My 89 LT -F250 quadrunner seems like the intake valve is stuck open or opening at the wrong time. How and why. It was working ok (never idled very good) but now won't start and I can feel the air pushing out of the carb.
before I pull it apart is there anything I can try?

 

Check the valve lash it is .001-.003 - Intake
.003-.005 - Exhaust

 

thanks bearl I had been avoiding checking the intake lash as the nut on the inspection cap was destroyed by the last owner and it was super tight. I suppose it tells me that the last guy had the same idea.
I'm gone for the next couple of days but it will be the first thing I check on the weekend.

 

First off Welcome to the forums tutor_baker !
I agree with forum member :bearl_baker , that's a good place to start , i would also suggest that you pull / remove the air filter and the air box to so you see if the choke cable see if the choke is sticking , even if the cable look's like it's working i would go ahead and remove the carb and give it a good cleaning with Berryman Chem dip , just make sure that you remove all rubber and plastic part's because the chem dip will damage them .

The main reason i suggest doing all this work you'll have to remove some of the plastic part's , air filter and air box to get to the valve access the valve's intake and exhaust Cap's/covers' to check the valve's ; and by all mean's mix some Sea Foam with enough fuel
enough for at least 3 or 4 tank's !

Sea Foam has a fuel stayblizer , it contain's a drying agent , upper clinder lubie , it will clean out the combustion chamber of carbon deposit's that get into the cylinder and cause
piston ring's to stick and scarring of the cylinder wall's ; it's still carries the same Satifaction Garranty or your money back Since it came out in 1940 it work's with all 2 and 4 stroke engine's ; both Gasoline and Deisel combustion engine's !

I I hope this help's get the job done .

williebee........

 

Hey Williebee thanks for the interest and help. I had the carb apart and cleaned up its good to go And I replaced the choke cable when I first got the machine its working good. I can throw a tissue on the carb intake and watch it blow off through a compression stroke. That tells me that the valve is open at the wrong time.

I'm most curious if it would be open all the time or just at the wrong time.

That is good advise to do all that maintenance while you have the plastics off and have access. I suppose most of us are guilty of driving the crap out of our machines and wondering why they break down once in a while.

I had the decompression lever off trying to put the spring on as it had fallen off, the shaft turned so I believe this started this mess to begin with. Is this possible since it doesn't affect the intake valve?
TH

 

The first thing I would do is a compression test. This will tell you what is up.

 

Thanks for that doc turbo. as with most threads I've read my compression tester doesn't have the right fitting. I'll be working on this machine today and hopefully riding befor the day ends.
Cheers to the weekend

 

Hope you get the problem solved soon and get back on the trail.
If you have to,take an old sparkplug and make an adaptor for your compression tester. Not fun and it takes some time but it worked for me.

 

Well guys the intake valve lash was non existant... once I got that inspection cap off the rest was easy and it fired right up.

Not sure why this happened the way it did but the bottom line is the machine is idling good and I'm going for a spin before dark

Thanks and I'll keep interest in the site. keep it going

 

Hey doc I was thinking about the sparkplug mod for the compression tester... I like the way you think dude!