This could be my dumbest question yet. Or not...

[drooker56]

There was a lot of work done to my bike before I got her. I never had a chance to ask the previous owner because he was in Iraq when I bought his house and the bike had been sitting in the yard under a shredded cover for at least 8 years. My question is: is there a way to tell if it has a big bore kit? I know these bikes are powerful/fast, but my god! I have never got the carbs tuned in perfect and she still nearly throws me off the back when I give it to her. I am just curious, a couple beers and i got to thinking...

[petejw]

Not a dumb question.
You cant really tell unless you remove the head and measure the bore size.
In theory you could fill a cylinder bore with fluid and measure the amount it takes to fill, but practically it would be hard to do accurately.

[Crazcnuk]

make yourself a fitting that you can screw into a sparkplug hole, and put a balloon on.

Spin the motor over by hand, on cylinder 1 from tdc to tdc on compression stroke.

Do this on yours and on a stock one, and see if the balloon blows upthe same amount.

[b.walker5]

No dumb questions, only answers..

There's no such thing as dumb question if you genuinely don't know the answer, there can, however, be a never ending supply of dumb answers to any question. Only way to tell with accuracy, as stated by petejw, is to measure bore and stroke. Also as stated by pete, in theory you could use a liquid but the method i would use for this would be (and here beginnith said dumb answer) to use a large syringe and inject a measured quantity of oil into the cylinder. Divide the suspected big bore size (1196cc I think but someone will correct if wrong) by 4. Fill a large syringe with 299cc of good quality engine oil and slowly inject into 1 cylinder at BDC. If it only takes 175cc or less then its standard, anything more than 175 then it's bored. If it takes the full 299 then its "big bored", if it wants more then theres a hole in the piston and your sump is getting full . Of course if you go down this road, then you've got the problem of getting the oil out again, which probably means you've got to take the head off anyways. If you're game enough to try it in the first place, you might get the oil out by turning the engine over and pumping it out the spark plug hole, but you'd want to be sure it was all out before you start it up, or you'll you have a fairly large bang from the hydraulic slug, and your sump will be getting full as above. We don't have a smilie for "tounge in cheek" but you get the idea.

[Cobia]

Possible dumb answer??

Rooker,
I believe the compression increases about 40psi, give or take 10psi, after an overbore job. Normally, your compression should be around 140psi, on the overbores it typically increases to around 180psi. You may want to take that into consideration before you go performing surgery to satisfy a curiosity. If it's blowing you off the back, it doesn't sound broke to me... If it ain't broke.....lol!!

[81xsproject]

This may seem a little simple, but don't the tops of BB-kit high comp pistons look quite a bit different tnad stock? With my buddies KZ, I was quite sure it had a BB-kit because of the way the top of the pistons looked throught the spark plug holes. That and it had about 170 psi on the compression tester. Obviously, we weren't SURE of that until the head came off. But, if you know what a set of standard pistons and a set of Wiesco pistons look like, you could probably tell.

On the flip side, that feeling that might just throw you off the back at WOT is a stock feature of the 11.

[trbig]

There's not enough height difference to see just by looking at the piston from inside the spark plug hole. The wiseco pistons are a touch taller domes than the 78-79 pistons, but are SHORTER domed than the 80 and up pistons.





I know the later stock pistons have a raised "3H5" on the top center of the pistons you could see through the spark plug hole, but unsure if the earlier ones have a "2H7" printed on them. Wiseco pistons have a serial number printed on top, that you may be able to see here...



...but I doubt you'd be able to see that number with much carbon on top of the piston. So if you see a 2H7 or a 3H5 if you have a later model motor in the bike, then it's stock. Something you COULD look for though.. is this is a 78-79 piston on the right versus a later model one on the left. Both the Wiseco and later model pistons have a noticeable deeper valve relief cut into the piston top.




A Wiseco piston height falls in between these two piston heights.


Tod

[bikerphil]

I know the later stock pistons have a raised "3H5" on the top center of the pistons you could see through the spark plug hole, but unsure if the earlier ones have a "2H7" printed on them.

No number (2H7) on top of the 78-79 pistons, just the forward arrow.

[bigray03]

I beg to differ with you

There's no such thing as dumb question if you genuinely don't know the answer, there can, however, be a never ending supply of dumb answers to any question. Only way to tell with accuracy, as stated by petejw, is to measure bore and stroke. Also as stated by pete, in theory you could use a liquid but the method i would use for this would be (and here beginnith said dumb answer) to use a large syringe and inject a measured quantity of oil into the cylinder. Divide the suspected big bore size (1196cc I think but someone will correct if wrong) by 4. Fill a large syringe with 299cc of good quality engine oil and slowly inject into 1 cylinder at BDC. If it only takes 175cc or less then its standard, anything more than 175 then it's bored. If it takes the full 299 then its "big bored", if it wants more then theres a hole in the piston and your sump is getting full . Of course if you go down this road, then you've got the problem of getting the oil out again, which probably means you've got to take the head off anyways. If you're game enough to try it in the first place, you might get the oil out by turning the engine over and pumping it out the spark plug hole, but you'd want to be sure it was all out before you start it up, or you'll you have a fairly large bang from the hydraulic slug, and your sump will be getting full as above. We don't have a smilie for "tounge in cheek" but you get the idea.

This question was not a dumb one at all, by no means. Just a good one. But boy'o'boy have I read some really, really dumb ones here. Say what you want but jeezy!!! I to have always been a huge fan of "THE ONLY STUPID QUESTION IS THE ONE NOT ASKED". Not so much anymore. I encounter very, very, very dumb sh*t every day from very very very dumb people, with very very very dumb questions, that come from very very very dumb minds. I am amazed on a daily basis with many people I encounter who just have not the slightest bit of anything to offer the world and have to be taken by the hand for EVERYTHING. Those are usually the ones where the dumb questions fall out of there mouth.

But your question, not dumb at all.

[b.walker5]

This question was not a dumb one at all, by no means. Just a good one. But boy'o'boy have I read some really, really dumb ones here. Say what you want but jeezy!!! I to have always been a huge fan of "THE ONLY STUPID QUESTION IS THE ONE NOT ASKED". Not so much anymore. I encounter very, very, very dumb sh*t every day from very very very dumb people, with very very very dumb questions, that come from very very very dumb minds. I am amazed on a daily basis with many people I encounter who just have not the slightest bit of anything to offer the world and have to be taken by the hand for EVERYTHING. Those are usually the ones where the dumb questions fall out of there mouth.

But your question, not dumb at all.

Okay.......???? I didn't ask a question....

[psycoreefer]

Hey, I'm in GR but you already knew that. If your interested in the fuse block replacement I just did it on my bike and your welcome to come and take a look in person, or if you need to look at an assembled bike or need a hand I'll work for a sandwich and a couple of beers. Good luck!