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  1. #1
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    Default Shovelhead Compression issues!!!!!!!!!

    Hello everyone, hoping someone can shed some light on the issues I've been having with my 74" shovel motor. Andrews BH cam, .020 over high comp pistons, super e carb, kick only. I just had the heads completely redone; seats re-cut, new valves, guides, seals, springs, collars...all brand new. Had the bike back together and was running very strong then suddenly one day i went to start it and it just kicked through the stroke with not much compression... then the compression would suddenly build just enough to start, then next day no compression again... besides a possible valve sticking open does anyone have any other ideas as to what this issue could be?? thanks in advance!

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    valve clearance needs re-setting probably,.... have you got solid or hydraulic Tappets ??

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    If solid tappets, re-lash them. I bet your gaskets have squished and your valves are being held a bit open.

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    At any time while you was riding it, did you feel a lost of power ...??

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    Quote Originally Posted by Dragstews View Post
    At any time while you was riding it, did you feel a lost of power ...??
    You beat me to it my friend....

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    I have Jims Hydraulic tappets in it and I've re set the pushrods several times (bring pushrod to no play but can still spin with fingers, then compress tappet 3 full turns down, let it bleed out, then onto the next one.) and no it never felt like it was loosing power, bike pulls pretty damn hard its a lot of fun.
    Last edited by Holyschmidt; 10-30-2018 at 5:48 PM.

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    Quote Originally Posted by Tattooo View Post
    You beat me to it my friend....
    Are you thinking what I'm thinking ... ??

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    Quote Originally Posted by Holyschmidt View Post
    I have Jims Hydraulic tappets in it and I've re set the pushrods several times (bring pushrod to no play but can still spin with fingers, then compress tappet 3 full turns down, let it bleed out, then onto the next one.) and no it never felt like it was loosing power, bike pulls pretty damn hard its a lot of fun.
    I say your valves are to tight...... 3 full turns are to much for me... That's a lot of flats......

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    Quote Originally Posted by Dragstews View Post
    Are you thinking what I'm thinking ... ??
    Yep I've seen it happen many times on new motors.....

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    He says it didn't bog down .... ??

    .../// http://www.jimsusa.com/pdf/instructi...ts/2275-IS.pdf \\\...

    Run though the valves again...
    Might want to do a leak-down test just for peace of mind...

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    Yeah That's a possibility, i was following that JIMS install sheet and my pushrods are standard harley with 32 TPI which calls for 18 wrench flats so that what i did, and they did bleed down properly in 10-15 minutes so i figured it was right...should I back each one off a turn and see what i get?

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    You could do that... You will still be in the hyd working zone of the lifter....

    What Tattoo and I concerns are all about is your motor is newly built.
    That first 50 miles has a super need to be babied, it can overheat, without you knowing, and suffer a seizer....
    Ring seal will be lost, not a good thing to happen ... Most of the time the bore will take a whooping and require to be bored to the next size up..

    Tis a grand Bummer to say the least.... Here's hoping that's not the case ...

    Last edited by Dragstews; 10-30-2018 at 7:30 PM.

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    I definitely rode it easy for probably the first 200 miles before i finally started to get on it. Ill loosen up the pushrods a bit and see if it helps otherwise....its almost winter in Minnesota so ill have plenty of time to take it all back apart and see what i got, thanks for the input everyone.

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    Just wondering what the compression reading is when you tried to start it with "not much compression", and a comparison after it was warmed up...be good to know to help diagnosis.

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    Definitely breakout the compression gauge

    And check the clutch, it may be slipping on you

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