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1982 XS400 SECA cam timing mark confusion

Discussion in 'The Garage' started by GoodMachine, Apr 25, 2019.

  1. 1982 Yamaha Seca XS400 cam timing (DOHC) craziness!!

    Hi everybody, this is my first post to the forum. I've been looking for a solution to this problem I'm having with no luck - I did find someone having the same problem on a different forum, but his post went nowhere (no replies, 5 year old thread now). I've also found a mention of it here but the thread goes off topic and the question isn't solved. I am a professional motorcycle mechanic running my own little vintage bike shop, (so go ahead and get technical!). I have the manual for this bike but it's confusing. SO, here's the problem:

    I am at the step of putting the cams back in and setting their timing after replacing the head gasket. I have the left cylinder at TDC, (timing mark lined up at crank, piston verified visually at TDC)....Then the service manual gets confusing. It talks about installing the cams with the "valve timing mark on the camshaft faces pointing up" -this is ok at first, the caps can all be installed without any lobes putting pressure on the valves. But then the manual says to rotate the cam so the cam timing mark is lined up with the cap... ok, so there's now 2 timing marks on the cam, but which is which? And I already was lined up with the cap.. so there's a mark on the cam "face", and I'm unsure what the "face" it refers to is, I originally assumed that it meant the dot/mark on the outside of the end of the shaft (facing up), but there's the mark on the bearing surface itself as well. The illustration in the manual shows the exhaust cam in a position that's impossible to get to, and then in the CAUTION! section it warns against turning the "left camshaft" - there is no left camshaft!
    Basically I just need a reliable procedure for getting these camshafts back in! (It ran perfectly before I took it apart btw, and disassembly was followed with the manual)

    Anyway I'm sure you guys know all about this cuz the cams need to be removed to adjust the valve lash, so this procedure can't be that messed up! Thanks
     
  2. Hi everyone - I was hoping to log in this, morning and see a huge robust discussion about the cam timing marks grief issue!! (cuz it's just such a juicy and interesting topic).Oh well, I have faith! I was wanting to post images of the page from the service manual in question - I'm actually using one I got from this site - it's the one that's separated into chapters (the first one in the service manuals section is for the SOHC bikes - mine is the DOHC). Anyway I can only look at the dang manual in my phone cuz my ever wise laptop thinks the files are "dangerous" and won't let me open them. (ACK!!!). If I can figure out how to get my laptop to cooperate I'll post the pics of the service manual. (I don't have a hard copy, I run a little shop from home working specifically on vintage bikes after being in the industry and seeing countless customers being turned away with nowhere to go for service for their "old" bikes, so it's not like I have a heap of resources available to me).

    So if anyone knows what's up or even has their own procedure for timing the DOHC I'm all ears. There's nothing worse than that sick/nervous feeling when you just aren't absolutely confident in your mechanical timing on an interference engine, or any engine for that matter...

    Oh and for reference this XS400 has an electronic ignition, no points. And the crankshaft timing mark lines up with the left piston at TDC, so I don't think its an issue of the mag having turned on the crankshaft and become misaligned (that happened to someone else here on a post with a SOHC XS400, the woodruff key has dislodged and the mag had turned on the spindle, thus misaligning itself).
    Any help would be very very appreciated, soooo close to getting this bike back on the road!
    Thanks :)
     
  3. spectra

    spectra XS400 Junkie Top Contributor

    This sounds like something @Jeff0133 may be able to answer......he rebuilt his DOHC Seca.

    I know there are a few other members with the same bike also. I have one but havent wrenched on it yet.......its in pieces waiting.......
     
  4. thomas2800

    thomas2800 XS400 New Member

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    Denmark
    Hi, did you ever find put how to fix it?
    Im having tre exact same problem… hope you could help me out
     

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