Ugh, petrol in no 1 cylinder....

[Shamrockez]

anyone changed the piston rings before - is it hard?

[manx1641]

Hi isn't there supposed to be petrol in the cylinder? or have i got the whole combustion principle wrong!

If it's oil, though are you sure it's the rings, not the valve guilds,
all so is it the new bug?

air cooleds are easy enough just whip the head off slide the barrels out, and there they are!

Never done a water cooled, but would be interested to know how to, can you get to the gugeon pin from underneath with the sump off, then slide the piston out the top,

[Shamrockez]

On our Splitty - my Newbie's a TDi :)

http://i14.photobucket.com/albums/a309/Shamrockez7/Joey/PIC_0153yu.jpg

The fuel is all along the barrel and piston in no1 and the others only have a small amount of oil. I think the petrol supposed to come through the inlet manifolds and down into the cylinderhead that way, not along the barrel - if that makes sense?

[manx1641]

yeah petrol in the newbug would be bad then!

Theres no petrol the other side of the rings so it can't be coming from there, only oil in the sump, the petrol should burn off when the engines running, so i'd hazard a guess that the fuel in the cylinder is there because it's not firing,
usual causes would be the plug or lead to that cylinder or poor valve clearance, if you wanted to change the rings though, your almost there, just give that barrel a tug, and it'll come off, then gently prise the rings out, should come out easily enough, i think you can buy slightly over sized rings to take in to consideration the wear in the barrel, might be an idea to have the barrels honed to ensure that they're nice and round, and it's probably a good idea to do all four,

When putting them back in, you assemble the rings on the piston then slide the barrel over the top, i tend to just squeeze the rings by hand and slip the barrel over the top, but you can use a ring compressor,


Out of interest, did you do a compression test before you took the heads off? that would tell you the condition of the rings before stripping it down,
was the engine running rough before you took it apart? probably a stupid question!

[Shamrockez]

Engine was running perfectly last week - did about 100 miles after the Bus had the winter of and he didn't miss a beat! Idled beautifully, no hesitation, no backfiring, no spluttering - perfect!

But last year we did get oil coming out of the breather, and around the dynamo stand which we were told indicated low compression and worn rings - and now I've found the fuel, I've kinda put 2 and 2 together.

Never done a compression test before - don't have the equiptment or know how to do it tbh.

Honing - I've heard that before and don't know what it is! :o

I think if we decide to change anything we may as well do all 4 B+Ps whilst we're there - are the new ones easy to fit and do they need honing?

[manx1641]

Hi, sorry the new suspension turned up for the beetle, now it handles well!

ok, oil from the breather would suggest worn rings as the compression usually created in the cylinder would be pressurising the block pushing oil vapour out of the vent,

a compression test is easy with the engine assembled, the tester is cheap and available from halfords (other car accessory stores are available, and probably cheaper) you just take a plug out, take the middle lead off the distributor so the engine won't start, screw the tester in the plug hole, turn it over about 8 times, and look at the pressure, do all 4, they should be similar, 120-130good if ones worn it'll show up lower, a small drop of oil in the cylinder and test again this will seal the rings briefly , if this cures the low pressure then it's your rings that are worn, if not it's your valves,

but as we've got the engine apart, it's a little late, you could, new barrels and pistons, and to be honest if your going to change the rings, then it's no more work, just need to remove the old piston as well, and reassemble with the new parts, instead of the old,
i take it' its a type 1 engine, if so i think new B+P's are about £100 and come with the rings and instructions, should all be honed ready to fit straight from the box,
when you take the gudgeon pin out to remove the piston check that it's relatively tight in the end of the rod, more importantly, that it's a good fit when it goes back in, if it's lose and the rod bush is worn then you'll wear your new barrels, hope that helps,

[Shamrockez]

General consensus on VZi is that we knocked the carb when removing the engine and the fuel has run down to the open cylinder (in this case no 1). Does that sound about right to you?

The oil coming out of the breather seemed to fix itself when we put a pipe on to the air filter. There was still a leak at the base of the dynamo stand, but I think new seals will solve that.

[manx1641]

Yeah that could give you a little fuel in the cylinder, some people have a bad habbit of reving the car just before they switch it off, this fills the cylinder with fuel, which then isn't burnt, it sits in the cylinder and thins out the oil in the rings, when you go to start it again the pistons are dry in the bores, which is like using an angle grinder on aluminium! causing excessive wear,

the hose to the air filter would help, as it sucks the vapour back in to the combustion chamber to be burnt off, i have heard that if the louvred metal gasket under the oil filler tower is put in the wrong way round it can cause excess pressure too,

i've just built my self an all new 1641cc type 1 for my buggy, with all the gucci bit's cost a little over £2k first engine i've built, it started beautifully once i reset my ignition system,

[Shamrockez]

Ooh - the metal louvre thing was in the wrong way round! I made a note of which way it came off, and then looked in the book and saw that it was wrong.

We probably ended up pressing the accelerator when undoing the cable from the carb - it was on quite tight.

1641 - very nice! £2k is owch, but an engine is going to last for years and years, so in the long run it isn't that expensive i don't suppose!