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Old 08-22-2019, 04:47 AM
vybrano vybrano is offline
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Default After 10 - 15 minutes of riding loses all the power

After driving my ATV (GY6 150cc, CVT transimission) for about 15 minutes it always loses all the power. First 30% of the throttle is OK, but there isn't anything beyond. Then let it sit for a 3 - 5 hours and it's back to normal. Again at full power.

Drive it for 15 minutes and it's without power. Let it sit for few hours and it's cured.

My only thoughts is either temperature or something is getting wet - it's raining season over here. HOT or WET is something what occurs within 15 minutes and goes away in a few hours on its own.

I only checked carburetor air intake filter, but it's not a problem. I don't know what to check next...

Here's the video, but audio/video is a split of second out of sync:

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Old 08-22-2019, 05:08 AM
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itsid itsid is offline
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can't check the video atm ..

but since you clearly said it's self-solving after a proper cool down period.
And you also say that in the low to mid rpms you have no issues
I can think of a few things ..
again I can't watch the video atm so I can't hear it running
but say the engine itself revs normally and there's just no power on the wheels
it'll be the belt (since it's the first thing to fail)
it has some slip, and if the variator or clutch sheaves aren't properly grabbing, the belt get's softer due to heat.
and slips more than it should.
if you pop the belt cover open you would see the belt has glossy sidewalls.
if it hasn't something other failed on the CVT (maybe rollers flattened out, mabye worn springs... maybe just oil or grease on the sheaves)

full CVT maintenance and a new [correctly sized] belt would solve the issue.

If the engine does not rev up to full speed at all,
chances are the CDI is overheating.
So next time that happens, immediately grab the CDI unit if it's hot to the touch,
get a new one and see if it makes a difference
Best thing do a five minute run, check the CDI temp to have something to compare to..
then run it until the issue arises and check CDI temp again.

And the last thing I could imagine is a failing head or cylinder gasket;
check if you see any dark spots around the cylinder seams that yould indicate a cracked gasket.
If you cannot see anthing, pop the head cover open and with the proper tool but without any force, try to "tighten" the head bolts;
if one is loose , DO NOT tighten it and call it a day!
instead remove all, check the internal threads and replace the gasket ..
reinstall with fresh bolts.

WAIT:
before anything else.. try a new spark plug!
once the engine looses power, remove the new spark plug (as quickly as possible) and take a picture of it's business end.
if your mix is far off, a wet plug could cause a severe power loss.
and evaporating all the fuel off a wet plug might take indeed several hours.

'sid
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Old 08-22-2019, 06:54 AM
vybrano vybrano is offline
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Definitelly looking forward to your opinion once you check the video - if anything changes.

To clarify, in video it sounds like engines is about to die. But when I drive it, it just rides very slowly, it doesn't die.
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Old 08-22-2019, 07:28 AM
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Quote:
Originally Posted by vybrano View Post
Definitelly looking forward to your opinion once you check the video - if anything changes.

To clarify, in video it sounds like engines is about to die. But when I drive it, it just rides very slowly, it doesn't die.
While you are waiting for Itsid, check all the things he suggested
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Old 08-22-2019, 08:27 AM
Karttekk Karttekk is offline
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Adjust the valves while you're checking things out. If they're too tight they won't close completely when hot and cause performance issues. My GY6 manual says to set them between .003 and .005 COLD engine. Not saying this is your problem but it should be done regardless.
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Old 08-22-2019, 09:18 AM
vybrano vybrano is offline
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Quote:
Originally Posted by landuse View Post
While you are waiting for Itsid, check all the things he suggested
It's 10pm over here and I'm in my pyjamas already.

Although it's funny how on point Itsid is.

CVT Belt - I'm about to change that belt for a some time now. Definitelly a posibility.

CDI overheating - CDI was originaly on such a spot, that I was kicking everytime I was getting off ATV. So I moved it inside of ATV right next to my light relays. So not only it's not cooled by air anymore, now I'm even heating ut up by these relays.

Cylinder/gasket - her I'm hoping he is wrong. I don't want to take apart the engine.

Spark plug - I have a new one. But If I'm drowning it in fuel, it probably doesn't matter if new/old.
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Old 08-23-2019, 04:49 AM
vybrano vybrano is offline
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Just a quick update, I let it sit overnight and it's OK again.

I spent an entire afternon changing throttle cable (shop didn't have right one, so I had to weld/make different holder at carburetor etc.). So only thing I managed to do in our matter today was take a quick video of CVT:

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Old 08-23-2019, 06:03 AM
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Soo.. tough, I cannot seem to understand your second video...
you rev or you hold?
And I cannot seem to see why a throttle cable would grab when cold but slip when warm either.

So I'll ignore your last post for now

Anywhoo first video sound more like a gunked up carb to me than anything else tbh..
but I can't seem to make sense from the fact it'd change over temperatures..
So I'm biased towards the CDI..
but still I'd love to see the spark plug test.

Reason for doing so with a fresh plug is quickly explained:
a fresh plug is shiny and clean, and within a 20-30 min ride it won't change too much either.
so we have a known "what it should look like" image stuck to our heads.
A well used plug is discoloured, past carb hiccups, oily residue and such stick to the formerly bright white isolator..
And there is very little difference between an oily and a wet plug if the plug is old (brown) on a photo..
but there is huuge difference if the plug itself was new. (white)

That's why I think it could help rule out a short-term mixture problem.

Now.. your latest reply..
you swapped the throttle cable, and the problem is now gone?
And the change in rpm in your last video was throttle position induced?
If both is a yes.. then great.

I think I wouldn't guessed a throttle cable problem at all..
(the two I ever had was a snapped cable.. binary mode .. remote control on/off essentially )

'sid
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Old 08-23-2019, 08:20 AM
vybrano vybrano is offline
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Forget about throttle cable, it was just broken and getting stuck, so I change it - nothing to do with this problem. In second video RPM are controlled by me (throttle). Purpose of second video is to show you CVT. Maybe you will tell me that the belt is not moving up/down in full range or it's slipping or you will see that something else is wrong with it. I don't know. To me CVT looks OK.

--------

Back to my problem.

1. I will do spark plug test
2. I will try to check temperature of CDI by touching it, I don't have spare one of this type, none of my motorcycles even uses this CDI, so touch test is only option
3. I ordered CVT belt already anyway, so I will change it

Once it's done I'm back. No more posts till then. Keep head/cylinder gasket for later.

--------

"Anywhoo first video sound more like a gunked up carb to me than anything else tbh.."

First video sounded to me like a mixture ratio being off. For this reason I checked carburetor air intake filter (getting wet and causing problems and then getting dry and everything being OK). But it turned out not to be a problem so I came here.
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Old 08-23-2019, 08:43 AM
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Ahhh got it!

No, I agree cvt looks to be working correctly..
and the engine sound (first video) suggests it's not the CVTs fault either.

Doesn't mean the belt is in good working order (I seriously can't tell from the video in what state the belt's sidewalls actually are)
BUT it's nothing to do with the problem you are having atm.
for me it's a good looking belt and the range seems to be okay as well.
it's a tad low on the clutch pulley for my taste,
but that's not uncommon on gy6es according to some google images, so no immediate worries there.

CDI temp:
if you have a pyrometer it can come in handy for this task, especially since you tucked it away
in a -what sounds like a- hard to reach spot

(Oh pyrometer is one of those fancy laser pointer thermometers you see all around for less than 20 bucks nowadays)

'sid
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Old 08-23-2019, 04:05 PM
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Quote:
Originally Posted by itsid View Post
can't check the video atm ..

but since you clearly said it's self-solving after a proper cool down period.
And you also say that in the low to mid rpms you have no issues
I can think of a few things ..
again I can't watch the video atm so I can't hear it running
but say the engine itself revs normally and there's just no power on the wheels
it'll be the belt (since it's the first thing to fail)
it has some slip, and if the variator or clutch sheaves aren't properly grabbing, the belt get's softer due to heat.
and slips more than it should.
if you pop the belt cover open you would see the belt has glossy sidewalls.
if it hasn't something other failed on the CVT (maybe rollers flattened out, mabye worn springs... maybe just oil or grease on the sheaves)

full CVT maintenance and a new [correctly sized] belt would solve the issue.

If the engine does not rev up to full speed at all,
chances are the CDI is overheating.
So next time that happens, immediately grab the CDI unit if it's hot to the touch,
get a new one and see if it makes a difference
Best thing do a five minute run, check the CDI temp to have something to compare to..
then run it until the issue arises and check CDI temp again.

And the last thing I could imagine is a failing head or cylinder gasket;
check if you see any dark spots around the cylinder seams that yould indicate a cracked gasket.
If you cannot see anthing, pop the head cover open and with the proper tool but without any force, try to "tighten" the head bolts;
if one is loose , DO NOT tighten it and call it a day!
instead remove all, check the internal threads and replace the gasket ..
reinstall with fresh bolts.

WAIT:
before anything else.. try a new spark plug!
once the engine looses power, remove the new spark plug (as quickly as possible) and take a picture of it's business end.
if your mix is far off, a wet plug could cause a severe power loss.
and evaporating all the fuel off a wet plug might take indeed several hours.

'sid


I agree with this guy but if those things don't work check your valve gap clearences cold then hot because when your motor heats up your exhaust valve might not close or seal all the way and you lose compression if they are off.
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Old 09-07-2019, 06:08 AM
vybrano vybrano is offline
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New thing, maybe new symptom?
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Old 09-07-2019, 11:54 AM
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itsid itsid is offline
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looks like you got more than one issue to deal with, huh?

that looks like fuel* dripping out your exhaust port.

means two things:
a) the exhaust isn't tightened up and/or it's seal failed
and most importantly
b) there's fuel in the cylinder.. LIQUID FUEL!
[your carb is overfilling and spilling into the cylinder...]
STOP RUNNING THAT ENGINE !!
if you manage to run into a hydrolock, thanks to fuel accumulating in the cylinder,
your engine will be gone for good!

NOW.. fixing:
remove the carb and clean it as good as you can.. TWICE!
check the needle valve for a proper seat and the floats for them to work correctly.
When in doubt.. buy new floats and needle and use those instead.
After that's dealt with
remove the exhaust, check the threads, and run the engine for a few minutes w/o exhaust
(I know I know.. terribly so... but once we sealed the exhaust we must be sure no more liquid fuel is comming out of there..)
So, cover the exhaust port with a single layer of clean rag,
just to see if it wettens or not.

If you're confident, reinstall exhaust with fresh gasket and bolts.

And while you're there check valve lash, this time is as good as any and you're already under than darn thing

'sid

PS *Well, I hope it's not water that is...
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Old 09-07-2019, 01:51 PM
vybrano vybrano is offline
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Thank you.

I'm not dealing with this carburetor anymore. Smashed multiple times, glued by JB weld etc etc. I ordered new one that will be here at Monday... . At least I hope,new CDI&spark plug etc. I ordered back then to solve first problem still didn't arrived.

This whole ATV always was and is just a trouble. But it was cheap.
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Old 09-07-2019, 06:05 PM
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Quote:
Originally Posted by vybrano View Post
Thank you.

I'm not dealing with this carburetor anymore. Smashed multiple times, glued by JB weld etc etc. I ordered new one that will be here at Monday... . At least I hope,new CDI&spark plug etc. I ordered back then to solve first problem still didn't arrived.

This whole ATV always was and is just a trouble. But it was cheap.
It sounds like it's vapor locking?, is the fuel cap vented. When it starts to die, take the fuel cap off and see if it starts running better. Maybe the engine needs a PCV type of vent also??
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Old 09-07-2019, 08:49 PM
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It sounds like it's vapor locking?, is the fuel cap vented. When it starts to die, take the fuel cap off and see if it starts running better. Maybe the engine needs a PCV type of vent also??
I don't know - should I try to run it now? Itsid sounds against it.
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Old 09-08-2019, 02:37 AM
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Vapor locking sounds alike... (regarding your initial issue)
BUT:
a vapor lock prevents fuel from reaching your carb and your
engine leans out and thus runs badly (or usually dies)

Since you have a dripping wet cylinder (I still hope it's fuel)
I'd say too little fuel shouldn't be the cause of the "newly found" issue

But I have to agree.. once you got the new carb, and that didn't solve the initial problem
with the engine running badly after a few minutes.
a vented cap (or a quick opening of the fuel cap for testing purposes)
is a good idea, to see if you indeed have a vapor lock starving the engine out!

I'd still lean towards a bad CDI to be honest.. but that doesn't mean it is
Since it's easy to check for a vapor lock I'd put it high up the to do list.
But again.. NOT before you fixed/replaced the carb I'm afraid

The best thing that happens is you wash all oil off the cylidner wall while running the engine
this way.. causing premature cylinder/piston wear.
the worst thing that could happen is you wash all oil off the cylinder wall and the piston seizes
and welds to the cylinder OR just as bad you run into a hydro lock and crack your con rod, crankshaft bearings or cylinder head bolts (whatever gives first)
And you'd be left with a paperweight too dirty to be of use as such.

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Old 09-09-2019, 02:50 AM
vybrano vybrano is offline
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Why does carburetor needs a vacuum? I swear to god there's no info about this on Google. My old carburetor has this port blocked (by JB weld glue). So I just go from manifold to petcock and it works without giving a vacuum to carburetor. But this new one has this port of course opened.... .
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•MERGED•
Anyway, I installed carburator.

What I noticed 1) a white smoke out of exhaust (burning engine oil?) 2) mixture ratio screw (at engine side, adjusting fuel) doesn't do anything, fully in or 5 turns out makes no difference (old carburetor the same)

Like....I'm really close to pulling a plug on this one.

What do you think?

I found this kit (about $17) and that's like last thing I'm willing to invest into this - if it would be a way to go how to fix majority of mentioned issues. Otherwise I'm close to done.
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What do you think?

Last edited by itsid; 09-09-2019 at 07:00 AM.
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Old 09-09-2019, 06:22 AM
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Quote:
Originally Posted by vybrano View Post
Why does carburetor needs a vacuum? I swear to god there's no info about this on Google. My old carburetor has this port blocked (by JB weld glue). So I just go from manifold to petcock and it works without giving a vacuum to carburetor. But this new one has this port of course opened.... .
Most carburetors function from vacuum. It pulls fuel into the carb where it's mixed with air and turned into a vapor which ignites in the combustion chamber. Raw fuel doesn't burn, vapors do. I agree with you, I would move on to another project, this has been nothing but aggravation for you. Sometimes it's best to walk away. You deserve credit for trying, it's the only way to learn. White smoke is usually coolant burning, blue smoke is oil burning and black smoke is excessive fuel burning indicating a rich mixture. Sell your machine for parts and start over with something else. Go back to this manual and refer to Section 3-21.

https://americanlandmaster.com/pdfs/...al-14589R4.pdf
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Old 09-09-2019, 08:05 AM
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I disagree I'm afraid.

There are still many hints left to be found..
And some questions you left unanswered!
IS IT FUEL?
wipe your finger and smell it..
if it's water or oil you MUST change your engine oil!

get your OLD carb, and open up the top cap..
A CV carb has a rubber diaphragm as a piston collar. (part 15 in the pdf karttekk linked)
Check if the old one has a ripped diaphragm or not.

if it is, carefully pull the piston comp up (still part 15) and push it down again,
and see if you get any resistance from the piston.
Such things can (if not working properly) act as a vibration fuel pump
It's meant to do the exact opposite (reduce vibration)
but it can can weird quickly if the diaphragm is ripped or punctured.
so instead it might be
pulling fuel up the main jet on the up stroke (partly intended behaviour)
and pushing it out the manifold on the downstroke (should've been evaporated but sometimes just isn't)
and if it does so quicker than anticipated
that'd explain a wet plug and fuel building up in the cylinder.

If you see such, chances are you have an old fuel/oil mix accumulated in your cylinder,
and yes that can lead to white-blue'ish smoke
(fuel can pass the piston rings reduce the viscosity of oil and wash tiny amounts of oil sticking to the cylinder wall below the piston up into the cylinder on the piston's down stroke.

When in doubt: change the engine oil,
at least check its level and smell test it for fuel.

I'd let the engine idle for a few seconds (half a minute or so) at a time allowing it to fully cool down after each run.
just so to be sure about the following question:
Does the amount of smoke reduce, stays the same at or builds up?


And don't forget if you see such wet cylinder chances are you have some sort of smoking liquid now built up in your exhaust as well.

If it gets less and less smoke you should hear the engine running "stronger" and smoother over each run. (happier we call it)
That is another hint.. telling me the problem is now likely gone,and we're removing the accumulated crap from inside the cylinder the hard way.

After say a total run time of ~5 minutes or so [say ten rounds]
you should know it get's better or worse or doesn't change at all.

Now say did NOT GET BETTER over the individual runs, or not noticable after say five such runs..
Do yourself a favour and remove one variant from this equation,
remove the exhaust from the engine..
it's a terrible loud aggrevating thing to run the engine w/o any exhaust.
BUT it helps you fixing this issue perhaps.
do the remaining runs and see if you still see clouds emerging from the exhaust port.

if you don't see any such smoke.. reinstall the exhaust.. it'll be solely his fault now proceed as below.

if it GOT BETTER (and only if) start the engine up, and allow it to idle for several minutes until you can be sure it reached operating temperatures looong ago .
if it's a happy running engine w/o hiccups and/or jerks,
rev it to 30%.. and I'm fairly certain you will see another intense cloud coming out the exhaust
rev it up and down a few times (as high as you feel confident) to flash off as much of whatever built up inside the exhaust chamber.

And in worst case
it got worse or -no matter what- wouldn't reduce at all.

I guess now it's time to see if you are willing to dig deeper.
you could open the cylinder head (remember my first reply?)
to see if there's something wrong with your cylinder piston or other.

And then decide if it's being worth to repair or not.

It doesn't make sense to buy a cylinder kit, if all you need is a fresh head gasket and four new bolts, right?
It doesn't make sense to buy a new cylinder kit if your head is fully cracked between the valves.
etc...

take a peek inside and judge what needs replacing..
and if it is cylinder piston or rings, I guess 17bucks justify replacning everything

'sid
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