Topic: 550/650 hybrid or 650 big bore HOW TO

[65Ch3v3LL3]

Personally I think those look like they'd produce too much compression.

The factory 9:1 '78 CB750 pistons produce 10.5:1 to 11:1 compression on a CB650.

Those look like they're at least 10.5:1 or higher on a '78 CB750 (which has a larger chamber) and would be quite a bit taller than the stock pistons.

So would a set of higher compression 69-76 pistons be a better choice then? Such as these 10.25 compression pistons. I'm just basing this off of what Soos had written about the earlier pistons really dropping the compression. I don't want to go larger displacement with low compression since I have no plans for boost.

[Pinhead]

It's hard to say without a better view of the top of the pistons but they don't look nearly as radical and would be closer to working with a 650's chamber (IMHO of course).

I'm just going by what Soos has written about using other pistons, and what my '78 CB750 pistons look like in my CB650 at 11:1 CR (no base gasket installed).

[65Ch3v3LL3]

Thanks for the input Doug. I appreciate the help. I think when I'm ready to do the motor I will try the last ones then. I have a guy that does drag bike heads for Star Racing that will do all my machine work. Hopefully he can figure all this out. I am definitely not an engine builder. Building the rest of the bike is no problem for me I just haven't ventured into engine work yet. On a side note I did score a complete 750 head with good sleeves for $28 shipped on eBay. So I have $7 in each sleeve. Not bad I thought.

[MoTo-BunnY]

was just reading lordmoonpie's thread about a deep sump on a 750 and remembered that the 650 has a deeper sump than the 550. honda specs the same amount of oil for both, but the 650 pan definitely took more oil on the 718 engine. good for a wet sump engine.

edited at top to include engine covers interchangeability.

Going over this thread as I am in the process of a few mods on my 500, including the CB650 pan and cam swaps, and saw this. I just thought I would contribute about the only things I can to this otherwise way-over-my-head-thread!    I hope this info helps someone out....

CB500 PAN:
weight**: 1.60 lbs. / .72 kg
capacity*: 1 3/8 quarts / 1.3 liters

CB650 PAN:
weight**: 2.48 lbs. / 1.08 kg
capacity*: 2 quarts / 1.9 liters

**(weighed empty)
*(measured to the top with water)



ALL PHOTOS ARE CB500 (Left) and CB650 (Right)

[img width= height= alt=CB500 (L) CB650 (R)  Oil Pans - Bottom]http://farm7.staticflickr.com/6049/6373911841_8657bba28c_b.jpg[/img]
see how I painted in between the fins on the CB650 pan?
all purdy though not like anyone can really see it once it's on the bike...lol... I just did it to match
the rest of my engine, basically and help radiate heat a tad bit more

[img width= height= alt=CB500 (L) CB650 (R) Oil Pans - Side view]http://farm7.staticflickr.com/6222/6373911417_c7633f04d2_b.jpg[/img]

[img width= height= alt=CB500 (L) CB650 (R) Oil Pans - Inside]http://farm7.staticflickr.com/6093/6373911933_71b517dd2a_b.jpg[/img]
Note the oil windage wall cast into the CB650 pan (R) to help prevent oil starvation at hard cornering

[img width= height= alt=CB500 (L) CB650 (R) Oil Pickups]http://farm7.staticflickr.com/6109/6373912025_725f1b5d5b_b.jpg[/img]
You will need the CB650 pickup (R) to use the CB650 pan on a CB500/550*
*(with additional 'nipple mod' needed for 550 application-see following posts)

[fastbroshi]

There looks to be quite a bit of difference between the two pickups.  The 550 one looks like a thick cast piece, the 650 one looks to be made of stamped sheet.

[bwaller]

Just a heads up for anyone going this route with a 550. Hondas attempt at improving c-shaft lubrication in the 550 involved using a trochoid pump which sources oil from that pickup. If you use the 650 piece it's best to solder in a fitting to accomplish this. Or modify the 550 piece to work with the deeper 650 pan.

[fastbroshi]

That little nipple would need to be added to the 650 piece?

[bwaller]

That little nipple would need to be added to the 650 piece?
[/quote[/b]]

Roger that.

[Ricky_Racer]

Just a heads up for anyone going this route with a 550. Hondas attempt at improving c-shaft lubrication in the 550 involved using a trochoid pump which sources oil from that pickup. If you use the 650 piece it's best to solder in a fitting to accomplish this. Or modify the 550 piece to work with the deeper 650 pan.

Just curious... Why did you choose to modify the 550 pickup rather than the 650?  Thanks.  RR

[bwaller]

I looked around and didn't find a steel nipple the right size for the 650 part. I noticed the 400F pickup neck is longer so cut a piece off and welded to the 550 part, problem solved, plus end up with an o-ring to help seal.

[Ricky_Racer]

Thanks for the reply! It looked to me like it would have been easier to mod the 650 pickup. I now understand why you chose the solution you did. Thanks again. RR

[Greggo]

Great thread!

[MoTo-BunnY]

There looks to be quite a bit of difference between the two pickups.  The 550 one looks like a thick cast piece, the 650 one looks to be made of stamped sheet.

Yes, that is correct except that is a 500 pickup (and not a 550) compared to a 650. See the posts about the additional nipple fitting on the 550 pickup, above.

[FuZZie]

Hondas attempt at improving c-shaft lubrication in the 550 involved using a trochoid pump which sources oil from that pickup

bwaller looks like you lowered that pick up location too, you thinking this will also help? 

[bwaller]

Check MoTo-BunnY's 650 oil pan picture above. It has three "legs" cast in the pan, so they need to be removed from the 550 pickup.

[FuZZie]

I see it, thanks!

[Howell]

was just reading lordmoonpie's thread about a deep sump on a 750 and remembered that the 650 has a deeper sump than the 550. honda specs the same amount of oil for both, but the 650 pan definitely took more oil on the 718 engine. good for a wet sump engine.

edited at top to include engine covers interchangeability.

Going over this thread as I am in the process of a few mods on my 500, including the CB650 pan and cam swaps, and saw this. I just thought I would contribute about the only things I can to this otherwise way-over-my-head-thread!    I hope this info helps someone out....

CB500 PAN:
weight: 1.60 lbs. / .72 kg
capacity*: 1 3/8 quarts / 1.3 liters

CB650 PAN:
weight: 2.48 lbs. / 1.08 kg
capacity*: 2 quarts / 1.9 liters

*(measured to the top with water)



ALL PHOTOS ARE CB500 (Left) and CB650 (Right)

[img width= height= alt=CB500 (L) CB650 (R)  Oil Pans - Bottom]http://farm7.staticflickr.com/6049/6373911841_8657bba28c_b.jpg[/img]
see how I painted in between the fins on the CB650 pan?
all purdy though not like anyone can really see it once it's on the bike...lol... I just did it to match
the rest of my engine, basically and help radiate heat a tad bit more

[img width= height= alt=CB500 (L) CB650 (R) Oil Pans - Side view]http://farm7.staticflickr.com/6222/6373911417_c7633f04d2_b.jpg[/img]

[img width= height= alt=CB500 (L) CB650 (R) Oil Pans - Inside]http://farm7.staticflickr.com/6093/6373911933_71b517dd2a_b.jpg[/img]
Note the oil windage wall cast into the CB650 pan (R) to help prevent oil starvation at hard cornering

[img width= height= alt=CB500 (L) CB650 (R) Oil Pickups]http://farm7.staticflickr.com/6109/6373912025_725f1b5d5b_b.jpg[/img]
You will need the CB650 pickup (R) to use the CB650 pan on a CB500/550*
*(with additional 'nipple mod' needed for 550 application-see following posts)

On our CB500 racer last two seasons we used evenso an 650 oilpan and the 650 pickup.
But for next season , building up the bike with a Davies frame , we try to reduce the weight of the bike by 20 kg's.
A part of that weight saving is to fall back on the original 500 oilpan and pickup.
Using the 650 pan I put 0,5 ltr more oil in the engine.
Difference between 650 pan and pickup and the 500 is a 400 gr. and 0,5 ltr oil is about 600 gr.
With that change we save about 1 kg.

[CB500Four]

Hoi René

Don´t know what sort of oil you tend to use,
but the oil i use seems to be lighter than yours.
If i save 0.5 l oil i will save round about 0.450 g.

But nevertheless i have the same doing in my mind.


Regards,

Heinz

[Howell]

Hoi René

Don´t know what sort of oil you tend to use,
but the oil i use seems to be lighter than yours.
If i save 0.5 l oil i will save round about 0.450 g.

But nevertheless i have the same doing in my mind.


Regards,

Heinz

Hallo Heinz,

Herzlich willkommen

I thought it's heavier then water.
But that's not trough, the weight density is about 0,88 .
So I save only 450 gr 

[bmxpuck]

this thread is incredible. been running a 78 550k for about a year and a half now. about 8 months ago i got a 650 for super cheap that wasn't running but was a complete bike. started pulling the engine apart just to kind of "see" what was inside. didn't really know what i wanted to do with it at the time and made a rebuild thread i should probably delete since i stopped on it. had been in the market for another 550 engine just to rebuild to eventually put on my 550k with the 650 cam and all of that. but after reading this thread, putting the 650 top on the 550 bottom with the 750 pistons seems to be the way to go.

currently in my arsenal of parts are essentially 2 bikes:
complete 79 or 80 650 engine, carbs and 4-4 exhaust
complete 75 or 75 550f engine and carbs

i'm trying to compile a list of the other parts that i'll need, any help with this would be appreciated:
750 carbs (would it be possible to use the 650 carbs if they were rejetted?)
750 pistons (ideally 811/812 or 836)
750 sleeves
what else? i've read through the thread a few times, but it seems like everything else is already in the 550 or 650 motor.

would like to compile all the parts before i really get into this. and i've got a buddy who works at a machine shop, so i'm hoping to get a good hookup on any of the machining i need done.

once i compile all my parts, i'll definitely keep a thread going about the whole process. stopped posting on my last 650 thread because i lost motivation on what the hell i actually wanted to do with the thing. now i have a real sense of direction on what i want to do with these things, so that should help.

puck

[linx]

Hi new to the site and its great. I was wondering does anyone have specs on the piston mod for 78 slight stepped up dome 750 pistons in 650 head. I see one post with no  base gasket  and 11:1 but specs of piston crown to gudgeon  height and piston mod would be great, a photo would be better if someone has one. I would like 11;1 or there abouts if someone knows what to do. Thanks heaps

[sinister902]

I now have everything in hand to do the hybrid motor, but have no idea how I am going to get the shoulders of the 836cc kit pistons machined to work now that Soos is M.I.A. If I had exact specs that would work, I could probably just drop off at a local machine shop....

I've got a complete 650 motor, 750 cylinders, and the 836cc kit....

[spdygnzlz]

I know this is an old thread but I just now picked up a '80 650 motor for cheap locally.  My 550 is pretty long in the tooth, pushing 58k miles, so it's due for a rebuild from what I understand. 

Can someone tell me if the rockers from the 650 will fit the 550?  I know the cam fits along with all the other parts paulages mentioned but saw no mention of the rockers. 

Also, would it make any sense to swap out the entire top end from the 650?  I'd have to reuse my carbs and would like to reuse the exhaust I just got from Motogpwerks, but it's not the end of the world either way. 

Thanks!

[sinister902]

If the exhaust is 1.5" dia it's too small for a 650. The 650 top end will drastically lower the compression on a 550 bottom end becaue the chamber is so much larger in the head if I've read this thread correctly.

Re-using your carbs may prove difficult, but start with larger main jets.....you'll have to spend time messing with float heights and needle clip position.

[Kemp]

Dynoman offers a piston kit to allow you to use the 650 head and barrels on a CB550. That seems the best way to go. You would need a CB650 aftermarket exhaust because of the bigger ports as noted in a previous post. Your displacement would end up around 591cc but you could use your 650 carbs and cam with probably very little rejetting as the displacement will be close to the CB650's 623cc and you might even be able to use a 650 airbox but not sure. The frames are very similar in the 79/80 CB650 to the CB550 as long as it isn't the cruiser version of the 650 the airbox might fit!