davidimurray
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| posted on 3/3/13 at 07:37 PM |
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Help - backfiring carbs
Hello
Due to work commitments i've spent the last 9 months working 80+ hours a week so had little time for the Roadster. Had a play with it again for
the first time today 
About 4 months ago I was kicked out of the garage that I was renting. At the same time the right house came up with a nice garage at the bottom of the
garden. Had the car trailered over, but when I came to load it, the car would idle, and would run at a few thousand RPM, but would not transition or
sit between the two without dying.
Stripped the carbs today and found a few little bits of crap in there and it also looked like the pilot jets were blocked. Everything stripped down
and cleaned out.
I then restarted the car which started without any problem but now I am getting lots of backfiring through the carbs -see the attached video. I also
attached my carb balancer just to check the balance which isn't perfect but I would have thought would be good enough.
YouTube Video
Engine is an 1800 Pinto, zx6r carbs and megajolt ignition
Any suggestions would be much appreciated as to what could be the cause. I've found getting the bike carbs to work properly a nightmare and
having had them running nicely I feel like i'm back at square one again
Gallery 1 http://www.facebook.com/media/set/?set=a.116893465324.130778.601005324
Gallery 2 http://www.facebook.com/media/set/?set=a.245243755324.181913.601005324&l=a9831a9319
Gallery 3 http://www.facebook.com/media/set/?set=a.440671625324.232627.601005324&l=3f0d42c523
Gallery 4 http://www.facebook.com/media/set/?set=a.490098255324.297598.601005324&l=efb083b7df
Gallery 5 http://www.facebook.com/media/set/?set=a.10150244028550325.366987.601005324&l=583fd5cd3a
Gallery 6 http://www.facebook.com/media/set/?set=a.10150550640070325.430417.601005324&type=3&l=fe779b358c
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austin man
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| posted on 3/3/13 at 07:49 PM |
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How confident ar you that the timing is spot on plus have you reset the TPS when you have rebuilt and refitted the carbs. Ususally back firing through
the carbs is related to ignition
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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trextr7monkey
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| posted on 3/3/13 at 07:59 PM |
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Hi - haven't looked at videos but any air leaks on inlet side will cause impressive backfires.
Hth
Mike
http://www.flickr.com/photos/14016102@N00/ (cut and paste this dodgey link)
Our most recent pics are here:
http://s129.photobucket.com/albums/p211/trextr7monkey/
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Ian.C
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| posted on 3/3/13 at 08:08 PM |
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If you tell me how you put a link to youtube like you have, I will tell you that your idle speed sounds high, but if its not your running lean on your
idle system.
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gremlin1234
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| posted on 3/3/13 at 08:42 PM |
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modern fuel can deteriorate quickly,
so try to replace any in the tank, and run it for a while (to flush through)
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tomgregory2000
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| posted on 3/3/13 at 09:05 PM |
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Could be running too lean
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austin man
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| posted on 3/3/13 at 09:12 PM |
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quote:
Originally posted by Ian.C
If you tell me how you put a link to youtube like you have, I will tell you that your idle speed sounds high, but if its not your running lean on your
idle system.
Just copy and paste the web address from the http staus bar
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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davidimurray
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| posted on 3/3/13 at 09:57 PM |
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Austinman - I will recheck the TPS calibration and timing in the morning. The timing should be ok but i may have misaligned the TPS when reassembling
the carbs
I will hook up the lambda sensor tomorrow and see what the afr looks like. currently the idle screws are turned out 3 turns so they may be a tad too
far - everything i read has them from 1.5 to 3.5 turns out!
Ian.c - you can add a video by copying the link from youtube, then clicking on the globe with a chain on it anf copying the link in there. With regard
to the idle it is at 1000rpm in the video as i haven't turned it down yet.
Gremlin, interesting point on fuel. Is this much of an issue as it's crossed my mind but I just dismissed it!
Thanks for all the advice, will let you know how I get on.
Cheers
Dave
Gallery 1 http://www.facebook.com/media/set/?set=a.116893465324.130778.601005324
Gallery 2 http://www.facebook.com/media/set/?set=a.245243755324.181913.601005324&l=a9831a9319
Gallery 3 http://www.facebook.com/media/set/?set=a.440671625324.232627.601005324&l=3f0d42c523
Gallery 4 http://www.facebook.com/media/set/?set=a.490098255324.297598.601005324&l=efb083b7df
Gallery 5 http://www.facebook.com/media/set/?set=a.10150244028550325.366987.601005324&l=583fd5cd3a
Gallery 6 http://www.facebook.com/media/set/?set=a.10150550640070325.430417.601005324&type=3&l=fe779b358c
Duratec Engine Swap https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f " target="_blank"> https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f
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sjmatthews
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| posted on 3/3/13 at 10:45 PM |
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I fitted a new set of bike carbs to my Pinto during build and found old/contaminated fuel to cause similar symptoms. The idle jet holes are so tiny,
they are very easily blocked.
Make sure you have fresh fuel (drain if more than 6 months old) and fit filters before and after your pump.
Otherwise check for inlet leaks by carefully spraying around with wd40, if the revs pick up you have a leak.
Good luck 
I'll be in the garage dear!
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iank
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| posted on 4/3/13 at 08:20 AM |
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To embed a youtube video into a post (not just have a link to it) you click the youtube button (furthest right) and past in the ID number only (i.e.
the bit of the link that looks like random letters and numbers)
you'll get something like
[youtube]2bVAAx3mMKY[/youtube]
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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r1_pete
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| posted on 4/3/13 at 08:45 AM |
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Check the seal between the diaphragms and the carbs/lids, that is the sort of behaviour you get when they leak.
There will be a raised lip around the diaphragm, and a locator tab, when I've rebuild CVK carbs I smear the lip with rubber lube, others fill
the recess in the carb and lid with lube, either way it ensures a good seal.
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mikeb
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| posted on 4/3/13 at 11:34 AM |
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mines runs exactly the same at the minute. mine are zx6r carbs on a CVH just running on edis at the min.
I haven't rebuilt my carbs yet.
Let me know how you get on!
I'd assumed is was a slight blockage or the ignition not being quite right.
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davidimurray
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| posted on 4/3/13 at 01:19 PM |
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Right - had a play with the car this morning.
First job reset the tps and check the timing which was ok.
Then hooked up the wideband lambda which showed everything was off the scale lean. So I then screwed the idle adjusters in half a turn at a time until
they were shut (from 3 turns out) and they made no difference.
Drained the fuel from the tank, popped out and got some fresh, put some in tank, disconnected pipework and ran through, also drained float bowls.
Restarted car, same again. Reset idle adjuster screws to 2 turns out, no change.
If I rev the car up, then the afr drops to about 15, it still pops a bit but no where near as bad. I seem to remember that before all these problems
started the idle afr was about 12.5
I also attacked the manifold with a can of wd40 for any sign of leaks and no discernible change in engine note.
Seems like i'm way lean - but why? And why are the idle air adjusters not doing anything. I did wonder about the fuel filter but then I would
expect the missfires to get worse when revved not better. Should i take the carb jets out again and re-clean them.
I cannot see why this would have any bearing on the matter but I haven't redrilled the mains yet, they are still at 1.3mm but at idle they
shouldn't be coming into play.
Cheers
Dave
Gallery 1 http://www.facebook.com/media/set/?set=a.116893465324.130778.601005324
Gallery 2 http://www.facebook.com/media/set/?set=a.245243755324.181913.601005324&l=a9831a9319
Gallery 3 http://www.facebook.com/media/set/?set=a.440671625324.232627.601005324&l=3f0d42c523
Gallery 4 http://www.facebook.com/media/set/?set=a.490098255324.297598.601005324&l=efb083b7df
Gallery 5 http://www.facebook.com/media/set/?set=a.10150244028550325.366987.601005324&l=583fd5cd3a
Gallery 6 http://www.facebook.com/media/set/?set=a.10150550640070325.430417.601005324&type=3&l=fe779b358c
Duratec Engine Swap https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f " target="_blank"> https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f
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whitestu
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| posted on 4/3/13 at 01:31 PM |
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If the idle jets are blocked turning the mixture screws will make no difference.
Stu
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avagolen
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| posted on 4/3/13 at 05:36 PM |
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What happens if you put the choke on?
In this cold weather mine will not even start unless I hold the choke slide fully on.
If you are running lean, this should richen it up and maybe stop the popping.
If it does, then maybe you have got some dirt in the idle jets.
Just my thoughts mind you.
Mine initailly would not run well and did pop on number 2.
Even pushed the manifild of in the early days.
It sorted itself out after a while - just kept running while trying to balancing the idle vacuum
and eventually I noticed number 2 had fully joined the party. It has not spat back for a while now.
Mind you, it has only been run in the garage as I still have to knock a wall down to get it out..
The Answer for everything, but never the last word....
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davidimurray
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| posted on 4/3/13 at 08:15 PM |
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Good news - it's working
Dropped the float bowls off the carbs and removed the idle jets. As predicted, 3 of the four were blocked again. Blew them through and made sure I
gave the bowls a good clear out. Reassembled everything and fired the car up. Was running better, but still blowing back and AFR still off the scale
lean.
Started winding out the idle screws and started to get a reading on the lambda, as the mixture got richer the engine started running and by the time
the afr was down to 14 the old Pinto was running nicely with no banging or popping. Even had a quick whizz up and down the alley to check everything
was working.
Thanks for all the help and advice.
Cheers
Dave
Gallery 1 http://www.facebook.com/media/set/?set=a.116893465324.130778.601005324
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Gallery 4 http://www.facebook.com/media/set/?set=a.490098255324.297598.601005324&l=efb083b7df
Gallery 5 http://www.facebook.com/media/set/?set=a.10150244028550325.366987.601005324&l=583fd5cd3a
Gallery 6 http://www.facebook.com/media/set/?set=a.10150550640070325.430417.601005324&type=3&l=fe779b358c
Duratec Engine Swap https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f " target="_blank"> https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f
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mikeb
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| posted on 6/3/13 at 10:57 AM |
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Good work David,
I'm hoping mine is the same issue, it did run ok when I first ran it over a year ago so I had assumed it was bad fuel or blocked jets
somewhere.
I havn't taken mine apart before are the idle jets easy to get at? Mine are zx6r carbs.
Mike
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