Sym Jet 2 stroke 50cc won't start

[dubloman]

I recently picked up a 50cc scooter that has been sat for 2 years, she turns over but won't start

Things I have done

good battery with booster charge

Fresh fuel with replacement fuel tank

we have good compression
great spark (new plug)
fuel is getting into the engine (as it's not starting its flooding) vaccum is working OK

We have changed the carb

checked the kill switch & changed

Cleaned the contact on the stator sender unit to make sure it has a good signal

We are going to check the woodruff key but I can't see it being that

We have taken the head off and the piston and rings are in great condition

If you have any ideas please make a suggestion

I am experienced but even those with experience get stumped and this is one of those occasions

Thanks

[Rune 75]

Have you checked the reedvalve ?

[humanshield]

Crank seals

[dubloman]

I have not but will add it to the list of things to check, didn't think of that one, would that have such an impact on her starting?.......I will check it

The redrec, would this have an issue on the starting? as I do have another one but want to ask has anyone had a starting issue that was caused by the redrec?

I have also found that the starter clutch does not appear to be engaging as it should but it is an intermittant issue. It was still turning over the bike up until an hour ago.

Thanks for the advice but if anyone has any additional ideas please let me know

Cheers

[dubloman]

Not sure how crank seals would effect the starting of the engine

I am not dismissing the suggestion, I am much more interested in it than to do that

Can you tell me why the crank seals would cause the engine not to start, I might be being thick but if you could be so kind in how this effects the starting and how is this diagnosed

I look forward to your reply with great interest

[humanshield]

Take the crank seals out....it'll never start and never run.

It doesn't take too much for them to dry out and lose their seal.

They're critical.

But that doesn't guarantee that's what it is.   Just my gut feeling.

Brent or one of the hard core 2T scooter guys here can chime in.   The vast majority of my 2T experience is with bigger 2T's like Yamaha 400's and 350's.

[geoffh]

Are you refitting the air filter assy these engines are fussy about that,your starter clutch springs may have rusted out (tiny little things)I,d use the kick start on a difficult engine,most people do away with the electric start eventually,and remember it,s been sat for 2 years,why was it parked up in the first place??

geoff

[dubloman]

Thanks for that

I am a diesel fitter and HGV mechanic and MOT tester OLD School, but my son has the 50cc scooter and we are trying to sort it out

I don't have much experience of 2 strokes as I was in the army at an early age so missed that part of growing up, I have 4 stroke 125's and 250's so the 2 stroke is a mystery for me. I am learning fast as I had steered clear of bikes for 40+ years but as my kids ride I joined them, I still have the best bike though......lol

I will do it as a matter of course, if I am changing them is it worth changing the bearings at the same time, the engine has only done 3200 miles but as I said it has been stood in a garage for two years

I appreciate your help as I am a fish out of water with the 2 strokes

Thanks

[dubloman]

Thanks Geoff

I don't know why it was parked up as that info is not available at the moment but I will ask

The starter clutch it nice and clean and I have 3, they are all doing the same thing, this could link into what humanshield has suggested that the crankseals have failed and it is moving a and the drive disc is not connecting as it should?

Who is the best company to get the seals and (if needed) the bearings

Thanks

[dubloman]

We changed the vaccum pump, whilst it is not pumping out fuel as much as it did the fuel that is getting into the chamber is still not igniting, we have had the stator cover off to check the woodruff key, again it was a bit dirty but fine. We have stripped the carb, cleaned it via ultrasonic cleaner and put it back together. We have checked the reeds on this and they are metal so I can't see it being that.

We are getting a great spark, fuel and compression

It has been suggested by humanshield the crankcase seal may have dried up and will cause it to turn over but not start, who sells the seals and does anyone know the sizes before I pull them. If we changed them would it be worth doing the bearings at the same time and is there anything else on this engine that could stop it from running?

If we have the 3 things

Fuel
Spark
Compression

It should start, but the crank case seals is something I have not come across before. If you can advise I would be grateful or if there is something else in the engine I would like the help, the gaskets, bearings etc etc

Please let me know as I am about to pull the engine out and do the seals but whilst it's out!!!!!

Thanks

[dubloman]

I need help with these seals, they look to be moist but should they have oil on them?

If not then they have both gone.

I hope someone can tell me as I have no knowledge on two stroke engines

Thanks

[geoffh]

It,s a big job doing the bearings,never been there,at 3200 they should be fine,if you,ve been trying to start it over and over all that unused oil,fuel will have gathered in the crankcase and make it impossible to get the air fuel ratio correct,you will need to pull the barrel off and syphon off any gunge that's in there.rags and pipe cleaners did the trick for me.

geoff

[gsx600racer]

Have you tried just shooting a squirt of gas down/in the spark plug hole, replacing the plug and kicking it over?

[dubloman]

Hi

Geoff, I appreciate your help, we will pull the head and remove any and all the fluid that is in the case, I assume from the pictures you feel the seals are OK (not done one of these before) but the bearings are not that big of a job as we have pulled the engine out and it's on the bench, just need to know where the best place to get gaskets for the case and the seals, I have measured them and one side is 32mm (might be 31mm) x 20mm x 7mm (I think)the other side is 15mm x 25mm x 7mm (I have not taken them off yet to keep things clean.

At 3200 miles I assume the bearings are fine but is it worth changing them or leave them?

GSXRacer, I have not tried easy start or fuel directly into the pot as there is enough fuel in the pot as it has been flooding.

Any guidance is appreciated

Cheers

[spaz12]

I would do two things:
A compression test so that you know you have enough compression and aren't assuming because the cylinder looks good. You can rent/borrow a tester from a local auto parts store.
A leak down test so that you can find any leaks in a motor that needs to be sealed to run. You can make a leak tester for about 15-20 dollars. Here's a thread on different ways to make them: 49ccscoot.proboards.com/thread/506/make-2t-leak-tester-ways

There is an issue with Photobucket, so some of the pictures are missing in the thread