POS tempermental greyhound engine

[OzFab]

Is the low oil sensor disconnected? That might have gone bad, if it's still hooked up. If it's disconnected, make sure the wire's not hitting the block.

it has good spark when i ground it on the engine.

hmm... maybe i should check coil gap

If I understand a low oil sensor correctly, it works by grounding the spark plug. If so, it's probably not the problem but, still worth checking

 

[Badot]

If I understand a low oil sensor correctly, it works by grounding the spark plug. If so, it's probably not the problem but, still worth checking

More air in the spark gap (when it's compressed) will give a higher resistance across it, making it more likely to find a path around the spark plug when being run than when just testing the spark. So if something like the killswitch (already mentioned) or the low oil safety were kind of half-tripped it could cause these problems. I'm leaning towards electrical issues on this one.

 

[Bluethunder3320]

the low oil sensor is long gone. i cant remember, but i might have taken the entire motor apart at one time. (the kart has had like 4 different motors)

it really sounds to me like an ignition problem.. hopefully i meet with him tomorrow because i want to check the coil gap...

or else.... predator

 

[Iron John]

More air in the spark gap (when it's compressed) will give a higher resistance across it, making it more likely to find a path around the spark plug when being run than when just testing the spark. So if something like the killswitch (already mentioned) or the low oil safety were kind of half-tripped it could cause these problems. I'm leaning towards electrical issues on this one.

I'm not sure if that explanation is completely correct. The kill switch and low oil switch do not see the high voltage that goes to the spark plug. The kill switch and low oil switch are on the primary side of the circuit, where the voltages are low. They are low enough that there is no such thing as half-tripped. They are open or closed. Only the high voltage (secondary) circuit would have a voltage potential high enough to arc across switch contacts. An intermittant line-to-ground fault in any of the kill switch/low oil circuits could, of course, shunt the primary circuit and, subsequently, sabotage the spark on the secondary side of the circuits.

 

[Badot]

I'm not sure if that explanation is completely correct. The kill switch and low oil switch do not see the high voltage that goes to the spark plug. The kill switch and low oil switch are on the primary side of the circuit, where the voltages are low. They are low enough that there is no such thing as half-tripped. They are open or closed. Only the high voltage (secondary) circuit would have a voltage potential high enough to arc across switch contacts. An intermittant line-to-ground fault in any of the kill switch/low oil circuits could, of course, shunt the primary circuit and, subsequently, sabotage the spark on the secondary side of the circuits.

Sorry, brain fart. I meant to make that two separate thoughts (weak spark OR bad killswitch/ground) but my head decided to put them together.

 

[Bluethunder3320]

i re gap'd the coil and 100 pulls later, it idled for 15 seconds then died. i got a new spark plug and changed the oil. i took the whole carb apart and cleaned it with the air gun. still didnt work.

hes getting the predator. i hate giving up on these though

 

[Iron John]

When it died after the 15 seconds, did it just quit like hitting the kill switch, or like it was running out of gas (too lean), or loading up from too rich (wet plug)?

Will it start with a small shot of ether?

Could you have an air leak between the carb and the manifold?

 

[Bluethunder3320]

When it died after the 15 seconds, did it just quit like hitting the kill switch, or like it was running out of gas (too lean), or loading up from too rich (wet plug)?

Will it start with a small shot of ether?

Could you have an air leak between the carb and the manifold?

it acted like it was running out of gas.

FOUND THE PROBLEM.
he got a honda 5.5 with a splined crank, so we tried swapping cranks. didnt work.

while we had the engine all apart, i opened the valve cover, to find that it was missing the lock nuts on the rocker arms. so the adjustments must have been all over the place.

the plan: put the greyhound back together and use the honda 5.5 head for extra compression.

ill probably pick it up tomorrow and finish it for him. then we ride!

 

[Badot]

Doh. It always amuses me when it's something so simple that no one in their right mind could get it wrong, so no one thinks of it

 

[OzFab]

Are you serious?

Doh. It always amuses me when it's something so simple that no one in their right mind could get it wrong, so no one thinks of it

All this time we've all been coming up with these incredible scenarios, thinking outside the box when we should've been looking in the box

Occums razor strikes again...

 

[r_chez_08]

D'oh! I think you owe that engine an apology...
Sounds like a plan with the honda head. And if it has a flat top piston- throw that in too, along with the stronger honda rod and FW (with 4* advance).
Sounds like a good free way to get a little more power.

 

[Swabbster]

D'oh! I think you owe that engine an apology...
Sounds like a plan with the honda head. And if it has a flat top piston- throw that in too, along with the stronger honda rod and FW (with 4* advance).
Sounds like a good free way to get a little more power.

its not his cart,

 

[Swabbster]

if its till apart check if it has a cast iron sleeve just curios

 

[Bluethunder3320]

yeah, it has a cast iron sleeve

my friend likes the idea of getting more power and using better parts, he gave me 40 bucks and all the parts lol hopefully i have some time to work on it tomorrow. its pretty much up to me on how to build this engine.

is the gx160 and gx200 rod and piston the same? the gx200 crank didnt fit in the gx160... it jammed towards the top of the stroke, and bottom too

any difference in the camshafts?

EDIT: does the honda flywheel have a 4* advance built in, or are you talking about getting a stepped flywheel key?

i believe the honda piston is flat top, id have to double check. it was CAKED on with carbon

 

[OzFab]

IIRC, the stroke in the 200 is 9mm longer

 

[Bluethunder3320]

IIRC, the stroke in the 200 is 9mm longer

is that by the rod or crank or both?

 

[OzFab]

A longer stroke is usually obained by shortening the rod & increasing the throw on the crank

 

[r_chez_08]

yeah, it has a cast iron sleeve

my friend likes the idea of getting more power and using better parts, he gave me 40 bucks and all the parts lol hopefully i have some time to work on it tomorrow. its pretty much up to me on how to build this engine.

is the gx160 and gx200 rod and piston the same? the gx200 crank didnt fit in the gx160... it jammed towards the top of the stroke, and bottom too

any difference in the camshafts?

EDIT: does the honda flywheel have a 4* advance built in, or are you talking about getting a stepped flywheel key?

i believe the honda piston is flat top, id have to double check. it was CAKED on with carbon

Rod is the same. Some pistons are flat top, therefore 3cc less volume at TDC, higher compression.
Crank has 9mm less stroke on GX160. Fitting a gx200 crank on a gx160 can be done but requires a different piston/ rod and block alterations.

GX160 camshaft has less duration- I put a clone cam in my 160.
Honda GX160 FW should have 4* advance. I can explain the reason for this if you want.

A longer stroke is usually obained by shortening the rod & increasing the throw on the crank

True, this can be done, but it creates a worse rod angle.
The GX200 or clone simply has a 9mm increased deck height.

 

[Bluethunder3320]

alright so the gx160 piston is not a flat top. looks the same as the clone's.

my friend lost the rod cap to the clone... so i put the gx160 cap on, and torqued it. it locked up..... when i loosened the bolts it got free again

so i plan to just use the gx160 rod (hopefully it fits)

 

[OzFab]

alright so the gx160 piston is not a flat top. looks the same as the clone's.

my friend lost the rod cap to the clone... so i put the gx160 cap on, and torqued it. it locked up..... when i loosened the bolts it got free again

so i plan to just use the gx160 rod (hopefully it fits)

That tells me the rod cap is too small. Using it as is may cause crank damage