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  1. #101
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    Coils fail from heat and vibration, but bad plugs and bad plugs wires will kill coils quicker; the high voltage won't have a good path to the plug (where it is grounded) and can burn through the insulation layers inside the coil creating a short.
    A high resistance in the coil's primary windings will result in low output with a weak or no-spark condition. As mentioned, the stock coils are not great, but have been around and used for years...like, how old are the ones you have now - 27 years old?
    The copper core wires you are using are not suppressor type plug wires. What plugs are you running - resistor type? - with a R in the code (i.e. BPR7ES)? if not, you should use resistor type plug caps - NGK 5K ohm are common, but not both; resistor plug cap + resistor plugs.

  2. #102

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    Looks like it was my plugs that killed the coils. I had the non resistor type(without the R). Just bought new plugs and coils are in the mail. By the weekend I should be good. In other news: my electric start is a no go. The starter spins but doesn't engage anything. Bought a second starter a while back so I replaced it with that and it's still no good. Did some reading and it's a very common problem on XS's. The spring clip on fourth gear wears out and looses it's spring tension. I could order a new one or bend back the original. We'll see what I do, I'll just manage off the kickstarts for now.

  3. #103
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    It's not the lack of a resistor in your sparkplug that killed your coils - older systems never had 'em, they were first introduced to reduce radio interference,then later required to prevent the electrical 'noise' from affecting sensitive on-board electronic devices.
    I think it just from heat, vibration, age, an understanding that they are not the greatest, and that we ask so much from parts that have to work so fast and so hard every time we twist the throttle...at a moderate 4,000RPM, that coil is collapsing the primary winding and getting a big jump of about 30K volts 33 times per second - shocking! Amazing they continue to function year after year.
    any rebuild kits out there for troublesome xs650 starters?
    Last edited by TriNortchopz; 05-20-2019 at 10:14 PM.

  4. #104

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    Oh, I was under the impression that I needed either resistor plug wires, caps or plugs(only one kind). And being that I had nothing, I figured that's why my coils went bad, so I opted for resistor plugs which are the easiest and cheapest option.

    As far as the starter, its not so much the starter itself that is bad, but the worn out spring clip on 4th gear in the trans where it engages(if i'm not mistaken). I followed along with this thread:

    http://www.xs650.com/threads/starter-gear-fix.18060/

  5. #105

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    Sorry for not keeping this updated, but I got her going! New coils, resistor plugs and adjusted/cleaned points. She's been running pretty good so far, and I'm enjoying the fuck out of riding it. The hardtail isn't uncomfortable as I've been told, but that could just be because I have a spring mounted seat. Either way, It's a blast to ride. Keep an eye out for me at bike shows around the trip state area, and say hi if you recognize me! Can't wait to road trip this bike all over the place.
    Chop on!

    Edit: Still haven't sorted out the starter issue, but that's alright. Kicking it is a lot cooler

  6. #106
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    Right on, good to hear you been ridin'!
    Can you share two photos; one of the stock xs before you started and a recent one with what you built...

  7. #107

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    Here's the before and after. It's one hell of a difference, and still tons I want to change/add on.
    My instagram is @davidz30 if you guys wanna follow me and my bike around on there

  8. #108

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    Hey all,(if you're still following this thread) I thought I'd give an update on some minor changes and some future plans of the bike. So heres what I changed up:
    pull back bars(still 7/8)
    ditched turn signals, horn,electric start(never worked anyways)
    1" shorter seat springs
    Round headlight

    Also, I tool this bad larry to Gypsy Run and it was a blast. blew my fork seals and crashed in the dirt, but it was still kickass.Some issues though. So my fender kept cracking by the mounts at the sissy bar, so I welded the fuck out of it before gypsy run (kept it raw w no grinding them down) and only minor hairline cracks now. So I'm going to be caving in and just buying a new fender. And, a much bigger issue, in my oil theres metal shavings and a tooth of a gear was magnetized to my drain plug. It was my first time changing the oil since owning the bike, so I don't know how long its been like that. So it looks like I'm going to have to either tear into the motor, or buy another one.

    Some plans for the future, which are very subject to change:
    I had the idea to run a disc in the rear, ditching the front brakes. My idea was to run a harley dual flange hub laced to an 18 rear wheel, because i love the 18 for this bike. My stock rear wheel is 36 spoke, and the harley hub is 40 spoke. so i'm hunting around for a cheap 18 inch 40 spoke hub. This whole set up is seeming like its gonna be pretty expensive, so I'm highly debating this, but if i can do it for cheap then I'd love the project.
    That also means a 21 spool up front and extended forks.(4-6 over)
    Next is a new lowbrow manta ray style fender, and what makes it easier is that I wanted a new sissy bar anyways, so hopefully I can come up with something. My idea for now was to make a narrow version of a trident out of round stock.
    Paired with that is a new seat. not digging the solo anymore. Maybe a cobra, maybe a 2 up, maybe a rigid solo. we'll see.
    Probably different bars/risers. 1" bar swap if I can do it cheap.

    All this is subject to change. The biggest issue is money and time over the winter. I just started school, I have work, and I bought a shoveled that needs loving on top of that. But a lot of these plans have been brewing for a while. some might just take longer than others.

    I'll keep you posted as I make progress. But biggest concern is the motor, so any advice would help a lot, thanks!

    side note:
    Give me your thoughts on a big bore kit/rephasing. And I know my carbs desperately need to be tuned, so any of you gurus have some advise?

  9. #109

  10. #110
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    Sounds like a good time has been had on that chop ya built! I remember that little spring that disappeared in the engine - from the shifting mechanism wasn't it? That coulda got ground up in there to form some of that metal on the magnet. That gear tooth - are you sure it's not a piece of a gear dog? Is there any kind of a skip in the trans in any gear, which would indicate a missing tooth. Try spinning the trans through the gears with the rear wheel, with clutch disengaged and rear wheel off the ground...any skip?

    Read the gear dogs break off, typically on the mainshaft third gear, caused by high loading during rapid engine deceleration - using the engine as the brake:
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    "This is almost always caused by decelerative forces, not the driving power or torque, in effect reverse torque production, the end result when the gearbox is subjected to the immense forces produced when substantial engine braking is used."
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    "This is the 3rd gear main-shaft on a late XS650 gearbox; as can be seen the driving dogs are not overly wide, when the bike is ridden hard and subjected to hard downshifts, the inertia of the bike is transmitted through the gearbox, and ultimately in this case through three drive dogs. The forces are high enough to shear the driving dog from the main body of the gear...Yamaha changed the gear tooth shape in 1978 to a more rolling design. By increasing the area of the gear tooth in engagement at any one time, it decreased individual tooth loadings. To differentiate the old and new tooth shapes, Yamaha machined a shallow groove around the periphery of the gear."

    Can just get new gears, there are overdrive 5th gear sets available: http://www.xs650direct.com/products-22.html
    or swap out the whole assembly from a triple XS750 for an even stronger set than the '78-on 650's.

    I think you are better working with what you got, unless there is more wrong than the trans, and you can find a very low mileage engine, or you just end up buying someone else's headache. How is the compression? Maybe do a leakdown test too.
    One area to wake it up is with the cams; "The XS650 camshaft was never a performance item; its design brief would have called for good fuel economy, ease and cheapness of production and reasonable power for an engine of its type...".

    Rephasing will increase power, but power costs money - you also need a new cam and ignition timing system.
    Sounds like that 'new' shovel you got is a competing interest and the school and $$ things will further reduce your ability to get your re-phased big bore engine done. If it don't need it, fix what's broke and continue to have a blast on it.
    Sounds like the rear fender was under stress and tension, leading to the cracking - careful setup will prevent that next time.
    Can't just swap out a spoked disc rear wheel from another jap bike? Most likely the cheapest option to achieve what ya want, maybe only additional cost once caliper, master cylinder, brake hoses, brake light switch and lever are setup, is a set of wheel bearings and axle spacers...and maybe a rear sprocket depending on fitment.
    Any problems with the drum you got now?


    Lots of great info here, which some you just read, including engine rebuild, re-phasing, 750 kit, building a re-phased 880, gearbox, carbs, clutches and more:

    http://www.smedspeed.co.uk/tech.html

    Chop on!

  11. #111

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    Wow, thanks for all the great info!

    Trans doesn't slip at all and it is 100% a tooth. looks exactly like one of the teeth on that 3rd gear. So it seems like going over the motor myself id my best/cheapest option. I just have to figure out what I'm doing so I can get it done. a new cam sounds like a good idea, after I get around to tuning the carbs. I definitely wanna get more power out if though, It was tough keeping up on the highway.

    Definitely the shovel has been grabbing my attention, but it doesn't need too much as it seems. And for now I wanna enjoy it stock while I save up money and parts. School definitely is gonna get in the way, but I'm no stranger to staying up all night to get er done.

    Getting a rear wheel off another jap bike isn't such a bad idea, just gotta look around for what might work. The drum now work decent, and definitely needs adjusting, but to have a disc i would just feel better since I wanna ditch the front brakes.

    as always, will keep you updated. Haven't ridden much after gypsy, but I need to get it out of my system before winter. A lot of changes to the bike are coming, and I'm excited to make it fit me that much better.

  12. #112
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    This could be helpful for your engine rebuild:

    Step-By-Step Yamaha XS650 Engine Overhaul Instructions
    https://www.mikesxs.net/blog/step-by...-instructions/

    This place, specialized in the XS650, may be helpful as a reference for specs of performance parts you want:
    https://www.heidentuning.com/xs650-s...es-guides.html

    one example of a full gearset from an 1981 xs650 for under $100:
    https://www.ebay.com/itm/1981-YAMAHA...QAAOSwRjVc9Wlf

    EDIT:
    Lots of reading here; Yamaha XS650 Technical References;
    "Listed below are quick-reference links to threads in the forum on specific XS650 technical topics."

    Saw a thread for wheel swaps, front end swaps and much more of everything XS: http://www.xs650.com/pages/tech/
    Last edited by TriNortchopz; 3 Weeks Ago at 1:21 AM. Reason: Tech refs

  13. #113
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    If ya wanna ride keep something PURELY built for reliability instead of getting spread out too thin on mods. Since the Yam is proven I'd sort that out and since engines are cheap I'd work towards having a ready to bolt in spare. On my 650 I removed the starter and replaced it with an expanding rubber engine core plug. They're so easy to kick it wasn't worth fucking with and the plugs are almost instantly removable should you need the e-start. Your local auto electric shop should be able to test and rebuild your starter motor or you can do that yourself.

    You can fab a piece of flat bar to match the inside of the fender and run your mount bolts through both in the frame and bitch bar mount areas. Fenders are to keep shit off the motorcycle. If you want them to be structural parts modify accordingly. Steel is cheap.

    Shovels are fun and cool and eat money. Look after yours carefully because preventive maintenance is king.

    I definitely wanna get more power out if though, It was tough keeping up on the highway.
    I'd pimp it then sell it for a larger displacement more modern motorcycle if you can't afford to keep it for around town fun. Dumping money into little engines just produces an expensive little engine needing specialty parts when those wear out. Your Yam looks good and could sell for enough cash to buy a five speed Evo Sporty. Nothing one can do to an XS will make it as capable a machine because there's no replacement for displacement. Never marry what you can pimp.

    You can always build another one that's even cooler. They've always been good bikes to flip. I was flipping them before they were fashionable to chop. They're stout engines and what the Brits should have done instead of clinging to 1930s twins. Too bad they lacked Brit styling but chopping totally fixes that by removing the fugly stock shit. If you have space to hoard XS650 parts and get them cheap that's not a bad idea. Restorers want the stock leftovers, especially bodywork and exhausts.

  14. #114

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    I definitely need to mange my expectations and realize that a lot of these mods aren't worth it. I see it as a fun little ripper for around town, so i'd wanna do mods related to that. I know I will most likely eventually sell it, but its fun and cheap to gain experience on. I could easily see this bike going though many versions.
    You may be right, I shouldn't worry too much about crazy mods, but focus on fixing it with some smart upgrades along the way. I'm just dying to know what's happening inside the motor and where all that metal came from. there was a lot of it. Reliability is definitely the most important, the shovelhead will be my broken beauty.

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