Valve Adjust By epdowd (Read 763 times)

[epdowd]

Adjusting the Valves on my GY6 150cc:
When I set the Timing Tab on the mark to the Left of the T as per instructions, the holes in the Chain Sprocket aren't aligned perfectly. With Large hole to the front I see approx. 1/4 of the Top hole and all and then some of the Bottom hole.
If I align the upper and lower holes on the Sprocket then the T mark is approx. 3/8 inch to the Right of the timing tab.
Now this scoot ran great untill I started fiddling around with the Carb to correct a lean condition.
What Timing positions do I believe. The T Mark or Top and Bottom holes ??
Thanks..

[Bashan]

I use the holes on the sprocket as a guide. I find you can't get the mark to line up perfectly, it keeps moving back and forth for some reason. Anyway, the valves are closed when you get close to that point anyway, it doesn't have to be perfect. I think the "T" mark is really to tell you you that you're at the right 180 degree point of the set. Did you look at the alternative set after the regular tutorial. I use that, it's simpler but Dr. JR hates it for some reason. What did you do to the carb? Move the needle or rejet? As I remember you were trying to get the plug to look picture book. I gave up on that, if it runs good and the plug doesn't look hot I don't worry about it anymore. You can let these things drive you over the edge. Rich

[epdowd]

Thanks again Bashan,, That is a relief , I was using the timing mark method,, had me worried for a while.. I'll go by the hole position.
Yep, I removed the airbox and put on a Uni filter. It ran great untill I messed with the carb. to correct the white ceramic. I changed the original main jet from 100 to 115, 125, 135. still white. It ran perfect with the 125 or 135. from idle to WOT.
Tested all of them at the WOT test.. So my demise came when I started changing washers in the needle jet,, something happened there. No matter how many or no washers I swapped, the scoot would only do max 25 mph. No change with the 1/4, 1/2 & back off throttle method, just plug along at 25 mph. I removed and tested the auto choke for the correct needle movement, checked good. No holes in the needles diaphram.. Made sure the diaphram gasket was seated properly. I had adjusted the valves before this all started, .004 and .005 and it was runnining fine, but decided to check them again and then this poser came up..
I gave up and ordered an exact replacement type carb. from Scrappydog.
P.S. I called Sherlock Holmes at 221B Baker street for help but no one answered

[Bashan]

I ended up with a 115 when I went to the uni and had to richen one notch with the clip, obviously a luxury I have that you were deprived of. I have no idea why they make some of them without the clip, a cruel joke. The 135 is ridiculous, I don't know what that's for, it turned my plug black and all it did was bog. I guess that's for the four valve head or something. I think I could have made the 125 work but that's pushing it at least on my scoot. I can't imagine what happened while you were changing washers but something irreversible happened. Luckily it doesn't cost a fortune to start over. Keep us posted. Rich