2-stroke headache By eagleridermb (Read 478 times)

[eagleridermb]

I'm hoping someone can give me an idea of something to look for that I haven't thought of.

F-act 50cc 2-stroke oil-injected scooter, 1E40QMB engine.

Extremely hard to get started, but once it starts, it runs OK. If you shut it off, it will crank back up immediately. If it sits more than a minute or so, it's hard to crank again.

Compression was low, so new 70cc top end was installed. The arrow on the piston points to the exhaust, confirming correct installation.

Tank-to-carb valve was replaced just in case it was the problem.

Spark is affirmative, or it wouldn't run well once it starts, so the CDI and stator must be OK.

Voltage regulator was changed by customer because he was having trouble keeping the battery charged. A local parts house checked the battery and told him it was OK. I have not begun looking for the source of the battery drain. This bike has a digital dashboard, and the clock stays on after the bike is turned off.

Carburetor was replaced and jetted to 90.

Expansion chamber and silencer are clear and unobstructed.

Air filter box and filter are both normal.

Gas was drained and replaced.

I'm leaning towards crankshaft seals, but this bike is only one year old and only has 1000 miles on it.

Anyone have any other thoughts before I go tearing into this thing to replace the crank seals? It just refuses to crank without grinding and grinding on the starter!

Thanks, -Eagle Rider MB

[richardthescooter2]

When was the last valve adjustment?

[tvnacman]

Pull a heavy gauge ground wire from the battery to the engine. Recheck the the spark plug boot. Be sure the plug on the cdi is electrically tight and connections at the coil.

John

[tvnacman]

Rich its a 2T . It has reeds.

John

[Alleyoop]

Well lets find out if it is FUEL related first:
When it is hard to start stop cranking and take the plug out and see if it is WET or DRY that will tell you what may be going on.

The mixture of fuel and air when first starting any scoot is always fincky and you have to have it adjusted properly for them start on 1 or 2 hits of the starter whether it be kickstart or electrical.

When first starting the spark is usually much weaker than after the motor is running and contributes for the need to have just the right amount of air and fuel.
Allwyoop

[teddy554]

have you check the auto enricher to make sure it is working and getting power to it, the only job that thing has is to give extra gas on the start up of the scooter, a auto choke

[rob63]

Does it make any difference to the starting if you kickstart it ? Sometimes the starter motor will drag too much out of a battery and make the spark weak.
Have a look at the fuel/air screw, if you wind it in and wind it out 3/4 of a turn, that is a good starting point. You can then adjust it out to about 1.5 turns if necessary as that`s the standard adjustment range for 2 stroke carbs.
When you`re cranking the motor and it eventually kicks in, how much throttle are you giving it, if any ? It might be worth checking which slot the circlip is in on the needle.
As Alley said, check the plug for signs of fuel. I`d be surprised if it`s a crank seal problem especially after only 1000 miles. I haven`t changed any for years, the standard of seals these days is a lot better than it used to be.

[eagleridermb]

New carb, so enricher isn't the problem. They're supposed to be closed (rich condition) with no power, so that shouldn't be the problem. I've played with the air/fuel mixture screw, and that doesn't seem to make any difference. I checked the reed valve to intake and installed a new gasket just to be on the safe side. I even installed a new reed valve (forgot to mention that). It was surprising to me that the compression was gone after only 1000 miles.

Yesterday I tried ether (starting fluid) and that didn't make (or help) it start.

I really feel it's a problem that fuel isn't making it up to the cylinder- and the crank seals is about the only thing left to check...

[jct842]

Crank seals have to be really bad to cause problems like that. What happens if you should squirt a bit of gas or starting fluid in the spark plug hole. Also is the plug getting wet? If it is using the reed valves...... some of them could be installed backwards remembering from a long long time ago. they were in a housing that could be removed and had a slight bend in them to keep them flat when installed in the housing.
\
edit: if you put your hand over the carb you should feel strong suction when the piston is on the up stroke if you have no leaks in crankcase.

[Alleyoop]

Well it is easy enough to check for COMPRESSION, why not check that first then. If you do NOT have a compression gauge use the old trick of the trade and stick your finger in the SPARK PLUG hole HOLD THE THROTTLE WIDE OPEN and crank it. If it blows your finger off the hole you have enough compression for the motor to run. If you just feel a LITTLE PRESSURE on your finger then you do not have enough compression for it to run.

Also Like I said crank it over and take the plug out and check if it is wet or dry, then while the plug is out check for compression.
Alleyoop