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Hi guys. 

My 6 is running tripple webbers and full stainless race pipe. When ever I let of the gas the cars popping and banging. Sounds great, but is this a sign that somethings needing adjusted. 

Thanks

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I didn't do this in the past. Not that I recall. Its very pronounce. I'm wondering if its a timing issue. 

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1 hour ago, murrayarnold said:

I didn't do this in the past. Not that I recall. Its very pronounce. I'm wondering if its a timing issue. 

Might be right. Ignition timing is easy enough to check. There's always the possibility it's the valve timing or a burnt exhaust valve.

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22 hours ago, murrayarnold said:

Hi guys. 

My 6 is running tripple webbers and full stainless race pipe. When ever I let of the gas the cars popping and banging. Sounds great, but is this a sign that somethings needing adjusted. 

Thanks

Have you set the misabs correct 

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Ah ha. The shock absorber washers. Everything is brand new. The complete internals and all manifold fittings. I very carefully installed everything myself. If there was a leak the engine wouldn't idle and the carbs wouldn't tune. I used a colour tune on every piston. And ballanced them. They idle perfectly with no spitting or popping. 

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I know. Thackery washers are installed correctly. I actually installed my first DCOEs 30 years ago. I do know how to install them. I am.very wrong. Ha. Really. 

Like someone said, and I am leaning that way, its a timing issue. 

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On 8/30/2020 at 5:34 PM, murrayarnold said:

Hi guys. 

My 6 is running tripple webbers and full stainless race pipe. When ever I let of the gas the cars popping and banging. Sounds great, but is this a sign that somethings needing adjusted. 

Thanks

My everyday car does this as standard! It seems the engine map deliberately squirts a little bit of fuel in on the over-run to generate what are termed 'burbles' to make the engine sound sporty. :D

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19 minutes ago, DRD said:

My everyday car does this as standard! It seems the engine map deliberately squirts a little bit of fuel in on the over-run to generate what are termed 'burbles' to make the engine sound sporty. :D

My Pi car does exactly the same thing. This feature was tuned-in deliberately by Revington TR. Their mechanic advised me that by the time I drive home (500 miles later) I find I don't like it, then I should ring him and he'll instruct me on how to re-tune......over a year later and he hasn't heard from me.

Richard.

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27 minutes ago, Richard71 said:

My Pi car does exactly the same thing. This feature was tuned-in deliberately by Revington TR. Their mechanic advised me that by the time I drive home (500 miles later) I find I don't like it, then I should ring him and he'll instruct me on how to re-tune......over a year later and he hasn't heard from me.

Richard.

Mine too!

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1 hour ago, Richard71 said:

My Pi car does exactly the same thing. This feature was tuned-in deliberately by Revington TR. Their mechanic advised me that by the time I drive home (500 miles later) I find I don't like it, then I should ring him and he'll instruct me on how to re-tune......over a year later and he hasn't heard from me.

Richard.

Hey this sounds good. My PI used to do this slightly on overrun, especially on hard acceleration,  so whats the secret to getting it back play with the MU adjustments?

But which one, dont want to mess it up or take it too far out?

Regards, Colin.

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My TR250 driver with CP cam and triple DCOEs doesn't fart or burble on overrun at all, let alone pop and bang - never did, and likewise with a Kent TH2 cam ( 295 deg. duration ) before that. I've only driven (1) P.I. TR6 and rode in another courtesy Racetorations; both guilty of farting and burbling on overrun. Do all of them do this?

Weber jets mix air with the fuel before entering the inlet tract, so even with throttles completely closed some air gets in.

As for Murray's issue, my guess is timing too.

 

Tom

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Hi Tom. 

Yep I think so. Strange its never been like this before. But the car drives OK. No pinking etc. But maybe it should run better. Its a black art all this isn't it. 

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1 hour ago, c.hydes said:

Hey this sounds good. My PI used to do this slightly on overrun, especially on hard acceleration,  so whats the secret to getting it back play with the MU adjustments?

But which one, dont want to mess it up or take it too far out?

Regards, Colin.

Yes Colin, MU adjustment required, but don't ask me how. I see you're not a million miles away from Revington TR, why not pay them a visit?

Richard.

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4 hours ago, Richard71 said:

My Pi car does exactly the same thing. This feature was tuned-in deliberately by Revington TR. Their mechanic advised me that by the time I drive home (500 miles later) I find I don't like it, then I should ring him and he'll instruct me on how to re-tune......over a year later and he hasn't heard from me.

Richard.

I like it but at a relatively low level. Some cars make ridiculous bangs which just annoys everyone else!

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@Colin - if everything else is set up correctly, then screwing *out* the A3 adjustment screw (try 1/2 turn for starters) will lean out the minimum fuel setting, which results in popping and banging on over-run. If everything else is *not* set up correctly then it may not. Alternatively, sacrifice a chicken (pref, a Silkie as they are good layers if you chicken(!) out) and cry "please make my car bang" while running around naked outside your next group meeting venue...

Cheers,
John

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I thought that screwing the A3 out should lean the fuel out on overrun and actually stop it banging, there should be hardly any fuel on the overrun?

John

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4 hours ago, JohnC said:

@Colin - if everything else is set up correctly, then screwing *out* the A3 adjustment screw (try 1/2 turn for starters) will lean out the minimum fuel setting, which results in popping and banging on over-run. If everything else is *not* set up correctly then it may not. Alternatively, sacrifice a chicken (pref, a Silkie as they are good layers if you chicken(!) out) and cry "please make my car bang" while running around naked outside your next group meeting venue...

Cheers,
John

Very good John, my "spindly legs", would match a chicken. Think I`ll leave it well alone for now, but thanks for the info, at least I now know which adjuster on MU is for leaner or richer.

Colin.

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Hi Colin,

The A3 screw is the minimum fuel stop. It has no effect other than to determine how much fuel is delivered at high vacuum (i.e., over-run), limiting how lean the mixture can get.

@John L- If the mixture is too lean you get popping & banging. Counter-intuitive, but I understand it's because an over-lean mixture doesn't fully combust and so you get unburnt fuel which then ignites in the exhaust. 

John

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