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  1. #1

    Default Compression issues. Engine seizure. Possibilities

    I was riding my 72 shovel back from Kernville CA Friday night when my bike turned off on the highway. The engine was smoking. I feared lack of oil due to a tiny pin hole leak, but my oil levels were normal. I let the bike cool a little.. I gave it a kick and compression was really high that I could barely kick it. After 2 kicks the pedal locked in places. I assumed the engine seized.
    I pushed it off the highway. 25 min later from when the bike shut off.. I gave it another kick.. and it was able to kick through. But there was no compression at all. Took a spark plug out of the front cylinder and there was a tiny bit of compression, but not enough to pop my thumb out. No compression at all in the real cylinder. Pistons are coming up and down. I checked my pushrods and they are all good and spinning at their lowest point. What can be reason for lack of compression?

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    Fuel issues, timing-ignition issues or a air leak or gasket failure was the cause, one, 2 or all 3 at once.
    Rings are gone, pistons will be badly scuffed, you COULD have holed a piston but I doubt it. Question is about the cyls, are they too badly scored?

    Very possible you also cooked the valves and they are not seating.

    There is something many call a "Soft Seize" and a experienced rider can feel it. The motor bogs down, loses power, you can just tell, This is not too painless.

    You had a hard seize, not the end of the world and many do worse, like STUCK! (Ive melted out frozen pistons with Acid, a bit tricky, but dissolves the aluminum to the point you can remove the cyl, but can kill your cases if not careful.)

    None of this matters. Bottom line is you should carefully tear it down. Engine experts say smart people carefully tear down a motor, Smart folks can look, measure and feel where there was problems so you can address them. -->Forensic analysis. You will learn a lot, and idiots keep repeating never learning why, so dont be an idiot. You can post pix and many people can give advice or help you interpret.

    I had several customers buy a badly built bike and it blew up or seized right after buying it. Used to be so predicatable with Iron head sporties we made bets on how long before a bike had issues.

    "Oh you bought an Iron head? Let me get my calendar, I want to get in on this!"

    But had it happen with British bikes too, unscrupulous mouth breathing knuckled draggers cobble together mismatched parts, worn out parts and their tool kit consists of a crescent wrench, vice grips and a hammer. Their idea of measuring is a tape measure. Slap it together and sell it to some rube.

    I hope that was not the case with your bike, but opening up an engine someone else built can the "Little shop of Horrors".

    But even exspurts make mistakes. Some is obscure tech details, for example on Nortons there was a whole series of pistons and rings that the average person will assume will work, but wont interchange. They changed the ring widths and depths a few times and hard to match up the right rings. Many people make that mistake, but there is others too. Some rings are meant for a specific cyl finish and break in. (Cast, Chrome or other materials) Some parts are defective or out of tolerance new out of the box. Old tech data is no longer relevant. For example many British bikes spec 3 thou wall gap for the rings, you cant run them that tight now.

    Investigate, take your time, measure, ask questions or get a guru on hand. Best of luck, sounds fixable!

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    ^PLUS 1 on the above ^

    Forensic mechanics, gotta love it.
    I learned that from reading Grumpy Jenkins' book on racing the small block Chevy. He was big on measuring everything on tear-down and comparing to fresh.

    One note on the '72 FL: the oiling system is the old style (the last year of it in fact) and I have seen several where the switch to a newer style oil pump was botched. Sometimes you won't know it until just such a scenario as yours. So, that needs to be explored during tear down.

    Jim

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    Might be a sheared oil pump key or similar. Teardown should reveal the cause and will be required to repair the damage. Post lots of clear, well lit photos of the whole sequence (good for your own reference too) and ask any question you're curious about. Have the factory service manual and parts catalog at hand (electronic copies are on the Carl Salter site etc).

    It's smart to break the compensator nut loose before pulling the top end. That way you'll have it easier when you pull the short block instead of dealing with connecting rods flapping about.

    A complete teardown and completely flushing (pull the oil tank, throw away the hoses, etc) the lubrication system is of course required so the pile of cash you're about to spend doesn't become two piles of cash. This could be a convenient time for a mild stroker kit.

    Make a spreadsheet with parts prices and labor estimates BEFORE you spend ANY money,
    and remember freight is cheap so if it looks wise to send off the work to a Shovelhead expert do that. Compared to everything else freight cost won't even be background noise and you won't need to ship any bad parts. There are good and bad ways to pack heads and cases for shipping. Ask questions before spending money. because assumption is the mother of all fuckups.

  5. #5

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    Dough, what are the causes of a soft seize? The way you described it feel like what I went through. Bike never locked up while stoping, but I did have my clutches pulled in until I made a complete stop. Didnít want to risk my chain breaking since I was shifting down but still had some speed.

    Iíve owned this shovel for about a year now. It has ran great all year and has never had any engine issues. The previous owner is a good friend of mine that put it together and has ripped this all around the states. Best Shovelhead

    Thank you for the wise advise! I will definitely break down carefully and upload clear pictures for advise!


    Quote Originally Posted by Dougtheinternetannoyance123 View Post
    Fuel issues, timing-ignition issues or a air leak or gasket failure was the cause, one, 2 or all 3 at once.
    Rings are gone, pistons will be badly scuffed, you COULD have holed a piston but I doubt it. Question is about the cyls, are they too badly scored?

    Very possible you also cooked the valves and they are not seating.

    There is something many call a "Soft Seize" and a experienced rider can feel it. The motor bogs down, loses power, you can just tell, This is not too painless.

    You had a hard seize, not the end of the world and many do worse, like STUCK! (Ive melted out frozen pistons with Acid, a bit tricky, but dissolves the aluminum to the point you can remove the cyl, but can kill your cases if not careful.)

    None of this matters. Bottom line is you should carefully tear it down. Engine experts say smart people carefully tear down a motor, Smart folks can look, measure and feel where there was problems so you can address them. -->Forensic analysis. You will learn a lot, and idiots keep repeating never learning why, so dont be an idiot. You can post pix and many people can give advice or help you interpret.

    I had several customers buy a badly built bike and it blew up or seized right after buying it. Used to be so predicatable with Iron head sporties we made bets on how long before a bike had issues.

    "Oh you bought an Iron head? Let me get my calendar, I want to get in on this!"

    But had it happen with British bikes too, unscrupulous mouth breathing knuckled draggers cobble together mismatched parts, worn out parts and their tool kit consists of a crescent wrench, vice grips and a hammer. Their idea of measuring is a tape measure. Slap it together and sell it to some rube.

    I hope that was not the case with your bike, but opening up an engine someone else built can the "Little shop of Horrors".

    But even exspurts make mistakes. Some is obscure tech details, for example on Nortons there was a whole series of pistons and rings that the average person will assume will work, but wont interchange. They changed the ring widths and depths a few times and hard to match up the right rings. Many people make that mistake, but there is others too. Some rings are meant for a specific cyl finish and break in. (Cast, Chrome or other materials) Some parts are defective or out of tolerance new out of the box. Old tech data is no longer relevant. For example many British bikes spec 3 thou wall gap for the rings, you cant run them that tight now.

    Investigate, take your time, measure, ask questions or get a guru on hand. Best of luck, sounds fixable!

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    [QUOTE=Shittits69;848151]Dough, what are the causes of a soft seize? The way you described it feel like what I went through. Bike never locked up while stoping, but I did have my clutches pulled in until I made a complete stop. Didn’t want to risk my chain breaking since I was shifting down but still had some speed.

    /QUOTE]

    There was some typos, was taking a break from weed-wacking and banged that out.
    But the causes would one or all of the 3 things I mentioned. -OR- it could the oil issue, but assuming its not based on what you described.

    So, Timing, either it moved, or you got some shitty gas and didnt hear it pinging and overheating. So the other is altitude,, what the fuel and timing does at Sea level gets inadequate when going over a Mtn Pass. Or you got a head gasket leak, intake leak? An Air leak will totally cook your engine,., Its like putting a welding torch against your motor. All that air-Oxygen will totally lean it out.

    ** I have had 2 shop customers who told me that (not my work) were riding their bikes (Different times, different people and 2 were Triunphs, one was Norton) But they had not been checking them and tightening or adjusting parts.
    So, ridden hard, put away wet. Anyrate, all 3 were motoring along and the cyls got loose, and looser loooser and then really loose. The base nuts unscrewed and fell off. The cyls were banging around loose. Was ugly! 1 sent for a truck the other 2 sent a friend to a local bike shop and they did a top end rebuild on the side of the road with new gaskets, nuts and hardware and new rings.

    Anyway, I have had people on break in not reset the valves and retorque parts periodically so things did come loose. Could you have developed an intake leak? Head gasket leak? Either one will seize up a motor quick.

    Fuel could be related or carb issues. Too many variables there, but we live in times of shitty gas. Besides clogging up because of added alcohol, many times theres other fuel issues. But a leaned out carb will smoke a top end.

    As to what it feels like you are doing about 50 down a street and then suddenly you can hear the engine change tone,, its hard to describe but each fire off should sound solid. A overly reach engine sounds "muddled" Lean tends to not be distinctive unless its knocking or pinging. But you can FEEL it! When it starts seizing it feels like you are riding thru mud. Bike feels bogged down.

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    I am an idiot and know nothing but you said your kicker pedal was stuck at one point. that happened to me once and i opened her up and ended up rebuilding the whole tranny. dont want to overlook that one either since a stuck pedal can mean the kicker gear stop is going by the board, and when that happens i have heard from others vastly more experienced than i, that your pedal can become a windmill at highway speeds... scary!

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