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Oh jeeze, did this motor just go belly up?

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I need some help fellas! I bought an old 83 Honda cr80r last week, Only ever heard it ran for a couple of seconds when gas/mix was poured directly into the intake.. Sounded great so I bought it. I got home, did the same thing, started right up first kick. So yesterday I had a day off from work and planned to get some work done on the bike, Cleaned the carb, put in a new carb gasket I had from my old ATV, drained the crankcase oil (which turned out to be trans fluid) and put new oil in 10w40 motorcycle oil, cleaned the air filter, cleaned the bike up a bit.

I put a little gas directly into the intake to help prime the carb, kicked it over and she fired right up... sounded great for about 15-20 seconds, I gave it a couple of short revs and sounded great, then CLANK CLANK CLANK CLANK (you get the idea) So I shut it right off... Took out the plug and used my hand to kick the kick start over slowly, I can't hear anything clanking, but it's definetly very loud when running, it increased with RPMs and sounded like I had rocks floating banging around the motor.

What did I break and how did it happen? Bike sounded fine, I didn't even get a chance to rev it high or warm it up! The bike was sitting for about a year the previous owner said also said the top end on this is new, weisco bored .010 over. I'm very afraid here, I thought I found a good bike.... I'd hate to see this thing get parted out or sit. I planned to let my nephew ride it tomorrow for Thanksgiving while I followed him on my ATV... I guess that plan is done!

I contacted the previous owner and he said everything was fine when he rebuilt it, and it did sound fine, for half a minute! He said to check the wristpin bearing but I know nothing about dirtbike engine internals. and why would it start up and run fine then go bad without any riding or high reving

Please help me trouble shoot

-Mike

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I'd post a video of what it sounds like but I'm to afraid to start it up again and risk further damage.

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Unfortunately, it's going to need to be tore down one way or another. You'll have to take it apart to fix it, so you might as well tear it apart and have a look now. A lot of folks do that when they buy a used bike anyway--you can never take someone's words about the condition of a used engine unless you can afford a worst case breakdown.

If you've never taken a 2-stroke engine apart, I'd try to find someone who has to help you and walk you through it. They're not complicated, but an experienced helper is always a good idea.

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Thanks for the replies. I was really hoping not to hear crank bearings in this thread haha anyway to confirm this before splitting the case? I was hoping it would just be wristpin bearing is there any way to check if it's the wrist pin or bearing causing the noise ? I eventually will redo the bottom end but rather not right now. Is there a way to narrow down the diagnostics with just the top end off?

Also when top end is removed do you need to re-ring? the rings are newer .

thanks

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Also, looked online for a bottom end kit can only find 1986+ can anyone link me to a basic kit?

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Yes, you ought to be able to make a good diagnosis by just removing the top end. With the cylinder off, it's pretty easy to see if, and what bearing is giving you problems. You might not have to split the cases if you're lucky.

Measure the ring end gap when you have it taken apart. If the ring is not worn out, then use it again, no problem.

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sound's to me to be mor elikely a crank bearing it would amke more sense

if what the owner has told you is true about the rebuild you will find he only rebuilt the top end and probly did not even check the bottom end

so i dont think the owner has bullshitted you mojority of the time they are telling the truth but there are a few bad egg's

im thinking he has just neglected the bottom end alot of ppl do just put new pistons and rings in with out checking it

and i honestly believe the bike siting for taht long would have caused it to let go so quick as there would have been no oil siting in the bearing's and was probly already on it way to floging out

its a catch 22 with 2nd hand bikes sometimes you get the deal of a life time other time's you get shit and got to throw more money into it

ether way tear it down mate get your self a manual if no one else can help you

and i would try and go to the dealership and just get a oem crank if they dont have them anymore im sure they would know where you could get a crank

and try not to cheap out

while you got the case's apart replace everything you can will save you head ache's later

if you can do a complete rebuild for peace of mind , dont stress about the gearbox to much just replace the bearing's the rest should be fine that take a flogging them box's and live a very long time

normaly its just bearing's what let go

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You just need a manual and an hour to pull the jug. We're all just guessing. Crank bearings, wrist pin bearing, wrist pin cir clip missing, spun piston ring catching port, etc..you can fix this but you may have a little trouble finding parts for an 83 . Pull the flywheel cover and rock the flywheel up and down by hand to check for left side bearing failure. It would have to be very bad to notice any movement. Once the jug is off you can check the rod big end bearing for movement, should not have any up and down slop,some side play is ok.what was the oil and mix ratio?

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