Author Topic: 400F big bore question... (Read 7724 times)

GroovieGhoulie · « **on:** January 02, 2007, 11:28:03 PM »

I see the Yoshima 466cc kits for sale on the 'net and they seem easier and more "drop-in" than the CB500 piston conversion.

My question is how much more power would I potentially be losing by not going with the CB500 pistons?

The Yoshima kit is 466ccs and with the 500 pistons, I would be getting 492ccs.

It just seems that the 500 pistons are more work:

Gotta press out the 500 liners and insert them into the 400 jugs
Gotta mill the 400 engine case to take the bigger bores
Gotta make a custom head gasket since I don't think anyone makes one that size.

And for how much extra gain? I mean how much can 26ccs really give?

Plus it looks like the 500 cylinders I have are worn, so I would need to have them honed and then try and find oversize pistons and rings (though I think DSS has them).

ttr400 · « **Reply #1 on:** January 03, 2007, 04:53:43 AM »

Well, for a full blown race motor you will see a difference with going the 500 route, but then it would be working with a lot of other goodies to make it all work, headwork, larger intake valves, CR carbs, cam, exhaust, stronger rods, and you would probably be talking in the 13000-14000 rpm range.
For a good fast street bike I would go with the 466 yoshimura kit. Kevin in Seattle is building one at the moment, plus he is the importer of those kits, he can also supply you with the valves, valve springs, cams, CR carbs etc.

Kevin

GroovieGhoulie · « **Reply #2 on:** January 03, 2007, 05:06:45 AM »

Quote from: ttr400 on January 03, 2007, 04:53:43 AM

Well, for a full blown race motor you will see a difference with going the 500 route, but then it would be working with a lot of other goodies to make it all work, headwork, larger intake valves, CR carbs, cam, exhaust, stronger rods, and you would probably be talking in the 13000-14000 rpm range.
For a good fast street bike I would go with the 466 yoshimura kit. Kevin in Seattle is building one at the moment, plus he is the importer of those kits, he can also supply you with the valves, valve springs, cams, CR carbs etc.

Kevin

I am intending a street motor, but taken to the closest edge of "race motor" that I can with the barest hint of civility.

I am wanting to see 75hp at the rear wheel. Can this be done while keeping the alternator and such? Reportedly it can, but I'm not sure.

Also, tracking down the carillo rods is turning into a real nightmare. Are they even out there?

ttr400 · « **Reply #3 on:** January 03, 2007, 05:23:02 AM »

75 HP is a bit optimistic, that is close on a 100% increase over stock.....!!! For a good streetable motor I would say in the 50-55 HP range. I'm going to dyno my racer at some stage to get it dialed in, then I'll have some no's for you.
Ask MRiek about the Carrillo rods? They make them to order anyway.

Kevin

GroovieGhoulie · « **Reply #4 on:** January 03, 2007, 05:36:04 AM »

Quote from: ttr400 on January 03, 2007, 05:23:02 AM

75 HP is a bit optimistic, that is close on a 100% increase over stock.....!!! For a good streetable motor I would say in the 50-55 HP range. I'm going to dyno my racer at some stage to get it dialed in, then I'll have some no's for you.
Ask MRiek about the Carrillo rods? They make them to order anyway.

Kevin

Optimistic, I know, but I want a "little 400/4" that can whip on period Kawasaki Z1s and such, just like they did back in the day. Also a bike that can whip the British Cafe bikes that guys around here ride. They have nothing but disdain for Japanese bikes and especially small-displacement Japanese bikes.

If it can be done with 55hp, perfect, but I want this thing to eat Z1s and Commandos for breakfast without blinking.

bryanj · « **Reply #5 on:** January 03, 2007, 05:49:24 AM »

Not wanting to be a dampner but no way will you get 100 and be anything like streetable OR reliable, that would be a drag motor with a rebuild every 5 runs (1 1/4 miles)

TomC · « **Reply #6 on:** January 03, 2007, 07:28:55 AM »

Hi 400Guys
How big can you go? If you have pressed in 500 sleeves. Why not use 550 pistons? Or maybe 750 pistons as in the 605 kits?
Is a very deep sump or oil pan a common after market part for the CB400F?
TomC

crazypj · « **Reply #7 on:** January 03, 2007, 09:58:08 AM »

You don't press in the sleeves. you bore block and shrink them in.
You could probably use 550 sleeves and pistons but I haven't tried it so I'm no sure.
The spacing between bores is too small to get really big bore, you don't want the liners touching, (unless you weld up a waterjacket for cylinder and head

)
I've got a 400F block with the liners out, I'll take some measurements and get back to you.
PJ

Tim2005 · « **Reply #8 on:** January 03, 2007, 03:21:11 PM »

75bhp is seriously optimistic. This article is well worth a read as to what it takes to keep a highly tuned one going

http://www.sohc4.us/index.php?option=com_content&task=view&id=74&Itemid=54

note the reliability.. new rings every 3 races and only 3 motors out of 9 not blowing up. Interesting that they made it to 13000 rpm on stock rods, I suspect they removed the rotor too as that's meant to break the end off the crank at 11500, though I missed a gear big-time on my 460 just before Xmas & was amazed that nothing broke... revs were astronomical for a moment. Also interesting that they seemed to use stock carbs, bored; no smoothbores there.

As for pistons... I have a 475 motor I used to run, Kawa 55mm pistons & liners, that was faster than I've ever had my 460 (54mm Yoshi), fantastic fun bike, it ran huge compression though. I picked up a set of Kawa 58mm pistons & liners last winter but they will not fit- there simply isn't the room, not just between bores but also without encountering the oilways. I've since picked up a set of 55.5 Kawa pistons so will resurrect that motor sometime. Especially if I can get a job lot of primary chains. I suspect that 56mm (492cc) is the maximum, I've never heard of a 400f running over that. The 460 is noticeably more reliable than the 475 was, tuning these motors is always going to be a trade-off between performance & reliability, and rideability needs to be considered too, I have a stock 400 I use wintertime when the traffic is heavy here & it's so much better for that.

BTW, I do like the waterjacket idea... have often wondered about that myself.. these motors get incredibly hot when tuned, notably the linked article mentions " He usually managed to do a respectable few laps and then would drop back in the pack as either he tired or the engine soured" ... I'll take a bet it was overheating.

malcolmgb · « **Reply #9 on:** January 03, 2007, 03:32:11 PM »

Water cooling an air cooled motor.

Now that takes me back to the early 1970's when the Yamaha 125 YAS3 was being raced, people were cutting off the cooling fins on the barrels just leaving top and bottom then 'Aralditing' aluminium sheet around to create a water jacket and similar with the head linked by small rubber pipes, not sure what radiator was used at time though. All in all it seemed reliable and better than the the air cooled machines.

Tim2005 · « **Reply #10 on:** January 03, 2007, 03:36:18 PM »

That's pretty much what I'd considered, inspired by a conversion of a race Kawa H1 instead of a YAS3 (with welding instead of aralditing), though building a similar jacket around the head would be pretty complex!

aptech77 · « **Reply #11 on:** January 03, 2007, 05:34:09 PM »

I hate to say this, but it all comes down to the rider. A bike can have all the power in the world, but it is only as use full as the rider is good. 90% rider 10% bike. GG, all the mods I did to my 400F, and I'm looking at about 55hp. The biggest improvement you can make, is head work. If you really want that kind of power, look at a bigger bike. There is a fine line between power and reliability. IMO............... $:-\$

GroovieGhoulie · « **Reply #12 on:** January 03, 2007, 10:02:26 PM »

Now is that 55 at the wheel or at the crank? 55 at the wheel should be about 65-70 at the crank right?

I want a motor that is (barely) streetable. A real fire-breathing monster.

Yeah, I know it's 90% rider, but the bike is still part of the equation. Would a 400, (500 really), with 55hp, theoretically, with the right rider, still eat Z1s and Commandos?

paulages · « **Reply #13 on:** January 03, 2007, 10:50:04 PM »

groovie--give cometic a call for odd sized gaskets. i thought a custom gasket would be in order for my 718cc (out of a 550) project, but they said that the bore size doesn't matter as long as the rest is stock. they said all they needed to know was that it is a 650 cylinder block, and whatever the final bore size ends up. the impression i got was that they have templates that they cut the gasket to, then bore the holes out according to the project, and press in the copper parts.

Pinhead · « **Reply #14 on:** January 03, 2007, 11:16:26 PM »

Hey paulages, how much for a custom gasket?

paulages · « **Reply #15 on:** January 04, 2007, 09:25:23 AM »

i can't remember exactly what they quoted me, but it was something like $20-$30 bucks for each (base and head).

mlinder · « **Reply #16 on:** January 04, 2007, 11:07:32 AM »

cb 400 f
400ish lbs (give or take 10 lbs)

Norton Commando
430ish lbs (give or take 10)
50ish rwhp (60-65 at crank)

Kawi Z1
510 lbs (give or take 10)
82 crank hp
Tons of torque

I don't think you can get anything like 75 hp at the crank, not without it 'sploding every 150 miles.
I think you'd be lucky to get 55 at the crank.
That still won't put you ahead of a norton.
On any track that had any straight aways, the Z1 would hand you your ass. Got enough twisties, might be able to keep up due to superior exit speed from better handling, but no, I don't think you'll be dusting any Nortons or Z1's.

aptech77 · « **Reply #17 on:** January 04, 2007, 01:52:02 PM »

About 55 at the crank. You will loose about 10% the the rear.

GroovieGhoulie · « **Reply #18 on:** January 04, 2007, 09:34:49 PM »

Well my goal for the weight loss program on the bike is to get it down to 300 pounds wet. Then with the uprated suspension and engine, it should have a beneficial power to weight ratio.

Lets go with aptech's numbers and say 55hp, (though depending on the alignment of the moon and how everything goes together, it could be 60-ish maybe).

300 lbs / 55 hp = 5.45 pounds per hp.

Commando (based on your numbers and going with the higher HP number):

430 / 65 = 6.6 pounds per hp

Z1:

510 / 82 = 6.2 pounds per hp.

So, given the right rider, and the right road conditions, I think a lightened 400F with a powerhouse engine could give them a run.

mlinder · « **Reply #19 on:** January 05, 2007, 07:47:30 AM »

How are you going to take of 100lbs and stilll have a streetable bike?

crazypj · « **Reply #20 on:** January 05, 2007, 08:25:08 AM »

Quote from: GroovieGhoulie on January 03, 2007, 10:02:26 PM

Now is that 55 at the wheel or at the crank? 55 at the wheel should be about 65-70 at the crank right?

I want a motor that is (barely) streetable. A real fire-breathing monster.

Yeah, I know it's 90% rider, but the bike is still part of the equation. Would a 400, (500 really), with 55hp, theoretically, with the right rider, still eat Z1s and Commandos?

No, it ain't ever going to eat Commando or Z1.
If Z has modified frame it handles pretty good, you can hustle it round through twisties (just don't chicken out and shut throttle)
I've got some pics of Z1-B my sister used to have with the frame mods. It REALLY surprised me how well it went round corners with undercarriage dragging (90mph+)
I've also built big-bore CB400's, its no contest, when you get major power boost on 400, the frame starts flexing so bad you have to slow down (or start cutting and welding on it

)
If you want to humiliate the big boys your going to have to get a bigger bike ( major modded 550 could work with about 75/80 bhp) or find crap riders on the big bikes
PJ

tsflstb · « **Reply #21 on:** January 05, 2007, 08:30:58 AM »

The first 30-40 lbs. are easy...seat, fenders, exhaust, airbox, handlebars, centerstand, unnecessary frame brackets, etc. Another 10-15 lbs. if you can run kickstart only with a smaller battery. After that it seems like you've got diminishing returns. Drill the rotor and use alloy rims for a few pounds. Alloy bit like a swingarm and gas tank start getting real expensive.

Dual disks, oil coolers, fork braces, steering dampers, and all those goodies add some weight back. I think you could get to 350 lbs. pretty easy though.

I'm planning on buying a couple of cheap bathroom scales this weekend (need to weigh a small trailer) and was going to roll my bike on there for kicks. I've done most of the easy stuff above, and I'm guessing 375 lbs. with a gallon or so of gas.

Of course, the bike doesn't do much without a rider and my personal power to weight ratio has gone to hell since Christmas. Pass the gravy please...

crazypj · « **Reply #22 on:** January 05, 2007, 08:45:33 AM »

Quote from: tsflstb on January 05, 2007, 08:30:58 AM

The first 30-40 lbs. are easy...seat, fenders, exhaust, airbox, handlebars, centerstand, unnecessary frame brackets, etc. Another 10-15 lbs. if you can run kickstart only with a smaller battery. After that it seems like you've got diminishing returns. Drill the rotor and use alloy rims for a few pounds. Alloy bit like a swingarm and gas tank start getting real expensive.

Dual disks, oil coolers, fork braces, steering dampers, and all those goodies add some weight back. I think you could get to 350 lbs. pretty easy though.

I'm planning on buying a couple of cheap bathroom scales this weekend (need to weigh a small trailer) and was going to roll my bike on there for kicks. I've done most of the easy stuff above, and I'm guessing 375 lbs. with a gallon or so of gas.

Of course, the bike doesn't do much without a rider and my personal power to weight ratio has gone to hell since Christmas. Pass the gravy please...

Ditto,

PJ

GroovieGhoulie · « **Reply #23 on:** January 05, 2007, 08:48:20 AM »

Oh well. More dreams dashed. Not that I'm surprised. That's the story of my life.

After I read the article about Yoshima's "Business Card" tearing up Z1s (yes it mentions that in the article), I had dreams of a tiny, lightweight Giant-Killer that people would think had nothing but would then embarrass them.

I guess it's not to be...

Oh well... $:-\$

tsflstb · « **Reply #24 on:** January 05, 2007, 08:54:04 AM »

I think you could still build a kick ass little bike, just choose the venue wisely when you want to run a Commando or Z1. You shouldn't be able to look straight ahead and see the finish line.

Edit...forgot you're based in my part of the world...build that bike and take it to Oak Hill or the MSR track in Cresson, but I'd stay away from Texas World Speedway. I usually run my 400 through its paces in a huge deserted church parking lot...lots of fun, but I need to get to a real track soon. I'm not winning any points with God dragging my pegs on His asphalt.

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Author Topic: 400F big bore question... (Read 7724 times)