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Kicking around the idea of a Big overbore SOHC 450

Alan F.

Veteran Member
Joined
Jun 1, 2020
Total Posts
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Total likes
185
Location
Haverhill, MA, USA
I've read some threads on the old HT site about overboring the SOHC 450 and how overbore pistons and rings are NLA from Honda. This got me thinking about how big you could safely go with a 450.

I'd like to do this with stock parts from another bike, young enough to ensure availability into the future.
Another key point would be to keep the necessary machine work to a minimum.

After looking around at lots of parts online I settled on a set of pistons with rings and cylinder jugs from ebay, in good shape for about $150 shipped. They're all from the same 13k mi. bike, a 2002 Triumph Bonneville T100 790cc.

Somewhere I downloaded a full size printable base gasket from a 450 (can't find it now) at each cylinder there is one stud nearer to the cylinder sleeve than the other 3:
s-l400 (2)~2.jpg
It seems the jugs can be resleeved larger but this stud will be the limiting factor.

I measured 5mm between that stud and cylinder sleeve holes in the base gasket. The cylinder sleeve hole measures 83.5mm

So 83.5mm with 5mm on each side = 93.37mm
Which will be the largest sleeve OD that the block will accept.

In one of the threads I read TOOLS1 say that a .100" cylinder wall (2.54mm) will be a good minimum.

93.37mm - 5.08mm = 88.29mm as our max bore.
So if I found an 88mm piston, with an 18mm wrist pin, with pin to piston top distance same as stock....
It'd fit easily.

The T100 piston bore is 86mm, wrist pins are 19mm
(I'm hoping the SOHC 450 rods can be reamed from 18 to 19mm)

The Triumph sleeves measure 96.16mm OD.
I don't know if sleeve OD can be turned down or not, but I've got the idea of boring the block to accept these sleeves and grooving the sleeve with a ball endmill 4.5mm deep to clear the stud bore.
96.16 - 4.5 = 91.66
Sleeve ID is already 86mm, 91.66 - 86 = 5.66mm
5.66mm divided by 2 gives us a cylinder wall of 2.83mm or .1114" plenty according to what TOOLS1 had said in an earlier thread.

These pistons use a 19mm wrist pin, I'd read Longdistancerider mention that the 400 uses 17mm wrist pins but the 450 uses an 18mm wrist pin.
Can these rods be reamed from 18 to 19mm?

And piston pin to piston top measurement would need to be close to stock, an exhaust valve relief in the piston top may need to be added.

The bottom of the Triumph sleeves will need to be altered to a shape closer to stock, and the top engine case will need modification to fit the fatter sleeves also.

I'm not sure what can be done for a head gasket, make a copper gasket I suppose.

Will the difference between combustion chamber diameters and cylinder bores be a factor? Will the chambers need alteration?

I think the head will flow well but I'm not so sure of a stock exhaust.

Carburetors will require larger jets, I'd have to look at the carbs the Triumph uses

Thoughts?
 
Quite an ambitious plan, should be interesting to watch.
 
It looks like these bikes came with 36mm KeiHin CVK carbs.

I'm not going to be trying this soon, I'll keep it in mind though and refine the concept.
 
I just pulled the trigger on some ebay auctions. I got an 82 CM450C block which between Partzilla and CMSNL seems to fit SOHC 450s up to 86 or 87.
And I picked up the Bonneville T100 block,sleeves and pistons with rings.

There's only so much I can do with second hand info, I need the parts in hand to tell definitively if this idea has any merit.
 
I was just reading post #1 and made a minor correction to one of the numbers I'd listed.

Also the other day I came across a method of turning down the outside diameter of a cylinder sleeve. Simply make a fat flanged slug that fits the sleeve ID, near press fit tolerances, center drill and tap the end opposite the flange, bolt on a flat cover plate to clamp the sleeve against the flange, and turn down on a lathe between centers. I swiped these 2 photos:

Screenshot_2020-11-13-18-03-38~2.jpg Screenshot_2020-11-13-18-04-02~2.jpg
 
Obviously still a lot more to do, but it looks like you could be on your way. So would we be talking 11mm oversize bore? I wonder if the strength of the rods might be a concern. I've never worked on any of the SOHC 400/450s and I'm not familiar with their ability to withstand high performance mods
 
With the Triumph sleeves ODs turned down to our theoretical maximum of 93.37mm that can fit the block, that means with the 86mm bore our sleeve wall thickness will be 3.685mm or .1450" which will still allow 1.395mm for subsequent overbore before the sleeve thickness drops to .100" or 2.54mm.
 
That's the thing, no one really has since these engines aren't raced yet. I'm wondering what the Honda engineers had up their sleeves, and why that one stud (they're bolts actually) is located that much closer to center than the other three?

I'm hopeful there is a connecting rod from a higher performance bike that could be near enough to fit, that search hasn't begun yet.
 
Does that translate to a larger piston than the 86mm Triumph piston? And if so, where would you find them (other than Wiseco or Venolia, etc custom made)? End up at 587cc with that bore?
 
Yes 587cc with the 86mm bore, I'm good with that for now.

99-09 VT1100C had an 87.5mm bore, that'd take it out to 608cc. Not sure about wrist pin diameter or deck height though.

I took a look at CMSNL at a connecting rod bearing for an 86 450 Nighthawk, here's the list of engines that used the same:

CB1000C 1000 CUSTOM 1983 (D) USA
CB350S 1986 (G) ENGLAND
CB350S 1986 (G) FINLAND
CB350S 1986 (G) SWEDEN
CB400A HAWK HONDAMATIC 1978 USA
CB400NC 1983 (D) AUSTRALIA
CB400NC 1983 (D) BELGIUM
CB400NC 1983 (D) EUROPEAN DIRECT SALES
CB400NC 1983 (D) FRANCE
CB400NC 1983 (D) GERMANY / 13 KW TYPE 2
CB400NC 1983 (D) GERMANY / FULL POWER TYPE 1
CB400NC 1983 (D) NETHERLANDS
CB400NC 1983 (D) NORTHERN EUROPE
CB400NC 1983 (D) SUPERDREAM ENGLAND
CB400ND 1984 (E) AUSTRALIA
CB400ND 1984 (E) EUROPEAN DIRECT SALES
CB400ND 1984 (E) FRANCE
CB400ND 1984 (E) GERMANY / 13 KW TYPE 2
CB400ND 1984 (E) GERMANY / FULL POWER TYPE 1
CB400ND 1984 (E) NETHERLANDS
CB400ND 1984 (E) NORTHERN EUROPE
CB400ND 1984 (E) SUPERDREAM ENGLAND
CB400P 1979 (Z) POLICE GENERAL EXPORT
CB400P 1980 (A) POLICE GENERAL EXPORT
CB400P 1981 (B) POLICE GENERAL EXPORT
CB400P 1982 (C) POLICE GENERAL EXPORT
CB400T HAWK 1980 (A) USA
CB400T HAWK 1981 (B) USA
CB400TI HAWKI 1979 (Z) USA
CB400TII HAWKII 1978 USA
CB400TII HAWKII 1978 USA
CB400TII HAWKII 1979 (Z) USA
CB450 BRAZIL
CB450 CUSTOM BRAZIL
CB450DX 1988-1993 BRASIL
CB450E BRAZIL
CB450P 1988-1993 BRASIL
CB450S 1986 (G) AUSTRIA
CB450S 1986 (G) EUROPEAN DIRECT SALES
CB450S 1986 (G) FRANCE / YB
CB450S 1986 (G) GERMANY
CB450S 1986 (G) GERMANY / 27P
CB450S 1986 (G) ITALY
CB450S 1986 (G) SPAIN
CB450S 1988 (J) CANADA
CB450S 1988 (J) DENMARK
CB450S 1988 (J) EUROPEAN DIRECT SALES
CB450S 1988 (J) FRANCE YB
CB450S 1988 (J) GERMANY
CB450S 1988 (J) GERMANY 27P
CB450SC NIGHTHAWK 1982 (C) USA
CB450SC NIGHTHAWK 1985 (F) USA CALIFORNIA
CB450SC NIGHTHAWK 1986 (G) USA CALIFORNIA
CB450SC NIGHTHAWK 450 1983 (D) USA
CB450T HAWK 1982 (C) USA
CB750C 750 CUSTOM 1980 (A) USA
CB750C 750 CUSTOM 1981 (B) USA
CB750C 750 CUSTOM 1982 (C) USA
CB750F 750 SUPER SPORT 1979 (Z) USA
CB750F 750 SUPER SPORT 1980 (A) USA
CB750K 750 FOUR K 1979 (Z) USA
CB750K 750 FOUR K 1980 (A) USA
CB750K 750 FOUR K 1981 (B) USA
CB750K 750 FOUR K 1982 (C) USA
CB750L LIMITED 1979 (Z) USA
CB750SC NIGHTHAWK 750 1982 (C) USA
CB750SC NIGHTHAWK 750 1983 (D) USA
CB900C 900 CUSTOM 1980 (A) USA
CB900C 900 CUSTOM 1981 (B) USA
CB900C 900 CUSTOM 1982 (C) USA
CB900F 900 SUPER SPORT 1981 (B) USA
CB900F 900 SUPER SPORT 1982 (C) USA
CBX1000 SUPERSPORT 1980 (A) USA
CBX1000 SUPERSPORT 1981 (B) USA
CBX1000 SUPERSPORT 1982 (C) USA
CM400A 1979 (Z) USA
CM400A HONDAMATIC 1980 (A) USA
CM400A HONDAMATIC 1981 (B) USA
CM400C CUSTOM 1979 (Z) USA
CM400C CUSTOM 1980 (A) 1981 (B) USA
CM400C CUSTOM 1980 (A) 1981 (B) USA
CM400E 1980 (A) USA
CM400T 1979 (Z) USA
CM400T 1980 (A) USA
CM400T 1981 (B) CANADA
CM400T 1981 (B) USA
CM450A HONDAMATIC 1982 (C) USA
CM450A HONDAMATIC 1983 (D) USA
CM450C 1982 (C) CUSTOM USA
CM450E 1982 (C) USA
CM450E 1983 (D) USA
CMX450C REBEL 1986 (G) CANADA / MKH
CMX450C REBEL 1986 (G) USA CALIFORNIA
CMX450C REBEL 1987 (H) EUROPEAN DIRECT SALES / KPH
CMX450C REBEL 1987 (H) ITALY / KPH
CMX450C REBEL 1987 (H) USA CALIFORNIA
CMX450C REBEL 1988 (J) AUSTRIA / KPH

This product fits to 97 models.



And then I read this: http://satanicmechanic.org/conrods.shtml

And learned that 69-78 CB750s should be on that list too, there's no shortage of stronger connecting rods now. But I've gotta find some measurements before I go down that rabbit hole.
 
Big end of the connecting rods is 38mm, Small ends are 17mm for the 400 and 18mm for the 450.

So center to center length of these rods is 1/2 of 38mm, and 1/2 of 17mm plus the 72.38mm measured in the photo above = 99.88mm connecting rod length.
 

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A 600+cc twin... shades of Brit bikes in the '60s and '70s but with balancers (which might not work as well offsetting the bigger soup cans)
 
A 600+cc twin... shades of Brit bikes in the '60s and '70s but with balancers (which might not work as well offsetting the bigger soup cans)

Well, first I'd want to weigh stock piston with rings, wrist pin and keepers for comparison to the upgrade parts. If they're close maybe the 450s solid balancers will do fine?

Reaming the small end of the 450 rods is my big fear. They need to go from 18mm to 19mm for these pistons, unless you know a reliable way to bush the piston's wrist pin bores? I've seen that in a few places online, even Longdistancerider had suggested it, but I don't know how well it would work at higher RPMs
 
Well, first I'd want to weigh stock piston with rings, wrist pin and keepers for comparison to the upgrade parts. If they're close maybe the 450s solid balancers will do fine?

Reaming the small end of the 450 rods is my big fear. They need to go from 18mm to 19mm for these pistons, unless you know a reliable way to bush the piston's wrist pin bores? I've seen that in a few places online, even Longdistancerider had suggested it, but I don't know how well it would work at higher RPMs


Alan,I had an OEM connecting rod small end(good solid cast iron rod w/ plenty of material)opened-up from 15-16mm on an XL185 engine I have to install a STD. Yamaha XT225 70mm piston(they use a 16mm wrist pin):it worked-out well.I had the stock 65.5mm XR200 size piston in it and went to the 70mm after getting the cylinder re-sleeved by a very qualified machinist.This machinist is also boring out the spigot hole size in my cases;the engine will be installed into a CB125 lightweight little bike.
 
Haven't spent much time with this one until now.
I don't think there's enough material on the rod small end to enlarge it and have it live. I think I would look at the APE site and talk with them about the Carrillo rods and bearings, they can probably suggest alternatives there. I'm guessing that they have found suitable bearings for turned cranks which is a weak area for this engine family. Damaged cranks are throw aways.
 
Haven't spent much time with this one until now.
I don't think there's enough material on the rod small end to enlarge it and have it live. I think I would look at the APE site and talk with them about the Carrillo rods and bearings, they can probably suggest alternatives there. I'm guessing that they have found suitable bearings for turned cranks which is a weak area for this engine family. Damaged cranks are throw aways.


I see your point:he is going for a huge overbore so I imagine he will be Really 'putting the power through it' on that engine,double time..
 
This is just an intellectual exercise thus far, some purchased parts are on the way to take acurate measurements from, but there is no bike planned right now. I'm not sure if I'd want a 450 Rebel with its full frame or a CB/CM frame with its lighter style. Or for that matter if a stock exhaust would even be a possible option. If anyone has thoughts on that, speak right up.

...Although I do have an untitled 78 CB400T frame..... and a 450 Rebel swingarm... but I have never tried very hard to integrate the two....
 
CMX450 differences?

According to https://4-stroke.net/library/honda-piston-size-chart.html

The CMX450 Rebel has:

75mm bore
26+1 heartline (wrist pin center) to top, +1 (appears to be above edge of piston top)
*20mm pin diameter?
60mm full height
Piston part number 13101-MR4-900

Connecting rod from CMX450 1987:
13210-MC0-010
Used in:
Honda Motorcycle 1987 CMX450C A - REBEL 450 Piston
Honda Motorcycle 1986 CMX450C A - REBEL 450 Piston
Honda Motorcycle 1987 CMX450C AC - REBEL 450 Piston
Honda Motorcycle 1986 CMX450C AC - REBEL 450 Piston
Honda Motorcycle 1985 CB450SC AC - NIGHTHAWK 450 Piston-Connecting Rod
Honda Motorcycle 1983 CM450E A Piston-Connecting Rod
Honda Motorcycle 1982 CM450C A - CUSTOM Piston-Connecting Rod
Honda Motorcycle 1983 CM450A A - HONDAMATIC Piston-Connecting Rod
Honda Motorcycle 1982 CM450E A Piston-Connecting Rod
Honda Motorcycle 1986 CB450SC A - NIGHTHAWK 450 Piston-Connecting Rod
Honda Motorcycle 1986 CB450SC AC - NIGHTHAWK 450 Piston-Connecting Rod
Honda Motorcycle 1985 CB450SC A - NIGHTHAWK 450 Piston-Connecting Rod
Honda Motorcycle 1982 CB450SC A - NIGHTHAWK 450 Piston-Connecting Rod
Honda Motorcycle 1982 CM450A A - HONDAMATIC Piston-Connecting Rod
Honda Motorcycle 1982 CB450T A - HAWK Piston-Connecting Rod
Honda Motorcycle 1983 CB450SC A - NIGHTHAWK 450 Piston-Connecting Rod

*Ok, 20mm wrist pins? This contradicts what LDR had said earlier, 17mm for the 400 series and 18mm for the 450 series. Someone is wrong, I doubt it's LDR.

But it sure would be easier and more reliable to ream the pistons for 20mm wrist pins.
 
As well as those oil return return areas at the rear outer studs, they're about a millimeter further out.
Those are the oil pressure feed for the cam and head. However if you used a 450 case the head oiling is external so those bolts are just normal bolts. Look at the 450 FSM for the oiling system and compare it with the 400
 
All very good points, thanks everyone. I'm only considering a 450 for these mods but there aren't many around here right now. Plenty of time to find the right deal, I have lots of projects to finish first.
 
Nothing wrong considering something 'out of the box' in a custom build:you may learn good things on what can or won't work for all of us,if any of us would ever consider doing an upgrade of our own ;)
 
450 cylinders arrived today.
Of the SOHC 450 twins that we got in the States,
CB, CM, and CMX these are the part numbers I find:
12100-MC0-000
12100-MC0-010
12100-MC2-000
12100-KK9-960
12100-MM2-670

The last 2 in the list are CMX450 Rebel, I don't know if these are interchangeable, but after a quick look at CMSNL these appear to have more in common with the CB450N and CB450S bikes that didn't come to the states.

I got the first one 12100-MC0-000.
After cleaning it up I'll make up a measured drawing to reference later so that the modified product will be as similar as possible to stock.
 
awesome thread, bro!

I'm only considering a 450 for these mods but there aren't many around here right now. Plenty of time to find the right deal,

if you build it they will come, but if not the Hon-dian is at your service.
 
I just wanted to place a note for myself here, I was reading a thread on HT where someone stripped out their head bolt threads in the cases by tightening without a torque wrench.... I will likely want to helicoil the head bolt threads early on.
 
Time for an update, I found the highest superseding part number for the CM/CB 400&450 big end connecting bearings, and the related fitment shows the whole list.
13218-413-015 fits:
CB1000C 1000 CUSTOM 1983 (D) USA
CB400A HAWK HONDAMATIC 1978 USA
CB400T HAWK 1980 (A) USA
CB400T HAWK 1981 (B) USA
CB400TI HAWKI 1979 (Z) USA
CB400TII HAWKII 1978 USA
CB400TII HAWKII 1978 USA
CB400TII HAWKII 1979 (Z) USA
CB450DX 1988-1993 BRASIL
CB450P 1988-1993 BRASIL
CB450S 1988 (J) CANADA
CB450S 1988 (J) DENMARK
CB450S 1988 (J) EUROPEAN DIRECT SALES
CB450S 1988 (J) FRANCE YB
CB450S 1988 (J) GERMANY
CB450S 1988 (J) GERMANY 27P
CB450SC NIGHTHAWK 1982 (C) USA
CB450SC NIGHTHAWK 1985 (F) USA CALIFORNIA
CB450SC NIGHTHAWK 1986 (G) USA CALIFORNIA
CB450SC NIGHTHAWK 450 1983 (D) USA
CB450T HAWK 1982 (C) USA
CB750A 750 HONDAMATIC 1976 USA
CB750A 750 HONDAMATIC 1977 USA
CB750A 750 HONDAMATIC 1978 USA
CB750C 750 CUSTOM 1980 (A) USA
CB750C 750 CUSTOM 1981 (B) USA
CB750C 750 CUSTOM 1982 (C) USA
CB750F 750 SUPER SPORT 1975 USA
CB750F 750 SUPER SPORT 1976 USA
CB750F 750 SUPER SPORT 1978 USA
CB750F 750 SUPER SPORT 1979 (Z) USA
CB750F 750 SUPER SPORT 1980 (A) USA
CB750F 750 SUPER SPORT 1981 (B) USA
CB750F 750 SUPER SPORT 1982 (C) USA
CB750F2 750 SUPER SPORT 1977 USA
CB750K 750 FOUR K 1979 (Z) USA
CB750K 750 FOUR K 1980 (A) USA
CB750K 750 FOUR K 1981 (B) USA
CB750K 750 FOUR K 1982 (C) USA
CB750K3 FOUR 1973 USA
CB750K4 FOUR 1974 USA
CB750K5 FOUR 1975 USA
CB750K6 FOUR 1976 USA
CB750K7 FOUR 1977 USA
CB750K8 FOUR 1978 USA
CB750L LIMITED 1979 (Z) USA
CB750SC NIGHTHAWK 750 1982 (C) USA
CB750SC NIGHTHAWK 750 1983 (D) USA
CB900C 900 CUSTOM 1980 (A) USA
CB900C 900 CUSTOM 1981 (B) USA
CB900C 900 CUSTOM 1982 (C) USA
CB900F 900 SUPER SPORT 1981 (B) USA
CB900F 900 SUPER SPORT 1982 (C) USA
CBX1000 SUPERSPORT 1979 (Z) USA
CBX1000 SUPERSPORT 1980 (A) USA
CBX1000 SUPERSPORT 1981 (B) USA
CBX1000 SUPERSPORT 1982 (C) USA
CM400A 1979 (Z) USA
CM400A HONDAMATIC 1980 (A) USA
CM400A HONDAMATIC 1981 (B) USA
CM400C CUSTOM 1979 (Z) USA
CM400C CUSTOM 1980 (A) 1981 (B) USA
CM400C CUSTOM 1980 (A) 1981 (B) USA
CM400E 1980 (A) USA
CM400T 1979 (Z) USA
CM400T 1980 (A) USA
CM400T 1981 (B) USA
CM450A HONDAMATIC 1982 (C) USA
CM450A HONDAMATIC 1983 (D) USA
CM450C 1982 (C) CUSTOM USA
CM450E 1982 (C) USA
CM450E 1983 (D) USA
CMX450C REBEL 1986 (G) USA CALIFORNIA
CMX450C REBEL 1987 (H) USA CALIFORNIA
CMX450C REBEL 1988 (J) AUSTRIA / KPH
This product fits to 75 models.


This info also helps me cross reference the big-end connecting rod diameter, and connecting rod width requirements.


In my search for a matching set of connecting rods for a SOHC 450 with very similar center to center length, a useful 18mm small end, and a big end diameter that will work, today's result is the Kawasaki ZX7 which was mostly the same from 1989 until 2003. There are plenty of cheap parts.


So 18mm small end, great but their length is 0.7812mm too long...well maybe I'll double up on base gaskets, or maybe add a spacer plate, or just mill the piston tops, I can work with that.


CM/CB big end rod bore is 39.014mm
ZX7 rods are 36.9824mm.
A difference of 0.7812mm.
I'd have to find a machine shop to ream the big ends and add recesses for the bearing tabs, doable for sure.


My research says CM/CB rods have a width of 22.6822mm while the ZX7 rods have a width of 22.86mm so some grinding to thickness will be required, easy.


I'd love to just convert a CB/CM450 to these rods and use their stock ZX7 pistons as "STAGE 1", but they're only 73mm vs the 450's 75mm stockers.
That search continues, I'd like to max out the 450's safe sleeve diameter in stage 1, I'm sure I can find something.


More to come, stay tuned.
 
It seems like CM/CB450 rods being about 10mm shorter than stock SOHC CB750 and ~12mm shorter than DOHC 750, 900 and 1000 rods...theyd be ideal for low boost turbo applications on a budget.
 
Math change
CM/CB big end rod bore is 39.014mm
ZX7 rods are 36.9824mm.
A difference of 0.7812mm.
39.014 - 36.9824 = 2.0316mm or .079924"

I don't know on the 450's but the 400's have negative deck height for the pistons of @.040"-.060"
 
Awe crap those Triumph pistons had 19mm wrist pins didn't they...

Yes LDR that. I've been trying to put all of these notes together on my phone, and I'm ready to smash it with a hammer right now. Those rods appear to have plenty of meat to enlarge them for the 450 crank bearings, they'd never get the same abuse that a 110hp 750cc zx7 engine with a squid in the saddle would give them.

But it appears that I've got to run the search again for rods with a 19mm .748" wrist pin.
 
Our member HamHawk, on HT he's HamHock, was experimenting with using Acura pistons for a 450. He's joined us but I know he was moving to Nevada and wasn't going to have work space for awhile. Might PM him and see what info he has.
 
Well, so far it appears the ZX7 rods will work with Ninja H2 pistons (76mm with18mm pins) and should make for a very light assembly at 459cc.

Zx7 rods will work with W800 77mm pistons for 471cc
 
More research. Places to start for sure.


Info based on:
18mm wrist pin clips 92033-1188 and
20.5mm wrist pin clips 92033-1099.


70.5mm is stock CB/CM400 @ 395cc


00-03 W650
20.5mm pins 72mm
= 412.04cc


91-03 ZX750
20.5mm pins 73mm bore
= 423.56cc


86-06 ZG1000
20.5mm pins 74mm bore
= 435.24


90-09 EN500
20.5mm pins 74mm bore


87-09 EX500
20.5mm pins 74mm bore


Stock for the 450 is 75mm = 447.09


83-84 GPZ1100
18mm pins 76mm = 459.09cc


90-01 ZX1100
20.5mm pins 76mm bore


03-09 ZR1000
20.5mm pins 77mm = 471.25cc


11-17 W800
20.5mm pins 77mm bore




78.5mm is the max with stock sleeves leaving sleeve walls thick enough to last, this would give 489.79cc




KVF400 81mm = 521.48cc


00-06 ZX12R
18mm pins 83mm = 547.55cc


86-06 VN750
18mm pins 84.9mm = 572.91cc


87mm would make a true 600 at 601.6cc


95-06 VN800
18mm pins 88mm = 615.51cc


06-21 VN900
18mm pins 88mm bore


I picked up a dirt cheap pair of ZX7 rods to measure before moving on.




Edit: corrected for differences between pistons with 18mm wrist pins that might work with stock 450 rods...
and
Pistons with 20.5mm wrist pins that may work with lightly modded 91-03 ZX7 rods
 
Will do, but unfortunately the day job calls.

There are 3 ZZR1000 Pistons with pins and clips on eBay for $~16/ea with free shipping, maybe I'll see if he'll part with them for $25 shipped...
 
I'm revising reply #40, I missed the bit in my notes that mentions that 92033-1188 is an 18mm wrist pin clip, but 92033-1099 is a 20.5mm wrist pin clip.

So some of these might be better with stock 450 rods and some might be better with the lightly modified ZX7 rods.
 
78.5mm is the max with stock sleeves leaving sleeve walls thick enough to last, this would give 489.79cc
00-06 Honda TRX350 was 78.5mm!
and had 17mm wrist pins.

This would seem to be the easy way to max out CB/CM 400s. Bore and reassemble with stock rods and wind up with an 8.5mm overbore, braap-braap!


But then there's the idea of piston compression height compared to stock. If anyone has a useful reference for crown heights i'd welcome the info.

Otherwise it's a matter of finding something close and buying one to measure.

img-Compression-Height-Measure.jpg
 
I was going to suggest getting a set from CruzinImage but they're out of stock. You'll want an actual piston to work against for dealing with the crown/dome section of replacement pistons.
 
I agree I'll need a piston in hand, it can be calculated but that's not good enough. I'd much rather find something from another bike that'll work with just cheap & easy mods so anyone can do it.
 
I received a call back, best offer isn't really the case. He picked it up as shown thinking he could rebuild it but there are broken welds at the frame neck. So for best offer for parts only he's been looking at EBay listing prices as a guide to what the market will bear.

I offered $100 for the engine and complete wiring harness, and I saved his number. Maybe if work takes me up that way I'll bring it home. He suggested he'd probably have it a long time.
 
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