The rocker cover is a simple part but a couple of points to note as you do not want any oil leaks. Also worth checking that the oil filler cap is sealing properly. My chosen way of fixing the rocker cover is to use a suitable fibre washer with a plain washer on top of that then a nylock nut to pull it down. Well used nylock nuts should be replaced, an M8 deep nylock nut is favourite. Never over-tighten the two nuts as there have been instances when overtightened nuts can collapse the rocker cover internal struts to the point that they interfere with the rockers and disable the engine. Make sure that you clean the gasket mating faces on cover and cylinder head. Again my preference is to smear a light film of suitable sealant on the rocker cover face to hold the gasket in place when fitting then check when in place before fixing down then just nip it up to make a seal.
Technical Is my engine a mix ?
- Thread starter Flock
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Technical Is my engine a mix ?
Will be doing that later this week when i get all the parts. This morning i tried to start the car but no go. It didnt Fire. I had to set the mixture screw 3.5 turns out in the end to get it to Fire. After a trip i readjusted again and got to approx. 2 turns. Will try later this week with New spark plugs. I will get there, Just takes a While
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Try leaving it at 2 turns out next time, and giving it full choke to start. 
Did that but it didn't even give a single Fire than. Took me about 15m to get it running idle. Touching the choke even the slightest made it die instant. Mixture 2 turns out, 2.5 turns out, 3 turns out....in the end 4 turns out and no choke did the tricky to get the engine to Fire up. After running around the block for 15m and setting idle and mixture i set it to to 1.5turn idle and 2 turns mixture. But probably i will not be able to get it running tomorrow with these setting.
So I set valves clearance today, cleaned and set breaker points, tried to set static timing, and put in new spark plugs and airfilter. Had some trouble starting the engine but in the end got it running and a very short test drive (started raining) i got the feeling the car was a lot more quiet than it used to be.
Problem I ran into:
static timing. I did this with a 12v lightbulb. Set to 10 degrees and rotated distributor head untill light when on/off. I have a wasted spark system so I guessed it wasn't important to point it at piston one. Now the strange thing is that when I rotate the engine 360 degreed the point where the timing is looks to have drifted about 10 degrees?
I have ordered a strobe so I can set it at 28 degrees (i assume that the much mentioned 18 degrees is actually 10 +18 = 28 degrees.)
Because I eventually got the engine running i'm not sure if my cold start has gone away. I'll try that tomorrow.
Problem I ran into:
static timing. I did this with a 12v lightbulb. Set to 10 degrees and rotated distributor head untill light when on/off. I have a wasted spark system so I guessed it wasn't important to point it at piston one. Now the strange thing is that when I rotate the engine 360 degreed the point where the timing is looks to have drifted about 10 degrees?
I have ordered a strobe so I can set it at 28 degrees (i assume that the much mentioned 18 degrees is actually 10 +18 = 28 degrees.)
Because I eventually got the engine running i'm not sure if my cold start has gone away. I'll try that tomorrow.
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You are right about 10 (base) + 18 (of centrifugal advance) naming 28 total at 3000+ rpm. You are also correct about not needing to worry about which cylinder is firing when you check the spark timing on these engines.
Regarding the difference in timing between the two cylinders, a worn lobe on the points cam or the shaft being bent off centre slightly, will cause that symptom. Check the points gap, then turn the engine 360 degrees and measure the gap off the other lobe, if there is a disparity that will be your issue.
In the case of my engine the distributer had been knocked when I got the car (the cap was broken) and the distributer shaft had been bent a little, I was able to tap it back into line fairly easily to even up the points gaps.
Regarding the difference in timing between the two cylinders, a worn lobe on the points cam or the shaft being bent off centre slightly, will cause that symptom. Check the points gap, then turn the engine 360 degrees and measure the gap off the other lobe, if there is a disparity that will be your issue.
In the case of my engine the distributer had been knocked when I got the car (the cap was broken) and the distributer shaft had been bent a little, I was able to tap it back into line fairly easily to even up the points gaps.
This is driving me nuts. Problem remains. First time I turn the key it starts over 1 time and dies. After that:
Using choke will do nothing except spinning the starting motor.
Using no choke will make it start over after 15 attempts, number 16: starts over and dies after 1 sec, 17: dies after 2 seconders, 18 dies after 4 seconds. Using choke or gaspedal makes it die immediatly. On attempt 22 i finally can use the gaspedal to rev it slight and then it keeps on idling. After about 10 seconders of fairly constant idling its ready for the rest of the day. It runs great , and starts everytime on the first attempt.
What I've tried:
Mixture screw (.50) settings: anything below 3 full turns makes the above impossible. It will not fire up, I have to be on minimal 3 turns to get it to fire.
Using choke: it doesn't fire up, and when iddling and i use choke just a littly initiny bit revs go up, using a little more choke and it dies.
What I've done:
new airfilter, cleaned and set breaker points, set static timing, valve clearance, new spark plugs (old ones were black), spayed brake cleaner around carb and checked fuel pump.
All this happened after I installed a new IMB 28 because the old one had a leak in the housing. With the old one it started first attempt by using half choke. I do not know the settings of that carb because I only had it for a couple of weeks and I noticed the leaking. Garage installed the new carb and starting problems started. I first thought it was my fault since they told me: new carb, new method of learning how to start. The say to use choke! But clearly that makes starting impossible
All signs it seem to be it is set to rich, (looking at the choke when it finally runs idle makes it die instant) but on the other hand....it's impossible to start with mixture screw less than 3 turns out. Garage even set i 4 turns out!
I really really want to learn and fix it myself. But I'm getting to the point that I do not know where too look next.
Using choke will do nothing except spinning the starting motor.
Using no choke will make it start over after 15 attempts, number 16: starts over and dies after 1 sec, 17: dies after 2 seconders, 18 dies after 4 seconds. Using choke or gaspedal makes it die immediatly. On attempt 22 i finally can use the gaspedal to rev it slight and then it keeps on idling. After about 10 seconders of fairly constant idling its ready for the rest of the day. It runs great , and starts everytime on the first attempt.
What I've tried:
Mixture screw (.50) settings: anything below 3 full turns makes the above impossible. It will not fire up, I have to be on minimal 3 turns to get it to fire.
Using choke: it doesn't fire up, and when iddling and i use choke just a littly initiny bit revs go up, using a little more choke and it dies.
What I've done:
new airfilter, cleaned and set breaker points, set static timing, valve clearance, new spark plugs (old ones were black), spayed brake cleaner around carb and checked fuel pump.
All this happened after I installed a new IMB 28 because the old one had a leak in the housing. With the old one it started first attempt by using half choke. I do not know the settings of that carb because I only had it for a couple of weeks and I noticed the leaking. Garage installed the new carb and starting problems started. I first thought it was my fault since they told me: new carb, new method of learning how to start. The say to use choke! But clearly that makes starting impossible
All signs it seem to be it is set to rich, (looking at the choke when it finally runs idle makes it die instant) but on the other hand....it's impossible to start with mixture screw less than 3 turns out. Garage even set i 4 turns out!
I really really want to learn and fix it myself. But I'm getting to the point that I do not know where too look next.
smart51
Established member
What sizes are the main jet and air corrector jet? I've found out recently that the main jet size does have an affect on starting.
There are 4 screws that hold the top on the carburettor. with that removed, the air corrector jet is on the top. It should have a number in the region of 190 for a 652cc engine or 215 / 225 for a 594. The main jet is at the bottom of the float bowl. The standard sizes are 115 for a 652 and 125 for a 594.
You account is confusing. An engine dying when you open the choke sounds like it is too rich. An engine not starting with less than 3 turns out of the idle mixture screw sounds too lean.
There are 4 screws that hold the top on the carburettor. with that removed, the air corrector jet is on the top. It should have a number in the region of 190 for a 652cc engine or 215 / 225 for a 594. The main jet is at the bottom of the float bowl. The standard sizes are 115 for a 652 and 125 for a 594.
You account is confusing. An engine dying when you open the choke sounds like it is too rich. An engine not starting with less than 3 turns out of the idle mixture screw sounds too lean.
If I open the top, do I need to replace the gasket (haven't got one here.)
Yes, it's confusing me too.
smart51
Established member
I've taken the top off mine about 10 times recently and the carburettor gasket is fine. The one between the carb and the inlet elbow is showing signs of giving up.
Ok, carb is fairly new and hasn't been taken off once, so I guess i'll just try. If it doesn't work out I can always order a new gasket.
btw, I really really appreciate all the help. I feel like I'm smart 1.5 allready. Long way to go to get to smart51....but I've got time!
btw, I really really appreciate all the help. I feel like I'm smart 1.5 allready. Long way to go to get to smart51....but I've got time!
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While you have the top of the carb off, it would be worth checking the float level.
smart51
Established member
Always good advice. I've recently worked out why.While you have the top of the carb off, it would be worth checking the float level.
The float sets the height of the fuel in the float bowl. This is below the level that the fuel will flow through into the venturi. As the air flow through the venturi increases, the fuel level in the tubes of the carb rises like in a manometer. When the fuel reaches the level of the nozzle, it flows into the engine. The float level sets the point where the main jet starts. So a smaller float gap = a higher fuel level = the main circuit starting sooner. It might make it richer too, I've heard.
Ok, I ended up removing the whole carb. No big deal indeed. Jets are 190 and 115 so that seems spot on for my engine. The 115 looked like it was blocked but that could have been a fuelbubble. I cleaned it and also some very minor debris in the floatchamber. Checked float (needed little correction on the 16mm mark and choke mechanism. Screwed it back on and starting was the same as in the morning. I understand the floatchamber was empty, but it shouldn't take 10 start attempts to get it full. In the end I had to set the mixture to 4 turns to get it started, choke only works the first cm (than it revs up for a brief moment but starts to bog, raising the choke handle further than 1cm and the engine dies.
After I got it idling nice I could turn in the mixture and the engine starting bogging at about 1.5 / 2 turns. Revving it gently by hand it had sometimes a small hickup.
I did notice their was a filter in the fuel inletpipe. I start to think (as a complete noob) that mayby the engine needs to be rich because it isn;t getting enough fuel? When I unscrewed the top (I had driven for about 15min earlier today there was about 2 or 3 cm of fuel in the chambre.
After I got it idling nice I could turn in the mixture and the engine starting bogging at about 1.5 / 2 turns. Revving it gently by hand it had sometimes a small hickup.
I did notice their was a filter in the fuel inletpipe. I start to think (as a complete noob) that mayby the engine needs to be rich because it isn;t getting enough fuel? When I unscrewed the top (I had driven for about 15min earlier today there was about 2 or 3 cm of fuel in the chambre.
That is entirely consistent with what has been said about the Spanish made under licence Weber carbs and I pointed out near the start of this thread. Some seem to work as they should and others do not. You were lucky that your supplier acknowledged this. I believe that a UK supplier had a lot of problems and said owners were better off getting reconditioned original carbs.
One of the things i'm beginning to learn is indeed to buy what and where. As a professional webshop owner (different business) i judge stores for a big part on their looks and advanced technical design. This doesn't always work with oldtimer parts. The People selling original refurbished parts are mainly People skilled in getting their hands dirty and less interested in webdesign.
The last 2 weeks i spoke to several People in the 500 world from whom i learned who to listen to and were to buy from. The store i bought the carb from didn't dissapoint. After my first question about the carb, which i bought 6 months ago, they didn't hesitate and delivered service!
All in all i learned a lot about the 500 and the 500 People the last weeks. Now i have to figure out how to explain to the wife that i will be spending a lot of hours in the garage this winter.
The last 2 weeks i spoke to several People in the 500 world from whom i learned who to listen to and were to buy from. The store i bought the carb from didn't dissapoint. After my first question about the carb, which i bought 6 months ago, they didn't hesitate and delivered service!
All in all i learned a lot about the 500 and the 500 People the last weeks. Now i have to figure out how to explain to the wife that i will be spending a lot of hours in the garage this winter.
