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

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

Hi - haven't looked at videos but any air leaks on inlet side will cause impressive backfires.
Hth
Mike

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.

modern fuel can deteriorate quickly,
so try to replace any in the tank, and run it for a while (to flush through)

Could be running too lean

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.

---

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

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

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]

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.

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.

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

If the idle jets are blocked turning the mixture screws will make no difference.

Stu

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..

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

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