[LonesomeRider]

So I bought my z400 brand new in 2003. Put a ton of time and money into it. Bought a raptor in 2007 and ended up riding that a lot more. Now I’m trying to get the Z back up and running. It’s in amazing condition for a 20 year old.

I had a quicksilver carb on it that started acting up. Can’t get parts or replacement for it anymore. Really loved that carb with my set up. I bought one of those fcr mx39mm knockoff carbs on eBay. Heard good and bad about them. Figured I’d try one for 116 bucks. It’s installed and seems to be functioning. Jetted according to posts I’ve read to get me started.

The issue is it hard to start but will start and idle like a champ for a few minutes then die. If I touch the throttle while it’s idling it will die. I’ve checked the oil level, the valve clearance, compression is good, battery is new. So I pulled the plug and hooked it back into the spark plug boot, grounded to the cylinder and turned it over a few times. The spark seems strong but sporadic. Not rhythmic and it stops and starts. Bunch of sparks then nothing then bunch of sparks.

Seems like I’m losing spark or misfiring. Does that sound like a bad coil or maybe something else? I don’t think it’s the carb being when it does start and stay running the idle is strong. I’ll try to get video of this later. Thanks!


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[LonesomeRider]

Tested the coil. It’s in spec. Cleaned it all up and the plug is firing consistent now. i have an actual Keith in fcr carb. I ordered a rebuild kit for it. Got it a while ago on eBay. Guess I’ll clean and rebuild that and try it. Maybe pull this carb off and take it apart. Maybe a jet is blocked.

 

[xbird]

If it sat for a long time, you should go through the entire fuel system top to bottom. i've had crap in tanks that pulls to the petcock filter after a bit of running, then blocks and kills it. sediment will fall away, refire and the issue repeats.

 

[LonesomeRider]

It sat for quite a while. Garage kept though so it wasn’t rusting away outside. The carb is new. I did notice the petcock was wet. When opening the drain on the bottom of the carb, gas keeps pouring out of the drain tube. Also I have a glass filter on the fuel line so I can see if gas is flowing or not. It’s frustrating. I’ll pull the knock off fcr carb and clean it just to be sure. When the rebuild kit comes in I’ll rebuild the original keihin carb too. This bike ran like a monster with the mods and Edelbrock quicksilver. Dyno’d at 38 horse and 86 mph. I out ran everything on a drag strip in West Virginia with it. Now I can’t get it to idle .. lol


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[xbird]

It sat for quite a while. Garage kept though so it wasn’t rusting away outside. The carb is new. I did notice the petcock was wet. When opening the drain on the bottom of the carb, gas keeps pouring out of the drain tube. Also I have a glass filter on the fuel line so I can see if gas is flowing or not. It’s frustrating. I’ll pull the knock off fcr carb and clean it just to be sure. When the rebuild kit comes in I’ll rebuild the original keihin carb too. This bike ran like a monster with the mods and Edelbrock quicksilver. Dyno’d at 38 horse and 86 mph. I out ran everything on a drag strip in West Virginia with it. Now I can’t get it to idle .. lol


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unless you were running ethanol-free gas, anything that sat in it likely has a nasty layer of gelled ethanol sitting at the bottom of it. it'll fool you in that you'll get flow, until you really start pulling the fuel through hard under load. than all that crap sucks over to the intake screen tube and plugs it. shutds down, and the gel falls away from the screen and lets fuel flow again.

 

[JOE G]

If it idles then dies when you give it gas until warm, I would be looking into a carb issue does it have an adjustable fuel screw? If So I would play with that a little, Also would not hurt to replace the Petcock with OEM Rator 660.

 

[LonesomeRider]

It really won’t stay running long enough to get hot. I checked the coil and ordered another just to have a spare. Also just got the 660 petcock this morning. I’ll replace that those weekend. Also got a rebuild kit in for the keihin fcr 39 mm. So I have that carb and the knock off fcr mx39mm. They’re almost identical. Yes the knockoff has a fuel screw. I plugged up the hot start and TPS cuz I don’t have that. Before I tear the carb back out I’ll try the original cdi box. I have a dyna FS on it now. Thanks for the suggestion!


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[JOE G]

I am wondering if the stator is going out on it, I'd swap CDI first as it is easier. But you do have the symptoms of a Stator on its way out.

 

[LonesomeRider]

I was leaning towards an electrical issue just because it will start just won’t stay running. I figure even if the carb wasn’t set perfectly, it would still stay running. I’ll do the voltmeter test on the Stator. That’s a simple replacement if needed. Honestly the bike is in amazing condition. I can’t wait to post some pics once I get it back together. It’s a cool looking machine. Thanks for the suggestion.


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[JOE G]

Stators can test fine but still not be so keep that in mind and they also tend to act up as they get warm.

 

[LonesomeRider]

Stator static test is good. I swapped cdi box out for the stock one and still nothing. I’m waiting on the mid body gasket set to come in for the branded kehein carb. I’ve already cleaned it with an ultrasonic cleaner and blew all of the different ports out just needs to be reassembled. Hoping to get her running soon. The only other thing it needs is replacement of the lower steering stem bushing. I’ll do that while I have the plastics off and gas tank removed.


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[LonesomeRider]

Stator test is definitely not good somehow it checked but it’s bad. Took off the cover and the generator is shredded. Screws came out of the flywheel gear and trashed the whole magneto. Screws were laying there. What a mess l….


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[LonesomeRider]

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[JOE G]

Yes Like I said above Stators can test good and be junk, Fairly common issues you have there, Loctite them when reinstalling.

 

[LonesomeRider]

I just saw a video today before I took this apart talking about loctite on those exact screws. Hopefully I can get the other halves of the screws out once I pull that flywheel. Fun… ordered the new parts. I’ll see if o can get those screws at the hardware store.

This new found problem might have been why the bike ran weird before. Maybe my Edelbrock carb was fine and it was one of these broken screws causing all my issues.


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[LonesomeRider]

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[JOE G]

From the Research I did they suggest not over torqueing those screws becasue they are weak and can cause them to break as well. I used new OEM Screws but a low torque value.

 

[LonesomeRider]

Calls for 19 ft lb from what I’ve read. I’ll definitely use a torque wrench on these so they’re all the same.


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[LonesomeRider]

Still unsure which FCR I have. I looked up the ID number on it and it doesn’t exist on keihin charts. Looking visually at the mid body rebuild kits it seems to be a Gen 3A. Whatever that means.


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[LonesomeRider]

Replaced the Stator put all back together with loctite and it fired right up. It’s got the cheap fcr knock off carb on it too. Sometime this weekend I’ll take it around the property and see what happens. I’m replacing he lower steering stem bushing first while I have the front plastic off. Pretty stoked that it’s running again.


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