[Jacobrblocker]

I just got a 300ex from a guy, but he had the wiring harness off. For the time being I just got a new cdi DC cdi box and wired it up. I have tested it outside the engine and it sparks.the engine has a good compression and I just cleaned the carb. Although I'm not getting any pops or anything trying to start the engine. Any ideas at why it will not even try to run?

 

[Jacobrblocker]

I just noticed this, the exhaust pipe seams too be sucking although idk if that's normal. Also i don't have a throttle cable at the moment so im just holding the throttle up a little and it seams to try to close every stroke

 

[SlammedRanger]

If the exhaust is sucking then it either jumped time. Or was timed wrong. The piston is on the down stroke when the exhaust valves are open which is wrong. It should be on the up stroke. Could also potentially be very very tight valve lash but i would think you would have had piston to valve contact to be so tight your getting exhaust sucking. Your exhaust should pulse pressure out. So no sucking exhaust is not normal. Welcome to the forums!

 

[Jacobrblocker]

I don't know how the timing could have been messed up. How would I be able to change the timings. I am probably going to try to set the valve lash .

 

[XplicitRacing6]

@SlammedRanger is right. If you are having a sucking through the exhaust then you have a timing issue... Re Setting the time is easy... Look for a Forum on here if you need some assistance... Good luck

 

[SlammedRanger]

If the timing chain tensioner fails it can jump time. At any point. It could even potentially happen when cranking it over. Mostlikely it would be while its running or riding though.

 

[misterclean59]

A stuck valve is possible too. You say the compression is good but have you actually checked it? A cam hitting a stuck valve or a piston hitting a valve can cause resistance that feels similar to compression.

 

[Jacobrblocker]

https://photos.app.goo.gl/6H9SJcKlvrZ93TNS2
Is this top dead or fire or is it both? The books says to look for a t and and f, but I can't find one.