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+--- Thread: Internal dimensions? (/showthread.php?tid=18391)
Internal dimensions? - Ward P - 30-12-2011
So I've got this little bike (GB400). . . the previous owner reckons it has been bored and new crank (650cc), but doesn't have any documentation on it. I've no reason to not believe him, but I thought it should have a bit more go - or have I just been riding a hayabusa for toooo long?
Same motor as the XL/XR600 - and from memory those things pulled monos off every set of lights whether you wanted to or not, and would pull 160kmph.
This thing is pretty docile in comparison, wont lift the front wheel, and won't go near 160.
I can tell that the head and barrels have been off, new looking gaskets everywhere, but is there an easy way to work out the internal dimensions of an engine without opening it up and measuring things?
Also the exhaust is pretty "open" could a lack of back pressure be hindering it? It accelerates and runs smoothly, but farts and backfires heaps on decel.
Just checked - RHS base of barrel is stamped 591cm3
so the barrel has definitely been changed.
RE: Internal dimensions? - Belzybob - 31-12-2011
(30-12-2011, 08:12pm)Ward P Wrote: It accelerates and runs smoothly, but farts and backfires heaps on decel.
Apart from jetting etc. type issues, that could be just air leaking into the inlet/exhaust system on the over-run. Old rubber boots and the like on the inlet or poor sealing on the exhaust side.
RE: Internal dimensions? - Ward P - 31-12-2011
(31-12-2011, 12:05am)Belzybob Wrote:(30-12-2011, 08:12pm)Ward P Wrote: It accelerates and runs smoothly, but farts and backfires heaps on decel.
Apart from jetting etc. type issues, that could be just air leaking into the inlet/exhaust system on the over-run. Old rubber boots and the like on the inlet or poor sealing on the exhaust side.
Thanks, just checked and exhaust has some movement. I'll pull it down to clean today and give it all a visual. - then stick up a couple of photos in the photo thread.
RE: Internal dimensions? - Zoro - 31-12-2011
Could get an indication by filling the cylinder at BDC with a measured amount of fluid/ oil the the plug hole?
Do the same with the piston at TDC, both valves closed, see what measurement you get and subtract it from the first measurement.
Will be a close indication of what you might have there without splitting it open.
RE: Internal dimensions? - Camel - 31-12-2011
(30-12-2011, 08:12pm)Ward P Wrote: .....but is there an easy way to work out the internal dimensions of an engine without opening it up and measuring things? Just checked - RHS base of barrel is stamped 591cm3
so the barrel has definitely been changed.
Unless it has been sleeved down....
You could always:
- Remove the sparkplug,
- Turn the engine over until it is at Bottom Dead Centre
- Take a graduated 1 litre measuring cup, fill it to the 1 litre mark with oil, pour it into the spark plug hole until the oil reaches the bottom of the sparkplug hole, note the quantity used, subtract it from 1 litre, subtract another 50ml (rough estimate of the combustion chamber capacity) and you should have a rough (very rough) but ballpark capacity of your cylinder.
That's assuming the piston and rings aren't so worn that the oil leaks past them!
How do you get the oil out?
With a straw?
I spose you've got a better idea?
Camel
RE: Internal dimensions? - Ward P - 31-12-2011
(31-12-2011, 04:24pm)Camel Wrote: [quote='Ward P' pid='257790' dateline='1325239958']
How do you get the oil out?
With a straw?
I spose you've got a better idea?
Camel
Might just use the straw to drink bourbon instead. But thanks for the input.
cheers!This is the little bugger, I've put a couple of pics in the photos section.
with a set of clip ons, a single seat and bar end mirrors it will look great.
RE: Internal dimensions? - Zoro - 31-12-2011
(31-12-2011, 04:24pm)Camel Wrote:(30-12-2011, 08:12pm)Ward P Wrote: .....but is there an easy way to work out the internal dimensions of an engine without opening it up and measuring things? Just checked - RHS base of barrel is stamped 591cm3
so the barrel has definitely been changed.
Unless it has been sleeved down....
You could always:
- Remove the sparkplug,
- Turn the engine over until it is at Bottom Dead Centre
- Take a graduated 1 litre measuring cup, fill it to the 1 litre mark with oil, pour it into the spark plug hole until the oil reaches the bottom of the sparkplug hole, note the quantity used, subtract it from 1 litre, subtract another 50ml (rough estimate of the combustion chamber capacity) and you should have a rough (very rough) but ballpark capacity of your cylinder.
That's assuming the piston and rings aren't so worn that the oil leaks past them!
How do you get the oil out?
With a straw?
I spose you've got a better idea?
Camel
Use a syringe and hose through the plug hole, remove what you can, wind the rest out with a rag over the plug hole on the starter. Nothing a bit of degreaser wont shift if you make a mess. Just an option
RE: Internal dimensions? - Camel - 31-12-2011
nah, bugger it, just take the tank off and the plug out, wheel it outside, aim the plug hole over the neighbours fence and then wind it over until the starter motor is smokin!
Oh, and stand on the opposite side to the plug.
Camel
RE: Internal dimensions? - Zoro - 01-01-2012
(31-12-2011, 08:36pm)Camel Wrote: nah, bugger it, just take the tank off and the plug out, wheel it outside, aim the plug hole over the neighbours fence and then wind it over until the starter motor is smokin!
Oh, and stand on the opposite side to the plug.
Camel
Sounds like a Cheech and Chong moment....
RE: Internal dimensions? - Maj - 01-01-2012
They use swept volume sometimes on cars at Bonneville,
pull the cams or pushrods and screw the graduated tube in the plug hole ,
fill with tranny fluid , turn over by hand and see max and min points, there is your quite accurate volume
RE: Internal dimensions? - Legend - 02-01-2012
A few of us used to race the xr500/600 range back in the 80's/90's and I looked at doing crank swaps and barrel swaps back then , at that time the engines were so much different that physically it wouldnt fit ??
Leonard.