gy6 project hard start By stellarfoxy (Read 2,412 times)

[stellarfoxy]

hello everyone! I've been using the information here for awhile but I've run into a wall, I've tried searching and tried everything suggested I've found thus far, to no avail.

first some history: about 6 months to a year ago, I acquired what I find out was a taotao power max 150cc that had been left in an abandoned heap behind a shed of a friends rental property. 85% of it was there, but it was missing a few key components, most importantly the entire ignition, intake and exhaust. having no experience with small engines or carburetors whatsoever, I set to work. I purchased an (allegedly) 26mm carb, uni filter, high end fuel and vacuum hoses, orange coil, correct ngk plug, both manifolds, battery, slant tip "performance" muffler, orange adjustable cdi, etc. in intervals. after installing just the coil/plug/stock cdi/intake without filter, it started, ran, revved, everything! so I installed the filter and exhaust. a couple weeks later I got/installed the exhaust and air filter and it gradually became much harder to start and keep running. I figured I'd stripped the plug hole so I tapped it to a 12mm- still hard start but it ran then died after a few minutes. checked compression, it was 150psi at full throttle. I adjusted the valves to .004/.005mm using the method where I do one valve at while the other is compressed. while I was in there, I decided to check timing, it was incorrect- when the cam holes were aligned, the casting mark was in the box after the "t" line. I moved the chain up a link and it sat on the "f" mark. it would crank and run like this but die after a couple minutes. set the chain back and it was even harder to start. I checked the tensioner (vary carefully!) and later replaced the chain which was difficult without removing anything but valve cover, yet the marks were the same (notes: woodruff key is in place and "t" mark lines up with cylinder at tdc, holding plug to valve cover always gives spark).

today I replaced the carburetor with another new one hoping I'd got a bum carb before or it was failing or whatever. it finally started after spraying starter fluid in one of the vacuum lines! I kept it running for about 20 minutes, it would rev and come back to idle perfectly (some backfiring but I'll deal with that once it's more solid). it seemed to run best with the timing dial on the cdi set back (less advance I assume?). I noticed that it also wanted to die with the enrichment circuit plugged in, but unplugging it kept everything happy and smooth. so I killed it using the switch and went to start it back up, with absolutely no success.

I'm wondering if I need a bigger idle jet, or to adjust the idle screw on the carburetor? it's currently at 2 turns out. also, after much deliberation about the timing issue, I assume the only reason it can be off like it is, is if the gear on the crank slipped, is that possible? I have no idea the history of this engine, any input is welcome. I think I covered everything but if not I will tell you whatever I know!

hope I'm not violating any rules and this isn't in the wrong area, lmk if I need to change anything.

[Alleyoop]

Ok First the timing EVERYONE thinks to line it up with the "T" but the "T" position is actually the LINE just before it same as with the "F" mark the LINE AFTER it is the "F" position.

So line line up the Cam with the two little holes even with the Top of the head and check the timing pointer on the case to see where it is pointing on the flywheel IT SHOULD POINT TO THE LINE BEFORE THE "T".

If it has a tach at idle after it is warmed up it should idle anywhere from 1500-1800 rpms you can set the idle speed using the IDLE SPEED screw on the throttle cable side.

Adjust the carbs Fuel Ratio Mixture to get the highest idle after the ENRICHER cuts off the extra fuel which is around 5 minutes or so.
Alleyoop

[stellarfoxy]

hello, and thank you for your response! I will try you get it started tomorrow, let it warm up, and adjust the idle air/fuel screw. it was idling fairly smoothly at 1500ish the whole time when I did get it cranked and let it warm up, but I didn't mess with any adjustments on the carburetor after it was started.

I am aware there are marks on the flywheel adjacent to the "t" and "f" marks- there are apparently two different types, one with the marks inside the letters (t| |f) and one with the letters inside the lines ( |t f| ). I have the second one, where there's a rectangle next to the "t" to the right of the line, with a diagonal dashed line in it. mine lines up with the top of that diagonal line, to the left of the mark next to the "t" if you're facing the outside of the flywheel, suggesting the timing is less advanced I believe? either way I can't adjust that without serious modification. I thought maybe it had jumped a tooth, so I moved it up one, and it aligned with the letter "f", not the line to the right of it, so that wasn't it either.

I'm wondering, since I have no baseline of afr, if having installed the higher flowing intake and exhaust than stock would require a larger idle jet?

also, the first carburetor I bought was supposedly a 26mm but it's identical to the new one, which was sold as a 24mm. they both fit the manifold and filter exactly the same. go figure haha

[jct842]

1 question: how will you be able to ride it with out title to register it?

[Bashan]

The valves are .004" and .005". Inches....not mm. We've said this before, jumping a tooth on the timing chain is a HUGE difference from the correct time. Here's how you time it. Get the piston to TDC with the timing tab about here:

Get the cam gear like this:

If you get things oriented like that it's timed right. If you jump a tooth it's WAY off IMO and probably wouldn't run. Things may not be exactly lined up like this when you're done but they will be very close. If they're close you have it right. The flywheel may migrate a little but not much.

[stellarfoxy]

jct: through a lot of work I managed to track down the last legal owner and acquired a title. I was extremely lucky on that front. made sure I did that before buying anything actually!

bashan: you're right, it's .004/.005 inches. I apologize, I wrote that incorrectly. I am very sure my napa-spec feelers don't have .004mm haha.

my flywheel markings are a bit different than yours, but there's still the box and dashed line (in your photo below the "t" line), my cast mark lines up with the top of that dashed line. and yeah, jumping a tooth sent it way to the other side. it's almost like the distance between the two cogs is a half-link off, but it ran either way (not very well) so I have to assume the crank cog has rotated on the crank or it's a manufacturing defect, but I couldn't imagine how it could rotate? is the crank gear pressed on where it could slip? the fact that it runs so well when it does get started, even though these engines are apparently very temperamental when cam timing is off even a little, makes me wonder if that's just how it came from the factory?

[stellarfoxy]

that line below the t is exactly tdc if that helps, makes me think the cog slipped and the marks are correct.

[Bashan]

I don't think the cam drive gear could slip. I'd be more inclined to think the woodruff key may have sheared and the flywheel rotated.

[cyborg]

My thought too Rich

[stellarfoxy]

bashan: I checked and replaced the woodruff key just in case, the line near the t is at exactly tdc. my cam/spark timing is off according to the holes in the cam gear.

cyborg: there's a chance it's too rich, but I was thinking it might be lean if anything, the intake/exhaust path is less restricted than stock and from what I can tell that leads to leaning the mixture? if I unplug the enrichment circuit from the harness it doesn't want to cut off at idle, I believe that allows more fuel when it receives no voltage? I'm not sure, I will check the plug tomorrow after it warms up and I adjust it based on the advice above.

thank you for the advice so far everyone!

[Deleted]

After checkin all of that. Put the stock CDI back in, If you have to play with the idle screw like backing it almost all the way out. Most likely your problem.

[stellarfoxy]

I've decided to forego everything else and tear down the entire engine, I've replaced everything externally and the only visible issue is cam timing, which isn't adjustable apparently. right now I'm stuck on removing the pressed on kick start gear from the crank, probably just needs some heat. I'll post if I find anything.

[stellarfoxy]

hello again everyone! since last post, I have replaced the crank and piston. the timing is now absolutely perfect (after tensioner installed)! stator flywheel timing line matches up with tdc, cam lines match timing line, tdc matches cam, etc. I cleaned up everything, replaced o-rings, reassembled everything exactly as it was removed, deglazed the cylinder, clocked the piston rings correctly, redid valve adjustment, used tons of assembly lube and an adequate amount of grey gasket maker to aid the gaskets- the compression is at 180psi, I have spark (on stock cdi), and I have fuel.

and yet it still doesn't run.

I'm wondering now if it's in the head. since the timing gear on the crank appears to have slipped- holding the old and new next to each other, the gear teeth were a different position compared to the rod- maybe the cam gear did also. I truly thought when the timing matched up, it was repaired. I'll keep you guys posted as I throw more parts at it.

[Bashan]

Can you get us some pix? The gear on the crank is not really called a timing gear, it just drives the cam sprocket. Maybe you could show us what you mean by the two different gears not lining up. I'm confused. If you have that much compression, and spark, and fuel, and the cam is installed correctly, it should start. If your head was at fault your compression would be bad. Is it doing anything, even hitting a little?

[cyborg]

You have spark,,you have fuel,you have compression,,,either your fuel is no good or you are out of time