5 replies to this topic

[bjd8747]

Hi,
Another question for you all! In a fit of enthusiasm I had a look in the float chamber of my carbs- it looked clean and tidy so I put the top back on. I took the piston out of the carb and checked the needle for wear. Again, it looked good so back it went. I had noticed that the accelerator pedal and the choke had been a little sticky, so I sprayed the spindle on the side of the carb and down the cable guides with WD 40. So far so good.

The problem is that the engine has developed an intermittant misfire and an erratic idle. Coming home from work the engine was misfiring. Going to work today I could hear the idle speed decrease while at traffic lights until it stalled. On a couple of occasions when I tried to restart her, I had to have the choke RIGHT out and my foot down on the accelerator before she would start. On the motorway, I eased off the gas and nothing happened. I pressed down hard and let it up and it stuck wide open. Cue panic. Stamped on it again and it came right.

Is it possible that the fittings are slipping around on the spindle of the carb? Has anyone any other ideas?

Thanks in advance,
Ben
p.s. the engine is a 998 block with a single HS4 carb.
p.p.s if anyone can describe where the piston lifting pin is for setting the mixture I would be eternally grateful

[Wil_h]

Firstly I'd try and sort the sticking throttle, as you have already discovered a wide open throttle amkes your arse twitch a bit.

Somtimes WD40 can just cause dirt to move around more making things worse. What you want is a can of carb cleaner (Halfords or car shop) use this to clean the outside of the carb, and the inside by taking the dashpot off again. thyen use WD40 to oil where necessary.

Next thing to check is that you havent disturbed any breather pipes on the the carb. If these are split or missing then it will affect running drastically.

Finally, make sure the dashpot has oil in it.

Wil

P.S. not all carbs have a lifting pin, if it's not obvious then it's probably not there.

[bjd8747]

'Firstly I'd try and sort the sticking throttle, as you have already discovered a wide open throttle amkes your arse twitch a bit.'

Well it did brighten up my morning!
Thanks for the help, I guess I shall dice with death until the weekend when I can put my fettling hat on again.
by the way if there is no lifting pin, then how best to adjust the mixture? Is it just trial and error?
Thanks,
Ben

[Jimmyarm]

If there is a lifting pin its on the left hand side as your looking in about halfway back from memory.

[bjd8747]

So it gets weirder. I set off for work this morning and all seemed good. However, after about 10 minutes she started to stall at junctions, i.e. completely die on me. She restarts with lots of choke, idling quickly and then in the space of about 5 - 10 seconds the idle is really slow and lumpy. I nurse her to work, leap out and open the bonnet, remove the air filter to find frost (!) on the metal linking the carb to the engine. Everything seems attached and there are no obvious gaps, wobbley bits or disconnected thingies. HELP!!

[Dan]

Firstly, the throttle cable is lined with Nylon. That means it's self lubricating and desgined to never be oiled. WD40 in it will as has been said cause trouble.

If you want to oil stuff, try using oil instead of WD40. It's not really oil, whatever it says on the tin. 3 in 1 is good light oil. For the carb linkages, a good clean with carb cleaner and a very light shot of spray grease is good.

As has been said, did you re-fill the dashpot after you replaced it?

Frost on the inlet is fairly normal, have you fitted an alloy manifold and not connected up the heating to it?

Sounds like you might have an air leak, is the dashpot back on correctly? Are all the hoses connected to the carb and breather canisters / dizzy? Could be contamination in the float chamber also, is it still clean in there? Nothing blocking the float travel?

Without the lifting pin (unreliable mathod anyhow IMHO) home tuning relies on the plateau method, a good ear or a Colortune is a very worthwhile investment.

Was it working properly before you started 'investigating'?

Edited by Dan, 26 July 2006 - 09:22 PM.