Author Topic: HOn CB500/550 Big bore kits (Read 8259 times)

kos · « **on:** October 14, 2009, 04:20:33 PM »

Anyone out there know of any big bore kits for CB500/550 SOHC fours that are using thinner rings for compression and three (3) piece oil rings. Not Henry ABE stuff, but racing quality?

Any help is welcome..

KOS

Mark@M3racing.com

bwaller · « **Reply #1 on:** October 14, 2009, 04:26:15 PM »

KOS email on the way.

Sam Green Racing · « **Reply #2 on:** October 14, 2009, 05:45:01 PM »

Mark, what about your own CB350 race pistons, what size are they and have they not got thin rings?

Sam.

mlinder · « **Reply #3 on:** October 14, 2009, 05:53:18 PM »

I think the M3 cb350 pistons are 67mm. Thats about... 8mm over stock 550 pistons.
Dunno how well that would go in a 550.

That'd leave room for only 1mm thick sleeves on stock 550 jugs.

Sam Green Racing · « **Reply #4 on:** October 14, 2009, 06:11:25 PM »

I was thinking along the lines of the 836 Wiseco pistons Mark, they were origionally made for the CB350 and with 750 liners in the 650 block like Paul did, you have your big bore 550.

Sam.

mlinder · « **Reply #5 on:** October 14, 2009, 06:13:55 PM »

What's the bore on the 836 kit? I can't remember.

Sam Green Racing · « **Reply #6 on:** October 14, 2009, 06:18:08 PM »

Me too and I don't have a calculator handy or I could work it out.

Sam.

Sam Green Racing · « **Reply #7 on:** October 14, 2009, 06:34:09 PM »

The Wiseco 836 are 65mm, Paul had 64mm pistons in his motor so I'm not sure what they were from or if pauls motor would stand another 1mm out of the bores.

Sam.

MRieck · « **Reply #8 on:** October 14, 2009, 07:26:46 PM »

Brent had Ross make a one off set

paulages · « **Reply #9 on:** October 14, 2009, 10:23:00 PM »

i have 64mm pistons in my c718cc cb550 big-bore, which is the 811cc kit for the cb750, or std. size for the cb350. i'd have gone with the 65mm pistons, but i found these for cheap. i used 750 liners, so they can handle whatever the 750s can... 65.5mm or so, right?

i got my rings from hastings, and have part #s if anyone needs light compression rings and three-piece oil rings for this size.

kos · « **Reply #10 on:** October 16, 2009, 08:01:37 AM »

Thanks for the information and input from the members. I do not want to make this engine Too big and have the liners end up being to thin. Also, class limit is 600cc. The last one we did at M3 used 4th over, OEM pistons and we got higher compression by welding in alloy material on sides of combustion chamber to end up with a "bath tub" chamber shape. With a cam that we designed, larger intake valves, bored standard carbs & four open meggas.... went fast enough to win a 3rd place at Daytona (a real HP track!) vs Yamaha two stroke 350's.

Anyone out there know of any Yoshimura kits laying around?

KOS
M3 Racing USA

Bill/BentON Racing · « **Reply #11 on:** October 16, 2009, 02:48:02 PM »

Paulage,shoot me those pt #'s,have a Yosh 812 kit,Thanks,Bill

paulages · « **Reply #12 on:** October 16, 2009, 07:57:15 PM »

Quote from: bellcow54 on October 16, 2009, 02:48:02 PM

Paulage,shoot me those pt #'s,have a Yosh 812 kit,Thanks,Bill

Will do, bill. I'll have to dig them up.. I have them in a drawer at the shop. Worst case scenario, hastings has them saved under my customer number.

turboguzzi · « **Reply #13 on:** October 21, 2009, 01:32:56 PM »

Mark, there are quite a few interesting pistons made for big bore 125-150 four strokes singles, very modern in design: light, slipper skirt, graphite coating, 1mm rings, etc.

Never looked into 64 mm as I run 57's for the 500 class, but I remember seeing some nice ones in 61-62-63 sizes. Most will have very low decks heights though, so require serious milling of the block. I went that way and pretty happy so far.

would be great to see the type of welding you've done to those heads and how the chambers ended up. How much bigger a valve did you fit? Did it require new seats?

Cheers

TG

the kit piston I am currently using is on the left

Bill/BentON Racing · « **Reply #14 on:** October 21, 2009, 04:51:31 PM »

TG,I like the one you are using the best,what coating?,also story behind middle piston? You still in 3rd for season? Some of these new 4 stroke dirt bikes have potential!,Bill

turboguzzi · « **Reply #15 on:** October 21, 2009, 11:23:25 PM »

bill,

its got some sort of graphite based layer to smooth out running in, the stuff has nill thickness and wears off with use.

will open the engine after last race and see how they held up.

the middle piston was the previous one i been using. from quite a decent japanese company but didn't hold up well, though I have to say that since I was in a rush, i installed it without reboring and also had some detination problems in one race. still, couldnt figure out why only one out of four smeared out like that.

Last race is this weekend, just need a decent finish. Will report.

TG

Terry in Australia · « **Reply #16 on:** October 25, 2009, 04:38:33 PM »

OEM 61mm (592cc in a CB550) CB750 pistons are pretty good quality, and the skirts can be machined down to suit, as can the crowns. Cheers, Terry.

turboguzzi · « **Reply #17 on:** October 26, 2009, 02:30:49 PM »

Yeah right Terry, 61 = 600 or so, don't know why i thought about 64's....

Kos, a certain Honda scooter, the GL-145/GL-PRO has 61mm pistons worth looking into with good deck height for a 550.

Personally, am still curios about the welded bathtub chambers you talked about. would be great to hear some more details.

TG

MRieck · « **Reply #18 on:** October 26, 2009, 02:42:47 PM »

Quote from: turboguzzi on October 26, 2009, 02:30:49 PM

Yeah right Terry, 61 = 600 or so, don't know why i thought about 64's....

Kos, a certain Honda scooter, the GL-145/GL-PRO has 61mm pistons worth looking into with good deck height for a 550.

Personally, am still curios about the welded bathtub chambers you talked about. would be great to hear some more details.

TG

It probably looks like the old Branch Harley heads.

kos · « **Reply #19 on:** October 26, 2009, 03:37:21 PM »

I'll look around for some pics . It was back in 1998-2000 we ran that bike. Welded in a lot of aluminum on sides of chamber. Used a die grinder to smooth and contour.

KOS

turboguzzi · « **Reply #20 on:** October 26, 2009, 07:38:22 PM »

So Kos, Mike,

Other than the obvious risk of heavy welding in the head and the labor, are bathtub heads good in terms of flow?

Gut feeling says that the added material will shroud the intake but we all know that air doesnt follow visual logic right?

You can surely create good squish areas with a bathtub design, something that should help especially the 750's.

I recall seeing some bathtub heads in recent tuned Ducati 2V belt drive twins. These have 60 degs included valve angle, pretty close to the CB500 so the geometry could be scaled.

TG

kos · « **Reply #21 on:** October 31, 2009, 07:27:00 AM »

You have to be carefull not to add too much weld material around the valves to avoid shrouding, but we got great numbers of airflow. Intake valves were 28.5mm and ex 24mm.

KOS

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Author Topic: HOn CB500/550 Big bore kits (Read 8259 times)