Race Pistons for CB200

[gehlsurf]

Hi! I was wondering if anyone had, or knew where I could find racing pistons for a CB200!! I can't find any at all. Just to let you know, I've tried Hap's Cycles, Megacycle, and I think it was called West Hills Honda? Megacycle is going to make me a cam, and they have "street aggressive" and "Track aggressive", lady said that you need Race Pistons for the "track aggressive". Anybody tried this with normal pistons? I trust her, she knows her shit, but just wondering, haha. Thanks guys!!

 

[teazer]

For the street, go with that 135-x1 mild cam. No other cam IMHO comes close. BTW Barbara Dour at megacycle knows her cams for sure but there is no such thing as a race piston for a CB200 on the market that I know of. What she was saying is that you lose a bunch of compression with that long duration race cam and need high comp pistons to make it work and you need pistons with deeper valve pockets.

We have tried every cam profile made for the CB77 and CB160/175/200 - or it feels like we have and our favorite for the street or race track is the mildest cam that megacycle makes. All the other cams lose bottom end and midrange and make nothing extra at the top - unless the motor is seriously large and seriously worked. Our motors have higher than stock CR, modified pistons, gas flowed high flow/high velocity ports and that's the cam we like and the one that dyno testing supports.

We do have a motor with 180 degree crank, special cam with different duration and lobe separation angles to try out when I work out the piston shape we need to have manufactured. Then I may change my mind if teh results support that outcome.

 

[gehlsurf]

Sweet!!! That's good news for me then!! You see, I'm running kinda low compression, 105 and 115 and it runs great (been like that for about a year now), but not what it could obviously, plus a bit of oil leakin out of the breather tube on the top. So I figured I'd rip back into it, have the valves reseated, new pistons, bigger carbs and while I'm at it, get a cam made. That's where my back and forth on the pistons and cam came from. But if it's not worth getting High comp pistons for the race cam, hell, it saves me a few hundred $!!!!

I'm not gonna race it on a track, it's just kinda my baby (my first build, and had others, kz305, kz750, xt550), but somehow I always still fall in love with this lil thing, so wanted to dive in and spruce it up a bit, ya know? Thanks alot for the advice man!!!!

Just out of curiosity, how much compression does your CB have? What size carbs do you think I should run? While I got your attention and your dyno tests, haha, might as well pry a bit more, right?

 

[teazer]

Not a lot. The one with a CB200 head I had welded up to change to a bathtub shape and then I had a pair of Wiseco Kawasaki 600 pistons specially machined to a very different crown and squish shape. We would be lucky if we got it close to 10:1.

The other is a basically stock (well that's my story) 1969 CL175 sloper motor which has very different pistons. On that we machined a lot off the head and barrels and also off the squish bands which are now at a different angle. Stock it made around 11hp at less than 10kand now on a good day it's between 19 and 21 and over 11. Pistons are much lighter than stock, ports flow very differently, valves are slightly reshaped, lightened and swirl ground, carbs are Keihin 26mm on the 180 and Mikuni 26mm on the 240. This is the 180 (CL175 motor). Don't try this at home...

And this is the 240cc CB160 with CB200 head

Your compression is a little low. It really needs to be perked up a bit. Have you tried a leakdown test to determine where it's leaking? That would be a good place to start.

 

[gehlsurf]

Yeah, I think I may try a leakdown test. Thanks alot for the info man!! Hopefully you'll see me post some stuff on it once I get all the parts in!!!

 

[skatetheame]

Teazer where did you get that fairing? I'm working on a 175 and would like to do something similar.

 

[teazer]

Those are off a Honda RS125 race bike. We got them cheap from crashed race bikes. Easy to repair and takes little modification but they are really small. They require clip ons and rear sets to work and full race riding position.

For the street something slightly larger might be better. Say the Cool One from Airtech or something similar might work.

My own preference for a street bike is a small scale version of the old Ducati 750SS fairing or a small Dunstall type ie just the top half plus screen and leave the motor exposed. With a sloper 175 or Cb160 it looks like a miniature Laverda SFC.

 

[tnainc1]

teazer,

Would you mind sharing generic info on your 240 build. Crank (stroke) and piston choices (bore size). I am prepping a 175 for flattrack purposes (10 year old rider) as he progresses his skills I want to up it for the 250cc class. Obviously, he will ride it in the Vintage class.

Thanks in advance for you assistance.

Dave

 

[teazer]

teazer,

Would you mind sharing generic info on your 240 build. Crank (stroke) and piston choices (bore size). I am prepping a 175 for flattrack purposes (10 year old rider) as he progresses his skills I want to up it for the 250cc class. Obviously, he will ride it in the Vintage class.

Thanks in advance for you assistance.

Dave

Hi Dave,

Stock crank. You can lighten it if you want to but it's not necessary. Pistons are Wiseco KZ550 61mm 615 kit with crowns machined to a new shape. Head welded and re-machined to a more bathtub shape with an angled squish band. Decent flat sided cam chain because they are stronger and cause less damage to rollers. Cb77 liners IIRC shortened and modified. Crankcases bored to take the larger liners.

CB200 oil pump piston in a bored CB175 oil pump.

Single primary gear with lightened gears.

Reversed A clutch plate with extra plates and stock springs

Megacycle Cam with R&D spring kit with Titanium collars

Lightened rocker arms

Light valve adjusters - drilled and broached for hex key

Ported head

Barrels decked and head much lower than stock to raise CR to work with those low crown pistons

Stock, but lightened valves

Other than that, it's more or less stock.

If you start with a CB200 you can raise the compression and there are other larger bore pistons than can be modified much more simply. They will not rev all that high, but will pull hard out of corners. CB200 motor is a bit of fat lazy dog compared to say a 175 or 160 but the head and pump are better, barrels are taller and it is easier to adjust cam timing and I'm pretty sure there are some suitable pistons.

You could also stroke the crank by machining it to offset the pins, but that's a lot of work.