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Only firing on 2!!


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#1 screech

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Posted 09 March 2005 - 09:31 PM

Didn't touch anything!
I'v had the rear subframe out and back in, put a new jet in the carb and a new lcb.
I'm only firing on 1 and 2, 3 and 4 are doing nothing.
Had the plugs out, 1 + 2 have been firing, 3 + 4 are just 'WET'.
New plugs, leads dissy cap and rotor arm.
NO Change!
Firing order - 1 3 4 2, anti clockwise on dissy cap.

HELP

#2 Jordie

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Posted 09 March 2005 - 09:35 PM

and plug 1 closest to radiator side of engine?

Checked points and condenser? are the plugs sparking if you test them?

#3 screech

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Posted 09 March 2005 - 09:47 PM

plug 1 at rad.
toke the plugs out and put then to earth and they all spark.

#4 Dan

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Posted 09 March 2005 - 09:51 PM

How's your gaps?

#5 dklawson

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Posted 09 March 2005 - 09:54 PM

Single carb? If you were running twins I'd expect that the rear one is flooding. You say you've got spark on all plugs but 3 & 4 are "wet" which implies to me flooding.

#6 screech

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Posted 09 March 2005 - 09:56 PM

plug gaps at 0.025 (if thats how you put it.)

#7 screech

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Posted 09 March 2005 - 09:56 PM

single hs4.

#8 Dan

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Posted 09 March 2005 - 10:20 PM

I've had a similar problem which turned out to be a blown head gasket between 3 and 4, I think it was because there was not enough compression for the spark to ignite the fuel which sounds like a nonsense but that is what happened to me. This was with twin carbs and what gave it away in the end was removing the air filters and seeing mixture being blown out of the rear carb mouth while the engine was running on two! Naturally this was quite scary and I switched it off fairly quickly for fear of a huge fire!
Try a compression test to check but sadly I think this may be what you have.

#9 screech

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Posted 09 March 2005 - 10:28 PM

:( NOOOOOOOO!! Someone else said that earlier, having him look at it tomoz for me will let you know, thanks for your help.
Well... if the head has got to come off :cheese: !! what can i do to it to make it a bit quicker.
Its just a 998cc wjth an lcb, single box centre DTM, alloy inlet, fixed jet.

#10 998dave

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Posted 09 March 2005 - 10:42 PM

Head gasket change takes about 2 hours, if you were near me I'd do it...
Make sure you clean the surfaces properly, and check it's all flat.

Dave

#11 screech

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Posted 09 March 2005 - 10:47 PM

don't you have to have the head machined or something.

#12 998dave

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Posted 09 March 2005 - 11:50 PM

Depends why the gasket blew.
If it blew cas the head got warped then yes, also if it blew cas part of the head is not flat then yes, the warped one is something that normally happens when it hasn't been torqued down correctly or has overheated.
It's possible that the gasket was just a bad one and has eventually given up the ghost.

So the questions are:

How old is the head gasket.
Have you overheated it recently.
Has it been left standing for a long time.

And you can check the head when it's off by cleaning it up (don't use any hard metal as you can damage the head further, I reccomend a plastic wallpaper scraper and the green scouring pads work well if used gently.
Check with an engineers square or another flat edge.

You should be able to see where the head gasket is gone.

I'm trying to think of other possibilities of one pair not firing, there isnt a blockage in the inlet manifold or anything is there? You can look as you make your way down to the head gasket.
Also are the tappets set right?
What happens if you swap the spark plugs and leads over, keeping the same timing?

#13 screech

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Posted 10 March 2005 - 06:29 PM

doh!!!
had dale round today, says the head gasket!!!
but if it is, shouldn't there be water everywhere?

dunno how old the gasket is could be original 1988 or not!
no it hasn't been overheated
its been standing for about 3 weeks.
there are no blockage in the manifold (had all that off to do exhaust.)

#14 Dan

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Posted 10 March 2005 - 06:37 PM

With the problems you have the gasket will have gone between 3 and 4 where the fire rings touch each other. So the oil and water systems are still all sealed up, but you've lost all compression in both cylinders. Always check the head and block for flatness when you take the head off but I think it's unlikely to be a problem in this case, just an old gasket.




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