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What is wrong with my bike?

Discussion in 'The Garage' started by got20z, Sep 9, 2019.

  1. got20z

    got20z 1977 XS360

    Hi guys,

    My current situation for my recent 360 project is getting it tuned. I'm going crazy trying to get this right and looks like riding season will end before I get it "dependably" road ready.

    A little background:
    Bike is a 1977 xs360. Only thing aftermarket in regard to it running is mufflers I bought on Amazon (stock ones weren't on the bike when I bought it). This is stock headers as well.

    The problem I have now in this stage of where I am with it is that it does NOT want to hot start once I've had it out riding for a few miles. I've tried to open the throttle a bit when doing this to help it start but that doesn't help.
    In addition to that it seems to hesitate (only at times) when idling once it is hot and the left cylinder will pop a little like it is lean. The hesitation at idle is getting me because in rare cases it will stall and that's no good either. At idle it will also fall on its face (sometimes) if I quickly snap the throttle back. Yesterday on a test ride once it was hot the idle would also hang but only sometimes. The spark plugs never really seem to indicate it is lean, they are dark and sometimes a bit damp as if it is too rich. I will clean them up and put them in and after another 5 mile test ride they look the same. It never really wants to start or run on the enricher either. Too rich? I don't know because half of my symptoms are rich and half are lean.

    Carburetors have been gone through, cleaned, blown out, etc about 6 times now. I thought maybe the mufflers were giving it an extreme case of running lean so today I put in one size up pilot jets (20). Seems to be about the same as far as it fixing my problem. I can't seem to find the equal spot where the need to be tuned. If I go up to 1.5 turns out the left side will pop like it's too lean then any more turns out it will stop doing that and just not idle that well and the idle will sometimes hang and very slowly drop back down.

    Things I've done:
    New air filters, new carb boots, carb sync with gauges and manometer, new needle valves, pilot jets. Checked all timing, valves, points (also are new), compression, spark. Sprayed around the intake areas and carbs to check for air leaks. Doesn't seem to have anything wrong there.

    The bike runs really good when actually riding it in all gears at all throttle positions.

    My other 360 has a very similar setup but only it has a MAC 2 into 1. I have the NGK BPR7EIX iridium plugs, 20 pilot jets, and 1 1/4 turns out on the fuel screws and it does pretty well all around. I haven't adjusted on it in over a year.

    Any thoughts? Sorry for the long post but wanted to cover all of the rhetorical "do you have spark" and "did you clean the carbs" questions.

  2. xschris

    xschris a lifestyle not a trend Top Contributor

    Check to make sure that you pilot mix screws aren't broken off in the carb bodies. This can happen with these type carbs. The xs360 also uses a specific type pilot jet not found on most other bs34 carbs. There is a thread on pilot jet differences in the forum.
  3. got20z

    got20z 1977 XS360

    Thanks for your post.
    The pilot screws are good. I was actually surprised of how they are in really good condition and the tips of them are still very sharp.

    I've noticed it's hard to find the stock match pilot jets for it. The size 20 ones I put in are the bleed style ones with the holes on the sides of the shaft. The original is not made that way. I figured that probably has a big effect on things but I do have the bleed style on my other bike and it runs well. Just puzzling since I thought I was working with pretty much the same machine here.

    Thanks again, I'll look into the thread more about jet differences. :thumbsup:
  4. NewHavenMike

    NewHavenMike 1976 XS360C Top Contributor

    The bleed and non-bleed pilot jets are NOT interchangeable. When you first get the bike running, you will need to make constant adjustments for a while until everything "settles" a bit, especially new points. Syncing, idle adjustment, and idle mix should all be done after you ride the bike somewhat aggressively for about 30 minutes.

    Plugs that look wet are very rich or its oil deposits. Chances are that you are too rich to begin with.

    How are you checking the timing? Good compression?

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