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post #1 of 22 (permalink) Old 02-20-2015, 08:36 PM Thread Starter
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piston interchange

Wondering if u can bore out a vt1100 which has a 87.5mm bore to 89.5mm (vtx piston)???

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post #2 of 22 (permalink) Old 02-20-2015, 08:37 PM
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post #3 of 22 (permalink) Old 02-20-2015, 09:43 PM
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Cylinder walls may be too thin.


VT1100 Manuals
https://skydrive.live.com/redir?resi...CHKWhOWhw9k2i8
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1995 VT1100C2 ACE

Motorcycle Accident Dec 19, 2012
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post #4 of 22 (permalink) Old 02-20-2015, 10:06 PM
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Quote:
Originally Posted by TEngle View Post
Cylinder walls may be too thin.

Agree, since the VTX bore is 2mm greater.
78.74015748031496 thou = 2 mm.

From memory, a 0.060 overbore is as far as I've ever heard of working well....that would be 1.5239999999999998 mm, so I'm going out on the proverbial limb and saying, "No....I don't think it can be bored that far."

There are MANY here who are better bike mechanics than I, so don't assume that's the final word.

But, as a former engine builder who only built small block Chevys, let me also throw this out there:
Fair chance that even if the jug WOULD stand that massive overbore, what are the OTHER differences?
Besides bore dimension?

Would also need to know CRITICAL differences, like:
Wristpin size / length, wristpin placement in the piston, compression height, difference in stroke vs difference in connecting rod length, difference in shape / size of combustion chambers.

If stroke, or rod length is indeed different, does anyone make a stroker rod? Or a stroker piston, with the ring grooves still above CL of the wristpin?

Another Stroker Killer is case interference.
Where's it gonna hit?
And, alas and alack.....it's gonna be tough to predict....unless you are a mechanical engineed and can CAD it all out.
OR unless you spend the bux for custom parts, and mock it all up, only to find.....

As the man who taught me to build engines to turn upstairs and live, useta say: "Serious horsepower costs serious money; how fast do you wanna go?"


I dunno.
But I gotta believe: if the conversion you have in mind was doable, there would be ads showing stroker parts!

JMO.

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The VT1100C2 ACEs: the '97 Flyin' Jenni, rescue dog Hobo LongNose, and the '96 on the right.

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Last edited by Gnarly; 02-20-2015 at 10:18 PM. Reason: ytpo.
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post #5 of 22 (permalink) Old 02-20-2015, 10:13 PM
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Quote:
Originally Posted by Gnarly View Post
Fair chance that even if the jug WOULD stand that massive overbore, what are the OTHER differences?
Besides bore dimension?

Would also need to know CRITICAL differences, like:
Wristpin size / length, wristpin placement in the piston, compression height, difference in stroke vs difference in connecting rod length, difference in shape / size of combustion chambers.
My thoughts exactly, Gnarly. You might be able to get the piston to fit, then find out it slams into the valves because it's .010 taller from pin to crown than the 1100 piston. Are the heads shaped the same? Are the crank journals the same? Etc.

You could certainly bore out the 1100 to something else that fits, but I really doubt it would be the VTX1300 piston. You may have more luck boring it out to another manufacturer's smaller engine displacement piston with a shorter pin to crown height, using a longer rod to gain more torque. There's lots of math to say for sure, but custom engine parts add up quickly and a pair of custom connecting rods might cost as much as a rebuilt VT1100.

So, I guess the real question here is, what's your goal?



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post #6 of 22 (permalink) Old 02-20-2015, 10:28 PM
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Neglected to mention: along with length / compression height / stroke, both ends of con rod would need to be examined / compared.
No need in building something perhaps also requiring a special thickness / width con rod bearing.

charlesvt: didn't mean to rain on an otherwise fine idea.
But concerned that you would need to feed this project cubic dollars.

~~~Ride safe; ride smart....in memory of the one and only 7x~~~

The VT1100C2 ACEs: the '97 Flyin' Jenni, rescue dog Hobo LongNose, and the '96 on the right.

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post #7 of 22 (permalink) Old 02-21-2015, 12:00 AM
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There is a LOT of math that comes into play, even if the wrist pin height is the same on both pistons. However, 2mm in width is only 1mm in radius people I see no reason why 1 mm couldnt be taken out of that bore.

But, i do not think you can turn an 1100 into a 1300 that easy. If its a higher comp piston and EVERYTHING is the same except for the bore, its POSSIBLE, but more than likely way more cubic dollars spent than comp points gained in the end.

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post #8 of 22 (permalink) Old 02-21-2015, 12:49 AM
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Im not going get in to number but im just going to say no it can not be done. Honda uses a block jug combo and made it all to thin to keep weight/balnce/ other things down. Ive thought about this a lot myself however if you can trust a motor shop to bore the motor over a large about to re sleave it so you got a strong wall your be able to go to a 1200 cc and you still cant use the 89. You can use a 88.2 or 88.6 cant rember . But now your talking big customer parts needing better cooling and so on for little gain.

There is no replacement for displacement however droping in a 1300 or 1800 vtx motor under a shadow might be something .

1997 honda shadow ace 1100
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post #9 of 22 (permalink) Old 02-21-2015, 12:55 AM
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A guy tried putting an 1800 in a Fury and too much of the frame needed cutting so he dropped the idea. Plus, shaft drive...

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post #10 of 22 (permalink) Old 02-21-2015, 08:59 AM
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a larger piston will not really increase hp much. if that's what you are looking for then look for a set of 85,86 pistons, they are higher compression. add the 85,86 cams and inner valve springs. you can find the cams and pistons relatively inexpensively on ebay, just make sure the cams are not scored. been done before. the OEM inner valve springs are still available from honda.



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