running on / pinking after turning off ignition

Post by **alex_holden** » Wed Oct 10, 2007 1:02 pm

You shouldn't really need to stretch the carb spring to make the piston close properly. with the damper removed it should slide up and down with very little resistance. I would try taking the carb apart and giving the parts a good clean with solvent.

Post by **Orkney** » Wed Oct 10, 2007 1:28 pm

no way dude !!! not unless i had a spare one to replace it with when i make a complete mess of it !!!
It wouldnt go all teh way down with the damper in even when running. Will try playing with the mixture later again and put soem more fuel in just in case.

Post by **bmcecosse** » Thu Oct 11, 2007 7:57 pm

But the spring should not have been stretched - and that may now be the problem.

Post by **MoggyTech** » Thu Oct 11, 2007 8:05 pm

If the piston is sticking it must be for a reason. These parts are machined to very close tolerances. If it's the piston sticking in the dashpot, there will be very fine 'witness' marks inside the dashpot and on the piston sides.

Commonest cause is needle not centred in the jet, or a bent needle. Thing is, when you find the actual problem, the stretched srping is going to increase piston damping, and give you poor performance.

There is nothing to be afraid of inside an HS2 carb, they are very easy to work on compaired to some carbs.

Post by **Orkney** » Thu Oct 11, 2007 8:23 pm

Yes that all makes sense, will unstretch the spring in the morning

Post by **bmcecosse** » Thu Oct 11, 2007 8:42 pm

'Unstretch' the spring - hmmmm!!

Post by **Orkney** » Fri Oct 12, 2007 7:19 am

Unstretch' the spring - hmmmm!

indeed - if it wont compress back to how it was i'll cut a bit off as a make do measure until i can get a new one

Think actually going to invest in a whole new top for the carb + needle (although the needle looks fine).
The inside of the ally pot cover was pretty filthy, quite a lot of black deposits, did best to clean it with penetrant and a cloth but its pretty stained.

Wonder if perhaps it might clean up with some brasso?

Post by **alex_holden** » Fri Oct 12, 2007 8:42 am

I just used white spirit and a toothbrush.

Post by **Orkney** » Fri Oct 12, 2007 8:55 am

its stained black Alex about the bottom 1/3 of it.
Course cotton cloth and penetrant not white spirit would budge it.
Going to give it a go with the brasso in a while, squish the spring and rich up the mixture a couple of flats - better take my coat when pop to the post office as i might be walking back

Post by **alex_holden** » Fri Oct 12, 2007 9:11 am

The colour doesn't really matter as long as the piston moves smoothly in the top. I'd be tempted to try green Scotchbrite rather than brasso.

Post by **Orkney** » Fri Oct 12, 2007 10:35 am

Well dashpot & cylinder all cleaned up - had to use cutting compound in teh end as it was discernibly un smooth in places.
Wound the spring back up a little and happy with that as the cylinder rises fully on full throttle and closes shut very sweetly.

Got it warmed up and gave it some decent throttle whilst observing the inlet. Actually managed to replicate the on/off of the engine, just wasnt enough fuel getting through. Upped it one flat and its improved, will give it a road test shortly and see how it does.

Post by **Orkney** » Fri Oct 12, 2007 12:28 pm

Well the test run didnt go so well, a bit cheesed off with it now ...
still doing teh missing thing at full power top gear on the way there. Riched the mixture one flat for the return trip, didnt miss but was still underpowered.
got back riched the mix one more flat and got it running smoother at revs on the dizzy twist. Tried it again and was superb for power but still over ran on stopping so back to square one.
Off to the garage in town this afternoon, stick a strobe on and look at the mixture from the emissions tester, hopefully nothing drastic that the rigth tools wont be able to sort out

Post by **alex_holden** » Fri Oct 12, 2007 12:43 pm

The dieselling might be caused by carbon deposits in the engine getting hot enough to glow and continue igniting the fuel without a spark.

Post by **Orkney** » Fri Oct 12, 2007 1:34 pm

dont know dude, will soon though, plugs came out clean - dont forget its only 5k on this engine.
Gut feeling is its a combination of a couple of things. Least once the mix & timing are known good then start looking elsewhere if it persists.

Post by **MoggyTech** » Fri Oct 12, 2007 1:35 pm

If you get the engine tuned right and still get running on, it's easy to fix.
Set idle speed to 700 RPM. When you switch the ignition off, dip the clutch, the extra drag stops the running on.

Assuming the engine isn't worn, poor performance is usually timing too far retarded, with possible overheating as well, which will make running on worse.

Quick setup.

1: Align timing marks to TDC slacken dizzy clamp
2: Wire a 5W 12V bulb between dizzy lead and battery + (If Neg Earth)
3: Hold rotor arm AGAINST direction of rotation aka hold it clockwise to take up dizzy drive slack
4: Rotate dizzy body by hand until bulb just lights
5: Tighten dizzy clamp

The mechanical advance starts at 400 RPM, and if you use a timing light after doing above static timing, you should get about 4 degrees BTDC at idle.

Start engine and let it warm up, remove air cleaner. Lift carp piston 0.8mm with either the little lifting pin, or a small screwdriver. If engine speed reduces increase mixture, if engine speed rises weaken mixture, mixture is correct when engine speed remains constant, or only just increases a little.

Hope this helps

Post by **bmcecosse** » Fri Oct 12, 2007 2:01 pm

Just keep advancing the timing till it pinks - then back it off v slightly.

Post by **Orkney** » Fri Oct 12, 2007 4:35 pm

Just got back from the garage

bit bemused to be honest, to say a slight transformation would be an understatement.
I'd often wondered how some of you guys are quite happy on a motorway cruising 65 - 70 (or allegedly more if youve got a fenchurch) given that scabby didnt sound at all happy @55 and beyond. Well i know now

The timing was about 5 degrees out the wrong way past the mark !!! Although i'd played with rotating the dizzy did the sensible and marked it before i started (been had by that before) so it was as before i tinkered.
Talk about luck too, the ex mot tester there and undeniably the best mechanic on orkney (he left for big money on the oil transfer tugs) happened to be passing so lent a hand too -

He's also going to come take away the dead landrover so really was worth being there.

Anyhow, amazing to drive it back, lost the rear end 3 times such is the difference. Will have to learn to drive it again now.
Didnt get a chance to look at the mixture as couldnt get it in the garage, and sods law it still ran on when i got back - but for the moment more than happy its running the way it is, the knowledge the timing is 100% correct is a great starting point to eliminate that.
So chuffed going to have a celebratory beer

Post by **MoggyTech** » Fri Oct 12, 2007 9:36 pm

Well done Orkney, watch that back end in the wet now that you have a Hot Rod Moggy

FWIW: My Traveller has a tendancy to run on after shut down unless I dip the clutch, worse on hot days or after a longish run. It even did it after I re-worked the cylinder head while doing valve stem oil seals a couple of year ago. This work included polishing the piston tops, cleaning and grinding in valves etc. Still did it the very next day. Now if I lean the mixture out to below 'normal' (2.5 Co on the GAS Tester) it does NOT run on, but it runs rubbish, so I just learned to live with it.

Not sure if the following will be of any use to anyone, but some Gas Tester figures I did with my MOT chap proved interesting.

Setting mixture using the carb lifting pin Co=6.5
Setting mixture using colortune Co= 4.5

Best to run them a little rich anyway.

Post by **bmcecosse** » Fri Oct 12, 2007 10:40 pm

Note that Minors are NOT subject to exhaust gas test at MOT - it's a 'visual' test only. ie Unless cloud of blue smoke - it passes.
My Traveller (High comp modified 12G940 head on 1098) does not and never has 'run on'. It's caused by something glowing red hot inside the chamber - sharp edge of head/carbon build up etc will do it - the chamber edges should always be smooted off/rounded with a fine file except in the narrow land between chambers of course!

Post by **Orkney** » Tue Nov 27, 2007 6:10 am

Giving this a bump as its still happening - well did yesterday and its getting oh so annoying. Not the running on itself but the not knowing the cause.

Just wonder if anyone has any thoughts.

Timing - been done at the garage - can only assume its correct as it was done properly - and it did it before the timing was done anyway.
Its running better than it ever did tuning wise and in terms of extra power compared to before. That and it seems to be barely sniffing fuel.

Going into factors today or tomorrow to get some injector cleaner for the range rover - looks like snow at the weekend

- tried a one shot bottle oof the stuff on teh daewoo couple weeks ago made one amazing improvement.
Anyway is it worth me trying a treatment of redex? Or is there anything better i can stick in the fuel?

I reckon so far BMC's analogy that some crud or such is glowing red- other thing that occurs is could it be a carb problem? (where is he lately?)

Any suggestions gratefully recieved.