Got the bottom end split. Anything is should look out for?

[yamabob83]

Guys/Gals,

The link above will take you to my problem. I have posted on here before about this same problem but have since replaced the cam guide which showed some wear into the aluminum. Didn't stop it! I have adjusted the cam tension replaced the cam bearings and still nothing. So now i have the engine completely torn down. As far as i can see i see no signs of heat or wear in the bottom end. Is there anything i can test to make sure the bearings are all still good and not making that noise? They all seem to be free. I have ordered the gaskets and stuff i need to put it back together but i wanted to pick your brains one last time. Oh also the oil pump has some grooves in the case part of the housing. It seemed like it was catching when i turned it by hand. I am going to replace the oil pump parts when i put it back together. I see a good bit of aluminum and steel shavings in the filters. Mostly aluminum though. When I tore the motor down for the second time i saw that the guide that i had just replaced was wearing again. Almost like the cam chain was off center. Lastly i have no electric start and have removed all the gears associated with it. Motor seems to run fine as you can tell from the video. If this doesn't work i'm gonna get a new motor i'm tired of dealing with it. Thanks for all the help!

Eric

 

[Purplezinger]

My very first 650 did the exact same thing. This was back in 1974. The higher the rev, the louder the whine. I changed oil, checked filters, everything I could think of. I talked to a mechanic at our Yamaha dealer. He had raced 650's for a couple of years. He told me one of my flywheels had twisted on it's pin.
He said the racing engines did that until they started welding the crank pins. When I split my crankcase, it popped apart as I removed the last bolts. We put the crank between centers in a lathe. Spinning it slowly, using a dial indicator, we found one flywheel was indeed out of true. Using a lead hammer we trued the wheel by knocking it back into place. When all 4 flywheels ran true. We tig welded all the pins. We did not replace any bearings. After reassembly the engine was quiet, no whine, and ran many years without fault until I sold it.
This may not be your problem but after watching the video it sure sounds like it. Anyone else is welcome to jump in here.

 

[yamabob83]

Wow sounds pretty crazy so what your saying is one of the flywheels was out of balance? Im assuming your talking the 4 disk looking deals that make up the crankshaft? Can i buy a new crankshaft assembly and swap them out? Or do i need to get mine looked at. Is it gonna cost more to get it fixed than to just find a new used motor? Is there a way for me to check this without putting it in a lathe and spinning it? Im about fed up with this thing and spring is here. Just exploring my options at this point.
Thanks

 

[yamabob83]

Will all year cranks drop into this motor? It is an 83 model.

 

[Purplezinger]

No, they not out of balance. They were out of alignment, i.e. not true to the center line. If you sighted a center line from one end of the crank to the other end, in my case one flywheel was slightly off that line. It had twisted, ever so slightly, at the connecting rod pin. At that time, I had a full blown industrial machine shop available to use. I worked with an old time machinist and that's how I repaired mine. I doubt this could be checked accurately enough without some type of precision measurement. As we welded each side of each flywheel, we checked the run-out before moving on to the next pin. This way when we finished all four flywheels were true to less than .001" Again, this may not be your problem but the sound in your video is the same. Talk to Hugh on this board, I know he does a lot of crank work and could maybe offer suggestions. There may be others as well.

 

[Purplezinger]

Trouble shooting an engine and in fact most things requires patience, persistence, observation, logic and education. Not necessarily in that order. It's my opinion that motorcycle engines are designed and built with a higher degree of sophistication and precision than other engines. It follows then that any maintenance, repairs and/or modifications should be at that same level. I've seen auto engines spread all over the floor, put back together and they ran just fine. Again this is just my opinion, but when motorcycle engines are rebuilt, it should in near "clean-room" conditions with "old-world" precision.

 

[yamabob83]

I get what your saying now. I'm by no means mechanically illiterate but i also don't rebuild many motors. I can get a crank assembly for a pretty decent price but need to know what year cranks will fit in this motor. Will a different crank cause any balance issues if i were to swap it out? Thanks

Eric

 

[Purplezinger]

I don't believe there are any balance issues, but early cranks don't swap with later cranks due to difference in connecting rod lengths. I really think any of the later cranks will interchange.

 

[XSLeo]

All the engines from 74 up use the same crank.

 

[xjwmx]

I'm glad to see this resurrected. I was talking to one of our pro mechanics down here with some experience with these and he said a couple xs650s have come in with a whine and it was due to a pit in a main bearing race. Mine has started doing it, but nowhere near as loud, and only until it's warmed up. He said the bearing whine was all the time, not just till it was warmed up. So....

 

[Ludlow]

I posted on a similar whine last summer. I thought it was the cam bearings. I also had a crack in my crank case, so I searched most of the winter for a deal on another pair of case halves. I finally found 'em and I'm reassembling now. I noticed one of the crank bearings isn't very smooth and when I spin it, it makes a little noise. After reading this post I think I'm going to rebearing everything while I'm here. Might as well since I've got all the gaskets and seals. Anybody got a line on cheap bearing sets that will last forever? While your at it, I could go for some frictionless motor oil.

 

[XSLeo]

I found some NOS bearings on Ebay about the same price as Mike's sells them. None cheaper. His bearingrs are probably as good as you will find.
You will spend Close to $400 for the crank bearings. If you put it new rod bearings you might as well put in new rods. Another $180 there.
I did all new bearings and rods on my 750 crank. Rebuilding wasn't too bad, truing is a bitch though.
Leo