Apollo 250 slowly died now won't start

[Rcsup1]

Hi all,

I have had this bike for quite some time and have done a lot to it. It was running great! Couple of weeks ago I took it out rode around the neighborhood and the bike started to sputter until it quit. Walked it home let cool of and it started again.

I took it out the following week same thing except this time it was harder to start once it cooled and it missed when rev'd

Take it out the next day very hard to start I get going and it's ok until the upper rpms where it start to sputter bad, it gets worst so I turn around and barely made it home. It has not wanted to start after that. Only a faint back fire here and there when cranked.

Here is what I have done so far. Cleaned the carb (mikuni rep) thoroughly. Installed new coil, CDI and rectifier. Still nothing. I tried spraying starting fluid ..nothing.

It has spark (i verified) but cranks over as easily so I can tell it not combusting, but it has fuel and has spark.

I' am at a loss at this point. Any help would be greatly appreciated.

[Biker_Andy]

Have you checked your valve gaps?

[JerryHawk250]

Yep, Needs valves adjusted.

[normragan]

May check your coil pack, That will sometimes give you the same problem

[TxTaoRider]

Start with a new spark plug, even if your old one appears to be firing. I dont think its valve lash (but you should check it) as they loosen up after they run awhile, yours got hot then quit. It sounds electrical.

[duck9191]

Originally Posted by TxTaoRider

Start with a new spark plug, even if your old one appears to be firing. I dont think its valve lash (but you should check it) as they loosen up after they run awhile, yours got hot then quit. It sounds electrical.

Valve lash tighten with wear and heat, which is why they have any clearance to begin with. When the bike gets to temp and they are tight you end up with the valve not seating and loss of compression which ends up with loss of power or not running any longer. Continued running like this will eventually burn the valve seats. He says it has spark still and that it turns over easy, if it's turning over easy the compression is probably low.

[TxTaoRider]

Originally Posted by duck9191

Valve lash tighten with wear and heat, which is why they have any clearance to begin with. When the bike gets to temp and they are tight you end up with the valve not seating and loss of compression which ends up with loss of power or not running any longer. Continued running like this will eventually burn the valve seats. He says it has spark still and that it turns over easy, if it's turning over easy the compression is probably low.

Sorry but that's not right.
They do get tighter as they wear, but they get looser on these when the motor gets warmer. The cylinder and head expand more than the steel pushrod and valves. That's why one of the first signs of the lash being too tight is they get harder to start when cold.

[Rcsup1]

Thanks all I will check the valve clearance, but the way it went out after it was running like a top has me inclined to think it's something electrical.. Who knows though these bike do really weird things sometimes. I'll update here once I find the issue.

Just to recap:
New coil (coil on plug conversion btw)
New CDI
New rectifier
Carb thoroughly (cleaned mikuni clone)
Sparkplug NGK iridium with maybe 3 hours on it.

The bike has spark (verified)
Spray starting fluid and nothing happens either.

[TxTaoRider]

Have you got a compression gauge?

[Rcsup1]

Update..... It was the almost brand new sparkplug! Swapped the old one back in to leave "no stone unturned" and it cranked right up! Go figure... SMH

[TxTaoRider]

Originally Posted by Rcsup1

Update..... It was the almost brand new sparkplug! Swapped the old one back in to leave "no stone unturned" and it cranked right up! Go figure... SMH

I've seen used spark plugs spark ok off the bike and not work worth a crap after they're installed. I'm glad it worked.

[Motoman36]

This happened to me Start running really shitty in stops I thought it was the carburetor I took it apart cleaned out everything put it back together try to start it same problem pulled the plug no gap I don't know what happened but a new plugin there she runs great check your plug

[Oldenslow]

The original plug in my DF250RTG looked peachy, and the bike was running OK. Put in a new NGK just for the heck of it -- and now it feels like I added a supercharger!

[OBrienx]

your intake manifold or air filter or the wire to the ignition coil


ignition coil is at the front right side. you can sometimes over time let the spark plug wire unscrew it self through use unfortunately and cause a low spark which might in some cases only allow a ok ish running condition at low speeds... you just cut the end strip it a bit and scre the spark plug cable back in and reinstall. also while its off test the coil and wire with a multimeter to check its condition. you put on lead of the multimeter in the plug end and one lead onto one terminal at a time at the back of the coil with the meter on ohms/resistance.. you should get 8k ohms total meaning the it can produce a sufficient spark up to the plug.

check the intake manifold between the carb and engine for cracks. when you hammer on the throttle often the intake stretches a bit and will cause a lean condition at high rpm and not at low rpm lower gears lower speeds because at higher rpm and speeds it flexes a bit and sucks in the air.

if the filter is clogged or restricted and or your using a exposed pod filter AHem .. you will need to make sure the amount of air going through the size of filter your using is enough for higher rpms and higher air demand. i seen a guy use a small flat stubby pod air filter and it was doing what your describing till he changed it to a nibb filter off amazon.

[OBrienx]

its most likly your spark plug cable is rusty or loos in the socket or your intake adapter is cracked though