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350 cc big bear 1990 (I think) won't start

  
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350 cc big bear 1990 (I think) won't start

 
Davids42240 Davids42240
New User | Posts: 3 | Joined: 02/08
Posted: 02/03/08
02:23 PM

I checked for spark that's good and I changed the plug for good measure.  The compression is 130#.  I just had it bored. I have a new wisco piston, rings and gaskets.  The carb was dirty i took it apart and cleaned it.  It acts as if its not getting fuel but when i put a little in the spark plug hole or the carb intake it still does not fire.  I wont even "putter"  The starter spins good.  I have checked and rechecked the timing TDC with cam lined with mark on case.  

Please help good spark
manual supply of fuel(not sure if carb is right)
good compression
Timing right I think
Thanks David  

 
wolf1 wolf1
Addict | Posts: 4283 | Joined: 11/07
Posted: 02/03/08
03:17 PM

130 lbs of compression is low for a 350cc
considering the 200cc yamaha blaster gets anywhere from 125-130.
a 250cc engine should get anywhere from 135-145.

and it's firing at the spark plug?
have you opened the drain plug on the carb to see if it is getting fuel into the carb?  
ALL REPAIR ADVICE GIVEN FREELY, I CANNOT ATTEST TO YOUR MECHANICAL ABILITY FOLLOW AT YOUR OWN RISK

Wolf Performance
...KEEP IT RUBBER SIDE DOWN!!....

 
Davids42240 Davids42240
New User | Posts: 3 | Joined: 02/08
Posted: 02/03/08
07:50 PM

I am getting fuel to the carb.  I am just not sure it is feeding the engine as needed.  What compression should i have The pistion is bored 1 mill over.
 I poured gas directly into the spark plug hole and tryed and then burned the excess out with torch when it wouldn't even tried to fire.
Then I took fuel and sprayed it directly into the carb and still didn't ever attempt to fire...what can i do to verify that its all mechanical "things" are right? before blaming the carb....
*note the spark plug is never wet when I have been cranking on it...carb DOES have gas in bowl.  

 
wolf1 wolf1
Addict | Posts: 4283 | Joined: 11/07
Posted: 02/07/08
08:39 AM

check the jets, it sounds like your main could be clogged.

if it is a 350cc it should be getting anywhere from 135- 155 in compression with it being bored it could go even more.(135 compression for some 4 cycle engines)
but it takes very little compression loss to keep your engine from starting. even losing a few psi on compression can keep your engine from starting.

see when the gas gets into the bowl, it is drawn up through the jets into the carburetor and then into the cylinder.

if you aren't getting gas into the cylinder then there are two possible reasons,  lack of compression to draw the air into the cylinder, and a clogged carburetor.

while the compression can be the cause it can be caused by four different things.
1) a blown head gasket
2) bad rings
3) bad valves
4) a cracked head or cylinder

if you have a 2 cycle engine then #3 would change to bad reeds if applicable.  
ALL REPAIR ADVICE GIVEN FREELY, I CANNOT ATTEST TO YOUR MECHANICAL ABILITY FOLLOW AT YOUR OWN RISK

Wolf Performance
...KEEP IT RUBBER SIDE DOWN!!....

 
Davids42240 Davids42240
New User | Posts: 3 | Joined: 02/08
Posted: 02/10/08
11:28 AM

Good News I managed to get the engine started after taking the carb apart 3 or 4 times and cleaning with air and carb cleaner.
I could not keep the engine running though.  I had the carb adjusted and even drove the 4 wheeler.  Then it quit. since then I havent been able to start it.

Question of the day for me is.

How much fuel should be in the bottom of the Bowl?
I have tried to adjust the float but cant seem to get it just right(I believe that may be the problem)

How do you keep the float from sticking?
I think that also might be a problem

Thanks again your info has been really great help  

 
wolf1 wolf1
Addict | Posts: 4283 | Joined: 11/07
Posted: 02/10/08
05:01 PM

take the needle valve out (under the float) and make sure it is clean. make sure the hole it goes into is clean and free of debris.

check the floats to make sure they aren't cracked.
they will fill with gas if they are cracked and weigh down.

the bowl should have anywhere from 1/2 half full to 3/4 full.
just enough gas to cause the floats to raise and shut the flow of fuel off.  
ALL REPAIR ADVICE GIVEN FREELY, I CANNOT ATTEST TO YOUR MECHANICAL ABILITY FOLLOW AT YOUR OWN RISK

Wolf Performance
...KEEP IT RUBBER SIDE DOWN!!....