treggo

Yak's '87 GSX400X Impulse.

91 posts in this topic

Yeah come to think of it I think I have the cylinder pairing wrong in my head, so would be sparking 180 out, just use the test procedure above to set it up as it was.

Set up your new coils, when you bridge the Black/Blue and Green/White terminals you should get a spark on #1 plug (far left plug if you are sitting on the bike).

If #1 doesn't spark and #2 does you can either swap the wires on the ignitor plug or just swap them at the coils.

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Fuel tank seal has been done. Basically spent a whole day doing another round of marine clean, then a good 2 hours of metal ready. Spent a fair amount of time drying it out with the heat gun. End result, meh it actually looks a bit thin at the bottom where all the rust was, and I can see an exposed rust flake towards the top of the tank, so who knows, maybe I didn't dry it enough.. Will run as is and see how we go.

Pre-sealant:

07F18518-32BA-4A7E-B249-A904F7CF6F47_zps

Post-sealant:

EDC581EC-2E5A-4DDD-8346-44D1B3CD46FC_zps

And while this was happening... Stripped some more stuff, gave the bum end a good clean to repaint some surface rust.

902EF64B-0D9F-4934-B35D-4AF9C7890A15_zps

B7F8BB0D-796A-4566-A9AC-BC250D2A98DC_zps

1984EE1F-EFF4-4796-9652-ADD465518A9B_zps

However as I was cleaning up the swingarm, I suddenly noticed what looks to be a big old dent in one side of it. Would this be wof fail?

2FB79F5D-F30B-4C2D-98D4-4A98DE34C507_zps

E689199C-A43D-41D9-A962-D0D9226D777B_zps

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So I swapped both coils out for a new pair, along with a new set of leads.  Had to space out the mounting holes for the coils which were about 10mm too narrow.

 

D5B69DC7-BA6E-409F-B8E4-FC4813494C8B_zps

 

chucked the fuel tank on and tried to start the bike.  

Took a while to get it to fire - the choke doesn't feel like it's doing much and I ended up just using my palms over the carbs to choke it.  Seemed to work and the engine fired up! 

revs fairly quickly but doesn't seem to want to get over 5000 rpm.  Not sure what's happening, if maybe the cdi is a bit buggered and that's why they piggy backed the other one on?  

Will take a video of the engine running tomorrow.  

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A couple of theorys for that symptom:

  • Has it got a fully charged battery? Check voltage to coils when revving. It may not be getting enough. (Have had this before)
  • Could be leaning out. CV carbs eh? Diaphrams all good?
  • A Blockage in the Exhaust? (Have had this before)
  • Is there enough fuel flow from the tank to sustain high revs? (Have had this before)
  • Did you try once it has warmed up?

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Yeah had another go this morning, seemed to go a bit better. Once it warmed up it started doing some weird stuff where engine speed would go up on its own to about 3000rpm for like 5 seconds. Did manage to get it to rev over 7000, so yeah probably a bunch of crap in the carbs. Was hoping not to have to touch them but yeah might pull them apart for a clean up.

Spent the rest of the day reassembling swing arm, rear brake and electrics. Still got quite a bit to do and a big pile of screws and bolts with no real order. Lesson learnt for next time.

Edit: here's a video

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when I first bought my CB it wouldn't rev out and setting the floats helped it.

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So I've had the carbs apart, cleaned everything, reassembled - bike won't run.  

One thing I didn't check was the float height.

 

when I first bought my CB it wouldn't rev out and setting the floats helped it.

 

So the problem I have now is I can't work out where exactly I'm supposed to be measuring to on the floats themselves.  The workshop manual I'm using is just too photocopy spec.  I know i measure from the gasket mating face on the carb body, but do I measure to the very bottom (when carb is right way up) of the float?  There's a seam right in the middle of the float which seems like it's in approximately the right place..   

 

float_zpslvpzgmcm.png

 

7839B71D-E878-4DF6-B0C8-4B5BEF840AAE_zps

 

 

 

Oh and I think I've discovered why there was a second CDI wired in - apparently these bikes have a 11k rev limiter, and by using one CDI per coil you get past this.  According to these guys anyway:

 

http://retro.400greybike.com/topic.asp?TOPIC_ID=3803

 

Purely academic at this point since one of the CDIs doesn't go anymore.  I'm happy enough with 11k anyway!

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Yeah bottom of float to gasket surface seems to be the standard way.

Spec for these carbs is 22mm, at the moment the tang makes contact at around 26mm so it's way too low..

 

C200F537-CA27-44A8-963F-F9D5F6FDF9B0_zps

 

What's the best way to bend these things?  I feel like I need to bend it inward so far that I have to bend the other metal tab as well.

 

42D156C1-A7A9-453E-BE92-D44C0ACAED9C_zps

 

287E6E19-14DD-4ADF-9D46-3D7A901DD889_zps

 

 

I guess I'll just bend away and see how it goes - weird that they're both so far out and the bike still ran quite happily when treggo owned it..

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having an incorrectly adjusted float will make the carb run richer or leaner. you can make up for that by adjusting the carb, but it will lean out/richen up where you dont want it to

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I thought that must have been you tootling through Naenae around 10ish, not many Impulses around these days.

 

I was going to wave and toot to say hi, but then realised it might look like some kind of gang initiation thing...

 

Ev.  :-)

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