CB450 overbore piston?

[joevirus563]

Hey!

I have a set of std piston honda with standard rings but would like to have a little more kick.

Tinking about 74mm piston or 75.3mm piston of Team Hansen.

What do you think? Will I really get more power ? I've ordered my mikuni vm32 already... are they still gonna fit?

should I stay with my std 444cc piston original from honda or go overbore with after market ones?

 

[Swagger]

Keep in mind, this is a 40-ish year old air cooled 2 valve vertical twin. Don't expect to have your arms yanked out of the sockets like a CBR1000 unless you get rear ended by a bus. which would be bad.

If you go any larger than 73mm you really should get new liners and that's where it can get expensive. You can certainly bore the stock liners out to suit but they'll become flexible and the rings will lose seal and you won't make the power you want.

If you're looking to pep it up a bit, try to find some 72mm pistons as this will leave enough liner thickness for them to do the job. Shave the head or run thinner base and head gaskets for a small bump in compression....again...don't go nuts.
You can get a pair of cams reground by Delta Cams in Tacoma for what...I think last time I have 450 cams done both came to $165. Not back and their horsepower grind is pretty lusty. With the slightly boosted compression, hotter cams and overbore your VM32s will suit nicely. A big hitter for a strong motor is the ignition...and these bikes have a crappy ignition.
Dynatek makes a nice little CDI box that you can trigger with your stock points that will make nice spark. Get yourself a pair of new coils and wires (Mikes XS has nice pieces for cheap) and the difference will be very noticeable.
You'll want to get an uprated clutch as well and the stock flywheel on these engines is in my opinion a little heavy. Shave just 10% of the weight off the outer most part and you should be amazed at the difference.

 

[joevirus563]

Keep in mind, this is a 40-ish year old air cooled 2 valve vertical twin. Don't expect to have your arms yanked out of the sockets like a CBR1000 unless you get rear ended by a bus. which would be bad.

If you go any larger than 73mm you really should get new liners and that's where it can get expensive. You can certainly bore the stock liners out to suit but they'll become flexible and the rings will lose seal and you won't make the power you want.

If you're looking to pep it up a bit, try to find some 72mm pistons as this will leave enough liner thickness for them to do the job. Shave the head or run thinner base and head gaskets for a small bump in compression....again...don't go nuts.
You can get a pair of cams reground by Delta Cams in Tacoma for what...I think last time I have 450 cams done both came to $165. Not back and their horsepower grind is pretty lusty. With the slightly boosted compression, hotter cams and overbore your VM32s will suit nicely. A big hitter for a strong motor is the ignition...and these bikes have a crappy ignition.
Dynatek makes a nice little CDI box that you can trigger with your stock points that will make nice spark. Get yourself a pair of new coils and wires (Mikes XS has nice pieces for cheap) and the difference will be very noticeable.
You'll want to get an uprated clutch as well and the stock flywheel on these engines is in my opinion a little heavy. Shave just 10% of the weight off the outer most part and you should be amazed at the difference.

Thanks Swagger for your comment... I'll give you a little more info about my current prep:

Dyna-S Ignition, Barnett clutch pad, Mikuni Vm32

What do you mean by the flywheel upgrade? Where can I find that?

Thanks!.

 

[Swagger]

You'll have to take it to a machinist and have material removed.
By taking weight off the outermost part of it you can significantly improve response but like the bore job....don't go crazy. A street engine needs more flywheel than a race engine...

 

[crazypj]

Suzuki GS500 twin is 74mm and two valves per cyl.
I have a pair of liners and pistons for one, (NOT for sale)
If anyone has a CB450 in pieces to take some measurements, we can compare notes

PJ

 

[joevirus563]

Suzuki GS500 twin is 74mm and two valves per cyl.
I have a pair of liners and pistons for one, (NOT for sale)
If anyone has a CB450 in pieces to take some measurements, we can compare notes

PJ

Thanks but the problem where is not to find piston... I want to know if 1) I will feel more power?!? 2) will it hurt the engine if I do that upgrade?

 

[crazypj]

Get a GS 500 block off eBay, get a CB450 block off eBay, shrink liners out of both, machine 450 block, swap liners, swap pistons.
You wont feel much difference unless you do other mods.
It would probably be easier to find a 500T motor

 

[Rocan]

Get a GS 500 block off eBay, get a CB450 block off eBay, shrink liners out of both, machine 450 block, swap liners, swap pistons.
You wont feel much difference unless you do other mods.
It would probably be easier to find a 500T motor

then he could always overbore the gs500 liners... hmm...525cc cb450... cool....

 

[Swagger]

74mm pistons on my 500T bottom end give 550ccs and enough compression to make turning the domes back something to consider.

PJ, do you know of a source for wrist pin diameters and ring land height other than trying to drag the info out of a manufacturer? What are you thoughts on reaming the small end to go up a millimeter or two?

 

[joevirus563]

Ok,

I'm really thinking about doing this upgrade. Any idea how much HP a 74mm piston kit will give my cb450? And also can someone confirm that my mikuni vm32 are still gonna fit... Let me know.

Thanks.

 

[Swagger]

I think maybe you've not done this before, huh?

You've got *maybe* 40hp to start with, but probably closer to 30. It's a matter or percentages, 5% is probably not outside the realm of possibility....that means at best 2hp. However....you'll feel the difference, especially if your compression goes up a bit. In reality...and this sucks from a "wouldn't it be cool if..." standpoint, pistons, cams, port work, hot ignition, your VM32s (tuned well) and a very precisely built exhaust.....will net you maybe 10-12hp total which is a massive increase when viewed as a percentage.

Best not to look for astounding gains from trying to build horsepower in these old engines. Better to consider how the engine/bike feels after that work. It's subjective, but you'll likely notice that the bike will accelerate much better, RPMs will spin up and decay faster, you'll feel it pull harder, longer as well. It's perception. I've seen CB450 (590cc) dyno pulls for ~65hp, but there wasn't much left to resemble to original motor. Everything was changed in some way and in reality it was a hand built engine that evolved from it's 450cc ancestor.

 

[joevirus563]

I think maybe you've not done this before, huh?

You've got *maybe* 40hp to start with, but probably closer to 30. It's a matter or percentages, 5% is probably not outside the realm of possibility....that means at best 2hp. However....you'll feel the difference, especially if your compression goes up a bit. In reality...and this sucks from a "wouldn't it be cool if..." standpoint, pistons, cams, port work, hot ignition, your VM32s (tuned well) and a very precisely built exhaust.....will net you maybe 10-12hp total which is a massive increase when viewed as a percentage.

Best not to look for astounding gains from trying to build horsepower in these old engines. Better to consider how the engine/bike feels after that work. It's subjective, but you'll likely notice that the bike will accelerate much better, RPMs will spin up and decay faster, you'll feel it pull harder, longer as well. It's perception. I've seen CB450 (590cc) dyno pulls for ~65hp, but there wasn't much left to resemble to original motor. Everything was changed in some way and in reality it was a hand built engine that evolved from it's 450cc ancestor.

Don't worry' I know that its not a brand now motorcycle.

But I want it to be original and to be quick in the city, might put a high sproket.

Original one dosen't have 45hp stock? Mine will have a brand new engine at the end .

 

[Rocan]

Don't worry' I know that its not a brand now motorcycle.

But I want it to be original and to be quick in the city, might put a high sproket.

Original one dosen't have 45hp stock? Mine will have a brand new engine at the end .

honda's power outputs were measured from the crank and were always on the high side... they didnt take into account any losses from the transmission, final drive etc.

 

[crazypj]

74mm pistons on my 500T bottom end give 550ccs and enough compression to make turning the domes back something to consider.

PJ, do you know of a source for wrist pin diameters and ring land height other than trying to drag the info out of a manufacturer? What are you thoughts on reaming the small end to go up a millimeter or two?

wrist pin , just look in service manual.
Crown height is a different matter though. I've had to measure all the pistons I've used.
I wouldn't ream small end I would (and have many times) bush piston

 

[Swagger]

wrist pin , just look in service manual.
Crown height is a different matter though. I've had to measure all the pistons I've used.
I wouldn't ream small end I would (and have many times) bush piston

Well crap...I was hoping there was a concise reference out there somewhere.
Good point regarding bushing the pistons but what a pain in the butt to make up just a millimeter...... .5mm wall is awfully thin. I suppose reaming out the pin bore in the piston a few mm and them pressing in and reaming the new bushing to spec is probably the best option. In highschool autoshop we reamed the small end on a V8 of some kind to fit completely different pistons but those were hefty cast iron rods and far lower RPMs....

 

[emy111]

hey guys.
i put todd henning 11.5 compression race pistons in a stock cb500t engine and the bike runs awesome.
in a cb500t those pistons should yield somewhere around 10.5 compression because of the different deck height.
i guess the cylinder wall may be a tad thin with those pistons, but i talked to henning and hanson and they both said it'll be fine for street use which is what my bike is used for.
fuck it. the thing runs awesome and is way more peppy.
the henning piston kit, which i bought on ebay comes with a copper head gasket, and getting that to seal properly is kind of a pain, but other than that... the bike runs awesome.
see my website for the build process (see parts 1-4):
http://www.chinonthetank.com/2013/02/cb500t-engine-rebuild-part-4/

-Ed

 

[Rich Ard]

Re: Re: CB450 overbore piston?

hey guys.
i put todd henning 11.5 compression race pistons in a stock cb500t engine and the bike runs awesome.
in a cb500t those pistons should yield somewhere around 10.5 compression because of the different deck height.
i guess the cylinder wall may be a tad thin with those pistons, but i talked to henning and hanson and they both said it'll be fine for street use which is what my bike is used for.
fuck it. the thing runs awesome and is way more peppy.
the henning piston kit, which i bought on ebay comes with a copper head gasket, and getting that to seal properly is kind of a pain, but other than that... the bike runs awesome.
see my website for the build process (see parts 1-4):
http://www.chinonthetank.com/2013/02/cb500t-engine-rebuild-part-4/

-Ed

Bike looks and sounds great - best luck after you re-anneal the head gasket.

 

[joevirus563]

hey guys.
i put todd henning 11.5 compression race pistons in a stock cb500t engine and the bike runs awesome.
in a cb500t those pistons should yield somewhere around 10.5 compression because of the different deck height.
i guess the cylinder wall may be a tad thin with those pistons, but i talked to henning and hanson and they both said it'll be fine for street use which is what my bike is used for.
fuck it. the thing runs awesome and is way more peppy.
the henning piston kit, which i bought on ebay comes with a copper head gasket, and getting that to seal properly is kind of a pain, but other than that... the bike runs awesome.
see my website for the build process (see parts 1-4):
http://www.chinonthetank.com/2013/02/cb500t-engine-rebuild-part-4/

-Ed

On my CB450 no problem at all with the cooper gasket!

You need:
1rs copper spray from permatex http://www.permatex.com/products/product-categories/gasketing/gasket-sealants/permatex-copper-spray-a-gasket-hi-temp-sealant-detail
Let dry
2nd I put a nice even coat 1mm on each side of the copper gasket
don't let dry, bold the head on the gasket *Not to spec
Wait 24h and torque down to spec. No leak at all!

Trust me, my head was a mess, with all sort of dings on it and that sort of sealed it all!

 

[Swagger]

So technically, since the 500T achieves it's extra displacement via a longer stroke, running 450 spec pistons in a 500t will always net you a higher static compression than they normally would in a 450. If you're running 11.5-1 450 spec pistons in a 500t, your static compression ratio should be in the neighborhood of 11.4 to one give or take a tick or two for base and head gasket choice. I am not aware of a 500T specific aftermarket piston but have used a few different 450 pistons after turning the squishband to allow for chamber clearance at the upper ring land.

+1 on the copper gasket with permatex spray copper, works a treat.