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 Misfiring & backfiring 
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Haggis Muncher
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Joined: September 13th, 2012, 7:38 pm
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Location: Denny, Scotland
Post Re: Misfiring & backfiring
Run at fast idle, take off hose from air filter, stick hand flat over top of carb until engine almost dies then release. your hand'll be covered in crap but the carb should have self-cleaned.


April 8th, 2013, 1:49 am
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Aircooled Idiot
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Joined: April 24th, 2010, 10:01 am
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Post Re: Misfiring & backfiring
Or spend 10 minutes taking it of and clean properly with compresed air, then you categorilly know the jets are fine.

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April 8th, 2013, 8:09 am
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viking bastard
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Joined: April 18th, 2009, 11:43 am
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Location: Meneac, Bretagne France
Post Re: Misfiring & backfiring
When arriving at fuel station and seeing a fuel truck delivery, I move up to the next station (unless crossing Oz) When pumping fresh fuel down to the underground tanks, all the sediment is hurled around. Some of that shit is pumped in to your tank causing trouble in your carburetor. It is common to call out shit fuel, it is not but sediment.

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April 8th, 2013, 8:58 am
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Firing on two.

Joined: April 22nd, 2009, 11:06 pm
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Location: Ecosse
Post Re: Misfiring & backfiring
Jameswallace wrote:
If you ran it low you could of sucked some shit up from the bottom of the tank. Can take a while to block sometimes

>groan<
James as the pickup is always at the bottom of the tank (otherwise if at the top the full 20l would be redundant) so the pump is lifting from the same point if it were full or empty there is also about 2l of fuel left in the tank when run dry so unless Sam had accidently filled up with 3 l of water its unlikley

this sucking in crap when run empty I reckon comes from old motorbike days where the petrol gravity fed from the bottom of a tank still had an upstand in the petcock, there was always a reserve tap drawing from the very bottom of the tank where you could get home on the last dregs.

there was a story where someone returning from a trip had run out of fuel in an isolated spot - poured the 1l if finest duty free whisky in the tank and continued. He was convinced the car actually ran on the 40% alchohol - all that happened was the watery whisky sank to the bottom of the tank lifting the remaining petrol in effect adding 1l of petrol to the empty tank.

Sam most likley to be something like degrading rubber in the pipework blocking the jet - what ignition do you run?

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April 8th, 2013, 9:06 am
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Firing on two.
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Joined: February 11th, 2009, 12:32 am
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Location: Chichester, West Sussex
Post Re: Misfiring & backfiring
Sean wrote:
Sam most likley to be something like degrading rubber in the pipework blocking the jet - what ignition do you run?


Old school, points and condensor. I have yet to fit the vellemen unit you got me, I'll put it in when I rewire the front end.

It is only happening with foot down above 45mph. She's idling fine.


April 8th, 2013, 3:50 pm
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Aircooled Idiot
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Joined: April 24th, 2010, 10:01 am
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Post Re: Misfiring & backfiring
As ken said. Main jet sounds partially blocked

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1988 2cv 652cc
1993 Toyota Hilux Surf 3000cc runs on Bio Diesel
2004 Toyota Landcruiser Amazon 4200cc runs on Bio Diesel
1998 Daihatsu Hijet 1300cc
2005 Susuki Bandit 650cc


April 8th, 2013, 4:54 pm
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Firing on two.

Joined: April 22nd, 2009, 11:06 pm
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Location: Ecosse
Post Re: Misfiring & backfiring
old/duff coils can do that too

you did switch the ignition off while you dozed in the services?

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April 8th, 2013, 5:06 pm
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Firing on two.
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Joined: February 22nd, 2012, 10:34 am
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Post Re: Misfiring & backfiring
ken wrote:
James.
about the nth time of saying this, but the intake for fuel pickup in all A series tanks is situated near the bottom of the tank, so running the tank low won't make any difference.
If there's any water or muck in the tank, it's just as likely to be picked up when the tank is full.

The only setup which runs the risk of drawing debris from the bottom of the tank into the fuel supply is on those motorcycles which have their reserve supply fed from a point lower than the normal supply...

ken


Jameswallace wrote:
If you ran it low you could of sucked some shit up from the bottom of the tank. Can take a while to block sometimes


About the intake for fuel pickup, are you sure that the bottom of the filter is not blocking the fuel sender's inlet pipe?

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April 9th, 2013, 7:56 pm
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Firing on two.

Joined: April 22nd, 2009, 11:06 pm
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Post Re: Misfiring & backfiring
ken wrote:
James.
about the nth time of saying this, but the intake for fuel pickup in all A series tanks is situated near the bottom of the tank, so running the tank low won't make any difference.
If there's any water or muck in the tank, it's just as likely to be picked up when the tank is full.

The only setup which runs the risk of drawing debris from the bottom of the tank into the fuel supply is on those motorcycles which have their reserve supply fed from a point lower than the normal supply...

ken


:lol: hadn't read that when id jumped in with the fuel tank level comment

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April 9th, 2013, 8:23 pm
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Firing on two.
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Joined: February 11th, 2009, 12:32 am
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Location: Chichester, West Sussex
Post Re: Misfiring & backfiring
Sean wrote:
old/duff coils can do that too

you did switch the ignition off while you dozed in the services?


Yep because she's an oldie there's only the one position on the key.

D Day today so I'll start with the carb and fuel pump. Given that I don't have a compressor I'll go with the hand on top trick.

I'll also see if there's any gunk in the fuel filter.

Watch this space...


April 10th, 2013, 11:57 am
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