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Author Topic: Spitting back  (Read 1221 times)

Offline RoyC

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Spitting back
« on: 22.04. 2018 17:56 »
Went to the Stafford show and the bike pulls well but occasionally misses and spits back through the carb.
Any thoughts on what the problem might be ?
New Champion N3c plugs fitted.
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My bike is a 1958 A7SS
Staffordshire UK

Online Triton Thrasher

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Re: Spitting back
« Reply #1 on: 22.04. 2018 18:40 »
First, do a service on plugs, points and valve clearances.

Then suspect weak mixture.  If it was ok before, but is now spitting back, there may be an air leak into the inlet manifold. Get it idling and spray WD40 or something at the joints between carburettor, Tufnol spacer, manifold etc.  If the engine speed changes, there’s a leak.

Could also be a loose carburettor top or dirty pilot jet.

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Offline RoyC

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Re: Spitting back
« Reply #2 on: 22.04. 2018 19:00 »
Quote from: Triton Thrasher on 22.04. 2018 18:40
First, do a service on plugs, points and valve clearances.

Then suspect weak mixture.  If it was ok before, but is now spitting back, there may be an air leak into the inlet manifold. Get it idling and spray WD40 or something at the joints between carburettor, Tufnol spacer, manifold etc.  If the engine speed changes, there’s a leak.

Could also be a loose carburettor top or dirty pilot jet.

Thanks for that Thrasher.
New plugs set to .020". I haven't touched the points and valve clearances yet.
This was it's first run out since I purchased and restored so don't know what it ran like before.
I have had the carb off so will do the WD40 trick first and work through the rest of the list until it runs OK.
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My bike is a 1958 A7SS
Staffordshire UK

Online Triton Thrasher

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Re: Spitting back
« Reply #3 on: 22.04. 2018 19:14 »
If the bike is newly on the road, it could be too-big slide cutaway, too-low slide needle position or pilot air adjuster screw set too weak.
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Offline RoyC

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Re: Spitting back
« Reply #4 on: 22.04. 2018 19:51 »
Quote from: Triton Thrasher on 22.04. 2018 19:14
If the bike is newly on the road, it could be too-big slide cutaway, too-low slide needle position or pilot air adjuster screw set too weak.

The only thing that I have done with the carb, besides taking it off when cleaning it, is to adjust the pilot jet.
I do run the carb dry when I run it in the garage.
I will do as you suggest, check for air leaks and richen the pilot air adjuster screw for starters.
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My bike is a 1958 A7SS
Staffordshire UK

Online Greybeard

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Re: Spitting back
« Reply #5 on: 22.04. 2018 21:37 »
Your problem is caused by the sidecar; take it off and throw it away.
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Greybeard (Neil)
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Online Klaus

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Re: Spitting back
« Reply #6 on: 22.04. 2018 21:45 »
Hi Roy,
have a look at the inlet valves. You told the bike is new restored so I guess there are new valves in. After a the first running the valves get in to her seats and he clearance get to nil.
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Offline RoyC

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Re: Spitting back
« Reply #7 on: 23.04. 2018 08:36 »
Quote from: Klaus on 22.04. 2018 21:45
Hi Roy,
have a look at the inlet valves. You told the bike is new restored so I guess there are new valves in. After a the first running the valves get in to her seats and he clearance get to nil.

Thanks Klaus, Engine was OK, so not restored.
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My bike is a 1958 A7SS
Staffordshire UK

Offline RoyC

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Re: Spitting back
« Reply #8 on: 23.04. 2018 08:41 »
Quote from: Greybeard on 22.04. 2018 21:37
Your problem is caused by the sidecar; take it off and throw it away.
Cant ride it with no sidecar fitted.
Went to Stafford show, getting used to riding it a little now.
It rides and pulls quite well.
Got best sidecar outfit award.  *red*
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My bike is a 1958 A7SS
Staffordshire UK

Online Greybeard

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Re: Spitting back
« Reply #9 on: 23.04. 2018 09:47 »
Quote from: RoyC on 23.04. 2018 08:41
Quote from: Greybeard on 22.04. 2018 21:37
Your problem is caused by the sidecar; take it off and throw it away.
Cant ride it with no sidecar fitted.
Went to Stafford show, getting used to riding it a little now.
It rides and pulls quite well.
Got best sidecar outfit award.  *red*

Fantastic! You must be very happy with that!  *smile*
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Greybeard (Neil)
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Supporter of THE DISTINGUISHED GENTLEMAN'S RIDE https://www.gentlemansride.com

Warwickshire UK


A Distinguished Gentleman Riding his 1955 Plunger Golden Flash

Offline RoyC

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Re: Spitting back
« Reply #10 on: 23.04. 2018 15:02 »
Quote from: Greybeard on 23.04. 2018 09:47
Quote from: RoyC on 23.04. 2018 08:41
Quote from: Greybeard on 22.04. 2018 21:37
Your problem is caused by the sidecar; take it off and throw it away.
Cant ride it with no sidecar fitted.
Went to Stafford show, getting used to riding it a little now.
It rides and pulls quite well.
Got best sidecar outfit award.  *red*

Fantastic! You must be very happy with that!  *smile*
Couldn't have got there without you lads on this forum.  *thanks*
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My bike is a 1958 A7SS
Staffordshire UK

Offline CotswoldsA7

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Re: Spitting back
« Reply #11 on: 23.04. 2018 16:58 »
Nice comment 👍
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Online Angus

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Re: Spitting back
« Reply #12 on: 24.04. 2018 15:47 »
Hi I saw Roy bike at Stafford it looks really good in the flesh, Roy was not on the stand at the time. I was wearing my teashirt but did not bump into anybody.
As an aside Roy where did you get crash bars, I had a set on another bike in the 70's and occasionally look for them online but have never found any.
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1961 A7 since 1976, 1960 A10 Gold Flash Super Profile Bike
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1950 Triumph T100, 1981 Ducati Pantah 500, 1959 AJS model 20

Offline RayC10

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Re: Spitting back
« Reply #13 on: 24.04. 2018 17:36 »
Didn't Roy's outfit win best sidecar at the show? I love outfits...just so much fun to ride, best drift vehicle  slippery roads  *smile*
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Offline RoyC

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Re: Spitting back
« Reply #14 on: 24.04. 2018 20:32 »
Quote from: Angus on 24.04. 2018 15:47
As an aside Roy where did you get crash bars,
Both front and rear are Britax.
Rear bars off ebay.
Front bars are ONS (still in box) from USA and were on ebay, I put in a ridiculous amount to make sure that I got them.
I saved a search and every time any came up, I got an email, I looked at quite a lot until I found any good ones.
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My bike is a 1958 A7SS
Staffordshire UK
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