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Running rich? '83 XV750

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Running rich? '83 XV750

PostAuthor: Bsidju » Thu Feb 07, 2019 5:54 pm

Just purchased this bike and I am a total noob, besides some basic mechanical aptitude.

Upon starting it smokes a lot and smells like fuel.
.
Spark plugs are blackened, but they spark to the frame just fine.

If I leave it idling it will sputter out within a minute or two.

In 1st it sputters and bucks and wants to stall.

I test rode it before I bought it and drove it about 30 miles home going up to 70mph with no issues at all, I was actually impressed with how smooth shifting and accelerating was.

I have opened the airbox and cleaned up the filter even though it looked pretty new.

I put 2.5 gallons of premium gas in with 4oz. seafoam and let it idle (with help) for a few minutes to get it to the carbs.

Any ideas of what I can do next?

:thanks:

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Re: Running rich? '83 XV750

PostAuthor: drainplug » Fri Feb 08, 2019 11:52 am

Look at the oil level in the sight glass for an overfill and smell the filler cap for gas. The petcock on these bikes can stick open, then the floats leak gas into the crank case and can cause major problems. if that is the case you can get a rebuild kit for them

I always change everything slippery on a bike that is new to me, you never know what the last owner didn't think was important.
So that's engine oil an filter (the hole points out) fork oil, rear end.
It wouldn't hurt to drain the float bowls in case there is water in them.
The other guy/gal sold the bike because they weren't riding it so you know it sat for quite awhile

























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Re: Running rich? '83 XV750

PostAuthor: bstig60 » Fri Feb 08, 2019 1:20 pm

:yup: Check the adjustment on the pilot screws, they control fuel for low RPM, starting and idle. Set them at 2.5 turns out from a soft seat to start with. Change the plugs to Autolite Ap63 PLATINUM.
"" put 2.5 gallons of premium gas in with 4oz. seafoam and let it idle (with help) for a few minutes to get it to the carbs. "" PUT IN HALF A CAN OF SEAFOAM FOR IT TO DO ANY GOOD....
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: Running rich? '83 XV750

PostAuthor: Bsidju » Fri Feb 08, 2019 6:42 pm

Ok, new plugs are OTW and I'm looking at rebuild kits.

Bstig60, I saw your link to service manuals and I gather that my account is too fresh for the download feature.

Could I get the files on exchange for a $20 donation to VTF? I figure if I'm going to pay for the manual, I'd rather support this great forum rather than a random company.

Thank you guys so much.

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Re: Running rich? '83 XV750

PostAuthor: Bsidju » Fri Feb 08, 2019 7:09 pm

Also, after poking around here for a while I'm getting the idea that I'm running on one cylinder, hence the loss of power. After changing both plugs with NGK's it gained power back for about half a mile or so, then right back to sputtering and dogging.


Any recommendations on rebuild kits?

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Re: Running rich? '83 XV750

PostAuthor: drainplug » Fri Feb 08, 2019 8:36 pm

Donation is a good thing but you need to have a minimum of posts to download from this site. I think a couple more and you should be good
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Re: Running rich? '83 XV750

PostAuthor: Bsidju » Fri Feb 08, 2019 9:58 pm

:cool: good to know, thank you.

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Re: Running rich? '83 XV750

PostAuthor: Flyingdog » Sat Feb 09, 2019 12:47 am

Here's my take and it'll give ya one more posting towards your manual d/l quota. Coarse, like anything else, you're final route would be totally up to you. :):

Bsidju wrote:After changing both plugs with NGK's it gained power back for about half a mile or so


This would show you that those NGKs would not be the problem, rather a good carb clean should give ya a good start to getting your machine back to running like a top.

Kits? Tons at various places. Ebay, Dennis Kirk, JPcycles, BikeBandit. I would suggest, though, getting a quality set. Something like K & L would save ya in the long run. Could even go to someplace like Jet R Us, and go for just individual parts. Going this way, may take alittle longer...meaning: How I go about it: I usually will do a complete cleaning of the carbs, put them back on the bike, without new stuff --->(unless it's obvious)<--- and evaluate how it runs. Then..if needed, then take them back off, replacing what I feel is needed. This way, I may or may not need anything after the initial cleaning. Clogged passages is the usual culprit. Coarse, over the years I accumulated pretty decent supply of gaskets, jets, needles, whatnots, so I don't have that lull, waiting for parts.
As suggested, changing plugs may or may not be beneficial for ya. In most cases, if new plugs fowl out that fast, it's not the plugs. Personally, JMO, I've never found these fancy metal plugs of any benefit, other than they last longer than good ole copper core plugs. Which is why they were invented in the first place. Unlike the routine maintenance of the 60's & 70s (or earlier), where cleaning and/or changing out plugs was done bout on pare with oil changes. People just didn't wanna do it anymore. Specially now-a-days, where 1/2 the time some people don't even know where the plugs are, let alone knowing "what they are". So...the 100,000+mile plug was used. Sure they "can" over come fowling, to a certain point. But they also demand more juice from the coils to fire. If you feel a hotter plug would help, you still can go hotter in the copper core family (cheaper) rather than the platinum/iridium route (expensive). But that's entirely your choice. Some love em. Some like the Chevy over Ford and vice versa. :bg:

Oh yea..good idea to also go over everything, making sure there's no vacuum leaks anywhere. Manifold, hoses to nipples etc etc etc. Any leaks will definitely put a damper on a good rebuild/tune-up. Enjoy.... :cl:
Last edited by Flyingdog on Sat Feb 09, 2019 10:55 am, edited 1 time in total.
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Re: Running rich? '83 XV750

PostAuthor: bstig60 » Sat Feb 09, 2019 10:48 am

You need a minimum of 5 posts to download. What do your plugs look like? Are the carbon fouled? If so, check the pilot screw settings, they should be approx. 2.5 turns out from a soft seat. I would also recommend checking the fuel levels using the clear tube method before pulling the carbs. Check for vacuum leaks as suggested... Check spark, you should get a bright blue spark...
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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Re: Running rich? '83 XV750

PostAuthor: Flyingdog » Sat Feb 09, 2019 4:05 pm

Might also check the spark plug cap, itself. Could show nice spark while you're checking (as in grounding out on engine), then "not", soon as you plug em back in. They have been known to go south at the worst moment. Specially if they're original. Just use VTF's search. You'll get oodles of checks, fixes and work arounds for faulty caps, wires and coils. One quicky, run the bike in dark area and spray water on em. See if things light up like a Christmas tree.
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Re: Running rich? '83 XV750

PostAuthor: Flyingdog » Sun Feb 10, 2019 3:18 am

bstig60 wrote: I would also recommend checking the fuel levels using the clear tube method before pulling the carbs.


Yes, thanks Bill..should have pointed that out. Checks and RE-checks, plus taking of notes, are very important before proceeding to tear into the carbs for the first time. Or any other function or yer bike. Getting a decent baseline established vs how the machine runs atm is pretty vital before first adjusting/setting stuff from one extreme to the other (specially on carbs), as I'm sure your well aware of. Really helps get ya back to that starting and/or that all to common "well..that didn't work"..... point. :bg:
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Re: Running rich? '83 XV750

PostAuthor: Bsidju » Sun Feb 10, 2019 11:59 am

There's definitely fuel in the crankcase. Petcock rebuilds are OTW and the carb rebuilds just got here. I'm pulling the carbs today to see if they need the rebuild. Will update with pictures a little later to get some insight. :thanks:

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Re: Running rich? '83 XV750

PostAuthor: Flyingdog » Sun Feb 10, 2019 12:17 pm

Another little tidbit I find very useful. When pulling the carbs, take those manifolds off and give them a good squeeze. Many times all those little cracks sometimes will open up big time. Then again some times they are just little surface cracking. 80% or more of times, if there's a vacuum leak it occurs at the manifold. Either the boot to cylinder or the manifold boot itself. You'll also find, replacing the four hex-head manifold mounting bolts, with like sized stainless steel allen heads, will make the next removal sooo much easier.
Just remember, all those little passages have an entrance and exit. Meaning, squirting carb cleaner in one area, it "has" to come out another.
Good luck and enjoy.
Last edited by Flyingdog on Sun Feb 10, 2019 3:55 pm, edited 1 time in total.
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Re: Running rich? '83 XV750

PostAuthor: Bsidju » Sun Feb 10, 2019 3:54 pm

diaphragm.jpg

20190210_153506.jpg

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20190210_152355.jpg
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Bsidju
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Re: Running rich? '83 XV750

PostAuthor: Flyingdog » Sun Feb 10, 2019 4:27 pm

Yep...that's a dirty carb. Looks like the screen "separated" from the valve seat. It snaps to the bottom of the seat.
But, all-in-all, I'd probly rate yours....a "2" on a scale of "10" of dirty carbs. Majority looks just varnished. Usually from gas evaporating cuz it was put up wet and not prepped for storage. Should be a breeze for ya..just takes rags, air, carb cleaner, carb cleaning wires, a dremel, some mirco drill bits (maybe), buffing/wire wheels, polish compound, good music, drinks of yer choice and patience. Hopefully the carb body around that emulsion tube is not pitted too badly. Can't tell what's shadow, crud or whatever shape the carb body is around the needle jet.


Now... here's an "8" of dirty carbs. After few hours of drill'n, scrub'n and buff'n for a buddy, he says the bike never ran better.

DSC_0047.JPG

DSC_0048 - Copy.JPG

DSC_0057 - Copy.JPG


That bottom pic is the only way I could get the float needle seat out..Drill the hole, pound the nail in, Vice grips and lotsa heat, tapp'n and a whole bucket full of twist'n & shout'n. :bg:
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