Topic: 550/600 clubman racer research thread.

[DavePhipps]

I'm hoping to be a newbie racer this coming year.
I want to take my 76 CB550 and take it out to 600. I'll be using the early CB650 head for a better combustion chamber and better valves. From the head down it will be cb550. I'm not wanting the longer stroke of the 650 rods.
According to the rules, I can use a 600cc 2 valve per cylinder engine.
I'm hoping for some suggestions for pistons size and compression ratio numbers. This is going to be a budget racer so the cheaper the better.
I'll be reviewing the howell, turboguzzi, and cb500four threads for more ideas.
Any advice is appreciated, and thanks in advance.

Bwaller if you're reading, this I wish you had a build thread.

[DavePhipps]

getting my piston size now.
http://www.bgsoflex.com/displacement.html


Bowling's Engine Displacement Calculator
Input Parameters Are the Following:
Number of Cylinders are = 4 to 1
Piston Diameter = 61.250 Millimeters
Piston Oversize = 0.000 Millimeters
Engine Stroke = 50.600 Millimeters
Computation Results:
Computed Engine Displacement (CID) is 36
Computed Engine Displacement (Litres) is 0.6
Computed Engine Displacement (CC) is 596.4


Now to research calculating compression ratios

[DavePhipps]

http://www.csgnetwork.com/compcalc.html

I need some help with the numbers here.
Info needed
Enter Head Gasket Bore Diameter.
Enter Compressed Head Gasket Thickness.
Enter Combustion Chamber Volume In CCs
Enter Piston Dome Volume In CCs Negative For Dished Pistons (Use '-') : I'll be changing values here alot
Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') : I'm not even sure what it's asking here.

[bwaller]

On a 550 I measured the chamber @ 13cc's, the 650 is much larger. Check back through Paulages build, I'm sure he measured the 650 head. For a 61mm bore, figure on a 62mm headgasket hole. Stock head gasket is 0.043", base is 0.020", you have options here as Cometic offers different thicknesses of both in different materials as well. I'm using a 0.032" copper head and a 0.010" viton coated steel base gasket to get even deck.

Again on a 550 boring to 61mm is as far as you can go on stock sleeves, and they are thin. You now need to figure what piston to use with enough dome (diameter too) to make compression in that larger 650 chamber. Off the top of my head I can't even tell you the stock 650 bore.

I had 60mm pistons made to take me out to the +5% overbore limit according to the class I want to race. It took a little work to get the 12:1 CR, and tight squish I wanted.

I have so little time to fool with this bike of mine a build thread would get boring I'm afraid. Somehow it has to be ready for next season though.

I was told several times and probably strayed from this biggest truth. It is better to get out there and race without spending huge money and make the bike faster after you get your feet wet. (Do as I say, Not as I do in this case  )

Good luck, there sure are good guys here to help.

[DavePhipps]

I was told several times and probably strayed from this biggest truth. It is better to get out there and race without spending huge money and make the bike faster after you get your feet wet. (Do as I say, Not as I do in this case  )

Good luck, there sure are good guys here to help.

I have to get new pistons and a rebore anyway. When I got the 550 the pistons were stuck in the sleeves. They didn't look too pretty when finally got them out.
I'm not too worried about making a real fast bike, and this is going to be a budget build.
It's all research at this point anyway.
I hate jumping into things without a good idea of what I want to do, and how to do it.

[bwaller]

It would be wrong not to mention two important goals here...weight, plus handling/suspension.

It seems there are many more 500's racing in Europe and many of those guys are close to 300lbs, not race bike light, but compared to stock pretty remarkable. The Davies Motorsport bike is projected to be 280!

In middleweight production or a similar class on this continent "period" is the key word so ultra light rarely applies. It just needs to be on your mind all the time, because removing big weight is like unleashing extra engine power.

I'm sure you've read all about handling/suspension improvements too, it's a good place not to scrimp.

[DavePhipps]

That's the reason I don't want to race vintage yet wieght and suspension.
I'm looking at the Clubman class with WERA.
The only restriction for what I want to do is 600cc air cooled 2 valve per cylinder.
Everything else is allowed.
I just want to get the bike to 600cc with a cb650 headand 61mm pistons. Modern adjustable suspension (monoshock too) and wheels, then get wieght down as much as I can. I've neen looking at Howells, and turboguzzis threads for ideas on that.
Dropping pounds from the bike and making it handle are really my main concerns. Frankly in my first year of racing I'm sure I will not be able to use any extra power effecctively. I need to learn to race well and I'll need a bike that handles well too.

I'm also looking for advice on bike geometry as my modifications will definitely change the rake and trail of the bike.

[DavePhipps]

Here's my laundry list for the bike so far.

FZR wheels
Solid state RR
4-1 with cannister
Fzr forks(modified caps for preload) and brakes
valve emulators.
rearsets
cb650 cam
cb650 head
61mm pistons
remote MC front brake.
clipons
fzr or other swingarm (Would prefer alloy)
fiberglass seat and fairing
total loss ignition
smaller battery
cut tabs
remove stator and starter motor

Do the gsx1100 con rods wiegh less than the cb500 ones. If so, add those to the list. 

[Kemp]

You could go with the CB650 pistons which are 59.8mm, they also have a nice dome to them which should help with compression increases, much higher than the CB550 piston. Also, they are designed to work with the 650 head so a bonus when milling head for compression, your squish should be decent. Displacement won't be quite as much but close to 590cc and longevity should be like stock. Using a 650 cam, CB750carbs with stacks and a tuned exhaust should net you 50hp at the rear wheel on a very meager budget. That's my 2 cents!!

[turboguzzi]

hei dave

just make sure that your rulebook allows all the more modern bits you want to use. here in italy we are limited only to period pieces, i.e. spoked 18" wheels, 35mm max forks, non floating discs, non remote MC, etc. which i guess is actually good, personally cant see the point of making a 70's bike look 80's.

i think that cb500four's project is closer than mine to what you have in mind. the main difference is that the 650 head is a very open chamber and you cant build into it much squish area (good to avoid detonation and have quick burning).

I am doing now a 750/810 kawi race motor and its got pretty open chambers too, so i am basically "bathtubing" it by welding the chamber sides, should yeld a nice 6mm squish ring all around.

[DavePhipps]

The only requirement for the class (WERA clubman) is 600cc air cooled 2 valve per cylinder.
anything else goes.
Yes it's more like CB500four's bike, but your threads have much more tech information in them, which helps a lot.
I mentioned earlier the gsxr1100 conrods that owell uses in his bike. Why are they used? Are they stronger or lighter?
Also did you get the documentation to prove your moel bike was raced? I saw your thread on the WERA forums.

[paulages]

The only requirement for the class (WERA clubman) is 600cc air cooled 2 valve per cylinder.
anything else goes.
Yes it's more like CB500four's bike, but your threads have much more tech information in them, which helps a lot.
I mentioned earlier the gsxr1100 conrods that owell uses in his bike. Why are they used? Are they stronger or lighter?
Also did you get the documentation to prove your moel bike was raced? I saw your thread on the WERA forums.

+1 on using the 650 pistons or re-cut 61mm cb750 pistons. if memory serves me correctly (i could search my own thread but i'm lazy), the 650 head has 23mm in the combustion chamber. this is a LOT of room compared to the 500/550 chamber. you'll either need some nicely domed pistons, a lot of decking, or some welding like TG is doing on his GPZ engine to even get close to the stock CR.

I have some 650 pistons in a bin. If you end up needing some, PM me.

[DavePhipps]

If I used the machined CB750 piston I would need 11cc of dome. I have no clue how to calculate the displacement of a dome.
I punched my numbers into this http://www.csgnetwork.com/compcalc.html
That would give me 11.1 : 1 CR. Should I go 12:1 for a racer?
Still help figuring out the dome would be great. Math is one of my shortcomings 

[DavePhipps]

eyeballing the pin to deck measurement, it doesn't look like the 650 piston would be a good choice. I have the gentlemens express measurement for the cb750 pistons somewhere. I'll  ckeck those out

[paulages]

eyeballing the pin to deck measurement, it doesn't look like the 650 piston would be a good choice. I have the gentlemens express measurement for the cb750 pistons somewhere. I'll  ckeck those out

the 650 piston would work just fine with the 650 head, but you'd have to deck the head to get the CR up.

To measure dome volume: drop the piston down the bore until the top of the crown is exactly level with the top of the bore. Grease the top ring. Get a piece of plexiglass and drill a couple holes in it, one for filling fluid and the other to vent. Apply a little grease around the top of the bore, and lay the plexiglass down. it should just touch the top of the piston. Fill the chamber with fluid (dyed alcohol works well) and carefully measure how much it takes to fill it.

Before or after this, you'll measure from the shoulder of the piston to the deck to find the volume of this section without the dome (pi * r2 * whatever depth measurement you find). subtract the amount you measured with alcohol from this number and you have your dome volume. if your valve pockets are deep, you might have to measure the volume there (by dropping alcohol in them) and subtract, but it shouldn't make a significant difference.

http://forums.sohc4.net/index.php?topic=56829.msg804506#msg804506

[Kemp]

In the CB650, the piston sits above the deck the amount shown in your picture (about 4mm). I think they designed it that way to sit nicely inside the head for a decent squish. I'm not sure you could get the compression you desire (12:1) with this combo but what you would end up with should be exactly the same mechanical architecture as the 650 so it should work exactly the same. The 650 has a 5mm longer stroke but it also has a 5mm taller cylinder so that is totally negated in your build when you use the 550 cylinder.

[turboguzzi]

The only requirement for the class (WERA clubman) is 600cc air cooled 2 valve per cylinder.
anything else goes.
Yes it's more like CB500four's bike, but your threads have much more tech information in them, which helps a lot.
I mentioned earlier the gsxr1100 conrods that owell uses in his bike. Why are they used? Are they stronger or lighter?
Also did you get the documentation to prove your moel bike was raced? I saw your thread on the WERA forums.

wow, sharp eye man. At the time i was thinking about building a kz650 based 750 racer and the cut off date was 1976, wasnt sure if the 650 was raced that year.

in any case, ended up building an open classer based on GPZ750 and cut off date in that class is 83', so problem solved, nevertheless, the wera froum is extremely interesting and friendly.

[DavePhipps]

Guzzi, where does one find GL145 pistons part #13101-kg2-000?
They don't seem to be around the U.S. at all.
I was looking at the akunar pro piston AKPRP011B but I'm not sure if it will fit.
Good luck with the 750, and keep us updated on it here too.

[turboguzzi]

Guzzi, where does one find GL145 pistons part #13101-kg2-000?
They don't seem to be around the U.S. at all.
I was looking at the akunar pro piston AKPRP011B but I'm not sure if it will fit.
Good luck with the 750, and keep us updated on it here too.

yes, i see where you are searching, been there, done that....

at the time, i managed to convince TKRJ to sell me directly but i met them face to face first in the milan show. maybe try with DSS or CMSNL?

if you cant solve, PM me and ill send you a link to the TKRJ guy i dealt with

Akunar pistons have very low domes as they are mostly kits for small motors, so not an easy solution either.

Glad to have now in my hands a wiseco kit for the kawi that is a simple bolt on Quality is indeed amazing even if the slugs are not exactly lightweight.

[DavePhipps]

the 650 piston would work just fine with the 650 head, but you'd have to deck the head to get the CR up.

To measure dome volume: drop the piston down the bore until the top of the crown is exactly level with the top of the bore. Grease the top ring. Get a piece of plexiglass and drill a couple holes in it, one for filling fluid and the other to vent. Apply a little grease around the top of the bore, and lay the plexiglass down. it should just touch the top of the piston. Fill the chamber with fluid (dyed alcohol works well) and carefully measure how much it takes to fill it.

Before or after this, you'll measure from the shoulder of the piston to the deck to find the volume of this section without the dome (pi * r2 * whatever depth measurement you find). subtract the amount you measured with alcohol from this number and you have your dome volume. if your valve pockets are deep, you might have to measure the volume there (by dropping alcohol in them) and subtract, but it shouldn't make a significant difference.

http://forums.sohc4.net/index.php?topic=56829.msg804506#msg804506

UNfortunately I don't have the parts to easure yet. I'm trying to find out what will get me close without buying psrts to experiment with

[Raef]

So form what was said earlier...

 If I use a 650 head, jug and pistons on a 550, I need to use the crank,  find a place to lose 5mm or have the 550 jugs bored in order to have the compression i need.

I have both complete motors, when the 650 was disassembled I found all the intake valves bent, not building this for any particular purpose I just need to decide where to go. Where is a good place to get valves, guides, springs for a 650

Mark

[DavePhipps]

Or just use the head and pistons from the 650.

[Raef]

Right now I am looking at getting valves or a whole dif head. I like the 650 cam chain set up better than the 550, but I don't know. Still collecting parts and finishing a project that is already sold

[DavePhipps]

650 heads coming this weekend or next week, thanks to DTcycles. this guy rocks!
I may take you up on those cb650 pistons paul.
I need to get my engines over to my house and start testing. I dread hauling the engines down the basement stairs, but that's where I'll be working.

[Raef]

Are significant gains to be had in aftermarket valves, springs and retainers over just finding a good used head complete, then doing the port work on it. Or should I  go aftermarket and just us the one I have.

The cam, chain and pistons all check out

Mark