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The $70 1981 XV750 Black Budget Bobber Build

Chop it, rake it, slam it, build it for show.
New parts, old parts, built from scrap. [Hammered out of bare stock & welded with sweat.]
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The $70 1981 XV750 Black Budget Bobber Build

PostAuthor: extremeodd » Sun Oct 06, 2019 4:08 pm

With all bikes purchased for such a cheap price, it needs tons of work. Forums tend to be a jackpot of collected knowledge on rather niche topics and this one has been one of the best sources in my searches and currently is the most active. Figured I should sign up and contribute where I could. This is my first motorcycle but I've been wrenching for 16+ years and in the last year built up a surprisingly fast 2 stroke bicycle. So none of this is too terribly foreign and thankfully this bike is fairly simple to repair.

How I got the bike: I was browsing FB marketplace and saw a nonrunning old Yamaha listed with the completely wrong model name for $200 that triggered my gut instinct on a 'good buy'. At the time I didn't have $200 so I quickly forgot about it. About a week later when I went to the marketplace again to see if there was anything that I must have, that old Yamaha was in my 'top picks for you' and the price was down to only $70! Figuring it was a typo but unable to pass up a potentially good deal, I messaged the guy. Turns out the price is correct and the fire sale is due to needing the money asap and it's the same as what the scrapyard was offering. So I went and picked it up as I figured at the very least the damn near new tires that were on it would be worth enough to cover the price if the motor was seized.

Here's how it looked after getting it home (and installing an ultra rare craftsman 10mm ratcheting shifter)
70493564_377607602915742_4403259373040697344_n.jpg

Video of it running before tuning


So far to get the bike running all I had to do was:
Find and install a starter that still had the removable gear attached (damn thing was $100 used)
Throw on the cheapest Walmart lawn mower battery that was big enough (its huge and hilarious, but was only $28)
Clean (not really needed) and tune the carbs($2 for carb cleaner)
Fill with oil($11)
Gentle application of starter fluid along with momentarily catching fire($2 for starter fluid)

To get it driving:
Filled and bled the front brake($3)
Removed and replaced a broken screw on the rear brake linkage($0.20)
Purchased and installed the world's shittiest pot metal aluminum amazon shifter($10)
Readjusting the clutch cable to allow the clutch to fully engage($0)

Getting signals and brake light working:
Resoldered 2 broken solder joints on the handlebar switch($0)
Soldered together cut brake lever wires($0)
Zip tied rear brake switch to the new battery as the tray was deleted to accommodate a ridiculously large battery($0)
Replaced brake light bulb($0, borrowed on from another bike)

Getting speedo and tach working:
Soldered broken tach signal wire where it splits to 2 wires just before the tach($0)
Replaced speedo cable ($15, wont be here till tuesday)

Addressing the paint job the PO did while s**t faced drunk (painted the tank and parts of the frame/chrome/engine/wiring/handlebars/gauges/seat with red spray paint):
Used a scotchbrite pad soaked in gasoline to soften/remove some of the paint on the tank and a plastic card to scrape off what got softened exposing the factory black($0)
Used the same pad to scrub off the chrome, engine and anything else unpainted($0)
Took a random can of matte black spray paint I had laying around and fogged the tank and parts of the frame to finish cleaning up the evidence of the drunken overspray ($0)

Quality of life issues:
Lubed the super stuff throttle cable with some 10w30($0)
Threw on a left side mirror($0)
Built manometer and synced the carbs to keep cylinder 2 from constantly cutting out during 20% or less throttle input($0)
Filled the bone dry empty front forks with 20w-50 oil through the air valves and pumped in air to spec($1)
Aired up the rear shock to spec($0)
Purchased and installed left side peg($12)
Removed, disassembled, polished/cleaned, and reassembled front caliper to address sticking issue($0, reused all hardware)

Grand total:
$184.2

After all of that, she now looks like this:
71144359_454974445115119_8823415443776602112_n.jpg


From what I can gather the bike has passed through the hands of several people that weren't super knowledgeable on diagnosing and addressing problems and fairly simple repairs snowballed into the bike being "worthless". As you can see from what I typed above, there has not been a single hard to fix issue on this bike. Hell, the only reason it wasn't running is someone started replacing the starter and sort of gave up midway through for whatever reason and slapping it together enough to sell it to the guy I got it from. Hence needing the left side footpeg, shifter, and starter with attached gear.

This bike still has fairly little value being an old virago that is missing all of its decorative covers and hasn't had the cafe racer or bobber treatment (yet) but I'm absolutely loving it and it's gotta be one of the best bikes to get your feet wet with both "restoration" aka getting the damn thing running and riding a motorcycle for the first time.

My future plans are to make it into a bobber as cheaply as humanly possible. With the seat subframe simply unbolting this will be a very simple and incredibly cheap build to pull off.

Essentially I will be copying an amalgamation of the 2 bikes below. Except, mounting the seat except farther forward and possibly attaching to the same point as the end of the tank, and attached by the nose so it's cantilevered out along with having a natural spring action (like the 2nd bike) I'll keep the exhaust the same as whats on there (stock with gutted baffles) along with all of the stock intake bits since it's been tuned for that setup and I'm not willing to spend any money on jets to retune the carburetors.

maxresdefault.jpg

1983-yamaha-virago-750-bobber.jpg


Mostly I want to do this because it looks like a fun project, that lower seating position feels amazing after I took a short ride without the factory seat in place, I figure it can't hurt the value of the bike any, and it'll be super cheap/fairly easy to pull off. Not to mention that it's all bolt-on stuff for the most part so it'll be easy to reverse.

I'm thinking it'll go like this:
Unbolt the seat subframe and discard
take an ebay seat with bracket for $35-50, fabricobble a mount from bits of metal, bolts, and curse words if it doesn't easily bolt to that doohickey that keeps the tank from sliding back
space the tank up 1-2in with the same hardware your bolting the seat down with
remove most of the relays and shove the wiring under the tank extending stuff as needed
bolt on seat
attach generic/cheap ebay 'bobber fender' to the swing arm
mount and hookup generic/cheap turn signal brake light unit to bobber fender
finally, if feeling fancy, some polymorph moldable plastic to make a decorative cover for the end of the elevated tank that extends down to the frame to cover the unpleasant tank seams and the exposed opening.

I have no doubts that nothing will go smoothly but that is the fun of working on a bike!
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Last edited by Jake on Mon Oct 07, 2019 4:59 am, edited 4 times in total.
Reason: Moved from New Members Introductions to Choppers Customs Cafe

extremeodd
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Re: Snagged a 81 xv750 for $70 so here I am collecting knowl

PostAuthor: bstig60 » Sun Oct 06, 2019 4:13 pm

:VTF:
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: Snagged a 81 xv750 for $70 so here I am collecting knowl

PostAuthor: Jake » Sun Oct 06, 2019 6:00 pm

:VTF:


Please add your location to your profile so no one has to ask in the future. With members all over the globe, some info is geographically specific.

Add your location at this link to your User Control Panel

Since your intro was a rather long post and contrary to the wishes of the forum Admin to keep it short, I have to move this thread out of New Member Introductions.

Based on what you posted as to your plans, I have moved it to Choppers Customs Cafe.
_______________________________________________________________________
“It ain’t what you don’t know that gets you in trouble.
It’s what you know for sure that just ain’t so.”

~Mark Twain


There is an old Chinese proverb - "Man with one watch knows the time. Man with two, not sure."
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Re: Snagged a 81 xv750 for $70 so here I am collecting knowl

PostAuthor: Flyingdog » Mon Oct 07, 2019 5:12 am

:VTF:
Kinda skimmed thru the posting, within yer long list of fine turning, this one jumped out at me.

extremeodd wrote:Filled the bone dry empty front forks with 20w-50 oil through the air valves and pumped in air to spec($1)


Spectro is the only (20/50) fork oil I know of..and that's for pretty much for track work, with highly modified dampen rods. Pretty sure you didn't use that.
If engine oil, I bet that rides as smooth as silk..(not) :bg: JMO: Sure wouldn't put fork oil in an engine, any more than I'd put engine oil in a fork. Special with a viscosity of 50 when things start to heat up. Forks heat up waay more than realized...and..dampen holes are really tiny for thick oil to push thru. ATF would be the closest to "any" alternative that I'd use..but even then..fork oil is for forks..I always say. Motor oil is for lube'n, not hydraulics. I mean, it's not like yer forks are going to fall apart, but somethings just jump out at me that make ya go..Hmmm. Kinda like "throttle tuning" an engine, when a person has "no" idea if engine oil is going where it's suppose to or even if the valves are ok ("one" possible source of your backfiring)..... ya gotta do with whatcha gots to get things roll'n, specially have'n that much work ahead of ya. Have fun.
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1981 xv750 Virago
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Re: The $70 1981 XV750 Black Budget Bobber Build

PostAuthor: extremeodd » Mon Oct 07, 2019 12:51 pm

Yeah, I totally tossed in some engine oil. Technically it's a mix of 10w-30, 20w-50, and some opti 2 2 stroke oil :lmao:

Honestly, it's a massive improvement over no oil and isn't a harsh ride at all. With the air pressure set within 25% of max spec and running ~9.4oz a 20w-50 mix, the forks easily make speedbumps feel like they are barely there so I'm not too sure what you are talking about with inferring that the ride will be rough.

The seals are all but completely shot so I really can't be bothered with spending the +/-$10 on the proper fork oil when it's all going to get wasted via leaking anyways. It's not like I blindly added the oil, I did quite a bit of research beforehand and found that a number of people will run various weight motor oils to achieve a firmer suspension than higher weight fork oils allow. With that said, I'm not sure if I came across anyone using 20w-50 but it'll do just fine until I replace the fork seals and upgrade to progressive springs.

Thankfully all of my oil passages are working just fine and the heads are getting a healthy flow of oil, can't imagine a single person who would start up an old bike and not check such a basic item. No oil flow spells death for any parts that are affected. Plus it's really easy to check with those obvious external oil pipes running to the head. I took care of checking that when I first added oil and swapped the oil filter.

Some of the popping on deceleration can be attributed to needing to adjust the valves. (EDIT: Ah, you meant the video. That was taken like 5 mins after the first start and it was running like hell until I went through the carbs and fixed the float heights, tightened a VERY loose jet, etc. At one point it was even throwing and keeping lit flames that were several feet long, that s**t is scary when it doesn't go away until you rev it. Now it only occasionally will pop once or twice doing a neutral rev. The only popping it currently has is upon deceleration from high rpm) The ticking is loud enough to indicate they could use some adjustments and I'll be taking care of that whenever I get my grubby mitts on a set of feeler gauges. Comparing to the few dozen videos of various xv700/750/920/1000/1100 bikes I've found, my valve tick is no louder than what appears to be normal for these engines so I'm not in a huge hurry to address it.

I've found it's fairly easy to 'turn on/off' the backfire on decel via over enrichining the pilot screw/setting the choke to above 0%. Also, it never occurs at idle, while cruising, or accelerating which typically indicates an issue with the fuel mixture.

Rode around for a while after making this thread and discovered that I was able to 'fix' a flat spot during acceleration from 2-3.5/4k with having the choke about 10% on. This, along with the findings with the decel popping is telling me that I might want to pick up some jets to get her fully in tune, makes sense with the PO cutting out the baffles. From what I've been reading 9 out of 10 times people don't properly up jet to adjust for the sudden decrease in backpressure and end up running lean/battling issues with popping on decel.

After the fun of getting a Dellorto PHBG carb to play nicely with a super high strung 66cc 2 stroke, getting one of these hitachis to run well should be easy enough. For adjustments, there's only the pilot screw, idle screw, sync screw, pilot jet and main jet. So out of all of the adjustments, there are 2 items you need to buy which means there aren't too many 'tuning combos' AKA what pilot with what main. That makes things far easier to manage compared to the ridiculous number of adjustment points the PHBG carbs have. Sure, syncing isn't a fun process but with a manometer, it's fairly straight forward and easy.

With the Dellorto you have the idle jet, main jet, atomizer tube, slide, needle, needle clip position, and idle screw to adjust. So for that little motor I was working with, that was: 3 idle jets, 14 main jets, 2 atomizer tubes, 2 slides, 11 needles, and 4 needle clip positions. This makes for 7,392 tuning combos which can be tedious to say the least. I would have killed to have a pilot adjustment screw.

Thanks for the input, I'll be sure to double check those items :)

extremeodd
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Re: The $70 1981 XV750 Black Budget Bobber Build

PostAuthor: extremeodd » Wed Oct 09, 2019 1:44 pm

While waiting on a few odds and ends to come in I decided to make a rough mockup of the seat I want to use and try to determine where I want to place it. Ended up taking a springer bicycle seat, pulled off the foam and vinyl, then using a propane torch I flattened it out and shaped it.

It looks rough and rediculous I will admit but it was an excellent proof of concept that gave me some more confidence in my seat choice. It also showed me that I'll want to elevate the end of it some more so I don't have to hang on to the handlebars for dear life when accelerating.

This is the seat style I'll be using. Not too sure if I'll utilize the springs or not.
https://www.ebay.com/itm/Motorcycle-Spr ... 2743467244
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8d40b3c8-38fe-49a6-8ae9-27acbfd5fca6.JPG

db6891f2-3b21-45d2-8b77-f8bfe3a77d2c.JPG
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extremeodd
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