Reconditioning Apollo 250

[KirkN]

The insulator blocks (or at least dramatically slows) the heat of the hot cylinder and head from transferring right to the carb and fuel in the bowl thru all that nice metal manifold and carb.

[Nydirtbike]

Gr8rcher

So I've been looking on youtube all night.
Is our motor less complex then the others? Do we adjust ours from the 2 bolts that stick out on left and right side. Did you have to replace the shimms?

[KirkN]

I watched, but didn't listen to the audio, of Gr8rcher's video, so I'm not sure if he covered this. If you have that same engine, there shouldn't be any shims that get replaced.

Those are screw-and-locknut style valve clearance adjusters. They are adjusted by first placing the piston at top dead center on the compression stroke (ie, both valves fully closed just as the spark plug fires). At that point, you use a feeler gauge to check the clearance between the bottom of the screw adjuster and the top of the valve stem.

That clearance is usually on the order of 0.003" or 0.004" for the intake valve and 0.006" or 0.007" for the exhaust valve. I'm not 100% certain on the specs for our motors, but that's a good guide.

To adjust the clearance, you loosen the locknut and loosen or tighten the screw adjuster to the desired clearance. While holding the screw adjuster, tighten the locknut and re-check the clearance (to be sure the clearance didn't change a bit when you tightened the locknut).

Done.

Pretty straightforward, and the only specialty tools required is a set of feeler gauges, available at most auto parts stores or tool stores.

Good luck with it.

Kirk

[Gr8rcher]

Setting for this motor is .003 MM on both.

[Gr8rcher]

The Mikuni is a tight fit but it fits, to adjust the pilot screw will be a PITA. I will try to have video later today.

[KirkN]

Originally Posted by Gr8rcher

Setting for this motor is .003 MM on both.

I think that's gotta be 0.03mm. 0.003mm is 1 ten-thousandth inch (0.0001").

Wow, even then, 0.03mm is only 0.001" and that seems just W-A-A-Y-Y tight to me. I've never had an engine with less than 0.002" intake and 0.004" exhaust.


*edit* just looked up in my own Baja 250's owner's manual: intake and exhaust clearance spec is 0.002" (0.051mm). Wow.

[Nydirtbike]

got it guys. Finally found a couple of pics. Yes there are no shims.looks pretty straight forward and Gr8rcher is right it is .003 mm. Going to get some feeler gauges today or tomorrow. Pretty sure i can handle this.

to put the engine at tic does to have to look like this:
once that is done then the valve have to adjusted right ?

[KirkN]

Yep, that looks right.

One thing, I think that you can have that line match up on both the top dead center (TDC) on compression and TDC following exhaust, and of course, you must adjust the valve clearance while at TDC on compression, when both valves are closed.

If you're at TDC following the exhaust stroke, both valves will be just a tiny bit open (recall that the exhaust closes just a bit after TDC and intake opens just a bit before TDC), so you'd have to have zero clearance right AT TDC. (After all, how could you have any clearance if the valves are being lifted?).

So, you'll want to rotate the crankshaft and observe the valve motion as you rotate it. It'll be obvious by watching the valves open and close when you're at TDC after the exhaust stroke and at TDC after the compression stroke.


And it cannot possibly be 0.003 mm. That would equal 0.0001 inch, and they don't make feeler gauges that thin.

It's either 0.03 mm (which = 0.001 inch) or 0.003 inch (which would be 0.076 mm)



Kirk

[Nydirtbike]

got it kirk
thanx its going to take a few for me to get this but I'm pretty confident i will.
ill try to make a video also

[Nydirtbike]

how is the top fly wheel support to be? The 2 lines on the fly wheel where do they have to line up

[Gr8rcher]

They will not be visible in the sight window toward the front of the engine.

[Nydirtbike]

ok guys i did it
i adjust the valves
ill start it up tomorrow
There were very very tight. I don't understand the bike is brand new. They don't check them before they leave the factory?

[Weldangrind]

Originally Posted by Nydirtbike

how is the top fly wheel support to be? The 2 lines on the fly wheel where do they have to line up

I'm not sure that I understand your question, but maybe this will help:

1. Remove the spark plug.
2. Turn the nut in the center of the left cover counter-clockwise only. Use a breaker bar (instead of a ratchet) for better control.
3. The Line you're looking for has a T with it.

[Gr8rcher]

Mikuni Carb

[Nydirtbike]

great video.

Where can i get the jets for the carb.
I want a 110 for main and 25