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Discussion Starter · #1 ·
My buddy's 660 started leaking oil out of the rocker cover, and we found a crack in the cover itself, looks to have been caused by strain on the upper motor mount.

He had the swingarm bolt come loose while riding a few months ago, and it started working it's way out, and I have a feeling that is when the crack started.

My question is, can one get away with removing the upper motor mount through bolt and just run the right hand bolt? This is a temp repair, while the parts are on order.

Thanks in advance!
John
 

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You could go to a hardware store and get a grade 8 bolt or the metric equivenent, think it's called a 10.2 or something like that.

Take a good look at that upper motor mount, they are know to crack.

What was done about the cracked rocker cover?
 

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i have the same problem kinda my frame cracked right after the motor mount on the left side an i got it welded up an havent had a problem since but i didnt know that that was a common thing on the 660s but i guess so
 

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Discussion Starter · #5 ·
Thanks!

I suspect that if Yamaha thought one motor mount was good enough, that is what they would have installed in the first place, but he wants to try it for a Glamis run.

So far, for temp repair, he has cleaned/boiled out the rocker cover, and is attempting a seal with JB Weld... :crazy: But hey, what do I know?

Thanks again,
John
 

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shit if that was me that could be a possible permanent fix. my boy has a gsxr 600 and his turned it into a stunt bike and he broke the clutch side case and oil poured everywhere so he walked it home and layed it on it side in the driveway cleaned and sanded the area, put the shit on and let it harden and its has'nt leaked at all and its been like that for a year or two :thumbsup:
 

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u dont want to use jb weld just get a local shop or someone u know who can weld an get it mig welded the jbwelb in never goin hold if it does its not goin last long think about it if the metal broke what makes u think jb weld some puddy mix is goin hold it trust me jsut pay 50 bucks an get it fixed right the first time
 

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Been having this same issue. Valve cover cracked around the left side mount, leaks oil. Welded it, crack just moved. Any objection to just leaving the upper motor mount off? I've seen lots of guys running the 660/700 hybrid engines with no upper motor mount, never read of any complaints. It seems like the strain just makes the crack worse on the valve cover. Even the Honda guys have been known to ditch the upper motor mount on the TRX450 because the frame cracks on high power builds. Or would it be better yet to leave the upper motor mount in place and just leave the bolt out?
 

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Lol i was just reading this when i saw u say somethin.. im not running a top motor mount in either one of my bikes.. i quit running them a long time ago... learned that on drag bikes with cut frames, the chassis will actually try to twist so much that it pull the head and could blow the head gasket or crack as has happened to most if u..being that none of u are running 14:1 compression or shooting nitrous.. then it wnt hurt to leave it out... imo...
 

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And if some people say somethin about the greater risk of blowing a head gasket with no top motor mount.. then its like Krawlin said... ive drag raced more than trail rode, most of the guys i run with ditch the top motor mount and cut the brackets off.. 90% of them are 660s n trx 450 with 14:1 compression n up or spraying a ton of nos and they rarely have hg issues..
 

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i see the top motor mount as a stabilizer...if it is not used, prolly be ok, long as the bottom mounts stay tight. keep an eye on them puppies. and keep an eye on the motor, make sure its not flexing much in the frame if ur jumping and cornering hard etc.
 

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I never used the upper mount when oval racing...........:D
But that's not as hard on it as drag racing..........
 

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Would it be OK to leave the upper mount in the frame just as a frame brace and stabilize the engine side to side, but simply leave that upper bolt out? My concerns are with my riding style, mostly trail but I do ride the MX track quite a bit, and I do jump the bike a lot. The trail riding I do is mostly high speed desert. I agree completely with what has been said about it causing head gasket issues, and in my case it caused the valve cover to crack at the left of the cast motor mount tab.

Or could I just used a single bolt through the right side tab just as a stabilizer? I modified my upper mount to use rubber bushings some time ago, in hopes it would help with prevent valve cover cracking, it's just too stiff to help now that it has already cracked on the left side.

Also, what do you folks recommend for sealing the cracked valve cover? I am a welder by trade, TIG welding is what I do all day at work, and I couldn't fix the cover, the location of the crack just holds in oil and can't be welded in a manner that would guarantee the crack wouldn't come back (full penetration and access to weld the back side of the crack). Part of it was fixable, but where the crack travels along the side/under that tab, I was unable to repair it. I have not had much luck with 2 part clear epoxy, (Loctite and JB brand), it doesn't seem to be able to hold up to the heat and it allows it to leak oil after a few hours of ride time. JB Weld (standard, not the quick stuff) cracked open last time I used that after about 10 hours of ride time. I purchased some JB Weld High Heat 2 part epoxy putty, anyone had good luck with that?
 

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Would it be OK to leave the upper mount in the frame just as a frame brace and stabilize the engine side to side, but simply leave that upper bolt out? My concerns are with my riding style, mostly trail but I do ride the MX track quite a bit, and I do jump the bike a lot. The trail riding I do is mostly high speed desert. I agree completely with what has been said about it causing head gasket issues, and in my case it caused the valve cover to crack at the left of the cast motor mount tab.

Or could I just used a single bolt through the right side tab just as a stabilizer? I modified my upper mount to use rubber bushings some time ago, in hopes it would help with prevent valve cover cracking, it's just too stiff to help now that it has already cracked on the left side.

Also, what do you folks recommend for sealing the cracked valve cover? I am a welder by trade, TIG welding is what I do all day at work, and I couldn't fix the cover, the location of the crack just holds in oil and can't be welded in a manner that would guarantee the crack wouldn't come back (full penetration and access to weld the back side of the crack). Part of it was fixable, but where the crack travels along the side/under that tab, I was unable to repair it. I have not had much luck with 2 part clear epoxy, (Loctite and JB brand), it doesn't seem to be able to hold up to the heat and it allows it to leak oil after a few hours of ride time. JB Weld (standard, not the quick stuff) cracked open last time I used that after about 10 hours of ride time. I purchased some JB Weld High Heat 2 part epoxy putty, anyone had good luck with that?
Use high heat silicone............
 

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Use high heat silicone............
And any input on the other questions? :confused: ???


I tried that already, it doesn't seem to be able to hold back the oil properly, and it never dries all the way through in the areas where it really needs to (I tried Yamabond and Permatex high temp, without much luck). Yes the crank case is vented properly, no obstructions, but oil does have a bit of pressure behind it when it's being flung by the rockers and cam spinning at varying speeds up to 9000 RPM, enough that silicone does not stop oil completely from seeping out of the crack.

I just applied some of that JB Weld brand high temp putty, provided it doesn't eventually crack open and actually sticks well, I have a feeling it out to do the trick, as it's able to be pressed firmly into the areas that it's needed.
 

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sealed a hole from water jacket to the intake port with marine JB weld. also reared 2 valve covers with it. so far so good.

are the bottom mounts good? the frame must be twisted or flexing... something aint right
 

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Bottom mounts were cracked, and then repaired and reinforced. I just don't want to risk breaking cases from not having any upper mount in place at all, that's 100+ pounds of engine wanting to move around. So is there anything wrong with leaving the upper mount in place, and not putting a bolt through it and the valve cover, just to add some lateral stability to the engine, but allow it to more fore and aft? The frame is not twisted, nothing shifts or is hard to install as though it has a tweak.

I'm not sure I am understanding what you think isn't right. The frame is not twisted, nothing shifts or is hard to install as though it has a tweak. The valve cover cracked, it leaks oil, I am trying to seal it, and prevent it from leaking again. I modified the upper motor mount so it functions much like an automotive motor mount (cut the tube off of the frame tabs, shortened it slightly, put rubber bushings and a steel sleeve through it, made new frame tabs with smaller hole, bolt running through it, so the tube can move fore and aft), in hopes that this would keep the crack from getting worse. The rubber is hard enough though that it doesn't really give much at all, it would prevent a good valve cover from cracking, but it doesn't keep the existing one from getting worse.


I don't mean to be rude, but I am after answers to the questions I am asking, I am mechanically competent and things like a tweaked frame are one of the first issues I look for when something like this happens. Not all of us on here are newbies, I just don't feel like dumping a bunch of money into replacing the head and valve cover on a 13 year old quad that I don't ride as often as I used to (a 450 will make you forget about the Raptor, lol).

Thank you for the input on the putty, that's what I wanted to know.

I just want input on using just the right side tab on the valve cover for bolting to the upper motor mount. Is the valve cover thick enough/strong enough there to do that, or will it cause it to break there too with just that right side bolted to the upper mount?
 

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ive never even herd of those tabs breaking, but if the one tab broke, then the other might, if u only bolt that one to the mound. u could try riding without the mount, and u should be fine as long u keep an eye on the engine, making sure it dont flex around too much in the frame, beings u are MX-ing it etc.



may old frame was cracked and welded at so many places, the 2 right side top engine mount bolts broke off in the frame, so it was only holding on one side. my bottom mounts were worn and my engine was kina flexing, pulling the left upper frame rail to the left, causing it to break....

so unless its a freak thing, something might be slightly wrong, is what im saying. hope u figure it out
 
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