do I have a big bore in my motor

[racer1150]

So I picked up a 1982 Gs1100e today. The guy I got it from thought it was a KZ and doesnt know anything about it just that his buddy left it there a long time ago. I know its a gs1100e since I used to have one. Anyhow it looks all hopped up. Is there a way to know if it may have a big bore kit other than pulling the pistons out?

 

[Flyboy]

When you say, hopped up, how exactly, just cosmetics, or obvious go fast parts, such as oil coolers, smoothbore carbs, etc?
Back to the question, the only definitive way to tell is to pull the head and Mic the bore, then you know for sure what you have got.
But there are a few things you can do to give you a rough idea before tearing the motor down.
Firstly, we need to understand, off the shelf big bore kits are exactly that big "bore", the stroke, which is a function of crankshaft journal throw remains the same, to stroke the motor, the crank would need to be changed.
So we now have a given that we can work with, the stroke, go look it up in the workshop manual, the bore will be the variable, make a note of the standard bore too.

Ususally a big bore kit, not only increases the bore, but also the compression ratio, to give extr grunt, so a good place to start is a simple compression test, if you get crazy high numbers, good chance the compression ratio has been bumped up.
That may or may not be due to big bore pots, though.
Secondly, work out what your swept volume per cylinder is, remove the plugs, rotate a cylinder to BDC and fill with a graduated pipette, to measure the volume, that will tell you straight away.
Thirdly, most after market big bore kits, have their logo and various other markings stamped in the crown of the piston, so just rig up a little inspection light that you can drop down the plug hole and get a good look around inside the cylinder, and have a look for the Wiseco name or something, I am not too sure, but the speed merchants like Blower Bike or Rapid Ray will tell you straight off, what to look for.
Just a few ideas, yes I know, i have the maths for the formulas what numbers to look for, but it is Sunday and the brain is in neutral, and I am off for Sushi, again, the go fast boys could give you those numbers off the top of their heads.
Hope that helps

 

[blowerbike]

So I picked up a 1982 Gs1100e today. The guy I got it from thought it was a KZ and doesnt know anything about it just that his buddy left it there a long time ago. I know its a gs1100e since I used to have one. Anyhow it looks all hopped up. Is there a way to know if it may have a big bore kit other than pulling the pistons out?

where are you from?

 

[Guest]

Compression will be higher with different compression ratio piston but other than tearing it apart or doing a Dyno no.

 

[blowerbike]

Compression will be higher with different compression ratio piston but other than tearing it apart or doing a Dyno no.

whats up hot stuff?


there are snap type bore mics available or you could find a shop with one and they could tell you the bore size by removing a plug.
FYI
most people give misinformation about all these hot rod parts that they was told about from the previous owner or they flat out lie.
assume its stock unless otherwise known/proven!

 

[Nessism]

You might be able to visually inspect the piston top for a higher than stock dome. Of course you will have to familiarize yourself with what the stock pistons look like but that shouldn't be too hard. Other than this the only way I can think of is to pull the head off and measure.

 

[racer1150]

@ flyboy

@ flyboy

Yes it has smoothbore carbs , I think vm29 or vm33 mm's I still havent mic them. Also it has a manual cam chain tensioner like the one a.p.e makes, and a side mounted oil cooler with the lines routed to the oil dipstick , also it has a big rear wheel ( 17 inch wheel on a 200 mm tire ) on a stock 1100 swingarm. It has stock forks that are lowered internally and polished front wheel and polished forks. I did a compression test and 1 and 4 are at 120psi. while 2and 3 are at 90psi.

 

[bobthebiker88]

you dont have a high compression engine, but what you DO have, is a mechanical issue. get that sorted. check valve clearances and make sure they're in spec.

 

[Guest]

Yes it has smoothbore carbs , I think vm29 or vm33 mm's I still havent mic them. Also it has a manual cam chain tensioner like the one a.p.e makes, and a side mounted oil cooler with the lines routed to the oil dipstick , also it has a big rear wheel ( 17 inch wheel on a 200 mm tire ) on a stock 1100 swingarm. It has stock forks that are lowered internally and polished front wheel and polished forks. I did a compression test and 1 and 4 are at 120psi. while 2and 3 are at 90psi.

Sounds interesting....any pics?

 

[rapidray]

Racer, the only SURE way to know is to take it apart & measure the bore. It can even have higher compression & still have a stock bore. Call me at 714-356-7845 if I can help. Ray.

 

[blowerbike]

ray,
what is the bore gage used at sanctioned events to measure the bore and stroke while the engine is assembled?
please don't tell me i dreamed this device up in my mind

 

[Steve]

... It can even have higher compression & still have a stock bore. ...

It can also have a higher compression ratio, but still have low compression numbers.

It will depend a LOT on the cam overlap.

.

 

[rapidray]

Terry, are you referring to a P&G? Actually, it only measures C.I.D., not bore & stroke. That's what the NHRA uses for both Pro Stock car & bike, along with many other classes, & you can ask Steve Johnson & Byron BOTH how many times those have been wrong! I know what you are getting at though. Unfortunately, I don't have access to one, do you? Ray.

 

[blowerbike]

Terry, are you referring to a P&G? Actually, it only measures C.I.D., not bore & stroke. That's what the NHRA uses for both Pro Stock car & bike, along with many other classes, & you can ask Steve Johnson & Byron BOTH how many times those have been wrong! I know what you are getting at though. Unfortunately, I don't have access to one, do you? Ray.

no i don't.
i had thought a mini-sprint guy i dealt with years ago told me about the use of those at races when size was in question from a competitor(soar loser).

 

[Guy]

Compression numbers are a bit low.
Did ya measure with the throttle open?

 

[Guest]

There is a tool that can measure bore thru the spark plug hole. Don't know the name of it

 

[woodman]

A friends Bonneville car P&Gd at 350 inches and its 367

 

[eric_banks32]

If you identify the piston dome/dish, and know the approximate cc of the combustion chamber you can use a burret with appropriate fluid to measure the cc of the cylinder. Make sure the piston is at BDC and the valves are closed. It won't be perfect but it should get you close.

 

[rapidray]

A friends Bonneville car P&Gd at 350 inches and its 367

See what I mean?!!! Ray.

 

[headsbikesmopars]

120 lbs on two and 90 lbs on the other two..sounds like it needs to come apart anyway. That is if the valves are all in spec. and no leakage at the head gasket. Then you will know for sure what you have.

Terry