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Old 07-06-2010, 08:53 AM   #1
acecycleins
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Default My Nephew's CR85R

Cuddy or any other 2stroke guys.

My nephew's CR85 has a blow-by issue off the manifold and the expansion chamber. I thought the dealer would hand me the correct parts after ordering them, but I was wrong. They gave me the rubber seals and what looks like a crush washer for a 04 85 Expert.

The original metal joint gasket was cleaned and looks fine and the joint seal was cleaned as well. The questions is: How much seepage should be happening? Before I pulled these things apart you could visibly tell that exhaust smoke was coming from the manifold area. Not huge but absolutely noticable. The parts look fine, but I'm not really a two stroke guy so I was wondering if the $11 worth of raplacement parts will seal the exhaust or if it's rather normal for these little 85's to have this issue.

Are there any other parts other than these two pieces that i should look into replacing (like the manifold itself) or is what I re-ordered going to fix his issue?

Kirk
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Old 07-06-2010, 12:42 PM   #2
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Manifold as in intake or exhaust. How many hours are on the bike that you know of? Is the bike losing power? And finally is it a heavy black sticky stuff that's creeping out? Pics would help although I am sure Cuddy would get straight to the heart of the diag. quicker then I.
Obviously gaskets will leak more when they have been crushed once previously. Check all the mounts to the exhaust and move the head of the pipe to and away from you see how lose it is completely bolted together.
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Old 07-06-2010, 12:56 PM   #3
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Quote:
Originally Posted by MOKE1K View Post
Manifold as in intake or exhaust. How many hours are on the bike that you know of? Is the bike losing power? And finally is it a heavy black sticky stuff that's creeping out? Pics would help although I am sure Cuddy would get straight to the heart of the diag. quicker then I.
Obviously gaskets will leak more when they have been crushed once previously. Check all the mounts to the exhaust and move the head of the pipe to and away from you see how lose it is completely bolted together.
Exhaust. No big smoke. Just light in color. No power loss. Just smoke coming off the front of the expansion chamber right at the manifold.
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Old 07-06-2010, 06:19 PM   #4
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Change the gaskets, note how loose is loose for the matting surface's of the exhaust. I am not sure what year I am dealing with but a lot of these pipes are held on with springs initially then require bolts past the main portion of the header.

I'd say your alright without seeing pics. Not also sure how your son rides it but it will load up after the rider putts around for a bit. As you probably know you have to be on the gas for this type of bike to run properly. Replace the gaskets and o rings depending on the last time these peices were replaced, besides it's eleven dollars? Ride it until it really becomes a problem
As long as your servicing it on time properly you should be ok. Good luck.
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Old 07-06-2010, 06:32 PM   #5
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By the way do you keep up regularly with the maintenance schedule? When do they state to replace these items. Tell me you have an owners manual.
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Old 07-06-2010, 06:42 PM   #6
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All this is new actually. I've been a street rider for 27yrs. I know enough about 2strokes for fake basics but when I pulled the pipe off it seemed as though there were o rings missing. Not sure, though, bucause this is the first time playing with a tiny motor. The spring certainly was holding it in place and accoding to the manual the torque for the bolts was a scant 7ftlbs. I just want to make sure I have the correct parts before buttoning it up.
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Old 07-06-2010, 06:46 PM   #7
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In my experience, all racing two-strokes, that is, all bikes having exhausts that are held on with springs, leak to some degree. They may not when brand spanking new, as the pipe end and exhaust spigot are unworn. (Been a long time since I've owned a brand new bike.)

Operational vibrtion takes it's toll on the joint, hence the spring mounting. In fact the engine and pipe mounts and frame flex all probably play a part in flex at that joint.

The only sure way to completely seal the joint is to replace all worn components, including pipe and spigot (probably part of the cylinder on an 85). The isure all pipe and engine mounts are secure and flex-free.

All this may not be worth the price of cleaning with a good degreaser after exery ride.
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Old 07-06-2010, 07:29 PM   #8
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He is correct if it's primarily held on with springs it's going to be lose. It's meant to be that way and will wear in and move more than expected.

An o-ring usually has a visible seat or inlay. Also I have used RTV to overcome a serverly worn matting surfaces. If it's new and has less than 100 hrs, I'd say your fake basics on two strokes is fine and your just worrying about nothing.
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Old 07-07-2010, 07:33 AM   #9
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All good then. Just making sure what I'm seeing is normal compared to street bikes. Guess I'm going to have to pony up for a Bultaco to learn some things. Got a friend that is willing to let me have one of his three for about $800. It runs even.
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Old 07-07-2010, 06:34 PM   #10
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All racing two-stroke MX bikes leak a little from the exhaust port/headpipe joint. It's like that so the vibration from the motor doesn't manifest itself into cracks and other bad news on the chamber side. I use to double-up the springs on my CR500, seemed to keep the pipe seated better. If you'll notice the whole chamber is rubber mounted, if it were mounted solid the expansion chamber would be toast in a few hours of riding.
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