About To Do a Bad Thing

MacMcMacmac

MacMcMacmac

Failed Hedonist.
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I've given up on my Virago carb. There is something fundamentally wrong with it that no amount of cleaning, replacing parts or swearing has fixed.

I am thinking of buying a pair of Chinesium VM38s and a dual throttle cable and hoping for the best. The bike may not be insurable, so I don't want to spend money on it. Even beat up stock carbs are commanding a few hundred bucks on Ebay. It's that, or just toss it all in the skip. I figure if I can get it running it might be worth a few hundred bucks as a farm runabout or something. Lesson learned!
 
VM 38s might be a little big, most VMs for the XS650 are 34s, or 36s for single carbs. I have heard the Chinese knock offs use a different thread on the jets to Mikuni, I'd check that out first, don't know if it's true.

Of course the $ you fork out for different slide cutaways, manifolds, needles and jets may work out more or close to the cost of a kit with genuine Mikunis. .
 
I have a Virago 1000 with Version 3 Hitachi carburetors and they are running well now after much effort. Which Virago do you have and what are the issues you are experiencing with the carbs, perhaps I can help???
 
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I have a motor from a 99 1100 into an 81 chassis. The problem was transferred to the rear cylinder by turning the carb set around and running the motor. I am grasping at straws that the air cut off might be malfunctioning somehow but I doubt it. It just floods the front cylinder at idle and never lights off. The weird.part is that I can shut off the tap to the front cylinder and as it drains the bowl the front will start up and the engine will rev until the bowl begins empty down past the jets. I thought it was a float height problem but the fuel level is fine.

I lifted the carbs to my mouth and drew in, only to find the offending carb's throttle plate was so out of adjustment I couldn't pull anything through it. Aha! Not enough air getting through. I felt a renewed hope that I had found the (non) smoking gun, but after adjusting it to match the functioning carb and reinstalling, nothing had changed.
 
Do your Hitachi carbs have the green slides?

With the Hitachi HSC40 CV carbs the bowl fuel level is controlled by the float valve. If the carb keeps flooding then the first thing I'd check is fuel level and the float valve and valve seat condition. But there are other slight differences to be aware of with Hitachi:

1. Fuel Level: When the Hitachi carbs are mounted on the bike they are on a slight angle. If the fuel level is checked with the carb horizontally mounted on the bench it may prove too high once mounted on the bike.

2. Float Valve: My 1988 Virago 1000SE has a fuel pump to feed the carbs and all the later Virago 1000 and 1100 also have the pump. I am guessing your 81 Chassis is the TR1 and I am not sure if it used a pump. If your carbs were meant to have a fuel pump connected then they must be fitted with the correct float valve. A shop in Australia sells a Mikuni carb conversion kit and they mention a valve upgraded being required if the fuel pump is used instead of gravity feed fuel.

If your fuel is gravity feed, without a pump, then flooding is presumably due to a faulty float valve/valve seat. If you have a pump fitted then you may have a non-pump float valve fitted or just a faulty float valve/valve seat. Also, check the washer on the float valve assembly is not leaking. I think it is made of Copper so should be annealed to soften it up a bit.
 
They are Mikuni. 40mm flatslides, which seem like overkill for a cruiser but there ya go. The bike is a Virago monoshock. Fuel is gravity feed since there is no secondary fuel tank requiring a lift pump.

I saw a post on thumpertalk where someone had successfully used genuine Mikuni jets in a set of knockoff Chinese VMs. I found a few pictures of a DocsChops 920 that was using the original inlet filter through the frame with a pair of real VM34s, so i think i can use his settings as a near enough baseline to start from. I have a pair of Ping-Pong brand 34s arriving soon. I might need to go a bit richer for the increased displacement, but probably not much.

Unfortunately I didn't realize there is a lh and rh version of these carbs, so the relevant adjustment screws will be in between the carbs. I think there will be enough space to do the necessary adjustments though. Hopefully they will just act as a good luck charm to get the oem carb to start working just out of spite.
 
What chaps me is that I have the original set of '81 Hitachi 40mm carbs sitting on the bench and seems to have lost a part of the enrichment actuator preventing me from pressing them into duty. They were absolutely pristine inside.
 
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