85 ALT 125 - Won't Stay Running

[atc007]

Def clean your petcock! We have to have fuel from the tank to the carb. One missing link in that chain,and we will not have fuel . Once you know you've got a carb full of gas,she should pop right off. You can easily hook up a IV bottle,some gas in a bottle to the carb, to verify. Also once you're running,make sure the vacuum line running from your intake to your fuel pump is UNDER the frame rail. A lot of guys back in the day after a carb clean would leave these over the frame,,,seat pinches it off= no fuel to carb. I would say make sure your valves are set at .003-.004,but if you're sure you have that much compression,it should def run. Also, the best way to truly clean a carb is compressed air,preferrably 175 psi,as opposed to 120. On that note, you can also take off the gas line to the carb and pressurize the tank,and fuel should flow right out at the carb.I suspect your gas is getting there,but your carb needs cleaned better. Assuming here,,,,,thank you for your service.

[TripleOG]

Well, once again i've removed the gas tank. This time I removed the petcock and cleaned it up with some gas and a toothbrush (it was all dirty from dried mud). After I cleaned it, I turned the lever from off, to on and then reserve.. each time blowing through the fuel inlet to make sure that none of them were blocked. None were. I also checked the lines and filters again.. everything looked ok.

I also took the carb off again and opened it up. It looked just as clean as the last time I put it back together. There is definitely gas getting to the carb because each time I take it off the trike, I unscrew the the drain plug and a significant amount pours out. I don't think I'm flooding because when I take out the spark plug, it's never dripping fuel.

Remember, I could get it started with starting fluid and keep it running if I stayed on the throttle.

What would having low compression do to the trike? Wouldn't it not start at all if the compression was too low??

What would off timing do to the trike? Also, would it not start at all if the timing was off?

What (besides a clogged pilot jet) would cause this motor to only run while staying on the throttle?

[350for350]

Just a wild suggestion, but have you checked your electrical components? It's possible that something is just barely good enough to run for a little while. Maybe recheck after it runs and then dies. Something could possibly be building resistance as it runs and gets warmer. I know it's a long shot, but you seem to have the fuel part pretty well covered. Maybe it's something else.

[TripleOG]

Just a wild suggestion, but have you checked your electrical components? It's possible that something is just barely good enough to run for a little while. Maybe recheck after it runs and then dies. Something could possibly be building resistance as it runs and gets warmer. I know it's a long shot, but you seem to have the fuel part pretty well covered. Maybe it's something else.

Honestly.. At this point, after everything that I've repaired, rebuilt and cleaned.. I'm thinking that it has to be a vacuum issue. I've only checked the lines from the fuel tank to the petcock and fuel pump.. to the carb. As soon as light hits, I'm going to check Every line on the whole machine.

There very well could be malfunctioning electrical components. Honestly, when I look at the wire.. all I see is a jumbled mess. For the first 12 or so years of storage, this thing was garage kept. But for the past 6 or so, it's been out in the element.. uncovered. I don't believe the light works anymore, so that may be a symptom of bad electrical components. I just wouldn't know where to begin with electrical diagnostics on this thing.

[atc007]

Pull your pullstart off. You need to remove the shifter too. Inspect the ignition, it is most likely very rusty in there. There is 1 coil you can access,pull that off and shine it all up .Make sure the wires are all fresh and not broken/cracked. A flywheel puller can be had for under $10 online. They are very specific,internal left hand threads. It would help immensely if you pulled it and cleaned the stator and flywheel up also. Adjust your valves to .003-.004 . Then you have done everything you can without buying a new exciter coil. Which I suspect is what you need. Pop your carb back off , You should be getting really good at it by now lol. With ether,carb cleaner,,anything with a straw,,, shoot cleaner through the pilot jet and verify it IS coming out inside the carb where it is supposed too. Also figure out the air holes in the back of the carb and spray through EACH one separately to verify each and every hole is unobstructed. Report back. Ignition is simple and you only need a $3 harbor freight ohm meter to diagnose a few wires.

[TripleOG]

Pull your pullstart off. You need to remove the shifter too. Inspect the ignition, it is most likely very rusty in there. There is 1 coil you can access,pull that off and shine it all up .Make sure the wires are all fresh and not broken/cracked. A flywheel puller can be had for under $10 online. They are very specific,internal left hand threads. It would help immensely if you pulled it and cleaned the stator and flywheel up also. Adjust your valves to .003-.004 . Then you have done everything you can without buying a new exciter coil. Which I suspect is what you need. Pop your carb back off , You should be getting really good at it by now lol. With ether,carb cleaner,,anything with a straw,,, shoot cleaner through the pilot jet and verify it IS coming out inside the carb where it is supposed too. Also figure out the air holes in the back of the carb and spray through EACH one separately to verify each and every hole is unobstructed. Report back. Ignition is simple and you only need a $3 harbor freight ohm meter to diagnose a few wires.

Funny, I did most of what you're suggesting.. last night. I tried taking the starter cover off.. for 2 reasons. 1, to inspect the condition underneath it. And 2, So I could use a drill to start it to save on my back and lungs. In the process, I ran into 2 more issues. 1, one of the bolts head broke off, and the body is still stuck inside. And 2, the gasket was disintegrated and in a pieces (i took a pic). What is the gasket for on the start assembly? Is it required to keep the vacuum lock?

I also, once again, took the carb off and opened it up. It looked just as clean as the last time I put it together. But I still shot carb cleaner through every port and passage and verified that it was coming out where it should be. But I gave the pilot jet extra attention.

The 2 things I am pretty intimidated by are adjusting the valves and timing. It's been 13 years since I've been in shop class in high school and I think I've forgot pretty much all of the little bit that I learned there. I just don't want to get to a point where I'm doing more damage than good.

I'm about to go out right now and see how immpossible it's going to be to get that starter assembly bolt out with the busted head. It was the last thing I did yesterday before the dark made me come inside so I couldn't get a good assessment. Hopefully it's not that bad.

[Shep1970]

Just out of curiosity is there a compression release on head? Like the alt185 did it work?, when its closed it looks like this pic. Im 99% sure gasket is just to help keep water out (pull start).

[TripleOG]

Just out of curiosity is there a compression release on head? Like the alt185 did it work?, when its closed it looks like this pic. Im 99% sure gasket is just to help keep water out (pull start).

Nah I don't seem to have that on my head.

[atc007]

In behind the stator is a oil seal. That is as far out as the oil gets. No vacuum or anything like a 2 cycle. A little heat and vice grips for the bolt,a small cole chisel works wonders if you can get at it. If you pull the plug out and both valve caps off. Pull the engine over slowly,you will see as the exhaust valve closes, the intake opens. This is called valve overlap. The next time the piston comes up to tdc that is the compression stroke. Both valves should be closed and therefore the rocker arms loose. This is where you safely adjust your valves. Simply set till a .003 feeler gauge is snug or a .004 will barely fit in. That is it. Unless you hear the timing chain slapping when it is running, your timing should be good. But a tooth off would give you these symptoms.I Strongly think you have weak spark,very common on these,behind a dirty carb.

[TripleOG]

In behind the stator is a oil seal. That is as far out as the oil gets. No vacuum or anything like a 2 cycle. A little heat and vice grips for the bolt,a small cole chisel works wonders if you can get at it. If you pull the plug out and both valve caps off. Pull the engine over slowly,you will see as the exhaust valve closes, the intake opens. This is called valve overlap. The next time the piston comes up to tdc that is the compression stroke. Both valves should be closed and therefore the rocker arms loose. This is where you safely adjust your valves. Simply set till a .003 feeler gauge is snug or a .004 will barely fit in. That is it. Unless you hear the timing chain slapping when it is running, your timing should be good. But a tooth off would give you these symptoms.I Strongly think you have weak spark,very common on these,behind a dirty carb.

Ahh.. I should have read this sooner. I just took both valve caps off and adjusted. Didn't know about the compression stroke. I don't know if I have a feeler gauge or not. But I can pick one up if I don't, I gotta run to the hardware store anyway to get some replacement bolts for the one busted off in there. And I wish it was that simple for the bolt. It's recessed in ever so slightly. Might have to find a small ez out set or just try to drill it out. I'll see what they got at the hardware store, maybe ask the owners opinions.

[atc007]

As long as the rockers were both LOOSE, you are ok. If they were tight,no good, need redone. Hardware store will have the bolts. EZ outs are very bad. Welding a nut to it is best,but there are other good methods of getting them out. You need to find the ohms of the exciter/pulser coil and ohm it.

[TripleOG]

As long as the rockers were both LOOSE, you are ok. If they were tight,no good, need redone. Hardware store will have the bolts. EZ outs are very bad. Welding a nut to it is best,but there are other good methods of getting them out. You need to find the ohms of the exciter/pulser coil and ohm it.

The intake valve had no play at all.. so I bottomed it out and went a quarter turn out. The exhaust valve had slightly too much play, but I left it as is because it was impossible for me to get a wrench on the tightner washer. Was impossible for me to get a flat tip screw driver on the adjusting screw too.. had to use a small pair of needle nose. Looking in hindsight, they were probably adjusted perfect before I loosened up the intake. We'll find out when I redo it on the compression stroke. But I'm gonna run to the hardware store before I attempt it again.

[coolpool]

Slow down OG, simple things first.
ATC007 mentioned hooking up an external fuel source and gravity feeding your carb; did you do this or did I miss it. This will rule out if it's your carb or not. Blowing clear on your fuel lines from the tank proves your tank, petcock and lines are good. Although, you'll still need to prove your gas cap isn't plugged which happens a lot. Pull your plug and check for a snappy blue spark. If you have consistent spark, stop messing with your wiring for now. Lazy spark, I suggest you unscrew the plug boot and trim off a 1/4" of wire and screw it back on as a preventative measure. I believe those diaphragm type pumps use the crankcase pressure to activate them, confirm that line is free.

[danbur55]

If these are like the quads the vent for the tank is a line on top of the tank

[atc007]

He has a float bowl full of fresh fuel Cool, yes,it is a line off the top of the tank for vent Danbur. Good idea to trim the primary coil wire,always, .But these are known for a weak stator, enough spark to see, but not run right.Just verifying everything else is where it should be