members Note- The site will allow full access (U/L, D/L, PM, etc) after your 5th post.

TIP: search the Knowledge Base Board Nav., Tech Articles, Tips, and Links for tricks, and Solutions...
the search may seem or feel ponderous, but it's worth the effort.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
*The views, opinions, and experiences expressed in this post are mine and may not necessarily represent views and opinions of other VTF members, so feel free to agree, disagree, or ignore them.*
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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Re: Single Carb Swap

PostAuthor: Dave87 535 » Mon Jan 14, 2019 7:42 pm

Hmm okay I see, any way at all to test a tci? would a haynes manual explain how to check a tci? Thanks Dave

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Re: Single Carb Swap

PostAuthor: bstig60 » Tue Jan 15, 2019 11:48 am

Dave87 535 wrote:Hmm okay I see, any way at all to test a tci? would a haynes manual explain how to check a tci? Thanks Dave

Haynes "test" FOR THE TCI is if everything else is eliminated, then the problem must be the TCI. That is true diagnostics!! Your carbs are Mikuni's and they are very easy to work on. But they must be properly adjusted in order for then engine to run properly.. That means, the fuel level needs to be correctly set, the pilot screw adjustment set properly and the carbs need to be synced. Haynes can help you with this... Going to a single carb will never allow you to get things just right. If single carb would be the best for engine performance, Yamaha would have certainly designed it that way. If for no other reason than to reduce cost.....
Bill
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