Help a Yamaha newbie.

27 replies to this topic
  • hattackk

Posted January 14, 2015 - 07:19 PM


Took a look at the coil pack. Here are my readings. Looks like the primary is bad. According to the manual it should be .2-.3ohms. I'm getting 1.5ohms at the primary. Secondary seems to within spec.

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Edited by hattackk, January 14, 2015 - 07:21 PM.

  • grayracer513

Posted January 15, 2015 - 07:47 AM


That's not really too far out.  Hard to say.


The links for the two vids require a player that can handle Quicktime, but either way, it doesn't work as just previously described.  The engine will hit compression at about 120 degrees before top dead center.  With a healthy engine, it is nearly or actually impossible to kick through the entire compression stroke, so the idea is to shorten that to just before TDC.  You don't want to go past it like used to be done with old British singles, though, because the kick starter doesn't turn the engine fast enough to get back to the compression stroke in one kick.  What you're trying for is to end up somewhere around 30-40 degrees before top, so you can kick it past the spark point and past that as it starts.  So here's how it should go:


  1. Without using the compression release, push the starter until you run up against compression (the "hard spot").  Stop.
  2. Hold the kick starter still in that position, pull the compression release, and push the crank down just about 1-1 1/2 inches farther. Stop.
  3. Return the kick start to the top, let go of the compression release, and with no throttle, kick through the whole stroke, forcefully, but smoothly.

On a cold start, if often helps to prime the engine with the accelerator pump by giving it 2-3 twists on the throttle.  In general, that's something you never want to do once it's warmed up, though. 

  • hattackk

Posted January 15, 2015 - 08:02 AM


I really appreciate the help and patience Gray! You are right about not being able to kick through an entire compression stroke. It is like a brick wall. I will try your method and see what we get. Ordered new coil pack just in case and will put a fresh plug in it. If none of this works I'm going to sprinkle some holy water on it and see if it sizzles.

  • hattackk

Posted January 21, 2015 - 07:10 PM


So I decided to take the bike to a friend of mine who is a motorcycle mechanic. He kicked it over a few times and instantly said something didnt feel right said it was way to hard to kick it over even being a yz400. Told me to tear the engine apart because something is wrong. Tore the engine apart tonight and valves and pistons are good. Looks like a healthy engine. Until I went to check the play in the rod. There was absolutely none. In fact the rod was seized up on the crank and wouldn't rotate. I think I've found my problem.

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  • hattackk

Posted January 27, 2015 - 12:08 AM


Just thought I'd give an update. Put the engine back together with new crank/rod assembly. It tried to crank a few times so I decided to pull it behind a truck and it cranked and ran. Had to give it gas to get it to crank and stay running. Hopefully with some carb idle screw and idle stop adjustment it will crank via kick starter.

  • hattackk

Posted January 27, 2015 - 04:14 PM


Got her running via the kick starter! Have to tweak the jetting though have the idle stop screw turned all the way in. It runs really strong!

  • hattackk

Posted February 07, 2015 - 07:53 PM


Update on the yz. Took her out for the first real ride today bike cranks and runs like a champ, once you know the starting procedure. Only issue is the bike slips under load in 5th gear. Feels like the clutch is being pressed in. I adjusted the clutch cable with no success. Having had the motor apart I inspected the gears and they all looked good. Not rounded off or anything. Not sure what is going on. I've researched this and see where a few say it could be in the dog box area while others say it could be clutch. At this point I'm a grand into the bike and questioning whether I should sell it before I end up taking a huge lost by trying to fix it. I jacked the bike up and let it run in 5th gear it ran fine. I don't hear any noises inside the trans. I even applied the rear brake to put it under load just the chain was noisy but no grinding or rattling in the transmission. I'm going to through a new clutch and HD springs in it to see if anything changes. If it doesn't would it be in my best interest to sell it and get something newer?

  • hattackk

Posted February 07, 2015 - 10:48 PM


I'm this far end so I'm going to see it through. Easier to sell a fully functioning bike later down the road

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