Gx 390 starter
- Thread starter Wilkr6
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bob58o
SuckSqueezeBangBlow
What type of starter are you using? Was it an electric start gx390 to begin with, or were you using a portable starter box thing?
bob58o
SuckSqueezeBangBlow
I assume you got the flywheel and the ring gear????
https://www.arcracing.com/6609gh3-ring-gear-for-gx340-gx390-billet-flywheel/
https://www.arcracing.com/6623-e-gx390-electric-pull-start-billet-flywheel/
https://www.arcracing.com/6609gh3-ring-gear-for-gx340-gx390-billet-flywheel/
https://www.arcracing.com/6623-e-gx390-electric-pull-start-billet-flywheel/
Timing advanced?
I'd pull and ground the plug wire and see if it cranks better. An old car trick was to disable the ignition and get it cranking then enable the ignition.
Or pull the plug out completely and see if it cranks over ok like that. If not then something is horribly wrong, lol.
Otherwise battery, cables, connections. Is it a genuine Honda starter?
I'd pull and ground the plug wire and see if it cranks better. An old car trick was to disable the ignition and get it cranking then enable the ignition.
Or pull the plug out completely and see if it cranks over ok like that. If not then something is horribly wrong, lol.
Otherwise battery, cables, connections. Is it a genuine Honda starter?
Yes, the flywheel has a gear ring.
---------- Post added at 11:16 PM ---------- Previous post was at 10:54 PM ----------
the ignition was off.
with two batteries in parallel, it does not make a full turn because the compression is too high. When I switch the batteries in line, he turns well but is not so good for the starter.
yes, an original honda
---------- Post added at 11:16 PM ---------- Previous post was at 10:54 PM ----------
the ignition was off.
with two batteries in parallel, it does not make a full turn because the compression is too high. When I switch the batteries in line, he turns well but is not so good for the starter.
yes, an original honda
anickode
Active member
A flywheel won't change anything whatsoever in terms of cranking. Even timing advance won't affect the torque required to crank it over.
what happens if you crank it off a different battery? Like with a set of jumper cables off a car battery?
Is it possible that your go-kart battery is just drained down, and needs to be charged? Did it start happening immediately after changing the flywheel? Or is it possible that in the process of replacing the flywheel, your charging system was damaged? Or incompatible with the new flywheel , and the engine isn't recharging your battery?
What size batteries are you using that you need 2?
what happens if you crank it off a different battery? Like with a set of jumper cables off a car battery?
Is it possible that your go-kart battery is just drained down, and needs to be charged? Did it start happening immediately after changing the flywheel? Or is it possible that in the process of replacing the flywheel, your charging system was damaged? Or incompatible with the new flywheel , and the engine isn't recharging your battery?
What size batteries are you using that you need 2?
That's incorrect. Just changing a flywheel may not but a flywheel that has built in advance or advancing the timing will absolutely effect how an engine cranks over.
anickode
Active member
I guess I worded that badly.
Timing advance won't make the starter physically unable to turn the crankshaft a full revolution with the ignition off, which is what he described.
If the starter can no longer turn through the compression and you have not done anything to change the compression, (or intake/exhaust timing, etc) then your answer is most likely either electrical, (flat batteries, undersized wire, loose connection, bad ground, etc) or the compression release is stuck.
Did you have thr engine on its side for an extended period of time (like overnight) while doing the flywheel swap? Could be some oil in the cylinder, effectively increasing the compression...
way more likely:
cam was changed as well and the compression release no longer works
OR (if governor removed) you messed something up by accident..
cam misaligned for example, or simply you forgot the small washer that's behind the governor and it now locks the compression release...
First things first:
remove the spark plug (compression = zero 'ish)
if the starter can crank the engine over happily.. it's unlikely an electric issue:
now remove the valve cover..
observe the exhaust valve when you slowly turn the flywheel by hand..
can you see how the valve lifts just before TDC slightly?
if so, the compression release should still work.
reinstall valve cover and spark plug.
do not try to start the engine for more than maybe 2seconds at a time.. the wiring is rather flimsy and might heat up past it's specs (i.e. you can smolder the insulation off creating a short)
but try.. and see if the two wires on the starter motor get hot..
if they do you need to service the starter (fresh wires and new brushes are likely the cause)
if they don't we're back at a mechanical issue (misaligned camshaft)
and you will have to pop the crankcase open again to see what's up.
'sid
cam was changed as well and the compression release no longer works
OR (if governor removed) you messed something up by accident..
cam misaligned for example, or simply you forgot the small washer that's behind the governor and it now locks the compression release...
First things first:
remove the spark plug (compression = zero 'ish)
if the starter can crank the engine over happily.. it's unlikely an electric issue:
now remove the valve cover..
observe the exhaust valve when you slowly turn the flywheel by hand..
can you see how the valve lifts just before TDC slightly?
if so, the compression release should still work.
reinstall valve cover and spark plug.
do not try to start the engine for more than maybe 2seconds at a time.. the wiring is rather flimsy and might heat up past it's specs (i.e. you can smolder the insulation off creating a short)
but try.. and see if the two wires on the starter motor get hot..
if they do you need to service the starter (fresh wires and new brushes are likely the cause)
if they don't we're back at a mechanical issue (misaligned camshaft)
and you will have to pop the crankcase open again to see what's up.
'sid
yes there is another cam installed without compression release and the compression is also increased. but that was already normal flywheel (actually I had no problems when starting). Since the flywheel now only weighs about 3lbs, the rotational energy that supports the starter when starting up is missing.
The electrics are completely new from the starter, so no errors in it.
Batteries are both charged. the operating battery has 12ah (for the ignition and the emergency start) and the auxiliary battery has 72ah (to start normal).
which small washer?
The electrics are completely new from the starter, so no errors in it.
Batteries are both charged. the operating battery has 12ah (for the ignition and the emergency start) and the auxiliary battery has 72ah (to start normal).
which small washer?
This may be your best option. Use a starter /generator off of something.
If your crafty you could put a manual compression release in the head.
http://www.vegascarts.com/SearchResults.asp?Search=Pulley&Submit=Search
If your crafty you could put a manual compression release in the head.
http://www.vegascarts.com/SearchResults.asp?Search=Pulley&Submit=Search
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VPULLEY-1.jpg
bob58o
SuckSqueezeBangBlow
The intermittent force from combustion needs the flywheels momentum to keep things spinning smoothly. The constant force provided from the starter motor shouldn't need that help. Once you turn on the ignition and try to start the engine, then the flywheel's mass might matter, but I don't see why if trying to turn the engine over with the ignition off the flywheel's mass/moment of inertia should matter at all. Maybe I'm wrong??
•MERGED•
Maybe toss the original flywheel back on and give the starter a whirl. If it still won’t turn over, you can eliminate the flywheel as the source of the problem.
•MERGED•
Maybe toss the original flywheel back on and give the starter a whirl. If it still won’t turn over, you can eliminate the flywheel as the source of the problem.
Last edited by a moderator:
anderkart
Moderator
Yeah, meybe the ring gears teeth weren't machined perfectly on your new flywheel, and it's binding up against your starters bendix gear.
bob58o
SuckSqueezeBangBlow
The suspense is killing me.
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