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Exhaust smoke after throttle shutdown
Posted: Sun May 26, 2013 3:18 pm
Author: z1000puddin
Guys,
I had a hundred or so miles on my 1075 zed. yesterday.
My mate following noticed that there was smoke coming from the exhaust when the throttle was shut-down. Noticeably when it was getting a good thrash.
The bike has new MTC piston & rings
28mm carbs with 112.5 mains & 17.5 pilots.
Open ally trumpets
Intend getting it dynod, but I am concerned about the smoke - Should this happen on a rebuilt motor ??
Or should I carry out a compression test. ?
The bike starts & idles well, pulls well although it may need a jet up one or two.
.The bike has done a couple of hundred running in miles.
Stu
Posted: Sun May 26, 2013 3:20 pm
Author: Charlie
How much smoke and what colour is it ?
Posted: Sun May 26, 2013 3:47 pm
Author: ZedHead
Blue smoke on over run. I would suspect valve oil seals.
Posted: Sun May 26, 2013 3:48 pm
Author: chrisu
Posted: Sun May 26, 2013 4:49 pm
Author: jimmock
ZedHead wrote:Blue smoke on over run. I would suspect valve oil seals.
I agree,
on over run it must be stem oil seals and/or guides.
Posted: Sun May 26, 2013 7:15 pm
Author: z1000puddin
Thanks guys,
I will get the compression check - just for my own reference.
I whipped out # 2 plug just to check - pic below - does this show a bit lean ?
Posted: Sun May 26, 2013 8:04 pm
Author: paulmceleney
no that what everyone want there plugs to look like that is the best
Posted: Sun May 26, 2013 10:16 pm
Author: KeithZ1R
Feck me the mythical "straw coloured plug" save it for posterity
Posted: Mon May 27, 2013 5:37 pm
Author: z1000puddin
So you would not advise messing about with the 28mm carbs then.
I thought my current set up of the mains @ 112.5 & pilots @ 17.5 was standard.
And as I have 4-1-2 underseat exhaust, open velocity stacks & andrews 2X Cams - I thought I would need to up jet.
Stu
Posted: Mon May 27, 2013 5:59 pm
Author: paulmceleney
Try 130 main jet this will make a difference
it will run better more power I have a under seat exhaust on my z1000 rebored to 1075 gas flowed head z1r cams 33 smoothbore carbs was running 28 mm carbs and 130 jets there is not much difference between z1r carbs and smoothbore carbs in power
Posted: Mon May 27, 2013 6:13 pm
Author: z1000puddin
Thanks Paul,
The 28mm carbs I have on are from a Z1B.
Do you think I need to go up as far as 130 on the mains ?
It seems a real big jump.
Stu
Posted: Mon May 27, 2013 6:33 pm
Author: paulmceleney
yes I ran 150 in my z900 which was a bit to big it still pulled well plus 50 to the gallon went to Germany with the 150 jets in but 130 should be spot on then adjust the air screws even moving them 1mm can make a difference just a little each time
Posted: Mon May 27, 2013 9:20 pm
Author: z1000puddin
Paul,
What would you suggest for the pilots ? Keep these @ 17.5 ?
What needle position should I set at ?
Thanks in advance
Stu
Posted: Tue May 28, 2013 5:15 pm
Author: paulmceleney
I would just change the main jets the pilot jets in my carbs which are 33 smoothbores are 17.5
Posted: Tue May 28, 2013 6:20 pm
Author: ZedHead
Charlie wrote:How much smoke and what colour is it ?
I would go back to this before deciding to play with carbs. Blue = Oil, Grey/White =Rich mixture which, looking at your plugs, I would say is not your problem.
I am not sure if leaking oils seal will show on a compression test? The blue smoke on over run is usually due to the increased vacuum when the throttle is shut off sucking oil passed leaky seals on the inlet side.
