After 10 - 15 minutes of riding loses all the power

[itsid]

a hammer to take apart a yt video?

taking it apart isn't much of an issue I guess..
the reassembly of the spring-pack might be w/o proper tools however.
So check all available videos twice and make sure you have the tools needed at hand

'sid

 

[Karttekk]

Why didn't you ask the vendor what those parts were? For some reason you don't seem to want to follow anything in the service manual. Most of the questions you have are answered right there. The only mention of a hammer is when you put the valve spring keepers on to make sure they're seated properly, unless that's what you're referring to. Scroll to page 29, Section 3-12.

https://americanlandmaster.com/pdfs/LUTV/150cc-service-manual-14589R4.pdf

 

[vybrano]

Why didn't you ask the vendor what those parts were? For some reason you don't seem to want to follow anything in the service manual. Most of the questions you have are answered right there. The only mention of a hammer is when you put the valve spring keepers on to make sure they're seated properly, unless that's what you're referring to. Scroll to page 29, Section 3-12.

https://americanlandmaster.com/pdfs/LUTV/150cc-service-manual-14589R4.pdf

According to manual I need a special tool... . That's why I was happy to find a YT video of a guy taking it apart/putting it back together just by a socket and hammer.

This is maybe like a once in my life, when I'm rebuilding an engine. And amount of a special tool required is just horrendous. Feeler gauge, compression gauge, holding tool of variator, adjusting wrench set for valves, grinding compound for valves, valve spring compressor.....I don't remember even quarter of them.

 

[vybrano]

So I rebuilded engine. Problem is, that I can't get it to start now... .

It seems like starter engine can't get it spinning fast enough to get it started. Out of 3 tries usually just once it gets moving. And very slowly. Like at half speed as before. And after a few seconds it just stops spinning. Reason probably is, that engine is very stiff. I almost can't turn flywheel over by one hand. Especially when I get to the "compression stroke" that's when I need second hand to turn it.

I tried to troubleshoot electric starter:
- I checked battery, it's at 12,6V
- switched different battery from my motorcycle
- cleaned all cables&connections between battery, solenoid, starter
- took out starter motor, it runs OK
- dismantled entire cylinder and rechecked that everything was rebuild correctly

None of that it solved. It just seems like a rebuilded engine is too tight/stiff and starter doesn't have enough power to get it moving fast enough. I can turn flywheel relatively easily until I mount cylinder head. That's when it get's hard to move. It's not piston rings against the cylinder wall. It's more like air pressure/vacuums etc etc of the closed cylinder. I don't know.

 

[JTSpeedDemon]

Is the cam timing mark lined up? Is the valve lash correct? Are both pushrods in?

 

[vybrano]

- timing is OK, how it was before taking apart and how it suppose to be according to manual
- valve lash is according to manual (0.08mm intake, 0.12mm exhaust)
- do you mean these 4 long screws that hold everything together? I didn't adjust them, didn't change anything about them

 

[JTSpeedDemon]

The pushrods connect the valve lifters down in the crankcase to the rocker arms.
You should have one pushrod opposite to each valve under the rocker arms.

 

[vybrano]

If I understand it correctly, than my engine doesn't have pushrods.

 

[JTSpeedDemon]

Oh, I just read back and it's a GY6.
I believe it's overhead cam, but I don't know.
I know almost nothing about GY6s.

 

[itsid]

good compression is good
but that sounds odd.

0.08mm intake? and 0.12 exhaust are different from the numbers I have (0.05 on both)
but again gy6es and their differences always cause some sort of trouble.
So if you have the exact manual for YOUR engine, then stick with the numbers in there!

Valve (or cam in this case) timing can still be upset,
even IF you remembered the mark on the flywheel and cam ..

I wouldn't try to start the engine up until you are sure everything is as supposed to be, to prevent ruining it just after fixing it because of a minor mistake.

Please post two pics:
one showing the Flywheel mark lining up,
and then (w/o rotating the crankshaft of course)
a picture showing us the cam gear and valves..
(ideally one showing the T mark, another showing that both valves are closed)

have you installed the piston the right way around or flipped it accidentally
(does it even matter on your gy6?? I can't tell)

if you have a model number and mfg mark on the engine itself, please write that down for us as well,
if you are unsure if the manual you are referring to is indeed the correct one.

'sid

 

[Karttekk]

Does it crank normally with the spark plug out? If it does you can rule out the crank bearings being torqued too tight. You did say it seems okay with the head off though. If it does, it's more than likely out of time. Try cranking it with the rocker arms loosened or off just and the plug wire off to start narrowing things down. Go back to just the head on with the plug out, then try it with the plug in bit plug wire off, then with the plug wire on, do a systematic step by step process of elimination. You'll get it.

 

[vybrano]

I got it running! YAY!

I got this feeling from your posts that you don't trust me I'm capable of getting cam timing and valve lashes right. So I put all old parts back. Got it running with old parts (proving I'm setting it right). And from there I started swapping for new parts.

And I noticed something. In some article or Youtube video I saw guy installing GY6 piston and saying "install piston by mark IN upwards towards intake". And my old piston was also installed by IN upwards towards intake. So logically I installed new piston without thinking much about it by IN upwards towards intake.

But on the closer look I noticed, that new piston has these two recesses on opposite sides. And it has to be installed by IN downwards towards exhaust to be consistent with installation of old piston.

Now I have to take it apart (I hope) for the last time and put there gaskets, set up timing and lashes precisely etc. etc. I gave up on lot of things somewhere around round 10 of having piston&cylinder out... .

 

[landuse]

Nice!!!! I hope it works for you

 

[Karttekk]

It's not that no one trusts you, we're just trying to keep you on the right path. If you weren't capable you wouldn't be able to do what you've done so far. The only way to learn is to jump in there and go for it.

As far as your piston, I hope you're right. This screen shot was taken right out of the American Landmaster GY6 150cc shop manual. Good work so far!

 

[itsid]

It's not that no one trusts you, we're just trying to keep you on the right path...

especially since valve lash is set differently on different make gy6es
(howhit [p.e. the American Landmasters] sets both identical between 0.08 and 0.12mm; wheras the other manual (mystery engine) calls for 0.05mm)
worth noting [since related]
the howhit has a fixed camchain tensioner (screw in type)
wheras the mystery one uses a simple variable one (spring pressure)
and I bet if you find another manual you'll find different values values..
the hole in the camgear is noted in one manual to be on top..
the other specifically claims the two adjacent dots (90° off)
to sit flush with the upper edge of the head (and the hole is what appears tobe one tooth offset in the pic)

Just because the engine runs doesn't mean the valve gap is set correctly I'm afraid.

not knowing what exact engine you got we're unable to tell what'd be needed..
we only know that setting them differently is incorrect so far

Hence our advice to be cautious and rather be checking everything twice.

Just as kartekk said.. it's NOT that we do not trust in your capabilities.
it's that we CANNOT fully trust in any document for gy6es that we aren't sure is spcifically made for the exact engine you're working on.
(hence we don't like them too much)

Plus: the build quality of some parts is shockingly horrific...
I mean who labels the exhaust side "IN" ??
(I so hope that's the solution for your problem)

just match the larger valve to the larger void in the piston of course,

I so hope there isn't anything else that's different from what we expect (piston pin size for example)

We just want you to finally have your engine fixed,
without having to pop it open in a few days or weeks to find another issue because of mismatching manuals/parts or instructions.

And yes, that means we are very carefull and as we cannot peek over your shoulders at all,
we ask twice for you to check twice

'sid

 

[vybrano]

Well, this is it. I think we are done here. Was riding it all afternoon and it looks/sounds pretty good.

There were some new issues, like broken vacuum line (easy fix), clicking sound from the engine (locknut got loose, valve lash too big), noise from under CVT cover (found inside a random forgoten screw). And there are still some older problems to solve. But nothing worth discussing or in need of your help.

Thank you to everybody who posted to this thread, especially to itsid.

Thank you, see you!

 

[itsid]

glad to hear that it's back up and running..
good to know that it indeed WAS the incorrectly labelled piston that caused the weird behaviour.
(will be taking notes for the next gy6 that shows up )



you're very welcome by the way..

'sid