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Timing issue

Discussion in 'The Garage' started by Surfrat28, Oct 6, 2017.

  1. Surfrat28

    Surfrat28 XS650 Enthusiast

    hey guys

    Hope everyone is riding while the weather is great! I have a 1978 Yamaha Xs650 bored out to the 707cc. I have currently made the bike into a chopper after the fong bros
    XS650 style. I am currently running stock pipes without mufflers. My electrical system is the Boyer ignition system. Everything else is stock.

    I thought the bike was a little to loud even with baffles so I added the stock exhaust pipes (after removing the baffles) and when trying to kick it over it kept Igniting before it hit the top while kicking it over thus almost breaking my ankle.

    - how to do the timing?
    - How do I prevent the kick back while kicking it?
    - Suggestions while running straight pipes and getting the bike quieter like Hughes hand built bikes.
    - Can I use a solenoid with the Boyer ignition??

    Thanks guys!!
  2. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    went back over your old posts and threads.............you state the bike is a 79...........Before you installed the Boyer ignition the engine had the Factory TCI stator, rotor, and TCI ignition box and the motor had points under the cam covers...........You have BS34 carbs on the bike.

    You have been getting carb jetting advice for the 79 BS38 carbs............BS38 cabs and their jetting has no correlation to BS34 carbs and their Jetting...........

    Yes, if the timing is out it will cause the backfiring...........also wrong jetting could cause this as well............

    Could you please post the engine Vin no....?

    Did you jet your carbs on the advice given in This thread ??

    Important you respond to the question above.............if yes to the question then the carbs will need to be sorted.
  3. Surfrat28

    Surfrat28 XS650 Enthusiast

    I am using stock jetting from that thread hat you had mentioned. When I got the bike the electrical system had been frankensteined together.

    If I used the jetting from that thread could the jetting be the reason why it is so loud/ why it’s so hard to start?

    Vin: 2F0-201102

    Vin: 2F0-201102
  4. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    Your bike is an 80SG..... ID Chart  27-10-15  02.jpg ....production date may be late 79 but the Model year went from Aug to July

    Yes the jetting is all up the shit, and that will make it near impossible to start or run, if it does manage to start. Be lean as hell if you have gone down to 127.5 or 130's as advised......

    Here is a graph for the carbs and the jetting. get a size below and a couple above to play around to suit your exhausts and air filters.
    Go through the carb guide, (compliments of 5twins, Grizld1), Posted PDF file......this is the holy grail to carb jetting.

    This is a graph from the guide for carb jetting for all the different carb set ups for the different models............Your carbs are BS34's.

    Carb jetting.jpg

    Attached Files:

    Last edited: Oct 7, 2017
  5. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    The Factory electronic ignition, (TCI), was still on the bike, but the PO had installed points and it looked like he was changing the ignition, for whatever reason, maybe the TCI unit wasn't working. All the components for the TCI ignition pics are in your first thread. http://www.xs650.com/threads/1979-kick-only-wiring-diagram-help.49247/#post-504272 .............these guys should have made sure the bike was ID'd properly, especially as all the components pointed to an 80 and later model with BS34's and the TCI ignition

    This is what can happen if help is done through a PM instead of in public............we can all make mistakes and usually someone will correct it or think of something that others have overlooked.........

    Sorry i missed the thread. 5 months of wasted time...............Done now.

    You can still set the cam chain and tappets while your waiting for your jets........ Thinking on it you will have the jets you took out so start from there and reinstall them, they should correspond to the graph above.

    Put the year of the bike and any changes made in your byline.....helps when answers are given.
    Last edited: Oct 7, 2017
  6. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    The pilot air jets Peanut shows in the first thread i linked to are the wrong type............. BS34 pilot air jets will be a smaller version of your mains
    Pilot air jet........................................Mains
    , P1000705 Text.jpg , P1000711 text.jpg

    Don't take to much notice of the jet sizes as i have an Oceania model BS34 cabs that are jetted different to the US model BS34 carbs

    Edited to clarify pilot jet to mean pilot air jet, as grizld1 pointed out
    Last edited: Oct 7, 2017
  7. grizld1

    grizld1 Grumpy old man Top Contributor

    Hey Skull, it's a real tough call, isn't it? Sometimes two or more heads are better than one, but sometimes some of those heads belong to guys who are large of voice and small of brain, and the poor OP winds up not knowing what the hell to think.

    I know that you know the difference, so excuse me if I clarify for those who may not. The pics show the pilot air jet located in the back of the intake bell; same series as Mikuni small round main jets, as noted. The pilot jet is a fuel control jet located inside the carburetor; for BS34 carbs, series BS30/96.

    Rat, you "do" a Boyer ignition at full advance with a xenon strobe timing light pointed at the alternator. Rev the motor until the the rotor mark stops moving to the left. If timing is too advanced (rotor mark appears to stop left of the full advance mark on the stator), retard it by loosening the screws on the Boyer timing plate and turning the plate counterclockwise. If too far retarded, turn the plate clockwise. A very little movement makes a big difference. And yes, I know your TCI stator has no full advance mark. A fast search will show you where the rotor mark needs to line up at full advance.

    Sorry, I don't know what you're asking re. using a solenoid with a Boyer ignition. The only solenoid on these bikes is the starter solenoid. It has nothing to do with the ignition.
  8. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    Thanks griz, edited my post.

    Yea, when someone only has a few posts up it isn't very hard to go back and check up on the back story..............
    Last edited: Oct 7, 2017
  9. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    Surfrat, any progress or were the waves to good............

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