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Discussion Starter · #1 · (Edited)
This Grizzly has 500 miles on it. It sat under a tarp for 14 years! A guy bought it, got it to start, and it died a few minutes later. He brought it to me and I found the center intake valve was bent. So FF and the head was repaired by a machine shop. I reinstalled it, cranked it over and it fired up almost instantly for a second or 2. Then when I try to crank it, the starter relay buzzes like the battery is weak. Charged the battery, same thing. I realized that the auto-decompressor may not have been working properly. So I took the cam back out and the weights on the compression release were sticky. I fixed that, made sure the stuff moves freely and the little nub is working and all that. I was careful with the cam timing, following the service manual, and still the same. I can barely pull the recoil starter. What am I missing? Is it maybe a weak starter? I cleaned the battery ground to the engine connection already. I didn't do the positive connection to the starter tho. Maybe I'll do that and report back. Thanks!
I checked the battery this morning after it sat all night with no charger on it and it reads 12.07 volts. I think it should be more like 12.8 or 13, no?
 

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I'de want to know how a low mile machine bent an intake valve.
Is the engine stock, any modifications at all?
Someone put a manual timing chain tensioner in incorrectly?
 

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Discussion Starter · #4 ·
It's very likely that the valve stuck due to all of the gummy, sticky residue/old fuel inside when I took it apart. The machine shop confirmed my suspicion. I used a good, less than a year old, car battery to try to start it, but it's the same. I went over the cam and decompress system this morning and put it back in and I'm getting nowhere. I have the starter off but I really don't know what to do with it. I put an amp meter on the + terminal on the starter while trying to crank it over (with the car battery hooked up) and while it was trying to get thru the compression stroke it would read about 8-9 amps. Then when I helped it turn over, it would go up to 12-15 amps while turning the engine, until it hit the compression stroke again. I'm not sure what/ if that means anything. Electrical is not my cup o tea! LOL

I'de want to know how a low mile machine bent an intake valve.
Is the engine stock, any modifications at all?
Someone put a manual timing chain tensioner in incorrectly?
 

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Discussion Starter · #5 ·
I gotta believe that it's not starter related. Like I said I have a helluva time pulling the starter rope. If that's normal, there's no way that anyone could pull start that thing. I think I'm gonna tighten up the ex valve that gets opened by the decomp and see what happens. BTW, I did set all the valve clearances properly when I got it back together.
 

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I can't belive the valve bent because it was stuck/gummed up.
Break a ring on an engine that's been sitting, sure, but bend a valve, nah.
 

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Discussion Starter · #7 ·
Well, that's what happened. I haven't seen a bent valve(s) before without seeing a broken cam chain or tensioner that failed.

I had the center intake replaced, and the shop cleaned up the rest of the valves, checked the guides, put new seals on, and vaccuum tested it.

I think I figured out why the compression release isn't working. I put my hand on the exhaust valve rocker and turned the engine over by hand and the rocker arm moves, but it seems a bit early in the compression stroke. So I need to move the cam timing back on tooth it seems. It's weird when I put the cam chain on it seems the sprocket is back one tooth too far. If ya move it one link,then it seems like it's forward one tooth too far. So, I remember when I put it back this morning that it looked like it was too far forward. So, now I just gotta find my allen wrench
Brown Tire Automotive tire Wood Eyewear
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I can't belive the valve bent because it was stuck/gummed up.
Break a ring on an engine that's been sitting, sure, but bend a valve, nah.
 

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Great to hear.
If you turn the engine over by hand a few times, the timing marks will move to where they will stay, then you can be sure where they are.
 

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Discussion Starter · #11 ·
So I got back on the Griz yesterday ( I was waiting for a gasket) and I fired it up, let it run until the cooling fan came on just to make sure all that was working. No leaks anywhere, but the carb seemed a little out of sorts. If I turned the choke off all the way, it didn't want to idle or it was tough to get it to rev. OK so, no biggie, gotta clean the carb a bit better. So, I did that, put it back on, and when I went to crank it over, it's hitting the compression stroke and stopping the starter cold. I can't for the life of me think of what the hell is going on with this thing. Right off the top off my head, I'm thinking that the decompressor weights are stuck again. IDK. Dang it! I'll check it out today. But, this one thing has me curious. It's the "cap,tensioner" on the right side of the head cover. #25 in the diagram. I've had it on and off several times, and, I don't see or understand what it does. I like to know, understand what/ how things work. I'm stumped on this one.


Great to hear.
If you turn the engine over by hand a few times, the timing marks will move to where they will stay, then you can be sure where they are.
 

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I'm not sure, but I'm still not sold on the idea that only one intake valve was so gummed up, so it stuck and bent.
Something else is going on.
I would need the engine in front of me and time to dig into it.
Keep posting what you find and what you think. Hopefully we can figure it out, as there has to be a cause.
Given it's a low hours machine, with one bad valve, I would start measuring all parts in the head.
At least then you could be sure it didn't leave the factory with out of spec part(s) causing problems. Uncommon, but does happen.
 

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Discussion Starter · #15 ·
The bent valve has already been clarified and rectified. A very reputable machine shop verified and took care of the valves. But, lets say for sake of argument that you're on the right track. Why did if start up yesterday, and, aside from some needed carb tuning, it ran perfectly. Now after taking the carb off and back on, it's back to not cranking over. Moments ago I took that cap off of the L exhaust valve and I can feel it open ever so slightly as I turn the engine by hand so it seems the decompressor is working. Is it opening too early like it was a few days ago? So maybe the cam chain jumped indicating the cam chain tensioner isn't working properly, maybe lending credence to your theory about the stuck valve? I have no %@# idea! LOL I'm gonna find out tho. I guess I gotta pull the head cover off again and check the timing marks.Any ideas on part #25 in the diagram above? The repair manual says nothing about it.

I'm not sure, but I'm still not sold on the idea that only one intake valve was so gummed up, so it stuck and bent.
Something else is going on.
I would need the engine in front of me and time to dig into it.
Keep posting what you find and what you think. Hopefully we can figure it out, as there has to be a cause.
Given it's a low hours machine, with one bad valve, I would start measuring all parts in the head.
At least then you could be sure it didn't leave the factory with out of spec part(s) causing problems. Uncommon, but does happen.
 

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hey,

I've worked on a few big bears, kodiaks and grizzly's, and have some experience.

I wonder if the middle exhaust valve was bent from an over rev - bouncing it off the limiter in park or neutral, so something like that. or perhaps the clearance was set incorrectly and the piston hit - seems like it would've ran poorly otherwise.

anyways, just wanted point out a few more things.

1) the pull start on these yamahas are not like pull starting a lawn mower, pull firmly but slowly (you'll yank your shoulder out if you yank on it fast), and will kick over.

2) My battery was recently giving me the buzz noise - turns out it was a loose connection on the negative post - almost like the post itself was loose.

3) I would tighten the left exhaust valve to .005" to be sure that the decompressor works easier and makes it easier on the starter motor. besides that, it could be that the decompressor mechanism is severely worn down and not able to depress the exhaust valve far enough to relieve the cylinder pressure.

as for the automatic timing chain tensioner, they work by using a spring and rachet system to automatically press the chain tight. so, to take out the tensioner, remove the centre bolt first, but be careful as there is a spring in there under tension (not big enough to hurt you, but big enough it will send stuff flying), then the tensioner body bolts. take note how far the plunger is sticking out - this indicates how stretched the chain is. To re-install, flip the ratch lever up and depress the plunger in, now bolt back into engine, put the spring back in and re-install the big centre bolt, this will automatically load the chain with the proper tension.
 

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Discussion Starter · #18 ·
So, the latest. I pulled the rocker arm cover and again I rolled the cam 1 tooth forward. It started right up. Now, prior to that, as I explained a few posts back, I did the same thing, had it running, but it would hardly run with the choke all the way off. So, after taking the carb off,somehow the cam got 1 tooth behind. For the life of me I can't figure out how/why that happened. I find it hard to believe that the cam chain is stretched with 500 miles and 50 hours on this machine. And old dude bought it new, used it for 4 hunting seasons, averaging 10 mph.And then covered it with a tarp for 14 years.
The only thing I can figure was the chain tensioner was stuck or hung up. I checked it out, per the manual, and it works perfectly. It started up yesterday, and the carb cleaning did the trick. I let it warm up and turn off the choke, stab the throttle and no bog. Awesome! And Crosby, the chain tensioner that you describe isn't anything like the one on this Grizzly. But, nevertheless, it works like it should.

hey,

I've worked on a few big bears, kodiaks and grizzly's, and have some experience.

I wonder if the middle exhaust valve was bent from an over rev - bouncing it off the limiter in park or neutral, so something like that. or perhaps the clearance was set incorrectly and the piston hit - seems like it would've ran poorly otherwise.

anyways, just wanted point out a few more things.

1) the pull start on these yamahas are not like pull starting a lawn mower, pull firmly but slowly (you'll yank your shoulder out if you yank on it fast), and will kick over.

2) My battery was recently giving me the buzz noise - turns out it was a loose connection on the negative post - almost like the post itself was loose.

3) I would tighten the left exhaust valve to .005" to be sure that the decompressor works easier and makes it easier on the starter motor. besides that, it could be that the decompressor mechanism is severely worn down and not able to depress the exhaust valve far enough to relieve the cylinder pressure.

as for the automatic timing chain tensioner, they work by using a spring and rachet system to automatically press the chain tight. so, to take out the tensioner, remove the centre bolt first, but be careful as there is a spring in there under tension (not big enough to hurt you, but big enough it will send stuff flying), then the tensioner body bolts. take note how far the plunger is sticking out - this indicates how stretched the chain is. To re-install, flip the ratch lever up and depress the plunger in, now bolt back into engine, put the spring back in and re-install the big centre bolt, this will automatically load the chain with the proper tension.
 

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Discussion Starter · #20 ·
Thank you, this thing has been a dang grind!

I just went for a little ride around the property and everything seems good. It starts right up, no more bog, nothing is leaking. But I can't get it over 17mph in High. I revved it up yesterday and it didn't seem like it was revving all the way. So a little ride confirms it. Seems like this bike should go at least 50, no? I looked up the jet sizes, but, unfortunately I didn't notice the main jet when I had the carb off. I know the pilot is stock #40. I'll have to adress it next week as I'm headiing out of town for the weekend.

Glad you got it fixed
 
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