2004 Hawk 50cc startup problems

[wildsvix]

Hello TGBForum! 
Im new to TGB but not unfamiliar to engines.
I recently bought a Hawk 50cc. It wasn't in good shape so I bought it to fix it up.
After some general maintenance I cannot get it to run. It starts and then dies out. I have to wait 5 minutes to get it to run again.

Things I have checked.

• Piston (It was placed the wrong way, so I turned it 180 degrees, with arrow pointing to exhaust port. OK
• Cables from engine (Generator) to cdi to battery. Bought a new CDI, OK
• Carburetor, blown and checked all things. Seems OK, I have not tested the choke. but at least it would run some or?
• Fuel lines, blow and suck to get it to work, OK
• Checked spark, OK
• Checked reed-valve, OK
• Tried without exhaust, same result
• Battery, replaced

   
Any suggestions what I can try next? Any help will be much appreciated. (PS: Sorry for my english  )

Greetings from Norway

[harry]

does fuel flow freely ?
test the fuel shut off
 remove the line coming from the shutoff at the carb & put it in a jar
suck on the vacuum line from the carb to the shut off .(i use a syringe on the
vacuum line)
 fuel should flow freely.

compressed air blown into the shut off can ruin it.

whats the compression?

how to test a auto choke:
http://tgbforum.com/forum/index.php?topic=220.msg864#msg864
 also check the plunger & needle are smooth with no nicks or dings

 oilyhans

[wildsvix]

Hello and thanks for your reply.

I think I got it!

The previous owner had put on a 747mm long belt on it, when
part nr. GE506RB01 cleary says 776mm long. I took the belt off and the scooter
ran just fine.

I will try buying a new one tomorrow, and see how that goes.

Thanks again oilyhans.

[harry]

i have heard that if you put on a standard
 minarelli belt   788x17x28  you will get more top end
i have not tried this so for now its a urban legend

 oilyhans

[wildsvix]

So it wasn't the belt after all. It just seems that the continuous variable transmission is having some problems. I bought a new belt, but it was the same length as the privious one. 

Same problems today... 

[harry]

are the fuel & vac lines correct?
sometimes the vac & fuel are mixed up ( i just had a scooter come in like that)
fuel was being dumped into the carb at the rear and right into
the intake & motor  instead of into the fuel bowl.

oilyhans

[wildsvix]

Fuel-lines looks okay, but it looks like the gear starter (Number 3 in attachment) is scraping agains the housing.

I have bought a new seal, (part_no: GA505OS03) See attachment. Number 1. So the distance gets bigger. I don't know.. but will try this later.

Did I mention the engine ran great when the front "continuous variable transmission"  (the one with the weights) was unmounted?

 

[harry]

the drive pulley  or variator  works on the output shaft of the crank
 opening and closing via the weights
in front of the starter gear and should not bind  on the case
unless the shaft is bent . but the drive pulley shouldn't have any
bearing on if it runs or not.

check the bendix gear is lubed (see the parts manual "starting motor")

what looks like starting gear messed up the case  might just be the machining
they had to do on the raw casting to make ready for the other parts like shafts
and such.

check the driven pulley or clutch make sure it turns freely . while your at it
you might check the final gears have lube correct type and amount.
since you had to turn  the piston around 180 i'd just check the other owners
work.... if you know what i mean...

if you have to remove the power train to make the motor run good
your carbs not tuned right or dirty or water is in the fuel  or blocked / dirty air
box or filter

oilyhans

[wildsvix]

I took out seal number 1, and found the bendix gear. It was lubed, but the seal closer to the
bearing(nr4) number9 was damaged. Do you think thats enough to make the compression low and the engine to run down?

[harry]

how low was the compression?
under 100 and you won't get the motor to run
low compression = low or no vacuum

 oilyhans
 

[wildsvix]

I don't have equipment to test this at the moment. But I will change the seal inside (nr 4)the bendixgear after I´v disassembled the engine.

Thanks again oilyhans

[harry]

if  you put your thumb over the spark hole
 and crank the motor  your thumb should pop off the hole
if you have 100psi or more...

oilyhans

[wildsvix]

bought a compression tester, it shows 135psi + -

Is it possible to replace seal nr. 4 without taking the engine apart?

[harry]

at 135 psi you have the compression you need.
do you see oil coming out there?

and yes you have to crack the case ...

oilyhans

[wildsvix]

I have changed the seal but the engine still won't run. Shall test some more tomorrow. 

Thanks again for your help. :-)