Technical Power Loss - Engine problem

[Marios500]

Hi all, altough I found similar threads on this issue and tried all of the troubleshooting suggestions I still have no luck.

Few weeks ago while driving our 500N 499cc it started cutting power and there was no acceleration (max speed less than 5). I pulled over, let it for several minutes and tried to step on pedal and suddently started accelerating again. I though could be dirt in the fuel system so I replaced the old fuel tank (had plenty of rusty dirt), the fuel gauge, the fuel filter, cleaned the fuel pipes woth air etc. Since i was doing some works I’ve replaced the coil, condenser, contacts, distributor rotor, plugs just to eliminate as much of the possible problems as possible. The fuel pump and carb and the starter motor have been replaced few months ago, with less than 100km since then.

Problem came back now and is even worst, with engine at idle to have some abnormal vibration, low revs and no power/acceleration. When tried to press the pedal few times today the engine went off. There is no leak from the carb or any other engine part. I’ve rechecked the contacts and the gap is correct.

Any suggestion or ideas are greatly appreciated. Thanks Marios

 

[bugsymike]

Hi all, altough I found similar threads on this issue and tried all of the troubleshooting suggestions I still have no luck.

Few weeks ago while driving our 500N 499cc it started cutting power and there was no acceleration (max speed less than 5). I pulled over, let it for several minutes and tried to step on pedal and suddently started accelerating again. I though could be dirt in the fuel system so I replaced the old fuel tank (had plenty of rusty dirt), the fuel gauge, the fuel filter, cleaned the fuel pipes woth air etc. Since i was doing some works I’ve replaced the coil, condenser, contacts, distributor rotor, plugs just to eliminate as much of the possible problems as possible. The fuel pump and carb and the starter motor have been replaced few months ago, with less than 100km since then.

Problem came back now and is even worst, with engine at idle to have some abnormal vibration, low revs and no power/acceleration. When tried to press the pedal few times today the engine went off. There is no leak from the carb or any other engine part. I’ve rechecked the contacts and the gap is correct.

Any suggestion or ideas are greatly appreciated. Thanks Marios

I was going to suggest a blocked vent at fuel tank, but as it is now getting worse then more involved.
Are there any differences between the two old spark plugs to give a clue, is there signs of overheating?
Have you tested the HT leads?
Does one cylinder have more power if you carefully remove one HT lead at a time?
Did the engine run well with the new carb before the problem started?
Any chance dirt under the needle jet in carb or even the main jet?

 

[Marios500]

I was going to suggest a blocked vent at fuel tank, but as it is now getting worse then more involved.
Are there any differences between the two old spark plugs to give a clue, is there signs of overheating?
Have you tested the HT leads?
Does one cylinder have more power if you carefully remove one HT lead at a time?
Did the engine run well with the new carb before the problem started?
Any chance dirt under the needle jet in carb or even the main jet?

Really appreciate your feedback. The old plugs were in very good condition, no sign of overheating on any of the two nor the coil.

The leads were ok, I haven’t checked if there is more power in one of the cyclinders, will do. The engine was running good for some time after replacing the carb.

I haven’t open the carb to check if there is any dirt since I had a filter just before the fuel pump that blocked some dirt but will do so.

 

[the hobbler]

I was going to suggest a blocked vent at fuel tank, but as it is now getting worse then more involved.
Are there any differences between the two old spark plugs to give a clue, is there signs of overheating?
Have you tested the HT leads?
Does one cylinder have more power if you carefully remove one HT lead at a time?
Did the engine run well with the new carb before the problem started?
Any chance dirt under the needle jet in carb or even the main jet?

Have you checked that the filter at the top of the fuel-pump is clear? If you had to change the tank due to rust, there isalways the chance that rust has blocked the filter. There is (depending on the model of carb) a filter in the top of the carb where the fuel enters the carb---have you checked that is also not blocked?