It is currently Fri Mar 29, 2024 12:51 am

All times are UTC [ DST ]




Post new topic Reply to topic  [ 10 posts ] 
Author Message
 Post subject: Lots of exhaust pooping
PostPosted: Mon Aug 22, 2016 3:02 pm 
Offline

Joined: Wed Jul 10, 2013 9:41 pm
Posts: 51
Location: York
Hello All, hope someone could help me.
I've got a blacktop zetec installed with bike carbs set-up by Bogg Bro's. Which is great. But what is getting annoying is that when I lift off the throttle I get a lot of popping though the exhaust. Yes this sounds good, if occasional, but every time & quite a lot is a bit much.
I was told by Boggs that it was due to the exhaust, which I have changed for other reasons, but is still doing it. The only thing I can think is that I'm using a CVH sportex manifold with zetec flange, would this be restrictive?
If not the above & short of taking it back to Boggs anybody any ideas?
Thanks Mark


Top
 Profile  
 
PostPosted: Mon Aug 22, 2016 4:22 pm 
Offline
Moderator
User avatar

Joined: Fri May 23, 2003 9:56 pm
Posts: 4483
Location: Sunny Yorkshire
usually popping is caused by unburnt fuel exploding in the exhaust. I cant answer your question exactly but the sportex manifold will be restrictive, I used a cvh 4 branch with an adaptor to get up and running with my silvertop, but then replaced it with a ST170 one which I modified to fit, you could definitely tell the difference.

_________________
Image


Top
 Profile  
 
PostPosted: Mon Aug 22, 2016 4:41 pm 
Offline

Joined: Fri May 23, 2003 11:04 pm
Posts: 22291
Location: County Durham.
As above.
I run an adaptor with a Janspeed manifold.
The manifold does restrict.
But mine doesn't bang and pop.
Too much fuel/air.
Check the mixture and check for air leaks.

Jason.


Top
 Profile  
 
PostPosted: Mon Aug 22, 2016 6:14 pm 
Offline
User avatar

Joined: Thu Jan 08, 2004 6:34 am
Posts: 4622
Running too lean.

_________________
Image
One day I'll be an old man and nobody's going to want to hear stories about sensible decisions and wise investments.


Top
 Profile  
 
PostPosted: Mon Aug 22, 2016 6:55 pm 
Offline

Joined: Wed Jul 10, 2013 9:41 pm
Posts: 51
Location: York
Thanks guys.
Jason - is that air leaks on the inlet or exhaust?
Mannion - when you say 'lean' do you mean not enough fuel?
As I say set-up by Boggs & has been like this all the time.
I'll work on the manifold in time.
Mark


Top
 Profile  
 
PostPosted: Mon Aug 22, 2016 7:39 pm 
Offline

Joined: Fri May 23, 2003 11:04 pm
Posts: 22291
Location: County Durham.
Usually inlet.
Making it run lean as Mannion said.
But can sometimes be near the exhaust headers too.

Were the cabs set up on the bench or on the car?
As good as they are. They can't get it 100% just by 'tuning' them on the bench away from the car.
Every engine differs slightly. Even brand new crate engines.
May just need a tweak.
But get an AFR gauge fitted or bung one up the exhaust end and see what readings you are getting.

Jason.


Top
 Profile  
 
PostPosted: Mon Aug 22, 2016 9:37 pm 
Offline
User avatar

Joined: Thu Jan 08, 2004 6:34 am
Posts: 4622
It's hard to diagnose an issue over the internet but those symptoms you described are fairly indicative of the car being too lean - The mix in the cylinders has too little fuel for the amount of air. If the mix is far enough out it will cause detonation which will fairly quickly wreck the surface on the top of the pistons if you ignore it.

Jason always gives good advice. You'll need to get an AFR meter on the car to know what's actually going on and from there you can set about correcting it.

_________________
Image
One day I'll be an old man and nobody's going to want to hear stories about sensible decisions and wise investments.


Top
 Profile  
 
PostPosted: Mon Aug 22, 2016 10:07 pm 
Offline

Joined: Fri May 23, 2003 11:04 pm
Posts: 22291
Location: County Durham.
Mannion @ FPE wrote:
I....

Jason always gives good advice. You'll need to get an AFR meter on the car to know what's actually going on and from there you can set about correcting it.


I dunno about that. But thanks.. :)

I've got an AEM AFR gauge... Not fitted it yet but that's what I bought it for...

But I have one of these too..
http://pages.ebay.com/link/?nav=item.vi ... 53&alt=web
Not the quickest of tools, but it works well.
I paid a LOT less than that for mine, second hand. But included all the pipes and instructions.
I'd recommend getting something like that.

Jason.


Top
 Profile  
 
PostPosted: Tue Aug 23, 2016 12:17 pm 
Offline

Joined: Wed Jul 10, 2013 9:41 pm
Posts: 51
Location: York
The carbs where set-up on the car on Boggs rolling road.
I will investigate air leaks all ways round.
So if running lean then it wouldn't be unburnt fuel in the exhaust?
Is the detonation what I'm hearing on lift off then? How is this when there isn't enough fuel. It's at its worst when lefting off when in gear (on load). Once out of gear (off load) it all but disapears.

The readings from my last MOT for CO - 0.514% & HC - 747ppm. Haven't changed anything since.

Sorry for all the odd questions, just tring to understand whats happening.
Will look into the AFR.
Mark


Top
 Profile  
 
PostPosted: Tue Aug 23, 2016 1:43 pm 
Offline

Joined: Fri May 23, 2003 11:04 pm
Posts: 22291
Location: County Durham.
Carbs do go out of tune over time.
Usually as parts wear, gaskets break down and leak a little, carb sidewalls get covered in gunk and emulsion.

I was out in the missus 1.1 today. I had the exhaust popping on that. Just like you said.. lifting off whilst going down the roof car park ramp at aldi.
Otherwise drove perfect.

Jason.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 10 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 34 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  


Powered by phpBB® Forum Software © phpBB Group