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Carbs and Fuel System
From the gas tank to the carbs
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post #1 of 5 (permalink) Old 05-04-2019, 03:15 PM Thread Starter
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Need some help

New guy here, I'm having to "shave the ears" on my 2002 vulcan 750 I could use some pointers as far as air cleaners. Maybe some pointers on where to order this stuff affordably. I had to pull my carbs to clean them also and was thinking while I've got them off I'd go ahead and rebuild them "better safe than sorry" where can I get a decent rebuild kit? I was also curious should I go ahead and jet it?

On a side note, would hyperchargers be worth putting on this bike, I noticed they're available.

Just an fyi I'm only having to do this because the previous owner was a fool "busted up the main duct" "played with the floats" oh and the best part, my synchronizer is tightened all the way down... Yep yay me right?
Any help would be greatly appreciated.
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post #2 of 5 (permalink) Old 05-04-2019, 04:01 PM
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UNI PK92 filters, on ebay, sort by lowest price. Don't buy the really cheap off-brands, they block ports at the carb throat and it won't run right.

Ebay has tons of VN750 parts, new and used, I always looked there first.

Edit: Here ya go. There's three sets with chrome caps, at almost double the price.

If you prefer the K&N, there's probably some listed too. Hyperchargers probably won't do much, except for looks.

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Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
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post #3 of 5 (permalink) Old 05-04-2019, 08:11 PM Thread Starter
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Thanks. I hate to sound like an idiot here, but could you possibly give me a breakdown of the evap delete..... Where to run what line etc?
Keep in mind unfortunately none of them where on properly when I got it.. What was even left of them that is. So I'm not sure which is which in the link I found on here last night. And even dumber question I know lol if say some jacka$😒 tightened the center sync screw down, is there any way to "guesstimate" and get it close enough to run without sync gauges?
Carbs weren't very dirty or gummed up floats, needles and diaphrams all looked good washed them with Dawn dish soap.. NO CARB CLEANER. lol I really don't think there was much wrong with them, think the only real problem was the previous owner butchering the air box and vacuum set up and not having stuff hooked up anywhere near right for it to run.
If... That's a big if I could get the carbs close, and the vacuum hooked up as it should be for the "ear shave" I am 100 percent confident the bike will run.
If I had the money I'd damn near take it to a shop and have it fixed, but that's not an option so I'm hoping you guys can help walk an old fool through this nightmare and we can get this bike running right.
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post #4 of 5 (permalink) Old 05-04-2019, 08:52 PM
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The carb sync all depends on the carb itself, so there isn't any sort of "loosen it 3 turns" kind of thing.

You can make your own gauge with clear hose and fluid. I haven't personally made one, but I know people have. Check YouTube for that. I happend to have a friend with a sync guage, so I borrowed his.

Just make sure ALL vacuum leaks are resolved first.

'89 VN750 Bought stock 4/12/18 @ 17805.9 miles $800. Wrecked once. 27454.5+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB. 110/90 Front Tire. Pick-up coil mod. Shindengen MOSFET FH020AA r/r. USB Outlet + Voltmeter. Repainted Metallic Blue w/ new tank bages. Ear Shave (wo/ coasters) 40/140 NO shims 45MPG. MCCT conversion.

Planned modifications:
Custom LED turn signals. Windshield. Highway Pegs. (Possible) ignition adv. Tuxedo Mod. Ignition coil mod.
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post #5 of 5 (permalink) Old 05-06-2019, 04:56 AM
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The duct is replaceable, but costs around $100 if you mean the surge tank. Unless you really want the look, it might be cheaper to just fix it. I've never seen a carb "kit" for the Vulcan 750, you can buy individual parts at places like Shouldn't need too many parts. There are a couple of super expensive parts in the Vulcan 750 carbs, the main diaphragms, and the coasting enrichener diaphragms. If those are ok, you should be able to buy all the other rubber and plastic parts for a reasonable price. I rebuilt my carbs once, when I had the engine out to replace the stator. And unfortunately I had to replace the coasting enrichener diaphragms. They were literally melted. I think it was caused by ethanol gas. They were $65 apiece and there are two.

Synchronizing the carbs depends on a whole lot of things. Aside from possible minor differences in the carbs themselves, engine compression and condition of the valves makes a big difference. If the compression is noticeably different in one cylinder than the other, you can help compensate for that by setting the carbs slightly different. I have a Motion Pro Mercury type synchronizer I bought 30 years ago, before they outlawed the sale of anything containing mercury. These are tricky, if you rev the engine too high, it can suck the mercury into the engine. You can also use dial type vacuum gauges. The idea is to get the intake manifold vacuum as close as possible between the two cylinders, at idle, then rev it up SLOWLY and see if it stays put. Sometimes it is impossible to get it perfect on a worn engine, if so you just have to get it as close as you can.

As far as removing the evap system, it's really not that difficult, but it would take several thousand words to try and describe it. My 2002 Vulcan finally had a serious engine failure at 108,000 miles, and I recently wound up buying a 1997 model with 21,000 miles on it. It still has both the air injection system and evap system on it. I can try to take some pictures when I remove it, but I have a cheap camera that doesn't take good closeups. The biggest part of the evap system is mounted onto the front of the swingarm. There is a rectangular cannister and a round vacuum pump. Just pull all the hoses off and yank it all out. Follow the hoses to where they go, remove them, and cap or plug what they attached too. An exception is the hoses on the two nipples at the rear of the gas tank. Just put hoses on both those, and run them down through the frame under the bike. I believe there is a hose that goes to the surge tank as well, but if you are not going to use that, you don't need to worry about it.

I am a motorcyclist, NOT a biker.

1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
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