Topic: One more thing ... ... another small block racer

[paulages]

Actually, comparing the curves yours seems to do everything about 1000 rpm lower, which could just be cam timing.

[Howell]

Hi there!

Here some more stuff for the analphabetics   (I love pics too).
First is a close up of the head and the lightened primary damper.
Second gives you a look through the hole of bottom of the crankcase
to my adapted primary chain tensioner.

Regards,

Hallo Heinz,

Did you have problems with the tension of the primary chain ?
Is this tensioner not mounted to close at the primary damper to have any effect and does it give so enough tension ?

[von_Wanderlust]

heinz, not that I dont believe you, but I thought that 650 heads look more like this....

i mean, if there are 650 heads that look more like a 500 but have big valves, I would like to know! maybe a german model?

I think he mentioned that he has filled it with welding and then shaped the head to match the lines of the 500 valve cover, this is why his head has the rounded look of the 500 and not the normal square profile of the 650.

After reading Paulages thread, I had thought about doing this myself but ended up putting it into the this-is-going-to-drag-my-build-out basket. But now after seeing Heinz's figures, and Paul's and Mikes comments, I'm reconsidering.

[turboguzzi]

heinz, not that I dont believe you, but I thought that 650 heads look more like this....

i mean, if there are 650 heads that look more like a 500 but have big valves, I would like to know! maybe a german model?

I think he mentioned that he has filled it with welding and then shaped the head to match the lines of the 500 valve cover, this is why his head has the rounded look of the 500 and not the normal square profile of the 650.

After reading Paulages thread, I had thought about doing this myself but ended up putting it into the this-is-going-to-drag-my-build-out basket. But now after seeing Heinz's figures, and Paul's and Mikes comments, I'm reconsidering.

i've seen weld added to match a 650 head to a 500 rocker cover when a friend pushed a 500/718 motor into a special paton frame.  but the external head shape remained the same
here it means also rewelding the whole 0-ring groove as well as remaking whole chunks of head around the valves. impressive work and good results too!
TG

[CB500Four]

heinz, not that I dont believe you, but I thought that 650 heads look more like this....

i mean, if there are 650 heads that look more like a 500 but have big valves, I would like to know! maybe a german model?

Ciao TG!

In my opinion there are only two typs of CB650 heads. The one whitch fits to the "piston carbs" (right terme???)
and the other one that fits to the "CV/SU carbs" (right terme???). This head is a poor choise because the ducts
are more bent and they haven´t all the same length. It seems to me that the head in your pic is such one.
There is no special german one.
By the way the groove for the washer is in the head/rocker cover, isn´t it?   Or i have mistaken something?

The valve sizes are OD 31.5mm for the intakes and OD 26.0 for the exhausts.

Unfortunately i haven´t another pic of the primary chain tensioner assembly yet. When i go to my garage to do
the next huge services on my bike i will take some pics of this item. But just now its too cold and i have no heater.

Regards,

[turboguzzi]

heinz, not that I dont believe you, but I thought that 650 heads look more like this....

i mean, if there are 650 heads that look more like a 500 but have big valves, I would like to know! maybe a german model?

Ciao TG!

In my opinion there are only two typs of CB650 heads. The one whitch fits to the "piston carbs" (right terme???)
and the other one that fits to the "CV/SU carbs" (right terme???). This head is a poor choise because the ducts
are more bent and they haven´t all the same length. It seems to me that the head in your pic is such one.
There is no special german one.
By the way the groove for the washer is in the head/rocker cover, isn´t it?  Or i have mistaken something?

The valve sizes are OD 31.5mm for the intakes and OD 26.0 for the exhausts.

Unfortunely i haven´t another pic of the primary chain tensioner assembly yet. When i go to my garage to do
the next huge services on my bike i will take some pics of this item. But just now its too cold and i have no heater.

Regards,

thanks heinz, maybe some of the 650 experts will explain the types of heads. do you know from which year is your head?

I think I got the idea how to make the tensioner,

I have the same problem with the temperature in the garage and my first race is in two months from now!

[CB500Four]

Hallo Heinz,

Did you have problems with the tension of the primary chain ?
Is this tensioner not mounted to close at the primary damper to have any effect and does it give so enough tension ?

Hoi Howell!

Fortunately i don´t have any problems with the tensioner until yet.
It is fixed at rough the same positon as in the CB650 and it works in the same way as it does iat the CB650.
At the CB650 there is at this position where my adapter will take the tensioner a chunk in the casting of the case.

Regards,

[paulages]

The slide carb heads are '79-'80, and the cv heads are '81-82.

By the way TG, I listed the deep 650 sump pan in the write up about compatible parts.. shoulda read closer.. could've ran that all last season. 

[CB500Four]

wow, this is great. EXACT same peak HP as my 718cc!

69.7. what are the odds? comparing the dyno charts, yours seem to actually build power earlier than mine,
which i'm surprised about given the extra displacement i have. i'm not surprised you got the same HP
with 100cc less though, as i believe most of the power in these engines benefits from the breathing.
anyway, beautiful work. makes me want to do a couple more mods to mine..

Hi Paulages!

I think if you mounts the same carbs as i and also a realy free silencer your engine should increase a little bit more power
than mine (in my estimation 75-78 HP). All mods for healthy breathing.
By the way would you reveal the secrets of your cam? Timings, duration, lift or somthing like this.

I will show tomorrow all the secrets of my piston mods.  
Must only made the pics. Today i have searched for the pistons, have found and cleaned them a little bit
for pretty looking on the pics .

Regards,

[turboguzzi]

The slide carb heads are '79-'80, and the cv heads are '81-82.

By the way TG, I listed the deep 650 sump pan in the write up about compatible parts.. shoulda read closer.. could've ran that all last season. 

gee man, at one point i lost track of the compatibility......

What about those heads then, any way to tell them apart? Still looks like a hell lot of work to shape the mating contour to match a 500 rocker cover but with that size of valves....might be tempted.

Do you know remember whats the span between the two further edges of the valves? less than 57mm? just wondering what would happen if I put such a head on a 500 cyl.   When I was helping redesign a british classic racer head, a knowlegeable guy told me that sometines he would notch the sleeves so that extra bigger valves could be fitted.

[CBJoe]

Hey TG,

Here's two pics i got from my frozen garage... 

'81 CV Type Head Had Different Intake Manifold Spacing and also has a groove for the gasket. 

'80 with PD mechanical type carbs has a smooth gasket surface. 

Cheers, Joe

[von_Wanderlust]

here it means also rewelding the whole 0-ring groove as well as remaking whole chunks of head around the valves. impressive work and good results too!
TG

Looking at CBJoe's pics, it looks like you only need to reweld/fill the o-ring groove on the later 81-82 heads, which means that not only do the 79-80 heads are better for compatibility through sharing the same intake/exhaust spacing as earlier 500s, they also don't need as much work. Handy to know! (Thanks CBJoe!)

Heinz, das motorrad ist fantastisch! (Hope I got that right!   ) The fact that it is already in the SOHC race bike gallery goes to show just how impressive that bike is! 

You've used the shorter 650 rods, i'm guessing because the DOHC pistons are taller? Any other reasons? I'm looking forward to the next update you have mentioned so that I can find out more.  

[Howell]

Hallo Heinz,

Did you have problems with the tension of the primary chain ?
Is this tensioner not mounted to close at the primary damper to have any effect and does it give so enough tension ?

Hoi Howell!

Fortunately i don´t have any problems with the tensioner until yet.
It is fixed at rough the same positon as in the CB650 and it works in the same way as it does iat the CB650.
At the CB650 there is at this position where my adapter will take the tensioner a chunk in the casting of the case.

Regards,

Hoi Heinz,

My question wass obviously not clear enough , did you have problems with the primary chain without the tensioner.

gr.René

[kayaker43]

I'm fairly certain that all 650 heads have a smooth surface (no groove) The photo just looks that way but if you zoom in you will see its just a mark from the o-ring.

I've also heard the the 550 cover will seal to a 650 head with no welding or grinding. Other say it won't, but there is barely enough overlap if you use a bit of sealant as well as the o-ring.

I have a Yoshimura ported head and the stock 650 head looks much better. The increased valve size is worth the trouble to make it work.

[turboguzzi]

Kayaker, do you have a 650 head open? would like to check some measurements....

TG

[kayaker43]

I do but its 1200 miles away,.. I won't see it again till Feb.

Sorry

[CBJoe]

Kayaker, do you have a 650 head open? would like to check some measurements....

TG

My apologies.... Kayaker is 100% correct.  I was deceived by my own picture.  I took the '81 head out and looked at it just now and verified that the gasket surface is smooth.

TG... what kind of measurements do you want?  I have the '80 and '81 heads on my bench at the moment. 

Joe

[turboguzzi]

Kayaker, do you have a 650 head open? would like to check some measurements....

TG

My apologies.... Kayaker is 100% correct.  I was deceived by my own picture.  I took the '81 head out and looked at it just now and verified that the gasket surface is smooth.

TG... what kind of measurements do you want?  I have the '80 and '81 heads on my bench at the moment. 

Joe

just the distance between the two most further away tips of the valves. would call it the maximum span between the EX and IN valves at the combustion chamber side.

[CBJoe]

55.90mm 54.89mm is what I measured for the max distance between the IN and EX Valves in the combustion chamber.

EDIT:  Replaced valve to valve measurement value and pic due to bad measuring technique.

Joe

[paulages]

Kayaker, do you have a 650 head open? would like to check some measurements....

TG

My apologies.... Kayaker is 100% correct.  I was deceived by my own picture.  I took the '81 head out and looked at it just now and verified that the gasket surface is smooth.

TG... what kind of measurements do you want?  I have the '80 and '81 heads on my bench at the moment. 

Joe

just the distance between the two most further away tips of the valves. would call it the maximum span between the EX and IN valves at the combustion chamber side.

TG- if your class will allow it, run the 650 head by all means. the ports start out about where you might have got yours with lots of work, and of course have bigger valves. you'll need taller pistons of course, but i'm sure you can figure that out.

[CB500Four]

Hi there!

Now the promised secrets of my piston works.
Here they are. Enjoy the pics.
Please don´t comment this posting because
i will do some more piston pics in such charts
(stock 650, mod 650, CBX1000).
Please wait until you have seen the whole thing.

Update comming soon
Regards,

[turboguzzi]

very tempting indeed, cant see why i couldnt use it. main issue is the fact that the CC diameter is bigger than the max bore I am allowed (57mm) to use

But by milling the head, I believe that I could reduce the diameter quite a bit.

anyway to distingush between the old (better?) and the later heads?

TG

[paulages]

very tempting indeed, cant see why i couldnt use it. main issue is the fact that the CC diameter is bigger than the max bore I am allowed (57mm) to use

But by milling the head, I believe that I could reduce the diameter quite a bit.

anyway to distingush between the old (better?) and the later heads?

TG

lots more options with the earlier in my opinion. the spacing is essentially the same as the 500, 550, and 750, so you CR's will likely be an easier fit. you may have noticed somewhere that Soos discovered gpz carbs to fit the later heads. the earlier spacing provides better port geometry if i remember right. i had both to choose form when i was building my engine, and the '70 head seemed like the clear choice.

[paulages]

Hi there!

Now the promised secrets of my piston works.
Here they are. Enjoy the pics.
Please don´t comment this posting because
i will do some more piston pics in such charts
(stock 650, mod 650, CBX1000).
Please wait until you have seen the whole thing.

Update comming soon
Regards,

amazing! i only posted very basic numbers from my piston mod. at some point i think we should compile your info into the 550/650 big bore how-to thread. this is great info and shouldn't be lost.

[CB500Four]

very tempting indeed, cant see why i couldnt use it. main issue is the fact that the CC diameter is bigger than the max bore I am allowed (57mm) to use

But by milling the head, I believe that I could reduce the diameter quite a bit.

anyway to distingush between the old (better?) and the later heads?

TG

Ciao TG!

I have measured the span between the OD´s of the valve seats and get 57.5mm.
The span between the OD´s of the valves that i have measured is similar to CBJoe´s
measurement. I get 55.9mm.
In my opinion you should choise absolute the older head. For the reason why see posts above.
I have milled my CB650 head round about 2.0mm down. And with your cam chain tensioner
it should work. The greatest problem in my opinion is to get the right pistons with OD 57.0mm.

By the way, work on piston charts is going on. Please don´t be angry .

Regards,