Gy6 trouble starting By chad (Read 1,991 times)

[chad]

I have a scooter with a gy6 engine I put a 80 cc big bore kit on it and it ran fine for a few weeks then one day it died and wouldn't start. I pushed it home still wouldn't start I replace the vacuum fuel pump the carburetor is brand new. It's getting good spark it's getting gas to the carb but it just won't start it tries and it's so close to firing up but just won't do it. Got a new cam the valves are dialed in. Please help

[tommikene]

Start with compression (especially after big bore work). If you don't have compression tester, you can get an idea by just trying using kick-start. If you can rotate the engine effortlessly (without noticeable resistance) then either get the tester and exact reading for your peace of mind, or consider it a compression loss. Something went wrong in your conversion

[tommikene]

I rebuilt mine 3 times, and only once had a compression loss after 1000km. Wouldn't start anymore. Redid the work and no issues. My scooter has 12'000 km as of now. Also an 80cc rider

First I did the 80cc conversion that lasted for 10'000km. Then a piston rod bearing failure, metal fragments from bearing ate everything inside. Rebuilt, then 1000km compression loss. Rebuilt again with new kit and now no issues. The kits can be faulty as well. Or, we can always make a mistake. 

[chad]

Thanks for info. Gonna re adjust the valves today to see if that helps. I read somewhere that if you don't get enough valve lash it cause starting problems possibly compression.

[chad]

And also for some strange reason I had to end up putting the lock nuts for the valves on the bottom of the lifters because they couldn't reach what's up with that. The valve taps are practically all the way screwed in. as far as I can tell all the lifters for the GY6 is are the same so I don't understand why these aren't working the right way

[tommikene]

There are 2 kinds of heads with different valve lengths however.

[cyborg]

Did you change the head?

[chad]

Yes

[chad]

Ok so can I get the correct lifters or do I have to get a whole new head with 69mm valves?

[tommikene]

That I don't know. I never had a wrong head with me. Maybe you can get the correct head assembly separately? At least no surprises after that bullet s bitten.

[chad]

Did some research turns out I can just replace the rocker arms tho I would like to have the 69mm head it has thicker walls. I'll get one when I can afford it right now $ is tight. My Death Star scooter is all have for transportation.

[chad]

Okay correct lifters installs still no change still won't start. Does anyone have any ideas what's going on with this thing

[cyborg]

Double check cam position,,and watch valve actuation as you turn it over to make sure valves are opening and closing

[chad]

Ok just rebuilt the whole motor again run great now.

[cyborg]

Excellent!!!! There's a piston right there