Spudhut001

Hello all.  Happy to be on this site.   The information is priceless.  Quick background on me, I have built hot rod cars from 1920's to 70's for many years. 

I currently have a 1991 Yamaha Moto4 250 2wd quad.   The bike is in great shape.   I bought it from an older guy who used it around his farm until it decided to stop running.   He figured it was an electronic issue since it was a "crank no start" situation.   He replaced the original CDI with a cheap Chinese unit and a stator with a cheap amazon part.   What was happening, as you started it, with the spark plug grounded, it would spark on the the push of the starter button - then no spark as it turned over - then spark when the button was released.   When I got the bike, he did give me the oem cdi and stator.

Fast forwarding, I picked up a manual.  I started to check all the electronic specs.

~The original stator, falls in spec per the troubleshooting methods as described by Yamaha.   I swapped out the china stator for the original.   

~The china cdi box was removed and i put the original cdi back in.   What I discovered was the original cdi did not give off any spark.  I picked up another original 'good used' cdi as I dont know if it is possible to test.

~new DK coil pack, spark plug and spark plug cover and swapped it in. ( I tested spark plug cover, the manual says it should be 10 ohms but the plug cover is showing 5 ohms.  Not sure if this is vital issue)

Now I am getting spark consistently out of the plug, grounded to head/fins. 

I have 2 china carbs.  One that came on the bike and a 2nd new in box.  Fuel is flowing from the tank to carb.

When I try to start, the bike just turns over.  Fuel appears to be flowing from the carb (clear yellow fuel line), notably when I put my hand over the carb, I get fuel on my hand from the vacuum.  Every now and again, it does burp or 'fire' a few quick cylinder cycles (like "3-4 fires in cylinder"  (boom, boom, boom)).  It burps back through the carb more than it does to try to start.  I tried starting fluid, it does pop, but nothing consistent to want to run or even go vroom!.

I have checked the timing and it "appears" to be spot on.   I even check to make sure piston is all the way up on the firing cycle.  Without over thinking this, I did notice as the flywheel is at TDC, the cam gear was off a little to the right, not completely straight up and down to timing mark as per the manual.  With all that I have done, I feel like the timing chain off, and timing is the main issue (replace timing chain), am I wrong?

I have adjusted the rockers per cold values in manual.  I did a compression check and with the throttle closed, im getting 114 psi roughly.   I did see some posts saying that the throttle should be open to get the correct value, Ill perform this and update my post.

Unfortunately, its still not starting/running.  

I'm at a loss and about to replace the timing chain.   I dont think it is a mechanical issue, but I need some fresh perspective....

Any help is greatly appreciated.

Hello - Quick introduction.  I live in Arkansas on a farm.   Built hot rods and customs for over 20 years.   I love to wrench and toy with machines.   I have 3 different quads (92' LT4WD Suzuki 250 Quadrunner, 91' Yamaha Moto4, 01' Honda Rancher ES)  and 1 82' Honda ATC.