Technical Is my engine a mix ?
- Thread starter Flock
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Technical Is my engine a mix ?
smart51
Established member
That sounds plausible. If the mixture is too rich anyway, adding more fuel with the choke would make it worse.
smart51
Established member
That spark plug is very fouled. What size idle jet do you have? You can remove it with the carburettor in place. It should have 45 or 50 stamped into it. How far out is the idle mixture screw turned? Turn it clockwise with a small screwdriver and count the number of full turns (then put it back). It should be between 2 and 3 turns.
The 652cc engine uses a BPR7HS spark plug.
The 652cc engine uses a BPR7HS spark plug.
smart51
Established member
This one is 0.55mm.
smart51
Established member
Here is an exploded view of the carburettor. Part 9 is the idle jet. Remove screw 12 (with rubber O ring 10 attached) and the idle jet should come out with it. It is on the face of the carburettor you can see when you open the engine bay.
smart51
Established member
50 is the right size, though 4 turns out is too many. Try it at 2 full turns (720 degrees). Also see what effect the choke has at this setting.
Towards 2 turns (from 3) it started to run rally bad. First time turning anything on a carb for me, so i have to figure out how to do this exactly. Mayby the motor was still to cold (i let it run idle for 10 minutes before tuning.) First i set idle to point that generator Light was coming on, than adjusted mixture to point it started running bad 2 to 2.5 turns out and stopped at 3.
Hi Flock, Smart is correct in stating the '7' level plug is recommended for the 652 engine, the '6' level plug has a slightly hotter temperature rating and will run better in older engines. I note the fouling on your plug too - is that the 6 or 7 level ? do you have any oil on the plug at all?
Ian.
Ian.
What i figured out is have a 110f block with a 650 head so it is 594 cc i think. But not sure since this engine seems to be a mix parts and the 650 part on the head is scratched away. I'm not comfortable with stripping the engine as i'm doing all this in a small garage.
smart51
Established member
That's not how it works. The engine size is determined by the barrels and pistons. These sit between the block and the head. It is possible to change them independently. To know the cc size of your engine, you need to measure the diameter of the pistons.
If the engine runs badly at 2 turns out and is improved by applying the choke (pull the lever on the carburettor by hand) then it is too lean at 2 turns. Turn it out more until it runs well.
Im not sure if it was the 6 or 7 plug on the photo. Also im not sure if i whiped it off before the photo or not (i think not). Anyway , New plugs are going in.
Accept for the starting, the car ran beautifull. Mayby after storting all this stuff out it will run magnificant!
Accept for the starting, the car ran beautifull. Mayby after storting all this stuff out it will run magnificant!
Mayby the previous owner didnt know the cc aswell and Just put the 6 and 7 plugs in 
. Hmmm. I wanten to check the tappen gaps this weekend (for fun) but am not sure if that should be .15 on all or .25 and .20. Mayby if i measure them and they are set correct it gives me a clue to what i have
. Hmmm. I wanten to check the tappen gaps this weekend (for fun) but am not sure if that should be .15 on all or .25 and .20. Mayby if i measure them and they are set correct it gives me a clue to what i have
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Good! If you can keep it fun, and not a chore, then there's loads to learn and enjoy and the 500 is a great little car to learn with.
With the tappet gaps, ultimately setting them to 0.15mm or 0.20/0.25mm won't make or break how the engine runs. The main thing, is that they are within that kind of range. If they are too small then theres a chance the valves will get held open when the engine get hot, which can cause poor running or worse, damage to the valves and valve seats. If the gaps are just a bit large the engine will sound rattly, or if they are really large then you loose some performance as the valves will not open as far as they should.
I don't know why Fiat changed from 0.15 to 0.2/0.25, but it could be as simple as knowing people ran into issues with the valves closing up so they added more margin for error in their specification?
Sounds like you have a realistic expectation thereGood to know. Thanks. I'm still in the noob knowledge that things might explode if i set them wrong. Slowly starting to learn that this car has survival 58 years of abuse, so it will probably survive me too
If you are going to to check / adjust the tappets (valve clearances) I would say check them first as they may not need adjusting, for this you will need to remove the rocker cover (13mm spanner or socket) then use a decent set of feeler gauges. If you have the spark plugs out that will be handy as it will be necessary to turn the engine over by hand using the crankshaft pulley. The simple way to adjust the tappets is to use the rule of 5. Looking at the rockers as you turn the engine over you will see them depress one valve after another as the camshaft applies pressure to a push rod and hence the adjustment end of the rocker arm to move it. The rule of 5 says that when no1 rocker is fully depressed you check and/or adjust the tappet on rocker no 4 (1+4=5) and so on. So when no 2 is fully depressed You adjust no 3 etc. Probably best to number the rockers with no 1 nearest you when you stand at the back of the car.
You should find that the adjusting nuts are quite tight and difficult to loosen and I would never recommend using an open ended 11mm spanner, use a ring or combination spanner. You will also need something to turn the adjusting screw, I have used a small (100mm) good quality adjustable spanner for this. To set the right gap the feeler gauge should be a nice slide fit in the gap not forced or sloppy And you will need to keep a grip on the adjusting screw when you retighten the adjusting nut. Then recheck the gap again in case something has moved. If so repeat the adjustment til you get it right. Nuts need to be tight by feel.
Yeah, i watched tons of video's and read all i could about it. Feel comfortable doing it, i ordered several parts i needed (gasket, spark plugs, tools, etc) so i can later on this week try to hopefully get everything right. Or Just taken things apart and put back together for the sake of learning. Within a week i went from 'no way im touching the car myself' to 'look at me, i'm a mecanic.'
