Won't start with fuel air and fire?

[TheRealFatShady]

I have a 200s that won't start.

Getting spark. I can see it at night and feel it always, brand new plug bought today.

Sprayed carb spray into the carb and even directly into cylinder via plug hole.
Finger over plug hole - Doesn't blow it off too well, but does have some compression. I know it's not a proper compression test, but I figure it should be enough to fire once.

My thoughts:

Timing off - Sparks fine outside cylinder, but may be off and not sparking at right time.
Valves too tight
Low compression - Rings/piston
Decompression lever/cable issue, this is the only one I've found that had it.

Any idea?

[mudslinger1m]

Well... I would figure that the valves are stuck open. take a air blower stick it in the plug hole as tight as u can and blow it.. if air comes out the exhaust or out the carb then u will know what valve may be stuck open??? Just a guess.

[Dirtcrasher]

Did it recently die? did you buy it this way? did you do any work on it recently?

That plug hole should blow off your finger......

[TheRealFatShady]

I have little history on it, I was told the guy couldn't get it to start and thinks it may be carb related. Gas in the tank (real clean inside by the way) seems old. There are brand new tires, so it must have run at some point in order for someone to spend that money on it. Need to fix the rear end up and get this going.

I have a 185s that blows my finger off the hole yet no matter what, won't get spark. (Literally everything except flywheel swapped from running bike....and the wheel still attracts my screwdrivers/metal tools), I may just use that full top end or just the cylinder and piston on this engine. At least this engine has spark.....

I'm guessing it ran but then people messed with it. Cracked plastics taped seat, half spraypainted, sprocket isn't mounted, one rear tire on....But it has new grips and a different type of throttle, they seem nice.

[rdlsz24]

Is your carb jetted right, and do you have an airbox/filter? Have you tried adjusting the valves?

Rob

[TheRealFatShady]

Have not done any work to it other than replacing plug and checking for spark/trying to start with carb spray.

I believe it was running rich, the first plug was real dark black and fouled out, but I tried all different choke positions while trying to start. I've run them without carbs, I figure spraying directly into the cylinder would bypass any jetting enough to make it start even for a few seconds. It did have the airbox (Yet no cover....how do people manage to do that?) on it.

Edit: Also, while I am still new to engines so my understanding may be flawed, even with tight valves, wouldn't the direct spray-to-cylinder kind of override tight valves where the fuel would already have gone through the intake?

[cybrman]

It's all about compression. If the valves aren't opening and closing at the right time then you won't have compression to make the explosion. Fuel flow is a separate issue (sort of...the intake valve's job is to cause vacuum to pull the fuel into the cylinder)
If its not blowing your finger off the hole then it probably isn't enough. Next step is to take the head off and inspect the valves. Very common for timing chains to stretch and jump
causing the exhaust valve to impact the piston. Almost all the machines I've bought have had this issue..some its just a matter of replacing the valve and a couple it was a new piston and valve(s). Also a slim possibility your muffler is plugged up, but thats a long shot. Try to feel some air movement out of the muffler when you turn it over. Good Luck!

[TheRealFatShady]

It's all about compression. If the valves aren't opening and closing at the right time then you won't have compression to make the explosion. Fuel flow is a separate issue (sort of...the intake valve's job is to cause vacuum to pull the fuel into the cylinder)
If its not blowing your finger off the hole then it probably isn't enough. Next step is to take the head off and inspect the valves. Very common for timing chains to stretch and jump
causing the exhaust valve to impact the piston. Almost all the machines I've bought have had this issue..some its just a matter of replacing the valve and a couple it was a new piston and valve(s). Also a slim possibility your muffler is plugged up, but thats a long shot. Try to feel some air movement out of the muffler when you turn it over. Good Luck!

Thanks for the advice. It does blow my finger off slightly, it definitely isn't as it should be (like my running 200s). Do you replace the entire valve and just do a top end gasket/valve guide seals while you're at it? I will inspect them tomorrow, hopefully it's doable without pulling the engine from the frame.

But the decompression valve, could that be partially to blame? Every other bike I got has had it removed, I have not honestly looked into it too much to see it's relation to the valves themselves, but I've heard they can be problematic so they were usually removed.

[cybrman]

Sounds like it ain't right...hopefully its just a bent exhaust valve. I've actually bent them back on occasion though for $15 it probably makes sense to get a new one.
If it were me I would definitely buy a timing chain (thats the reason the valve is bent in the first place usually) and replace valve's, piston/rings if necessary along with a gasket kit which will have the valve seals and all the gaskets you need. They sell em for just top end or for the whole engine.
You can do it without pulling it, but I sometimes remove most of the motor mounts to give myself some play to make it eaiser to get to all the bolts.
As for the timing chain it isn't too bad if you do it methodically. Feed some rope in the plug hole to jam up the piston and allow you to remove the clutches under the right cover (make sure you have things tightened down as far as the head goes)
The manual will give you step by step instructions on how to remove the clutches and everything to get the timing chain out and put the new one in.
I haven't done a 200 yet but plenty of 250's in principle everything is the same.
Have fun! Get er running right and then you won't have to worry about it! (In theory ;)

[beets442]

Get manual, check timing, adjust valves, check compression, set carb or you'll chase your tail.... Beets

[TheRealFatShady]

Update:

I put a little oil in the cylinder hoping to lube the rings and pulled a few times. Then added carb spray and the plug, few pulls and nothing.

Swapped the decompression valve to the opposite position ('off') and pulled. Two or three pulls and it started. It died after a few seconds, but after another 2 or 3 pulls it started up again.

I'm going to clean the carb and use fresh gas, after fully removing all decompression valve parts/cable and the parts in the recoil. Hoping it's not low comp. due to rings, but merely that decomp. lever causing the issue.

Thanks for the help! Will keep you all posted