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  1. #1
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    Default Front Cylinder Gasket Leaks

    1991 Sportster 883 Deluxe

    Hi All - My front cylinder base gasket has always leaked, but now the front cylinder rocker cover gasket is ruining every pair of pants I own. Good timing as winter will soon be here. I know, I know....shush with that sort of language.

    Anyways, I have never torn apart a Sportster engine, but I do have the service manual. A few very green questions to get the ball rolling :

    1. The bike was sold to me as an 883 bored out to 1200. To date, this is all hearsay. I assume before buying gaskets, pulling everything apart and measuring first will be the sanest route. I assume a calipers on the cylinder is all I need? Or are there other indicators that I can use?

    2. The rear cylinder is tight as a drum, no leaks. Can I assume it's Ok to only service the front cylinder this time around?

    3. Any tips or tricks that anyone has to offer regarding gasket replacement, I'll all ears.

    Thank you in advance for any replies.

  2. #2

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    Yes, you can do one head/cylinder and leave the other alone. Do remove the head first, and measure the bore to see if it has indeed been bored to 1200. 883 bore is 3", and 1200 bore is 3.5", so a ruler is all you need. The head gaskets are different for the two bore sizes, plus the head gaskets are available in different thicknesses, and you want to match what's there as near as you can.

    A reminder for the novice:

    When you pull the cylinder up out of the case, stop and stuff clean rags in the hole so a broken ring or piece of gasket or anything won't fall into the crankcase. Then slide the cylinder off the piston.

    Jim
    Last edited by JBinNC; 09-30-2019 at 1:50 PM.

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    Those Alum jugs are notorious to warp at the bottom ...

    Might be a good idea to make sure they are flat ...



    This tool works great for doing that job, also removes the gasket if it stuck to the jug without causing any harm to the alum.

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    I perform a compression test on both cylinders before tearing down one or both to check top end health. If the rear has good compression I wouldn't molest it.

    Online orders are so quick these days unless you know what you need I'd wait to find out. Inspect the bore of the removed cylinder under bright light and if in any doubt post CLEAR, WELL LIT PHOTOS of bore and piston.

    The pigtail kits to prevent seepage from the cylinder to crankcase oil passages work well.

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    Thanks all for the info. Once I start digging in, I will repost.

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    Ok, two months later and we have already seen some cold-ass temperatures here in Wisconsin (9 degrees, anyone?). Last night I finally ventured out into the garage, got the propane heater going, and started to dig in.

    Right now I'm just removing the peripheral do-dads : fuel tank, carburetor, upper motor mount, front motor mount. Tonight I'll pull off the front jug exhaust and maybe the intake manifold if I can get at it?

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    Green question. I've read the service manual a few times now and it seems like I'm dealing with three major parts : 1. rocker box, 2. cylinder head, and 3. cylinder. With replacing the gaskets I assume the only order of operations would be : Pull rocker box, pull cylinder head, and then pull cylinder and then slowly put it all back together with the new gaskets in place? This is correct, no?

    Related, from the service manual, it goes into detail about the sub-systems one could take apart and/or service (i.e. rocker arms, valves, valve springs). I assume I can forgo taking these systems apart and just service my gaskets and call it good, no? Or is there something I must do while these components are apart?

    Lastly, more specifically, when putting the piston back into the cylinder, I'm guessing I need a piston ring compressor? Is there a trick to this or can I go get the Harbor Freight piston ring compressor and call it good? This is actually the only part I'm kind of worried about.....but I am guided by ignorance at the moment. Any helpful words would be appreciated and thanks for helping me with this job!

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    What are the compression test readings?

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    Quote Originally Posted by farmall View Post
    What are the compression test readings?
    Farmall, I freakin' love you. It's funny because I knew you were going to ask me that. I hadn't read this thread since I first posted and I started tearing things apart last night. I looked at it today and was like "Shit! I didn't do the compression test! Farmall is going to totally call me out..."

    I'll hook up the battery and see what I can do tonight. Two years ago compression was great, but that was two years ago on a 28 year old motorcycle. Thanks for the reminder.

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    You will want to get that back wheel off the ground so you can put it in high gear and roll the motor over with the wheel. This is a must when working on the top end.

    When you start to disassemble the rocker box, remove the plugs and roll the motor over until the front cylinder is on its compression stroke. Both valves will be closed, and you will be able to wiggle both rocker arms back and forth on their shafts. They only move a couple thou, but you will be able to feel it. Then you can go about removing the rocker box without spring pressure on the rockers. Remove the five small screws from the lower box first, and then the four larger screws. The springs in the tappets will push the box up as you remove the large screws.

    Break the torque on the head bolts in small steps until all four are loose. The head is easier to remove than the rocker box assembly.

    Jim

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    Quote Originally Posted by farmall View Post
    What are the compression test readings?
    I asked Farmall this in a private message, but I didn't hear back. I wasn't sure if I could run a quick compression test w/ the carb removed so I did it both ways (carb off / carb installed) to see if there was a difference. No change in readings. With the carb on or off, both cylinders came back at 125psi.

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    Quote Originally Posted by JBinNC View Post
    You will want to get that back wheel off the ground so you can put it in high gear and roll the motor over with the wheel. This is a must when working on the top end.

    When you start to disassemble the rocker box, remove the plugs and roll the motor over until the front cylinder is on its compression stroke. Both valves will be closed, and you will be able to wiggle both rocker arms back and forth on their shafts. They only move a couple thou, but you will be able to feel it. Then you can go about removing the rocker box without spring pressure on the rockers. Remove the five small screws from the lower box first, and then the four larger screws. The springs in the tappets will push the box up as you remove the large screws.

    Break the torque on the head bolts in small steps until all four are loose. The head is easier to remove than the rocker box assembly.

    Jim
    Thank you for this, Jim. It's hard to see in the picture, but the back wheel is off the ground about 1". Lowbrow has a great video that details the rocker box gasket replacement that is in-line with your advice :


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    Quote Originally Posted by PBRStreetgang View Post
    I asked Farmall this in a private message, but I didn't hear back. I wasn't sure if I could run a quick compression test w/ the carb removed so I did it both ways (carb off / carb installed) to see if there was a difference. No change in readings. With the carb on or off, both cylinders came back at 125psi.
    I'm bad at checking PMs. Best to keep all questions in the same thread to help everyone. You did fine. Those readings are good and most important, they match.

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    Made some progress last night. Got the rocker box off. I was kind of surprised how loose some of the bolts were. Wonder if that was contributing to the leak?

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    The next challenge is getting the intake manifold off. The 1/4" hex head bolts are in a tight spot.

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    I think I'll stop by Harbor Freight on the way home from work and get a set of these ball-end hex sockets. Then, when I put the intake manifold back on, I can use my torque wrench and get the torque specs correct rather than going for feel with manual Allen wrenches :

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    Last time I was at HF I saw they had some nice plastic scrapers that might be good for getting the old gasket material removed and not messing up the aluminum heads.

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    Oh, and for getting the piston back into the cylinder I was going to pick up this guy unless someone knows of a good DIY tool that will work.

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    As per usual, thanks for the help and advice.

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    You might want to reconsider the HF sockets. I tried a set and they were crap, did not fit and when I mic'ed them they were all a bit bigger than my Craftsman allen set.

    Craftsman, Snap-on, or even Husky make a much better set for not that much more money.

    Great job so far!
    -DB

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    Buy quality tools one time and own them for life.............

    I've got tools that I have had for 50 years.............. Take care of them, keep up with them and don't let anyone borrow them unless they use them in your shop................ And you will have them forever.............

  17. #17

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    Quote Originally Posted by Tattooo View Post
    Buy quality tools one time and own them for life.............

    I've got tools that I have had for 50 years.............. Take care of them, keep up with them and don't let anyone borrow them unless they use them in your shop................ And you will have them forever.............
    Hell, I don't like people using my tools in my shop. Some people can break an anvil in a sandbox with a cornstalk.

    Jim

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    Quote Originally Posted by JBinNC View Post
    Hell, I don't like people using my tools in my shop. Some people can break an anvil in a sandbox with a cornstalk.

    Jim
    LOL Yep I agree............ I was being nice just in case he had a good friend needing help............

  19. #19
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    Quote Originally Posted by DoomBuggy View Post
    You might want to reconsider the HF sockets. I tried a set and they were crap, did not fit and when I mic'ed them they were all a bit bigger than my Craftsman allen set.

    Craftsman, Snap-on, or even Husky make a much better set for not that much more money.

    Great job so far!
    -DB
    Sage advice on the tools, fellas. I'm usually a Craftsman guy, but daycare is the wallet vacuum as of late, and I like to provide my daughter with the best. With this, they back-up a truck to my house monthly that I fill with Benjamins. For the short duration, I'm Ok being a Harbor Freight guy.

    Regarding HF, they didn't have those sockets on hand so I picked up a set of long ball-end Allens to try. Pffft, they didn't fit either. With this, I got out the angle grinder and found my own solution. Those suckers were tight. Not sure how I'm going to accomplish the torque specs when I put it back together, but it might be two grunts & done.


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    A few minutes later and lots of 1/8 turns the head was free :

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  20. #20
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    I was too excited to not pull the cylinder! Moving the rear wheel to put the piston to bottom dead center was neat! So cool to see that sucker go up and down!

    Three minutes later I had the cylinder off.

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    Ok, so now I have a table full of parts. Next few steps will be to clean off the old gasket material, measure, and order new gaskets. Thoughts on cleaning the top of the piston or just leave it? Thanks, men.

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