you're more apt to have backfiring and poor engine performance with valve timing- and it wont go away when warm or cold starting. It's a carb (enrichment) issue.

 

I was talking about valve clearance, not valve timing .

Tight valves are a classic cause of hard starting on GY6 engines when cold.

 

valve clearance issues (which effects timing) would still cause other issues along with hard starting (not just hard starting)- the motor would run rough warm or cold- don't you remember timing the valves / solid lifters on the old mopars and fords? Getting covered in oil while fine tuning the valve lash-

 

I disagree. Valve lash is never set to zero. The clearance is required to make up for differential thermal expansion of the engine, and to allow for wear.

On the GY6 engine the valve seat expands more than the valve gets longer, so the valve clearance gets bigger as the engine warms up. In other words, the valve clearance is less when the engine is cold.

Valves and the valves seat wear over time. That also decreases the valve clearance. So as time goes on eventually you get an engine where the valves arent closed fully when the engine is cold, and the engine is very hard to start or won't start at all.

The classic symptom is hard starting, but once it starts for even a few seconds it runs and starts normally after that (valves heat up very quickly) - until the engine is allowed to cool all the way back down.

I have a couple GY6 powered quads, and can testify from personal experience that you *must* periodically adjust the valves or hard starting when cold is exactly what will happen.

The procedure for adjusting the valves specifies that it be done on a cold engine - because this is the worst case condition - and that way you are guaranteed no to have valves that are too tight (until they wear that way).

Technically you are correct in stating that valve lash adjustment affects valve timing. But the effect is very small - I did some rough calculations this morning and came up with less than 0.5 degrees for a change of 0.004" in valve clearance.

I'll let you have the last word, and then it is probably time to agree to disagree...

 

Hmmm- and I suppose you "let" your wife out of the house...?
Not looking to get the last word LE- just discussing the topic

I never said the lash should be set to zero.

But I also have to disagree with you- the "thermal expansion" of a warm steel valve sitting on a steel valve seat compared to a cold valve is not enough to cause it to have a gap- not even close. We're talking about .0001 of an inch. A cold valve is sitting in a cold engine- even if the two heat up at different rates- still not enough to cause a "no start" issue.
There's more thermal expansion between the aluminum piston and molly rings in a steel cylinder liner.

Using the wrong oil will have more effect on cold starting then the "thermal expansion" of a valve. If a valve & seat is so worn out that the lash is way off spec- it's not going to matter if it's hot or cold- it'll always run like crap. Even with such a tiny gap- it'll should still start right up- it'll just be acting as a compression relief valve like found on many 2 strokes and larger 4 stroke engines.
A simple compression test before and after squirting oil in the cylinder will tell him if he has a leaky cylinder.

but that's all moot- his problem is with the enrichener circuit-

 

IDK, but there is one of your problems right there.

 

wanted to add- I've rebuilt hundreds of small engines, many of which had burnt, cracked or worn valves. The motors would backfire, pop, smoke, have no power and run like crap- but unless the valve stem was broken or there was a real bad mechanical failure, they would always start. 95% of the time if it was a "no start" - it was due to an electrical or fuel failure.

Also- the op stated it fired right up after he "shot gas into it"- That's a big red flag for a carb issue. I'd bet my neighbors farm that it's a carb (fuel) issue.
And I'll certainly eat a plate of crow if it turns out otherwise

 

To be continued! I tested the enrichment mechanism by appling 12 volts to it and could not get it to work. The carb has been thoroughly cleaned. I will have a new enrichment mechanism and the ceramic resistor(?) today or tomorrow. As soon as I get that put on, I suppose I'll know if that is the problem or not. I appreciate everyones input on this problem....it's almost like going to mechanics school! Stay tuned for the results!

 

careful putting current through that resistor- you'll fry it...

 

I am still waiting on my new enricher and resistor. While I was waiting, I decided to further study the existing enricher. I put power to it and it extended out far enough to cut the fuel from flowing thru the passage. When I took the power off of it, it opened the passage. I bypassed the resistor to do this. My question is: what detects the need for enrichment...some sort of heat sensor( I have not seen anything obvious, yet)? For it to be able to enrich, the needle must be retracted up into the coil/selenoid, meaning the power must be interupted for that to happen. From what I can tell, the enricher needs to be energized to make the needle extend out enough to close off the passage so no more fuel can enter the carb(Once engine is warmed enough, it does this). I just can't figure out how it senses the warmth to send the signal to energize the enricher to make it close off the passage. Any ideas?