Running badly - terrible noise

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Animammel
Posts: 45
Joined: Sun Jan 20, 2013 7:22 pm
My Bike: ZX400 G
Location: South Africa - Western Cape

Running badly - terrible noise

Post by Animammel »

Hey guys -

So got home from work today on my break, old man been working on the bike, we finally got her to start and run but now there is a problem it seems.
As he explained it - it ran beautifully for about two minutes, backfired and now sounds terrible, kinda like a thumper, very chunky sound and now we are very worried. anyone had issues like this before? I asked if it may be running on three cylinders but the sound does not match.

Rebuilt the motor. Timing should be fine, all setup up as the manual stated.
Carb rebuilt - new spark plugs, coils work fine just seems mechanical now.

A worried chris
Cheers
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RedexRobB
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Posts: 7212
Joined: Fri Aug 30, 2002 7:37 pm
My Bike: ZXR400L3
Location: Ipswich, Suffolk

Re: Running badly - terrible noise

Post by RedexRobB »

can you get a video up? Id say its probably running on 3 cylinders or less if its lumpy. The other thing to consider, re the carbs set up properly and balanced?
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Animammel
Posts: 45
Joined: Sun Jan 20, 2013 7:22 pm
My Bike: ZX400 G
Location: South Africa - Western Cape

Re: Running badly - terrible noise

Post by Animammel »

I shall put up a video tomorrow evening after I take a look at it again.

Will check out the carbs again.
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banner001
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Posts: 2584
Joined: Sat Sep 24, 2011 3:27 pm
My Bike: ZXR400 L4
Location: Nuneaton

Re: Running badly - terrible noise

Post by banner001 »

To check for which cylinders are firing run the bike for about 10seconds and see which downpipes are getting hot or warm.
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
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Animammel
Posts: 45
Joined: Sun Jan 20, 2013 7:22 pm
My Bike: ZX400 G
Location: South Africa - Western Cape

Re: Running badly - terrible noise

Post by Animammel »

Ok all sorted - as I thought it was not that it was not firing on all pistons, something got down into one of the cylinders and bent the one valve stem, lucky for us we had the old head.

Bike runs beautifully.

thanks for the quick replies - really helps
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