problem with crankcase cracks

[addison]

Hi all , i have just recently join your forum hoping you could help me track a whirling noise i have been hearing from the motor on my 72.... unfortunately i have ( i think ) found a bigger problem.Let me give you some background , I brought the bike out of storage last summer and started playing around with it in my spare time ( I wanted to make it in to a cafe ) it had been in storage for 15 years. Once it was running again it started making this whirling sound ( very simular to the sound identified as the #4 starter gear on a you tube video i had found ) but that apparently was not the problem as the whirling still persisted after i removed the # 4 and releated and bump started it. Right now I am more concerned with the cracks i am seeing on the crankcase just below the cylinder block. Both sides have them , can anyone give me advise ? What would cause them , do i need a new motor ? if it is fixable what would be involved ? . I farm just outside Calgary Alberta Canada so i am going to get real busy soon so if i am going to ride this season i will have to make a decision quick. Thanks for your help , and by the way this forum has been helpful to me already . peace
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[dwyatt]

Those might just be casting flaws. They are known for crappy casting on the motor parts. Probably the only way to know for sure it to tear down the motor and see if they go through. I don't see any oil leaking, maybe you'll be lucky here?

 

[danno]

I also think they may be casting imperfections. Several of my XS 650s look the same as the pictures of your 72.

 

[tx650]

I'd agree with the above as I had the same on mine.
You might be able to polish them out,just depends on how enthusiastic you are.
As for the whirring sound,well I personally wouldn't ride it unless I had it sussed out.
It could be any number of things so maybe the best way to go is the "Elimination process" Good luck....

 

[Pierrax]

See bellow what I found on my engine.
I removed those flaws and polished before they go in the engine.

 

[gggGary]

+whatever on so so casting clean up by Yamaha all those decades ago. Corrosion just highlighted what was always there, no worries, run that puppy like you stole it.

 

[addison]

Thanks for the help guys , I was really expecting that it was the end of the road for the old girl.
It is possible that they have been there and never noticed , I will continue to try to find the source of the
noise before i get serious about the cafe project. Has anyone come across a audio clip of bad cam chain damper or cam chain related noises ? I have noted some talking about plastic bits in the oil , unfortunately when i changed the oil out i wasn't looking for plastic. Does the damper have plastic on it ?? I think that would be the next place to look, unless anyone has a better start point.
Thanks again
Peace

 

[retiredgentleman]

Addison;
I agree with the others here..................those are just left over from the casting process.

As for noise ..................these engines are noisey compared to modern engines. Set your valve clearances with the engine cold. Adjust your camchain tensioner with the engine hot. Tune up the carbs and drive the bike this summer, and just monitor how it runs. The front camchain guide commonly comes apart (sometimes as black plastic pieces in the oil sump). The plastic part separates from the aluminum backing.

If the engine has lots of kms on it and has never been apart (hard to believe for a 72), then it needs to come apart for parts replacement, valve seal replacement, valve regrinding, probably new rings etc. What are the compression numbers?

Or, you can just ride it and fix things as they break.

There are a few XS650s here in Calgary (I live in the Tuscany sub-division). I have a 78SE. My friend Nima has an 80SG. Norm from Airdrie has a 79SF. How far out of Calgary are you?

 

[Sundie]

I vote just change the oil regularly and keep checking for bits. IN my experience, you'll find huge bits of engine before there's an noticeable problem. The engines are tough, and severely overbuilt. If you can actually blow up a stock one (not avoiding maint) i'd be very impressed.

 

[addison]

Hey Guys , You were right about the crack's, I used a fine file to see if I could get one to disappear and it was gone in a few strokes. Thanks again for the info.Regarding the noise ... I will go through the " engine tune up"in the front of the manual perhaps i missed something when i did it last season.If nothing changes I will just have to ride and monitor it.I am not the best mechanic so sometimes it needs to be good and broken before i find it.lol.
If i can get a audio clip of the noise i will post it, one more question ... while i had my clutch out last week i noticed my decompression lever ( at the head ) moving when i rotated the motor with a ratchet
( I was hoping i would be able the hear or feel something ). Does that seem right ? I dont know exactly how the decompression works.
Thanks
" retiredgentleman " It's good to know there is more xs riders in calgary , I live 1/2 mile off the #1 going east about 1 mile east of the langdon turn off near the scales.
peace

 

[tx650]

I'd be putting my money on the cam chain/tensioner
Not too hard to fix
From memory I think the decompression lever opened the right exhaust valve to allow the starter motor to spin faster without the resistance.
Owners of the mighty xs1 would notice that the sump would hold half a litre of extra oil as there was no electric starter.
The mighty Yamaha 650 the older it looks the better it looks.

 

[inxs]

- decompression lever should be adjusted so that there is minimal free play at the decomp lever with the cylinder at TDC...the mechanism depresses the rh exhaust valve by acting on a tab on the tappet

 

[retiredgentleman]

Addison;
Sounds like you're not too far outside Calgary. There's a motorcycle night every Thursday evening at the A&W at corner of 16 Ave and 4th Street. It will get going when the weather gets warmer..............maybe late April...........May for sure. Usually lots of older bikes and some new ones as well. I try to go when I can. Get your bike going and drive it down to the A&W