Help on a top end question
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Road Master
Joined: Mar 2006
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From: Snowflake, Arizona
Help on a top end question
I could not get my carb running right, so had my bike at a small, local, harley only shop. While it was in he checked the timing, compression and leak down on my 1981 80 cu in shovel. My leak down was very good (almost perfect he said), but my compression is 88, but from the compression number, he said it appears I have a valve problem, and he suggested a top end rebuild while I am at it. Also, I have no exhaust smoke.
I also have never pulled the top end of a Harley, and would have liked to watch it done once, but that is out, so I am on my own. For now I am just riding it, but want to consider my options.
If get brave and do the top end, my 80 is .040 over and no more builds left in it, so I would have to go new cylinders. It is costly, but a new top end with new heads and cylinders
from S&S (J&P Cycle #432-994) is $2000, and with the pistons are fitted to the cylinders.
Having never seen the top end pulled. Yes, I have the 1978.5-1983 service manual and and parts manual and will get a few speciality wrenches per CaptG's post. Question (1): Do the whole top end while I am at it? Question (2): Should I go the S&S route, or are there other better or less costly options? Question (3): Should I attempt the new cylinder and top end myself?
Thanks in advance, long answers are appreciated and will be studied....
Hogback
I also have never pulled the top end of a Harley, and would have liked to watch it done once, but that is out, so I am on my own. For now I am just riding it, but want to consider my options.
If get brave and do the top end, my 80 is .040 over and no more builds left in it, so I would have to go new cylinders. It is costly, but a new top end with new heads and cylinders
from S&S (J&P Cycle #432-994) is $2000, and with the pistons are fitted to the cylinders.
Having never seen the top end pulled. Yes, I have the 1978.5-1983 service manual and and parts manual and will get a few speciality wrenches per CaptG's post. Question (1): Do the whole top end while I am at it? Question (2): Should I go the S&S route, or are there other better or less costly options? Question (3): Should I attempt the new cylinder and top end myself?
Thanks in advance, long answers are appreciated and will be studied....
Hogback
Road Warrior
Joined: Dec 2007
Posts: 1,286
Likes: 64
From: SoCal
HogBack,
Aside from any valve and cylinder machine work (if you are using your original heads and cylinders that do not come with matched pistons) there are two things to consider before you dive into this project: wrist pin bushings and a piston ring compressor. 1)The wrist pin bushings should be checked by a knowledgeable person ie. a machinist and be replaced and resized if necessary. 2) A cheap piston ring compressor can be had by using a hose clamp that has a wide enough band to cover the rings (or ya could stack two side by side to get it wide enough) but you must smooth the inside of the band to remove any sharp edges or burrs, or you will need to purchase or rent one that comes apart. It is possible to assemble the pistons part way into the cylinders with the piston pin hole still exposed and install the cylinder and piston as an assembly onto the rod. Ya just gotta be careful the piston doesn't slide out of the cylinder while you are doing it or it all has to come off again and start over. Doing it this way you don't need a ring compressor that comes apart. It is totally do-able, but you will probably have to do it a couple of times to develop your technique. The rest of the work is "nut and bolt" practice.
Be sure to align your intake manifold before you tighten down on the heads.
S&S makes good stuff. If you are flush enough to spring for their heads and/or cylinder/piston combinations, I am pretty sure you will not be disappointed.
Aside from any valve and cylinder machine work (if you are using your original heads and cylinders that do not come with matched pistons) there are two things to consider before you dive into this project: wrist pin bushings and a piston ring compressor. 1)The wrist pin bushings should be checked by a knowledgeable person ie. a machinist and be replaced and resized if necessary. 2) A cheap piston ring compressor can be had by using a hose clamp that has a wide enough band to cover the rings (or ya could stack two side by side to get it wide enough) but you must smooth the inside of the band to remove any sharp edges or burrs, or you will need to purchase or rent one that comes apart. It is possible to assemble the pistons part way into the cylinders with the piston pin hole still exposed and install the cylinder and piston as an assembly onto the rod. Ya just gotta be careful the piston doesn't slide out of the cylinder while you are doing it or it all has to come off again and start over. Doing it this way you don't need a ring compressor that comes apart. It is totally do-able, but you will probably have to do it a couple of times to develop your technique. The rest of the work is "nut and bolt" practice.
Be sure to align your intake manifold before you tighten down on the heads.
S&S makes good stuff. If you are flush enough to spring for their heads and/or cylinder/piston combinations, I am pretty sure you will not be disappointed.
Last edited by megawatt; Nov 23, 2008 at 01:44 PM.
Thread Starter
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Road Master
Joined: Mar 2006
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From: Snowflake, Arizona
Thanks Megawatt
No I am not flush, do you have any suggestions on options? For example, what would you do if not the S&S route.. The reason I was looking at that option was the piston are prefit for the cylinders and I thought it may be less than a machinist to hone a new set of cylinders to the new pistons. I have a ring compressor for small block chevy and mopar.... My concern is that it has been so many years since I have worked on any motors for anything, and the fact I have never never seen a top end job on a Harley...(monkey see monkey do)
Thanks
No I am not flush, do you have any suggestions on options? For example, what would you do if not the S&S route.. The reason I was looking at that option was the piston are prefit for the cylinders and I thought it may be less than a machinist to hone a new set of cylinders to the new pistons. I have a ring compressor for small block chevy and mopar.... My concern is that it has been so many years since I have worked on any motors for anything, and the fact I have never never seen a top end job on a Harley...(monkey see monkey do)
Thanks
Road Warrior
Joined: Dec 2007
Posts: 1,286
Likes: 64
From: SoCal
If your heads just need a valve job, just have that done. Does that little local shop you spoke of do machine work? You know that the shop should check 'em out good and let you know if they see anything wrong with them. The cylinders and pistons as a set are a good idea. I'm sorry but I haven't had to buy any cylinders for a Shovelhead for a long time so I'm in the same boat as you regarding where to get 'em. I'm sure you'll shop around and find the best deal. If your engine is basically stock, cast pistons are the cheapest and will do the job just fine. If it's hot-rodded (or you plan on heating it up someday), hypereutectic or forged would be the better choice. The bore is 3.498 inches on an 80 inch Shovelhead, does your ring compressor accommodate that size?
If you have successfully reassembled an internal combustion engine before, I imagine you will be just fine. Take your time, of course, and ask questions if something doesn't seem right to you. It ain't sorcery, just common sense and a shop manual.
I wish you good luck and hope ya have a good time to boot.
I was just thinking, if that local shop you spoke of does your machine work, they will probably help you with questions since they got some business from you. Ask 'em up front if they will help you since you want to learn this stuff.
If you have successfully reassembled an internal combustion engine before, I imagine you will be just fine. Take your time, of course, and ask questions if something doesn't seem right to you. It ain't sorcery, just common sense and a shop manual.
I wish you good luck and hope ya have a good time to boot.
I was just thinking, if that local shop you spoke of does your machine work, they will probably help you with questions since they got some business from you. Ask 'em up front if they will help you since you want to learn this stuff.
A simple question...Is the compression equal (within 10%) between the cylinders, 88 +/-. If so, there is probably no reason to take the motor down. If it's running good, your plugs show no oil fowling, and you aren't huffing smoke out the pipes, leave it alone. My .02
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Road Master
Joined: Mar 2006
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From: Snowflake, Arizona
Megawatt: Thanks for the input. No machine work local. 30 miles away is a good small block Chevy and Mopar machine shop, but he said he does not do enough Harleys to get good at it... I Just cranked the ring compressor..it works down to 3.25... Common sense and a shop manual... I hope I did not get disqualified on the common sense...too many basket cases in the country who like me thought they could do it....(LOL). Bee studying the manual... already have a few question... Thanks
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Road Master
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From: Snowflake, Arizona
Widowmaker: Thanks. Glad to hear that it is not so bad to work on...my courage is getting greater...when it comes time. Thanks again... for your thoughts and the reminder of what I need to be thinking about...
Hogback
Hogback
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Road Master
Joined: Mar 2006
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From: Snowflake, Arizona
sqdeal: Thanks. With what you said, along with the others...looks like I need to not do anything right now and just keep riding it, which is what I had hoped. Everything except compression looks good... maybe even that test was questionable. Thanks to all who took the time...again your thoughts and suggestioned are of great value fellas...
Hogback
Hogback
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