49cc 2 stroke engine

Their is a vacumn pipe from carb to the valve on the bottom of the fuel tank ,,,check it out is pipe split is there a vacumn ? has the valve jammed .

This is a 2 stroke engine - an outboard motor?

Two strokes are quite robust. The usual mistake people make with these engines (think of chainsaws, lawn mowers and hedge strimmers..) is to use car engine oil instead of the correct two stroke oil. Motor oil is completely incorrect and fouls the spark plug.

The other fault is to mix fuel and two stroke oil in the wrong ratio. Most chainsaws etc .. use a mix of 25:1 Too much oil causes oiling and misfiring of the plug. Too little oil causes excessive and fast wear.

Your engine starts up. That tends to suggest that everything is working ok up to a point.

However, look on the following link which deals with an overheating problem for that engine:

http://www.etecownersgroup.com/post/25hp-etec-problem-6107593

run fault codes and check for speed limiter related fault

does thr engine rev upwhen started than idels back down.try idel control switch and map sensor

Assuming your engine is in good mechanical condition, there are only a few options.

1. You may have a vacuum leak.
2. The pickup in the distributor may be worn to the point that it is sloppy at idle but normal at higher rpm.
3. Idle control valve/motor may not be working properly.

It probably isn't an ignition related problem as the problem would normally get worse as RPM increases. I've seen #2 about 5 times in the past year or 2 so it's not uncommon and would recommend replacing the entire distributor if you come to that conclusion, but would definitely check all vacuum hoses first.

Those old engines were made to last - compare the weight of the motor to one of similar capacity nowadays; the old ones were made of cast iron which is quite heavy, the newer ones like the C270CDi Mercedes motor weighs about 30-40%less due to aluminium parts. Longevity suffers, but you need less power to drive the engine, giving you more power to drive the car. Furthermore, the common rail injection used nowadays are a lot more flexible and powerful, due to the fact that the exact amount of diesel needed per cylinder stroke is injected, whereas the old system injected a fixed amount per stroke, whether you are doing 20mph or 80mph. So, it overfuels at low revs and underfuels at higher revs. To prevent it from burning too lean the engine has a rev limit, roughly where the mixture is running at "100%" effectivity. The newer motors use computers to make the decisions based on 83452 different inputs, the older ones just measured the diesel needed and the air supplied.

So, the sad news is that the only way to get the car to perform a lot better is to put in a new moter eg. C270CDi, or put in a REAL motor like a 350Chevy :-D but leave the 300D badge on and see the other guys $h@ their pants when this "diesel" smokes them!

these were the best engine ever built by Toyoya they always had a tendancy to do this ,make sure all the vacuum lines are connected nand the idle should be set at 800 rpm. you seem to have to give them a bit of revs to over come the problem

i think the dist is adjable try advanceing it some times the after market caps are a little diffront

Check the fuel delivery, first. It could be fuel pump or an obstruction. The best way is to start the car in park, then run over to the engine compartment and rev up the throttle. Keep idle higher than normal. If it wants to die, rev throttle higher to compensate. If it makes no difference, verify fuel pressure when engine dies. Usually ignition related wont even allow the car to start. Any service engine indication?

check the distributor to make sure that the rotor is pointing at the no. 1 cylinder when that cylinder is at top dead center on the compression stroke. It sounds like your distributor rotor is 180 degrees out of time. The engine will run but will do what yours is doing.