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Engine knock driving me NUTS **HELP**

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Engine knock driving me NUTS **HELP**

PostAuthor: dsobieralski » Thu Jul 12, 2018 9:06 am

Greetings,

I want to thank everyone beforehand for their time in reading this and helping me to diagnose it.

Yesterday, I bought a 1982 Virago 750. It was in pretty sad shape and I didn't pay much for it ($300). The guy that I bought it off of told me that the motor spun freely, but that there were electronics issues preventing it from starting. I got it home and started to dig into it and this is what I found:

1) The engine was seized up (trying to bump the starter did nothing). I ended up taking out the plugs and putting some oil down into the cylinders and let it sit to lube everything up.

2) I checked the crankcase oil and it was bone dry. Not only was it bone dry but a bolt was missing from the center of the side case on the gearshift side and once I started to put oil in it, then it started to run out that hole. I found a replacement screw for it and got the oil up to level. No additional leaks.

3) I put the bike into gear (both the clutch and brake handles were broken off) and gently rocked it back and forth to free pistons inside the cylinders. There was a nice expulsion of oil out of the spark plug holes and the engine was free!

4) The starter button on the handlebars doesn't work. I took it apart and ran a meter off of it and I am only seeing .35V at the switch. All of the relays under the seat click when I turn the key on.

5) I checked for spark and I am getting spark on both cylinders

5) I jumped the starter and it sounds horrible (I hear this is common *can of rocks syndrome*) but the motor does spin freely; however, this is where my worries begin. There is a distinct knock or clicking sound coming from somewhere (I am not sure if it is the front jug, the back jug, or down below. It is a loud click/ping and almost sounds like a recoil (I don't know how else to explain it.) I took the starter off (because I thought maybe it was an extremely noisy starter). After the starter was removed, I put the bike up on the center stand and put it in 4th gear. I took out the spark plugs and rotated the tire (while in gear) and the clicking can definitely be heard. What is weird is that the clicking is very predictable. What I mean by that is if I spin the wheel and it clicks and I stop and then turn it backwards to that same point it will click again. I have read that sometimes the chain tensioners located somewhere behind the cam plate can go bad and allow slap it the chain which could be making this noise. It seems to be coming from both cylinders (or down below.. I honestly cannot tell). The engine still has decent compression, but the clicking sound almost sounds like a rod knocking, however, after watching some YouTube videos I am starting to think that it may be a good idea to check the tensioners and see if they are broke or if the chain is sloppy.

Does anyone else have anything else that I can check on my way to figuring out if I got hoodwinked on this purchase or not? Any help would be greatly appreciated. I am not a master mechanic or anything like that, but I know how to turn a wrench and I have worked on smaller bikes in my youth (and in my 20s I was partial to 80s Honda 750s) I have a tech manual for it, but before I start tearing into this motor (not really knowing what I am looking for) I was hoping to pick some of your brains so that I can try to be successful in fixing it.

If any of you would like to hear/see what is sounds like, then please let me know and I will snap a quick video of it (complete with audio) and upload it to YouTube and post a link.

dsobieralski
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Re: Engine knock driving me NUTS **HELP**

PostAuthor: mark75 » Thu Jul 12, 2018 3:00 pm

adjust the valve lash, then do a compression test, also a 'leak-down' if possible - that'll tell you the condition of your valves/rings

keep your battery fully charged,
mind the so-called "safety" switches,
make sure all your grounds [battery neg.] are all shiny & tight - the frame acts as ground point. handlebar switches ground thru it and the contact points can get gunked-up inside/under switch.

the "box-o-rocks" is part of the viragos charming vocalizations :naughty:
FWIW: the XV engine is normally kind of noisy.
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Re: Engine knock driving me NUTS **HELP**

PostAuthor: Flyingdog » Fri Jul 13, 2018 6:37 am

dsobieralski wrote:2) bolt was missing from the center of the side case on the gearshift side and once I started to put oil in it, then it started to run out that hole. I found a replacement screw for it and got the oil up to level. No additional leaks.


Are you talk'n bout #11?--> https://www.yamahapartshouse.com/oempar ... case-cover

If so, you could remove what ever you plugged the hole with and put a socket on the crank nut (within that hole for setting valves) and turn the engine. Was thinking, this may give you a better position to isolate the click. Rather than being at the rear wheel. A stethoscope would help out, too. Being in neutral..if the click is still present, least you can eliminate the output shaft back. If I'm understanding what you're trying to tracking down, correctly. (A click at the same point during engine revolution?)
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Re: Engine knock driving me NUTS **HELP**

PostAuthor: dsobieralski » Fri Jul 13, 2018 7:02 am

Actually the oil was coming from more like #3. The bottom of the case and center. The click is not present while in neutral. Only, when trying to turn the engine over. I am taking it to a retired MC tech and see what he can do with it if I can load it into the back of the truck today.

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Re: Engine knock driving me NUTS **HELP**

PostAuthor: Flyingdog » Fri Jul 13, 2018 7:24 am

Hmm..#3 is the oil level sight glass. But, if you're talk'n 'main' case bolts, it's a vertical gasket and a pita if it starts leak'n. Not impossible, but...pita. So...there's "no" tick turning the engine over while in neutral? Don't get it. Who knows, could have sat for years without oil and cam chain link rusted in some weird kink. Good luck track'n it down.
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Re: Engine knock driving me NUTS **HELP**

PostAuthor: dsobieralski » Sat Jul 14, 2018 7:26 am

Thanks and I will keep this updated in the hopes that it will help others.

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Re: Engine knock driving me NUTS **HELP**

PostAuthor: dsobieralski » Thu Jul 19, 2018 2:37 pm

Update:

I just got back from vacation in FL (which was nice BTW) and got the bike over to my retired tech. He is worried that the bike had skipped time and bent a valve and told me that these motors are "interference" motors and that if it skipped time due to a bad tensioner..etc that it very well could have bent a valve and that would require taking the head(s) off which would also require taking the engine out of the bike. Now, very bad news and I think my $300 purchase may just end up having to be split up into parts. He said that he will know more when he digs into it tomorrow, but I am not too hopeful.

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