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Discussion Starter · #1 ·
Ok, I have a Raptor 80 that wouldn't start. Kid says he was going up a hill and then it just quit. And then after that having it roll down a hill in gear wouldn't start it either. It has spark and just cleaned the carb. So I thought I should do a valve adjustment. I put the engine at TDC, although it wouldn't go to exactly TDC, as the engine would get some resistance near TDC, and then it would fly past it when I turned the crank more. So when the engine was near TDC on the compression stroke (the valves were not moving so I assume it was close enough). Well the valves had about .25" of clearance. So I adjusted the intake first, that went smooth enough. Then I adjusted the exhaust valve. Well that gave me tons of trouble. Something is not right with it. The engine wont turn manually now (thank god I didnt try starting it). I have the adjuster almost all the way out and it still gets very tight at a certain point in the cycle. I'm not sure exactly what the problem is. There was a 4 year old kid turning the crank bolt in the opposite direction, not sure if that did anything. So, what the problem/solution? Did the exhaust valve break off or something? Did turning the engine backwards somehow make the cam chain come off or something?

So to sum that up:

-Vehicle cut out all of a sudden. Has spark and clean carb.
-Valves were super loose. Probably .25in of looseness on each.
-Tried adjusting them, intake went fine. Exhaust gets super tight even when the adjuster is almost all the way out.
-Engine couldn't be turned to exact TDC, would get resistance about 5 degrees near it and then would zoom past it when you overcame the resistance.

Please help.
 

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Ok, I have a Raptor 80 that wouldn't start. Kid says he was going up a hill and then it just quit. And then after that having it roll down a hill in gear wouldn't start it either. It has spark and just cleaned the carb. So I thought I should do a valve adjustment. I put the engine at TDC, although it wouldn't go to exactly TDC, as the engine would get some resistance near TDC, and then it would fly past it when I turned the crank more. So when the engine was near TDC on the compression stroke (the valves were not moving so I assume it was close enough). Well the valves had about .25" of clearance. So I adjusted the intake first, that went smooth enough. Then I adjusted the exhaust valve. Well that gave me tons of trouble. Something is not right with it. The engine wont turn manually now (thank god I didnt try starting it). I have the adjuster almost all the way out and it still gets very tight at a certain point in the cycle. I'm not sure exactly what the problem is. There was a 4 year old kid turning the crank bolt in the opposite direction, not sure if that did anything. So, what the problem/solution? Did the exhaust valve break off or something? Did turning the engine backwards somehow make the cam chain come off or something?

So to sum that up:

-Vehicle cut out all of a sudden. Has spark and clean carb.
-Valves were super loose. Probably .25in of looseness on each.
-Tried adjusting them, intake went fine. Exhaust gets super tight even when the adjuster is almost all the way out.
-Engine couldn't be turned to exact TDC, would get resistance about 5 degrees near it and then would zoom past it when you overcame the resistance.

Please help.
I have heard some of these units loose a screw which holds the butterfly in the carb, check to see if you are missing one, and you know where it ends up if it falls out..........
 

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Discussion Starter · #3 ·
I have heard some of these units loose a screw which holds the butterfly in the carb, check to see if you are missing one, and you know where it ends up if it falls out..........
I do recall a missing screw on what I think was the carb plate/butterfly thingy. Could any other thing cause this problem? The engine was able to turn before hand. I did the intake with the ATV level. But I did the exhaust with the front end jacked up at an angle. Similar to going up a hill (like when it cut out). Hmmmm....

Any other opinions on why the engine wont turn and the exhaust valve gets super tight even when the adjuster is almost fully out? Does anything bad happen when you manually turn the engine the opposite direction?
 

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I do recall a missing screw on what I think was the carb plate/butterfly thingy. Could any other thing cause this problem? The engine was able to turn before hand. I did the intake with the ATV level. But I did the exhaust with the front end jacked up at an angle. Similar to going up a hill (like when it cut out). Hmmmm....

Any other opinions on why the engine wont turn and the exhaust valve gets super tight even when the adjuster is almost fully out? Does anything bad happen when you manually turn the engine the opposite direction?
Nothing wrong with turning this particular engine backwards............
Find the screw................
 

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If that poses no luck, make sure you valves aren't too tight. My Kawie didn't turn after I adjusted them. I loosened them to the minimum clearence and it started right up.
 

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Discussion Starter · #6 · (Edited)
I can't even turn the crank back to TDC with the adjuster loosened as much as it will go. So I don't know if the valve is radically bent, or if the screw is in the valve. But it's the exhaust valve so if the screw is in there, it must have passed through to the cylinder, right? Or is there a way for the screw to go from the intake side to the exhaust side without passing through the cylinder? I'd rather have to replace a valve rather than have a damaged piston and cylinder.

I don't have the special service tool to hold the "magneto rotor" still to loosen the cam bolt. How can I remove the head without this special Yamaha tool?
 

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Discussion Starter · #8 ·
To remove the head can I have another person hold the flywheel bolt with a wrench while I undo the cam bolt? I'm eager to pull the head off and inspect the damage and find the screw.
 

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Discussion Starter · #9 · (Edited)
Yep, took the head off and saw that the screw managed to bend the intake valve and get compressed between the piston and the head. Left a nice impression of the screw threads on the piston and head. Flattened the screw a bit too. Will have photos later. I think the cylinder is fine though.

Will everything be ok if I just replace the valves? Or is it totally not good to run the engine with screw thread impressions that are not touching anything (like the edges of valves or mating surfaces)? Where is a good place to get these replacement parts? I bet that Yamaha will not warranty this even though I hear they know about this drastic problem. I'll have to take the valves out to know if the sealing portion of valves/head is damaged. I really don't want to drop the money on a new head.

Not sure why I had so much trouble adjusting the exhaust valve since it was the intake valve that was damaged. Maybe the screw got lodged between the exhaust. Not sure. Oh well, that's the least of my troubles now.

Still need to take the piston off.



 

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I'm not to sure about whether its safe or not to run it like that. Just glad to hear you got to the bottom of the problem.
 

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Yep, took the head off and saw that the screw managed to bend the intake valve and get compressed between the piston and the head. Left a nice impression of the screw threads on the piston and head. Flattened the screw a bit too. Will have photos later. I think the cylinder is fine though.

Will everything be ok if I just replace the valves? Or is it totally not good to run the engine with screw thread impressions that are not touching anything (like the edges of valves or mating surfaces)? Where is a good place to get these replacement parts? I bet that Yamaha will not warranty this even though I hear they know about this drastic problem. I'll have to take the valves out to know if the sealing portion of valves/head is damaged. I really don't want to drop the money on a new head.

Not sure why I had so much trouble adjusting the exhaust valve since it was the intake valve that was damaged. Maybe the screw got lodged between the exhaust. Not sure. Oh well, that's the least of my troubles now.

Still need to take the piston off.



Isn't that amazing that a screw can do that, change the valve or valves and run it, as long as the rings aren't jammed in their grooves, you should be good...................
 

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Discussion Starter · #12 · (Edited)
Do you mean the rings in the pistons? Doesn't seem jammed at all. I'll take a photo of the piston (still attached to the rod) and you tell me if it definitely needs replacing or not.

I need to rent a valve spring compressor. But I know any random valve spring tool won't work. What particular type of valve spring compressor tool do you recommend?

It's my cousin's son's ATV and they aren't concerned about having everything in 110% top shape, as long as it runs well. If it was my ATV i'd definitely get a new head and piston. So I'm not sure if it's ok for the engine to just replace the valves.
 

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Do you mean the rings in the pistons? Doesn't seem jammed at all. I'll take a photo of the piston (still attached to the rod) and you tell me if it definitely needs replacing or not.

I need to rent a valve spring compressor. But I know any random valve spring tool won't work. What particular type of valve spring compressor tool do you recommend?

It's my cousin's son's ATV and they aren't concerned about having everything in 110% top shape, as long as it runs well. If it was my ATV i'd definitely get a new head and piston. So I'm not sure if it's ok for the engine to just replace the valves.
Judging from the pictures , I would change the valves and grind the seats, put it back together............
 

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Discussion Starter · #14 ·
What is the thread for the bolt I need to buy in order to thread into the rocker arm shafts. Neither the Clymer nor Yamaha OEM service manuals specify the thread, just says "thread bolt into rocker arm shaft to remove" or something like that.

Also, I'm looking into machine shop prices/services. There is an option for "VALVE SEATS REFACED" or "SEAT REGROUND MINIMUM". Not sure which I need as the prices are very different.

I rented a valve spring compressor from Autozone, but I'm pretty sure it's too big to work with this head.
 

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What is the thread for the bolt I need to buy in order to thread into the rocker arm shafts. Neither the Clymer nor Yamaha OEM service manuals specify the thread, just says "thread bolt into rocker arm shaft to remove" or something like that.

Also, I'm looking into machine shop prices/services. There is an option for "VALVE SEATS REFACED" or "SEAT REGROUND MINIMUM". Not sure which I need as the prices are very different.

I rented a valve spring compressor from Autozone, but I'm pretty sure it's too big to work with this head.
I have no idea since I never had one of theses engines apart............
Just have the valve seats reground minimum.............
 

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Discussion Starter · #16 ·
Ahhh... needed some parts for a Polaris too so I just took the head to the local motorcycle/ATV/snowmobile dealership and they will do the valve work (including price of new valves) for $80. So that headache is gone. They said I should check to see if the rod is bent though. I hope it's fine. Taking apart an ATV crankcase is something I do NOT want to do. I have never worked on an ATV before (But I'm a big car guy).
 
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