Big Bore Big Block Kit i just found on a new source!

CalsXS2

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Sorry guys. It's been a long time and I'm WAAAY out of the loop now. I'm going to have to relearn everything,,lol.

So I have a 76 engine in my 72. If I use a bbk can I still use my stock air box and side covers? Will this bbk turn this bike into a hard to tune monster?
 

BowlingSS

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Just rode my 81 with the BBK. Lot of torque. I rode my 73 which I just rebuilt the top end and then rode the 81. A big difference. Mine is still smoking a little. I knew I should have honed those cylinders. Anyone else having smoke problems? My other XS650’s I just rebuilt do not smoke at all.
 

WideAWAKE

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Sounds like he’s having smoke problems from the BBK.

what about the honed finish they had looked off to you??
 

GLJ

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Just rode my 81 with the BBK. Lot of torque. I rode my 73 which I just rebuilt the top end and then rode the 81. A big difference. Mine is still smoking a little. I knew I should have honed those cylinders. Anyone else having smoke problems? My other XS650’s I just rebuilt do not smoke at all.
Just curious. How are you breaking it in?
 

Paul Sutton

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How far did you ride the BBK Bike? Motor oil in the combustion chamber from installation takes quite some time to burn off, at least 20 miles. What is your running in procedure in terms of miles versus oil changes?
 

SomervilleXS650

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Anyone else having smoke problems? My other XS650’s I just rebuilt do not smoke at all.

+1 on smoke with my new BBK. On Saturday I started it to break in my new cam (spec sheet recommended first 15min of use to be above 2000 rpm) and to then adjust the idle. Thing was smoking like a bastard. Thing is I had also cleaned the motor up quite a bit when it was out and given it a rub down with ACF-50 to help keep the aluminum from oxidizing. This will also take some time to burn off. I also have new headers installed.

So truth be told, in very bad form, I have no ability to isolate variables and thus no idea where the smoke was coming from. What I can say is that after I rebuilt the motor last year I don't remember it smoking quite as much. So I'm a little relieved to hear that others are seeing it. And for what it's worth, it seems to have reduced quite a bit after running it for 20 min or so and a 2 minute spin around the block
 

WideAWAKE

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They do come delivered in quite a bit of (I’m guessing cosmline) grease that should be cleaned really well before install.
 

SomervilleXS650

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You recall what your ring gaps and side clearances were?
Piston skirt clearance?
I don't recall offhand Jim, but I know I checked them and they were within tolerances based on a 750 BBK spec sheet I had found in one of the old posts (the new BBKs from yamaha650.com didn't come with any install info/specs). I will need to check my service manual when I'm back with the bike, I think (hope) I recorded the actual values, but may not have if they were just within recommended tolerance

They do come delivered in quite a bit of (I’m guessing cosmline) grease that should be cleaned really well before install.

My guess is this is my problem. I'm a dope and didn't scrub it down before installing. Great example of how all the reading in the world doesn't help you not make boneheaded mistakes :doh: Why there are real pros and then the rest of us.

I should be clear....my smoking is primarily coming from the EXTERIOR of the motor. Ironically, now that I've burned out all the assembly lube my exhaust seems to look great. :laugh: :shrug:
 
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SomervilleXS650

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Yes big difference from smoke coming off the outside of a engine to smoke coming from the inside of it.

Ha, yes, agreed (I'm not a great mechanic but I at least know this). I was excited to see a similar report to what I had observed over the weekend so I think I glossed over the implied context of @BowlingSS's post being "interior" smoke, lol.
 
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