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Old 02-12-2011, 08:47 PM   #1 (permalink)
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the time has come...

Before the snow flew this winter as some of you know I picked up an 85 xlv and it had 110 psi in mag and 90 psi in pto. It ran really good the few trips I put on it and i knew I'd be tearing into it at some point. Today I ran into a slight problem from the get go. It would really boggy at low rpms but once past 5k rpm she took off like mad. I thought it was from the warm weather. The high today was 36. It seemed to run on one cylinder till a higher rpm and then it kicked in the other somehow. We put on 40 miles and once we got back we did a compression test. I found 60 psi in the mag and still 90 psi in the pto cylinder. Once I got home I took off both heads and found a chunk of the top Piston missing and I could see a broken ring. I noticed 2 big chunks out of it. Cylinder walls looked good though.

What's it gonna take for me to fix this thing? Just pistons and rings? I will post a pic soon of what the piston looks like. Is this job hard to conquer?

Thanks!
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Old 02-12-2011, 09:37 PM   #2 (permalink)
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Should not be to bad. I did a top end rebuild on a Phazer last spring. I think the sleds are similar. Keep parts seperated and clean them as you take them off, and any that seem questionable go ahead and replace. If the walls look good just hone them, but if not you may need to have them bored. Piston choice is whatever you feel comfortable with, oem or aftermarket. Everyone has an opinion on pistons. Once your done run a tank of oil/fuel mix thru and limit how high the rpms go at least one season. Cost vary but probably looking at $250 and up, depending on rings,pistons, needle cage, pins , and so on. With that being said, if you are not comfortable doing this, have someone else do it. Good luck!
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Old 02-12-2011, 10:23 PM   #3 (permalink)
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Thanks for the response Phazer!

Here are a couple pictures that I took tonight of the mag side with the head off. Can anyone tell me what they think caused this?



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Old 02-12-2011, 11:13 PM   #4 (permalink)
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Wow...ummh! Not seen that before. If thats an 85 sled. I'd say those are original pistons. Likely just age/ wear. Yamadad is more qualified to speak on why they gave out like that, than me. The ones I had to replace, had a hole blasted dead center of the piston. Looked like they were sand blasted. I'd interested to see what others may say.
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Old 02-12-2011, 11:29 PM   #5 (permalink)
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I can't know for sure if they are factory or not. It just looks like the edges deteriorated from age or a ring caught.
Here were my symptoms.
From the get go it was really boggy, you had to give it almost full throttle to move the sled. After gaining speed slowly it would eventually take off like hell obviously with more throttle. We stopped after a bit and I checked plugs and found this one cold to the touch and my pto plug was hot. Put a new plug in the mag side and went about 1 mile and checked it again and it was like brand new but a little wet. It obviously wasn't firing but I did have spark. So I was running on 1 cylinder until I gained enough rpm and the 2nd cylinder kicked in. After another 10 miles I checked the plugs again and it was light brown but nothing like the pto side. I burned fuel excessively today too.

Is this a good tell tale that I had low compression? Would it act like this?
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Old 02-13-2011, 04:11 PM   #6 (permalink)
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Can someone tell me the take down procedure on this 540 engine? I'm guessing it goes something like this:

1. Plastic shroud
2. Heads
3. Intake + carb
4. Exhaust and y pipe
5. 4 nuts in each cylinder and knock em off with a rubber mallet

Does this sound right?
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Old 02-13-2011, 09:38 PM   #7 (permalink)
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your procedure sounds close. i would diagnose those pistons as the ring catching a port due to worn cylinders or the ring land pins deteriated from wear and the rings caught a port.

if your intersted, i have two fresh cylinders, pistons, rings, pins and pin bearings that have been installed but never ran(fired). make you a deal if your interested.
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Old 02-13-2011, 10:17 PM   #8 (permalink)
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Originally Posted by yamadad4 View Post
your procedure sounds close. i would diagnose those pistons as the ring catching a port due to worn cylinders or the ring land pins deteriated from wear and the rings caught a port.

if your intersted, i have two fresh cylinders, pistons, rings, pins and pin bearings that have been installed but never ran(fired). make you a deal if your interested.
Thanks for your response Yamadad! Was hoping you'd chime in.

I suppose I really won't know what caused it unless I remove the cylinder right? Can you pm me with what you might be looking to get for the pair of cylinders/pistons and other stuff? I was hoping to just get by with a couple new pistons/rings and needle bearings. According to what I've read I have an aluminum alloy cylinder with a cast iron sleeve, are those able to be honed or bored? Sorry wish I knew more about these sleds, I'm gaining experience just slowly.

Thanks!
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Old 02-13-2011, 11:01 PM   #9 (permalink)
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your cylinders can be bored and oversized pistons should be available. judging from your pictures, i am guessing the cylinders are out of round. any machine shop can verify the bore trueness, typically at no expense.

if in fact the bore is true and the piston ring lands simply failed, you could get away with pistons, rings, etc.

pictures of the sides of the pistons once removed will tell more of the story.

regardless, the bore needs to be verified.
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Old 02-15-2011, 10:26 AM   #10 (permalink)
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I didn't have my good camera easily accessible but I took a couple pictures with my phone of my pto piston for reference, how does this one look?



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Old 02-15-2011, 06:29 PM   #11 (permalink)
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that side is looking good. rich on the safe side.

is that from the camera angle, lighting or whats the marking at the 7:00 position on the piston? almost the same markings in the cooked piston picture.

when you get the bad piston out, take a picture of the pin side so we can see how much blow-by from the rings
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Old 02-16-2011, 07:10 AM   #12 (permalink)
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i would say piston worn...rocking back and forth (piston slap) caused ring to catch exhaust port. for an 85' machine, i would say it worked as intended and lived out its designed life. new pistons, bore job....like new. good luck.
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Old 08-06-2011, 03:04 PM   #13 (permalink)
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I'm back!

I got the itch really bad to get my sled back in shape. Just a short time ago today I started tear down. I plan on removing the whole engine and replacing oil seals as well. I got just about everything removed from the engine and its about ready for removal from the chassis. I can't believe they built the frame around the clutch so you need to remove it prior to pulling the engine, wow. Just waiting on my brother now to see if he can find time to help me remove the clutch, pull the engine so I can clean it up and begin tear down.

I still don't know what I'm up for yet, hoping my cylinders are ok too so I can just hone them and replace with standard size pistons. Hope no other damage shows up while doing the take down.

Any tips or tricks for guys that have rebuilt these 540's? Yamadad?

Just want to make sure I do it right. I have the shop manual.

Thanks!
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Old 08-06-2011, 03:10 PM   #14 (permalink)
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BTW I'm sorry I never got back to you guys.

I will take pics of the tear down and what the pistons look like and post them when the time comes.

Another quick question: What size bolt will fit in the end of the clutch for extracting? 85 Yamaha XLV
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Old 08-06-2011, 04:55 PM   #15 (permalink)
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go get a clutch puller for it.
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Old 08-06-2011, 10:12 PM   #16 (permalink)
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Yeah I could get a clutch puller but I know alot of people make their own so was gonna maybe try that route. If it doesn't work I'll probably end up buying one.

Here is the progress I made today on the sled. After removing seat, fuel tank I was able to pull out the air box and detach carb. Also removed exhaust pipe, oil tank, and etc....

Is there anything else I should be removing along with the clutch before I pull the engine out?

I would like to degrease the whole engine and spray it down with high pressured water after I plug all the ports.

I am thinking about removing the battery as its shot and I don't really need electric start. Free up a little weight.

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Old 08-06-2011, 10:20 PM   #17 (permalink)
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clutch puller is the best way to go. you will find those threads on the clutch to be a 5/8" sae and i believe 16tpi.

as for the rebuild, pay attention as to how it all comes apart. label all the hardware, take pictures for reference. an eye for detail is required, lube all the parts well and dont cut any corners.

if you have to split the cases to change the seals, and i think you do, be careful not to damage them. thats probably one of the worst jobs on the rebuild and sometimes best left to experienced hands.

good luck!
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Old 08-06-2011, 11:10 PM   #18 (permalink)
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Quote:
Originally Posted by yamadad4 View Post
clutch puller is the best way to go. you will find those threads on the clutch to be a 5/8" sae and i believe 16tpi.

as for the rebuild, pay attention as to how it all comes apart. label all the hardware, take pictures for reference. an eye for detail is required, lube all the parts well and dont cut any corners.

if you have to split the cases to change the seals, and i think you do, be careful not to damage them. thats probably one of the worst jobs on the rebuild and sometimes best left to experienced hands.

good luck!
Thanks Yamadad for the response again. I failed to mention that I took multiple pics and neatly labeled baggies for the parts I removed and put them all in a box.

About the crank....

You say its probably the worst part of the rebuild, great. What does it take for the novice to do this successfully? Or how much "if you had to guess" would it cost me to get it cracked open? I'm guessing I need to crack the case halves to put in the seals.

Thanks

Last edited by mosabi; 08-06-2011 at 11:26 PM.
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Old 08-06-2011, 11:16 PM   #19 (permalink)
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careful with the homemade puller idea. a cheap bolt will cost you lots more money if things dont go well. depending on the last time that clutch was pulled, even with the proper tool, removal can be a fight. cheap bolts bend, break or damage clutch threads.

if at all possible, mark out or map the location of the engine mounts to the chassis. this will help you later keep the alignment close between the clutches if you dont have the tools for alignment after the re-install.

look for the tach drive cable attached to the oil pump. this will need unhooked to lift the motor out, either from the tach or the pump. oil pump cable can stay attached if you unhooked it from the carb plate.
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Old 08-07-2011, 09:46 AM   #20 (permalink)
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the key to splitting cases is blunt force, but you dont want to damage them.

you also need to protect the sealing surfaces on the 2 halves. read that as dont be enticed to gouge them up by driving a screwdriver between the halves.

a trick that i have used with success is picking up some slightly longer bolts with the same thread that hold the cases together. once all the bolts are removed, use the longer ones in the four corners and sometimes along the center and use the bolt head as a striking area with a hammer to spread the cases. slow and steady with patience prevails here.

sorry if i scared you, i get nervous every time i split a set for fear of damage. the cases are fragile to a degree and usually dont take well to the wrong beating or prying.

a good shop should do it for under $30, especially if its all cleaned up and you have the bolts out.

you will also need a flywheel puller as well. strike a deal, have it done at the same time.
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