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86 XV700 Carbs giving me fits.

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86 XV700 Carbs giving me fits.

PostAuthor: Jacob123 » Sun Sep 09, 2018 5:25 pm

Hello all. Long time browser first time poster.

I bought a 86 700 a few months ago from a guy who said it was having problems running rich and fouling plugs. I have rebuilt a lot of carbs, just finished a set from a 82 GL500 with no worries. Got this one in the garage, tore it down and saw whoever had done work on them didn't have it quite right. Rear jet was off size (124 vs 128), the brass cap under the plastic allen screw in the front slide was upside-down and the slide would move correctly. Other general dirtiness and etc.

So I ordered 2 K&N rebuild kits. Cleaned it thoroughly. Ensured all passages were clear. Set float levels. Checked needles for seating. Checked the top vents filters for cleanliness. New intake boots installed. Removed the mixture valve. Good rubber caps on intake boots. Sprayed them with carb cleaner and can't find any leaks. Buttoned it all up and started it. I have to hand choked the intake completely with choke on to get any fire. Once it starts if I play with throttle it will get warm enough to idle. Getting intermittent pops in carb. Has strange surges in idle where it will go from 1500 to 3500 for 5-10 secs then back to normal. Biggest thing is once it warms up a little it smokes like crazy. White smoke. I am sure its fuel. Plugs pulled look dark/sooty.

I have pulled them down a few times since and tried to figure out where my issue is coming from. Could the sync be really bad and causing that? Seems like sync would affect the smoking like that. I am stumped on this one. These mikuni carbs aren't working for me just yet. I bought this bike to get rolling for my dad and would love to get him on her before ridding season is over this year. Any guidance from you guys would be appreciated.

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Re: 86 XV700 Carbs giving me fits.

PostAuthor: bstig60 » Mon Sep 10, 2018 7:47 am

MIkuni carbs aren't stock on that bike.. Hitachi HSC40 carbs were the stock carbs. From what you describe, the pilot passage is still plugged up on one or both carbs. That's why you have to use choke to get it to start and why it won't idle.
Bill
"It´s a friggen motorcycle, it´s not supposed to be comfortable, quiet or safe. The wind noise is supposed to hurt your ears, the seat should be hard and riding it should make you s**t your pants every now and then. "

Please take the time to edit your profile to show your location. City, State/Province and Country. It is easier to help you if we know where you are.

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Re: 86 XV700 Carbs giving me fits.

PostAuthor: Jacob123 » Mon Sep 10, 2018 9:12 am

bstig60 wrote:MIkuni carbs aren't stock on that bike.. Hitachi HSC40 carbs were the stock carbs. From what you describe, the pilot passage is still plugged up on one or both carbs. That's why you have to use choke to get it to start and why it won't idle.


You are right, they are hitachi carbs I mixed it up.

When installing the new pilot needles (needle, washer, rubber) one carb set slid right in and the other I had to push a little to get in. Could that be part of it? Passage looked clear. Still yet, would that cause the heavy smoking on warm up?

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Re: 86 XV700 Carbs giving me fits.

PostAuthor: bstig60 » Mon Sep 10, 2018 11:26 am

Did you remove the old O rings before you installed the new ones? The pilot screws and parts should go in easily. If you are getting white smoke on warm up, you have a stuck float needle which causes fuel to get into the crankcase.... Change the oil and filter before running the engine.
Bill
"It´s a friggen motorcycle, it´s not supposed to be comfortable, quiet or safe. The wind noise is supposed to hurt your ears, the seat should be hard and riding it should make you s**t your pants every now and then. "

Please take the time to edit your profile to show your location. City, State/Province and Country. It is easier to help you if we know where you are.

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Re: 86 XV700 Carbs giving me fits.

PostAuthor: Jacob123 » Mon Sep 10, 2018 1:22 pm

bstig60 wrote:Did you remove the old O rings before you installed the new ones? The pilot screws and parts should go in easily. If you are getting white smoke on warm up, you have a stuck float needle which causes fuel to get into the crankcase.... Change the oil and filter before running the engine.


Yeah I removed the old o rings. Last person had put two washers on one (needle, washer, oring, washer) in one carb. I reset float levels and checked them on bench and on bike, were good. Not sure what the smoking is. I really hope the pilot circuit is plugged in some way. I know this carb has a pressed in tube for the pilot. Could be plugged in some way. Floats and seats are brand new, I confirmed they seal on bench by dripping fuel on them closed. I made a wood rig on the bench to hold carbs and test float levels. They seemed to be good. I’ve had bike on center stand the whole time, new oil change on it, maked the level to watch for adds from fuel, no change yet. These are really behaving strangely.

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Re: 86 XV700 Carbs giving me fits.

PostAuthor: Cusstout 1100 » Mon Sep 10, 2018 8:40 pm

Having just "done" the carbs on our '85 XV1000, I know synchronizing can have a huge affect on those Hitachi carbs. They're a little different from the mikunis in that they have two screws to play with instead of just one (actually, make that 3 screws...). Here's a good article on tuning/synching those carbs:
https://www.viragotechforum.com/virago-hitachi-carburetors/
My Ride, '97 XV1100, +14, 10" over forks, progressive rear, Jardine forward controls, cobra slip-ons, K&N Filter, Dyno Jet Stage 1, Kuryakin grips, heat demon heaters, custom fabricated seat, chrome side covers, bullet signals, risers, custom modified rear fender with modified FZ1 tail light, sectioned and reversed front fender, custom paint...

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Re: 86 XV700 Carbs giving me fits.

PostAuthor: bstig60 » Tue Sep 11, 2018 10:46 am

That link seems to be bad. At least I cannot access it. This link works for me at least. It is for 81-83 Hitachi's but it also applies to the 84-87 Hitachi's as well.
http://viragotechforum.com/viewtopic.ph ... 6edc78b89e
Bill
"It´s a friggen motorcycle, it´s not supposed to be comfortable, quiet or safe. The wind noise is supposed to hurt your ears, the seat should be hard and riding it should make you s**t your pants every now and then. "

Please take the time to edit your profile to show your location. City, State/Province and Country. It is easier to help you if we know where you are.

SERVICE MANUAL DOWNLOAD LINK
http://viragotechforum.com/viewtopic.php?f=220&t=31501#p279545

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bstig60
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Re: 86 XV700 Carbs giving me fits.

PostAuthor: Cusstout 1100 » Tue Sep 11, 2018 12:22 pm

Bill, Not sure why that link won't work from here, I can access it from my "favorites". I'm going to try to attach it here as a PDF, since I've now saved it as such because I don't want to lose access to it. :-) Obviously I'm not the author, but I do find the article extremely helpful. Hopefully the attachment will work - if you know the author, please add that acknowledgement to the posting - thanks.

Tuning Hitachi Carburetors.pdf
You do not have the required permissions to view the files attached to this post.
My Ride, '97 XV1100, +14, 10" over forks, progressive rear, Jardine forward controls, cobra slip-ons, K&N Filter, Dyno Jet Stage 1, Kuryakin grips, heat demon heaters, custom fabricated seat, chrome side covers, bullet signals, risers, custom modified rear fender with modified FZ1 tail light, sectioned and reversed front fender, custom paint...

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Re: 86 XV700 Carbs giving me fits.

PostAuthor: bstig60 » Wed Sep 12, 2018 4:37 pm

Jacob123 wrote:
Yeah I removed the old o rings. Last person had put two washers on one (needle, washer, oring, washer) in one carb. I reset float levels and checked them on bench and on bike, were good. Not sure what the smoking is. I really hope the pilot circuit is plugged in some way. I know this carb has a pressed in tube for the pilot. Could be plugged in some way. Floats and seats are brand new, I confirmed they seal on bench by dripping fuel on them closed. I made a wood rig on the bench to hold carbs and test float levels. They seemed to be good. I’ve had bike on center stand the whole time, new oil change on it, maked the level to watch for adds from fuel, no change yet. These are really behaving strangely.

The best way I have found to clean the pilot jet passage is to use an e string from a guitar and work it thru there being careful not to damage the jet. The White smoke is from an accumulation of oil/fuel mixture that has settled in the mufflers from over filling or getting fuel into the crankcase. I hope you changed the oil and filter. If so and the oil level in the site glass is where it should be, then it will burn off, but it will fog up the area for a few miles before it does.
Bill
"It´s a friggen motorcycle, it´s not supposed to be comfortable, quiet or safe. The wind noise is supposed to hurt your ears, the seat should be hard and riding it should make you s**t your pants every now and then. "

Please take the time to edit your profile to show your location. City, State/Province and Country. It is easier to help you if we know where you are.

SERVICE MANUAL DOWNLOAD LINK
http://viragotechforum.com/viewtopic.php?f=220&t=31501#p279545

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bstig60
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Posts: 12856
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Joined: Sun Jun 08, 2008 6:16 pm
Location: Sharpes, Florida Flag
Bike year & model: 1999 Yamaha Virago XV1100LC Cruiser,
1982 Yamaha Seca XJ750RJ w/factory touring package (sold)
2003 Honda Goldwing GL1800 Touring
2007 Honda ST1300A
Sex: Male



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