how to set timing on gio 250cc
 

just replaced everything on my gio 250 cc dirtbike. New piston,rings,cylinder head. Need to know how to set up the timing before i try to start it again.
Can anyone help????

not for sure on this, but i believe the first step is to make sure that they crankshaft is at tdc and that the cam shaft is at tdc..

i have not done that type of work for a atv motor but i have for a car and everything gets put at tdc before installing the timing chain/belt

thanks for quick reply.
It is an MX bike 250cc 4 stroke air cooled.
have no timing chain or belt. It just has two rods that ride from top end with valves down to the crankcase. Two rods ride on a toothed wheel. Wondering if there would be some type of timing marks in the bottom end that i need to line up first.
Rebuilt bikes with timing chain before, line up your markes ,put chain back on and away you go.

It sounds like you have a pushrod motor, and that you haven't disturbed the igntion. Did you remove the flywheel? If the cam isn't in the head and you didn't remove the flywheel, my guess is that the timing will remain the same.

just removed the top head cover, removed the top end by taking 3 bolts out of the head that the rods were connected to. took out head bolts and removed head with valves. removed cylinder and then piston. did not touch the lower end or ignition.

It sounds like you didn't even remove the rockers; is that right?

yes i did remove the rockers. they are held on by 3 bolts, It has like a plate at the top of the head. took the two rods out that go down through to the bottom end. then took the top end of the motor off as well as the piston.

I've never dismantled one of these engines, but I have dismantled Honda overhead cam engines (and plenty of small block V8 pushrod engines). My guess is that you're good to go after adjusting the valves.

Timing is established two ways: the relationship between the magnetic pickup and the flywheel, and the relationship between the crankshaft and camshaft. If you didn't disturb either relationship, you're good.

Anybody else have a comment?

I've never disassebled any motorcycle engine, so I'm unsure. :?

In theory, if the crank and camshaft have not been removed or even turned over with the head off, one would think the timing should still be the same.

got a photo of your motor and bike

You have the older pushrod motor. These zongshens were used for a while on china bikes.

If you want to adjust your valves this is when you must find TDC for the timing of the VALVES. This is NOT ignition timing.
If you are installing a new camshaft for the valves, then again you MUST find TDC and align the marks on the camshaft with whatever point of reference the manual specifies. On newer 4T MX bikes they use the marks on the cam to be level with the top of the cylinder head for example (SOHC/DOHC system).

If you want to adjust the dirtbikes ignition timing then you do not have to find TDC at all, you need to have a timing light and you need to remove the plug on the case where the top of the flywheel will be. There is an indicator on the flywheel for TDC which is where "0 degrees" is for your timing light.

To change the timing on a bike you need to remove the flywheel cover, and remove the bolts/screws on the stator and adjust the stator position to advance/retard ignition timing.
You have to recheck your position change with the timing light every time as far as I know. For these bikes I would just leave it at 0 degrees

is this a GY motor? push rod

the engine timing is done in the lower section. No need to time if you have not disturbed the crank/cam.

The ignition timming is static. so you cant change this. The pick up from the fly wheel is in the flywheel cover.

is it this type of engine?

a GY or CG clone?

http://i31.photobucket.com/albums/c3...5/IMGP4356.jpg

the engine code on these are stamped just in front of the gear changer behind the front sprocket cover.

on re-assemble, make sure you do the rocker gaps (3 thou) both valves. Also remember is TDC to adjust these. Very clever design.. they use 1 lobe for both valves. any way.. If both valves are compressed at TDC then its on its power stroke, turn another 360deg and you should be both valves closed. This is where you adjust the gaps.

good luck