Question about Big Bore kits.

[Crazy Damian]

When I got my 1979 xs1100sf, i was told about it from the previous owner, he had sold it to a friend, he also informed me that it had been bored over by the PO to him, that person I'm sad to say has gone to cruise with the lord.
So my question is this, is there a way to tell what it has been bored to without taking the motor apart and measuring the pistons.
Also, when these were bored, what was the standard sizes for bore kits at the time?
He claims it was bored to 1300cc, but that sounds a little high to me.


Damian

[natemoen]

1300 is near imposible without MAJOR redoing of about everything and custom made pistons.

1179 and 1196 are the two available big bore kits.

[BA80]

I have heard of these being bored to 13 but it requires a lot of expensive machine work and parts.

The largest these can be oversized to with stock jugs is 1196 the next step down is 1179. I believe the 1196 is 3mm over stock, not sure what the 1179 is.

[Crazy Damian]

not worth it

1300 is near imposible without MAJOR redoing of about everything and custom made pistons.

1179 and 1196 are the two available big bore kits.

sounds like almost not worth the trouble to go from 1100 to 1179 or even 1196.

[crazy steve]

sounds like almost not worth the trouble to go from 1100 to 1179 or even 1196.

If you're looking for a big power increase, it's not....

[Rasputin]

So does anyone have a correct reply for this question? I know I am interested because I have a bike that is reported to have a big bore kit in it and I would love to know before I start work on it. I have no answer for it but many members may have experience with this issue that can pipe in.

[crazy steve]

So does anyone have a correct reply for this question? I know I am interested because I have a bike that is reported to have a big bore kit in it and I would love to know before I start work on it. I have no answer for it but many members may have experience with this issue that can pipe in.

Well, not exactly 'the' answer, but I can relay a method used by HD owners to tell if a bike has been bored... I'm not sure this will work here as the bore size increase isn't that much, but it might...

On a known stock-bore motor, pull number 1 or 4 spark plug. Turn the crank until you're at BDC (bottom dead center), or 180 degrees from TDC. Stick a long, thin rod in through the plug hole and move it around until you've got the maximum length in the bore as measured to the top of the plug hole. Note this amount. Repeat this in your 'bored' motor; you should get a longer length if it's bored.

The Harley guys know which lengths corrospond to which bore sizes, but you're talking overbores of up to 13/16" on those so it's not hard to tell. A 3mm difference may not be enough to get an accurate measurement.

[TomB]

To check cylinder size without strip down....

Remove spark plug.
Wind to TDC.
Fill cylinder full to plug hole with thin oil.
Wind to BDC.
Using a full 1/2 Litre measuring jug of same oil, fill cylinder to plug hole again.
Subtract the amount of oil left in jug from 500cc (1/2L) to reveal cylinder size.

And multiply by 4 to get engine capacity (but I didn't need to say that did I LOL )

Tom




.

[GLoweVA]

Tom, I agree with the theory of your test, but wouldn't 'thin' oil run past the piston rings and 'leak by' thus throwing the reading off.
Wouldn't a heavier oil, like 20/50 work better and at the same time if any is left over, it's the same as the regular engine oil, so no harm done.
So, something like 300cc of oil would be ballpark.

Then the next question is how to get the oil out?
Turkey baster, miti-vac, shop vac?

[daveyg]

With the plug still out turn crank by hand one revolution.90% of oil should run out. Then crank with starter a couple revs, and the rest should blow out. Now reinstall plug.

[GLoweVA]

Daveyg, are you trying to be funny?
That would make a huge mess!
But it sure would look cool!

[Mathh]

I have heard of these being bored to 13 but it requires a lot of expensive machine work and parts.

The largest these can be oversized to with stock jugs is 1196 the next step down is 1179. I believe the 1196 is 3mm over stock, not sure what the 1179 is.

RC engineering made 1220cc big bore kits in those days ...

[daveyg]

Daveyg, are you trying to be funny?
That would make a huge mess!
But it sure would look cool!

Well u would want a big drain pan under the bike, and a rag or plastic draped over the head for the starter turnover, and once u reinstall the plug u might want to pressure wash the bike... u asked how to get the oil out... I told u how to get it out. Just trying to keep it simple.

[TomB]

Tom, I agree with the theory of your test, but wouldn't 'thin' oil run past the piston rings and 'leak by' thus throwing the reading off.
Wouldn't a heavier oil, like 20/50 work better and at the same time if any is left over, it's the same as the regular engine oil, so no harm done.
So, something like 300cc of oil would be ballpark.

Then the next question is how to get the oil out?
Turkey baster, miti-vac, shop vac?

Yep you're right thicker oil would be less likely to run past the rings but if you get a move on it ain't an issue, thinner oil is used coz its easier to read the measuring jug than 20W/50. And if your thin oil pours past your rings I think you have bigger questions to ask than how big is my cylinder


And getting the oil out? I was gonna say ....Starter motor and duck

But seriously, I use a big medical syringe with a 6" piece of plastic pipe attached to suck the oil out.

Also, if you like you could drop some thicker oil onto the piston, just enough to seal the piston bore gap, then use water, a bit of the oil would float on the water but the surface tension of the water and the oily piston would hold the water above the piston, and its easier/cleaner to get out ......starter motor!!!



.

[BA80]

Face it boys, the only way to really tell is pull the jugs and measure.