Author Topic: Big Bore question: 500 pistons in a 400 (Read 7976 times)

GroovieGhoulie · « **on:** July 20, 2006, 01:23:10 PM »

I know the jugs will have to be resleeved, but would it work? The stroke on the two bikes is nearly the same (50.6mm for the 500 versus 50mm for the 400), so the bigger pistons alone should bring the 400 close to 500ccs and since one of the big bore kits already offered for the 400 punches it out to nearly 500ccs (493cc), then it might be able to be made to work right?

What would have to be done to the head for something like this? I imagine a new cam and probably new carbs as well.

cmorgan47 · « **Reply #1 on:** July 20, 2006, 01:54:09 PM »

kaz yoshima got it up to 490......after breaking quite a few motors in the process.....

http://sohc4.us/?q=node/155

as for what else to change, sounds like pretty much everything.

crazypj · « **Reply #2 on:** July 20, 2006, 02:06:26 PM »

I did one using 500F liners and pistons (in 1988) Worked real well. came out at 491cc I think? Needed an oil cooler (used CB650 take off plate and a Yamaha cooler) Did thousands of miles before getting sold. saw it a couple of years later (1993/94) so it was still running. smoked a bit and looked really rough
PJ

Tim2005 · « **Reply #3 on:** July 20, 2006, 02:47:09 PM »

I believe I'm right in thinking that the 500 has bigger gudgeon pins so you need different rods such as Carillo's. Certainly the Yoshi 495 kit uses rods with a 15mm bore.

As for other mods- headwork, cam, oil cooler, carbs, exhaust, ignition would all be very desirable. A 460 kit is an easier option as you can use standard rods and just bore the cylinders, retaining the stock liners. Plenty of potential in these motors, but there doesn't seem to be many people tuning them nowdays (except me..).

GroovieGhoulie · « **Reply #4 on:** July 20, 2006, 05:16:31 PM »

Well sort of like Yoshima, I want to see how much I can squeeze out of the little 400. I have my 400 stocker, but have been tossing around the idea of picking up a 400F motor and taking it as far as I can.

As far as breaking parts, all the "R&D" has pretty much been done already, so I can just use the knowledge gained from previous attempts to hopefully do it right.

I'm really thinking of being different and going with a 400 Cafe that can blow away stock 750s.

Noel · « **Reply #5 on:** July 20, 2006, 06:47:09 PM »

Quote

I'm really thinking of being different and going with a 400 Cafe that can blow away stock 750s.

You got my vote. Easy for me, though, because I'm not the one who has to try to make it work!

ttr400 · « **Reply #6 on:** July 20, 2006, 10:25:50 PM »

The yoshimura 56mm 2 ring slipper kit is no longer available, this kit has a 15mm small end and required Carrillo or RSC rods and new sleeves. There was also a 54mm kit 10.1 CR kit to fit with the stock rods. also no longer available. you can still get the 54.5mm 9.6-1 CR, uses stock rods and a straight re-bore.
I have fitted the CB500 56.5mm pistons to a 400, you will need Carrillo rods with 15mm small end, there is a company in ozz and the UK that will also do the rods, the Honda RSC race rods are no longer available. also requires new sleeves to be made, boring of the block and enlarging the upper crankcase to fit, copper head gasket. with all that work you must work the head and combustion chambers to get the full benefit and then throw on a good pipe and a set of 26mm CR's. you will most certainly blow away a 750 and a Z1000 up to the ton but leave them for dead on a twisty track...!!!
Oh I almost forgot a good cam with HD springs etc and an up rated oil pump for more oil flow, just like Kaz.
Check out my web site there is lots of info including how to do the oil pump.
I have just nearly finished my racer, I will update later when I get it going and tuned with some dyno figures.
54mm = 458cc, 56mm=492cc.

Kevin in South Africa.

pmpski_1 · « **Reply #7 on:** July 20, 2006, 10:54:55 PM »

Disclaimer: I know nothing about building engines, and very little about the 400.

Doesn't the 400 have a really high redline (compared to the bigger bikes)? How will putting the larger pistons affect the redline? Or will it not affect it at all because you're not changing the stroke?

GroovieGhoulie · « **Reply #8 on:** July 20, 2006, 11:33:15 PM »

Regarding an exhaust:

What would be the best way to go? Try and find a 4-into-1 or go with 4-into-4 megaphones like the racers?

GroovieGhoulie · « **Reply #9 on:** July 20, 2006, 11:40:17 PM »

Wow! This REALLY has my gears turning. I like being unique and I haven't heard of someone giving a 400 the full treatment (except ttr400 of course).

Please keep me updated on HP figures. Kaz never could spin them much past 12500 as the bottom end would break.

Would LOVE to see how it can turn out.

Also, could you maybe give some insight into cost? These things are cheap compared to the cars I am used to tinkering with, but an idea would be a good thing.

crazypj · « **Reply #10 on:** July 21, 2006, 12:25:42 AM »

You dont need to spend stupid amounts of cash on Carrillo or similar rods. all you need to do is make 8 'buckets' to fit standard pins into larger pin holes. I've done quite a few on different bikes and never had any problems (after all, even a cheap steel is still stronger than the alloy piston) Pistons get a little bit of work to compensate for the extra weight. Its how I put Suzuki GS1000 pistons into CJ250 Honda, 14mm overbore (had to use CB350 pins as they are longer than CB/CJ250 ones)
I'm going to put some GSX-R1100 pistons (78mm) into CB360, I know they will go as I've already done a cylinder and case bore last year (not mine, guy in Kentucky or Carolina, forget which)
PJ

ttr400 · « **Reply #11 on:** July 21, 2006, 01:03:03 AM »

The stock redline is 10.000 RPM, with a fully worked motor with super duper rods and bolts I would expect it to rev to 13.000 RPM or more! Yes as per Kaz the stock rods or actually the rod bolts can't handle those sort or high numbers before spitting the rod out of the case, and that we don't want to do!
Depending on the style of racer you want to build, for an RC replica I would go for a 4-4 just for the looks and sound alone. Otherwise I would go for a yoshimura or a MC again(Kevin in Seattle can get them) 4-1 pipe.

How much $$ to do all of this?? well I would estimate for a full house motor with all the bells and whistles and excluding carbs and pipe, about $6.000.00. Just for interest with a donor motor supplied, I would do it for that and would include:

Full tear down,strip clean measure all parts etc.
Mod/ported cyl head. ceramic coated combustion chambers.
New valves and H/D springs, Ti retainers.
New inlet manifold rubbers, matched to head and 26 CR's.
Machine new sleeves and mod block to fit, bored for CB500 pistons.
Machine top crankcase.
New web cam race camshaft.
Align and balance rockers.
H/duty cam chain with all new adjuster parts and slotted cam sprocket.
New main and big end bearings.
New primary chain.
new gearbox bearings.
Bush selector forks.
undercut and anti-friction coat all gears and shafts.
Carrillo rods.
CB500 piston and rings with ceramic coated tops and anti-friction coating on skirts.
Balance crankshaft and con rods.
Barnet or stock clutch plates, barnet springs.
If race only motor, cut alternator end of crank, remove all kickstarter mech. remove all parts not required for starter motor.
Modified oil pump.
Oil cooler take off.
Dyna ignition and coils.
Spark plugs: 1 or 2 numbers colder, 9 or 10's.
Billet points, tappet and crank covers,exhaust manifolds,sump plug, oil filler cap.
Billet motor mounts.
Modified sprocket cover.
Breather tank in place of starter motor.
All gaskets, o-rings and seals replaced with new OE parts.
Camshaft degreed and motor set up ready to run.

Whew, I think that's about it. what Have I forgoten?
Kevin

Terry in Australia · « **Reply #12 on:** July 21, 2006, 02:59:39 AM »

Quote from: crazypj on July 21, 2006, 12:25:42 AM

You dont need to spend stupid amounts of cash on Carrillo or similar rods. all you need to do is make 8 'buckets' to fit standard pins into larger pin holes. I've done quite a few on different bikes and never had any problems (after all, even a cheap steel is still stronger than the alloy piston) Pistons get a little bit of work to compensate for the extra weight. Its how I put Suzuki GS1000 pistons into CJ250 Honda, 14mm overbore (had to use CB350 pins as they are longer than CB/CJ250 ones)
I'm going to put some GSX-R1100 pistons (78mm) into CB360, I know they will go as I've already done a cylinder and case bore last year (not mine, guy in Kentucky or Carolina, forget which)
PJ

This is interesting PJ, do you have any pics of these "buckets"? My cousin once turned up a brass "sleeve" when he bored my 3 horse briggs mower engine out to 5 horse but needed to sleeve the conrod's wrist pin hole to take the smaller wrist pin of the 5 horse piston.

Trouble is, the sleeve was quite thin (about 1mm thick) and the engine only lasted a couple of hours? I can understand the theory of the buckets, but I doubt if there'd be enough room left for circlips etc?

Show us some pics mate, if I could make some on my lathe I could use my spare Suzuki GS1100GK pistons (72mm) in a CB750 engine for a displacement of 1060 cc! Cheers, Terry.

cmorgan47 · « **Reply #13 on:** July 21, 2006, 05:38:38 AM »

Quote from: GroovieGhoulie on July 20, 2006, 05:16:31 PM

Well sort of like Yoshima, I want to see how much I can squeeze out of the little 400.

I'm really thinking of being different and going with a 400 Cafe that can blow away stock 750s.

kaz is my hero.
he's the wallpaper on the computer i'm using right now.

do it.... big ups...make people cry.

Quote from: GroovieGhoulie on July 20, 2006, 05:16:31 PM

What would be the best way to go? Try and find a 4-into-1 or go with 4-into-4 megaphones like the racers?

4-1, and the 1 is chopped short and right under your foot

dusterdude · « **Reply #14 on:** July 21, 2006, 07:24:47 AM »

pj beat me to it,but i was gonna suggest to rebush the small end of the rod to fit the pistons.

ttr400 · « **Reply #15 on:** July 21, 2006, 08:51:10 AM »

What pj is refering to is the other way round duster, the small end needs to be 15mm not 13mm. bushing the piston to take the 13mm pin. Yes I can see this would work, not the way I would go. Honda changed to a 15mm pin for the high performance kit for a reason, and I don't think I would trust all my work and expensive parts to this, especially the sort of revs and speed your going to produce, around a 50% increase in HP.

Kevin

dusterdude · « **Reply #16 on:** July 21, 2006, 10:52:59 AM »

ok,so we need to bore it out a little,is there enough meat in the rod to do that.

crazypj · « **Reply #17 on:** July 21, 2006, 11:10:18 AM »

Quote from: ttr400 on July 21, 2006, 08:51:10 AM

What pj is refering to is the other way round duster, the small end needs to be 15mm not 13mm. bushing the piston to take the 13mm pin. Yes I can see this would work, not the way I would go. Honda changed to a 15mm pin for the high performance kit for a reason, and I don't think I would trust all my work and expensive parts to this, especially the sort of revs and speed your going to produce, around a 50% increase in HP.

Kevin

Kevin,
thanks for explaining to Duster.
I've done this, it works.
may not be the most elegant solution but it costs virtually nothing compared to the not unreasonable $6,000 estimate (its about how much I'd want to do that much work, with all those parts)

If you already have a block with damaged fins but good liners and pistons,
Why Not?
Its better to recycle it in my opinion than to scrap suff
I bought a sheet of copper to make a head gasket and new circlips. cut bigger holes in base gasket, bored cases when needed and except for labour, I'm done
(and, when I'm doing things as a HOBBY I dont charge myself

)
I always intend to use lower than stock redline with the heavier parts fitted but somehow it never seems to work.

The 550 is the only one I built while working at a Honda dealers, all the others have been done on a very old Colchester lathe and vertical mill ( I forgot who made it as I trained as a turner originally so I like lathes

)
My 550 with 750 pistons revs out at about 13,500rpm, (82mph in second gear, someone can do the math for stock gearing but 13.5K is close)
I fited a decent ignition system as the points bounce at about 10,500 (who needs electronic rev limiter?)

Terry,
its very much like a bush for the piston. the pins are only slightly short so you make an internal lip on bushing and the overall length when a pair are fitted has to be the same as a standard piston pin for the pistons your using. its a very simple turning job. for the 400/500 conversion I made them slightly longer than needed towards the inside to help locate pistons when fitting block, dont remember what steel I used but it wsasnt just any old piece of pipe (wasnt a real expensive one either though)
You can do quite a lot of work on stock pistons to lighten them, but its a bit time consuming to get all four equal. You can change the rod bolds for better ones.
I'm not an engineer so I dont know how to work out stresses involved therefore things I make are probably stronger than they need to be.
thats all from me for now,
PJ

Terry in Australia · « **Reply #18 on:** July 21, 2006, 03:48:14 PM »

G'Day PJ, well I'm a believer mate, like you, I know a lot of money can be saved if you think outside the normal "Remove the standard part and replace it with an ultra-expensive aftermarket part" box. A lathe and a mill is a terrible thing to waste, ha ha!

I might have a play with some left over GS1000 parts, the stock pistons are 70mm and I've got a few of those. (970CC in a CB750?) I'd rather use brass or bronze for the "buckets" though, because of the self lubricating properties, would this be ok do you think mate? Should they be a "press fit" into the pistons? Cheers, Terry.

GroovieGhoulie · « **Reply #19 on:** July 22, 2006, 07:02:35 AM »

For ttr400, or anyone else who knows:

How much of that very comprehensive list would you modify for a "street" motor? I'm not planning on a full-blown racer, but I would consider doing everything on the list, except removing the alternator and electric start.

crazypj · « **Reply #20 on:** July 22, 2006, 09:47:53 AM »

Hi Terry mate,
I didnt use brass or bronze as I didnt have any at the time. (not sure I would though even if I did have some

)
There is plenty of oil 'up there' when engine is running so you dont need the extra lubricty??

, I used steel as its stronger in thin section, just in case it needed to be

Made a tight sliding fit, that way you have extra bearings (about 0.0003"~5" clearance each side, I dont think it was really necessary but did it anyway)
I polished an old pin down with 400/500 grit wetordry to be that much undersize and used it as go/no go gauge (you can measure the OD easy with mic.)
If clearance is too big it sounds exactly like loose tappets but doesnt seem to cause any problems (been there did that, made new buckets as I didnt like the noise

)
Have fun making bits and putting it together, may as well try as it will keep you out of trouble chasing sheep in the outback.

PJ

bill440cars · « **Reply #21 on:** July 22, 2006, 01:12:58 PM »

This is just one of the reasons that I like this site so much. While I may not be able to do some of the things mentioned, I definitely am enjoying the details and possibilities of things you can do to these motors. I don't have the availability of a lathe or a milling machine, so my involvement (with out spending much) is somewhat limited. Keep the info and ideas flowing though. I'm totally IN to what's being pit out here.
Later on, Bill

aptech77 · « **Reply #22 on:** July 22, 2006, 03:47:43 PM »

aptech77 · « **Reply #23 on:** July 22, 2006, 03:57:43 PM »

Didn't Kaz also mod the case to be able to fit the rods and 492cc pistons. My friend who helped me finish my est. $6000 cafe racer knows Kaz very well. He has ran into a lot of badass racers after 30+years in the bizz. http://www.sohc4.us/gallery/v/members/personal/James/

Terry in Australia · « **Reply #24 on:** July 22, 2006, 04:28:16 PM »

Quote from: crazypj on July 22, 2006, 09:47:53 AM

Hi Terry mate,
I didnt use brass or bronze as I didnt have any at the time. (not sure I would though even if I did have some )
There is plenty of oil 'up there' when engine is running so you dont need the extra lubricty?? , I used steel as its stronger in thin section, just in case it needed to be
Made a tight sliding fit, that way you have extra bearings (about 0.0003"~5" clearance each side, I dont think it was really necessary but did it anyway)
I polished an old pin down with 400/500 grit wetordry to be that much undersize and used it as go/no go gauge (you can measure the OD easy with mic.)
If clearance is too big it sounds exactly like loose tappets but doesnt seem to cause any problems (been there did that, made new buckets as I didnt like the noise )
Have fun making bits and putting it together, may as well try as it will keep you out of trouble chasing sheep in the outback.
PJ

Thanks mate, I'll try mild steel (only because I have some in the garage as I type this) you're probably right about the benefits of steel for small section stuff over brass or bronze, and I'll keep the clearances tight as the wrist pin doesn't obviously need to move inside the piston. Now I gotta go finish off some more oil coolers................ Cheers, Terry.

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Author Topic: Big Bore question: 500 pistons in a 400 (Read 7976 times)