siezed AV7 BOTTOM end why?

i was breaking in my new moby project yesterday and its running great. 20 miles of breakin, jetted rich, plenty of oil, really breaking in nicely. i pull over to tighten my novi nut and when i go to restart, no go. i turn the engine by hand and feel huge resistance, squeaks, snags, etc. I figure "nice one steve, you siezed another".

i wheel it home, drop the engine, tear it apart and prepare for carnage. To my suprise, the cylinder, piston, and rings are all pristine (i guess thats a plus). I thought i had fucked my port job up or something, and snagged a ring. but instead my crankshaft is wicked tight in there. it will turn, but with huge resistance... feels like itd feel if you left it in the rain for 3 years or so and just let it rust.

i really just wanna know what gives. im happy that my top end is ok, and im going to get a whole new bottom end setup but why did this happen in the first place? Ive built about a baker's dozen AV7s at this point, so i wouldnt immediately attribute it to build problems. i just want to know why this happened, what usually causes bottom end siezure, and how to prevent it... that way this doesnt happen again! thanks for reading.

Re: siezed AV7 BOTTOM end why?

have you had the flywheel off? it sounds like maybe a stator coil came loose and is dragging on your flywheel. (I'm trying to be optimistic)

Re: siezed AV7 BOTTOM end why?

haha well i appreciate the happy thoughts but yea, the flywheel is off. everything under the flywheel is good to go, dont even think the timing slipped.

seems to me like straight up bearing failure, i just dont know why. the bottom end had been used previously, but maybe 300 miles on it? thats not too shabby at all in my book

Re: siezed AV7 BOTTOM end why?

The Human Beans /

happend to the beans 2 times.

we attribuited to low oil mixture. and small oiling holes that go to the main bearings. and those added rpms and heat of course

Re: siezed AV7 BOTTOM end why?

my low mileage stock av7 crank failed recently. the big end con rod bearing for some reason got too tight. i got it out before it seized, but it was definitely more stuck than it should have been. maybe the same happened to you? in any event, that sucks.

Re: siezed AV7 BOTTOM end why?

My big end connecting rod failed recently too.

Maybe they catch some sort of crank flu?

Steve did the crank bearings sieze or did the con rod bearing sieze? Is anything blue from heat?

Re: siezed AV7 BOTTOM end why?

feels like the crank bearings. but the con rod doesnt seem to smooth either. i really havent looked into it at all, was so pumped my top end wasnt siezed i just ordered a new bottom end and figured i'll get to it later.

Re: siezed AV7 BOTTOM end why?

fishsticks /

good thinking steve! what i would have done/need to do. could it possibly be over-tightening of the case halves? Too much pressure on the bearings. Its all still a mystery to my why somethings never work.

Re: siezed AV7 BOTTOM end why?

it might be... ive done a bunch of av7 builds though, some for customers and i've never had this happen. im just pleased that the cases are coming with bearings and seals installed from the factory, so they will be flawless. ive been wanting to do this for a while i guess this is a good excuse.

ill let you know what i figure out, if i figure out anything.

Re: siezed AV7 BOTTOM end why?

ordering new bottom end now... dunno if anyone shops from FFreddie and Ed at all (i believe theyre in cahoots) but im getting set up with cases, cranks, seals, bearings, con rod roller bearing, wrist pin clips, and a full gasket set for $87.95. ummm crazy good prices? yea i think so. figured id give em a plug

Re: siezed AV7 BOTTOM end why?

who is this ffreddie and what is his shop?

Re: siezed AV7 BOTTOM end why?

dunno what his shop is, but he's on the forums. has all sorts of nice av7 and av10 things, including aftermarket 50cc top ends. i think he has a biturbo av7 top end.... innnnteresting.

Re: siezed AV7 BOTTOM end why?

Ok so I had the same thing happen. Keep in mind that the stocker cranks actually have no bearing in the big end; they are a bushing. 30 years + some dirt + high rpms = poop crank

It happens. Fortunately there are lots of cheap stock replacements floating around and some SICK doppler and malossi bits as well. Get a doppler and never look back.

Also Steve, do you frequently refer to youself as "steve" in your head when you think? Just wondering..

Best of luck man!

Re: siezed AV7 BOTTOM end why?

the crank I sent has bearings in it... keep the prices close to home please

fred

Re: siezed AV7 BOTTOM end why?

Freddie, is this in response to my post?

Re: siezed AV7 BOTTOM end why?

sorry fred... do you have a shop or webshop or anything where the prices are clearly listed?

ooh yea ok thats fair. i guess i mustve let something get in there... i thought i was pretty surgical about the whole operation but i guess there's room for improvement. thanks for the tip.

well usually i call myself Steve, and its generally preceded by "nice one..." or "smooth move..."

Re: siezed AV7 BOTTOM end why?

no big deal..and its not for carpy. just prices varry depending on how well I buy. so I like to keep it quiet

fred

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