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

[paulages]

I went back and looked through that old thread..it would take it up to 570 cc. Now if i did go with the just the 650 pistons and heads in bored 550 jugs would i be able to keep the 550 cam chain? Im guessing this is the reason for using the 550 cam sprocket on the 650 cam correct?

yes, just use the 550 cam sprocket. i'd love to see what that combo ported and with a hot cam would do. you'd have to measure existing clearances, but i bet you could deck the head a bit and bump up the compression ratio also.

[kayaker43]

Remember the 650 head will want bigger carbs and the exhaust spacing is the same but the head pipe diameter is larger. You wouldn't gain much until you swapped carbs and put a 650 exhaust on it.

Then again used 650 motors are cheap and you get a better clutch too, but a motor swap will still need carbs & exhaust plus converting the charging system.

It turns into a project no matter how you look at it. The straight cam swap with no other mods is the biggest bang for the buck. Don't expect a lot of bang,.. but it is cheap and easy.

[DarkRider]

You may just get to see it by next spring now that i have a spare 550 F engine to throw into my 550 K. I will play around with the Ks original engine and see what i come up with.

[bill440cars]

You may just get to see it by next spring now that i have a spare 550 F engine to throw into my 550 K. I will play around with the Ks original engine and see what i come up with.

    Be interesting to see, Chris.  Lead on brother.

[paulages]

i talked to les barker a couple weeks ago, who built my race bike in the 70s (he still builds for the formula 160 guys up here, and makes tons of cool #$%*). he said he put lots of 650 heads on 550 bikes back in the day. as a matter of fact, i think he's done just about every combo possible here. i wish i had met him prior to my build, as he's done pretty much the exact same thing, but it was fun having to figure it all out anyway. he has lots of great tips on these bikes i'll try to share here.

[Ecosse]

i talked to les barker a couple weeks ago, who built my race bike in the 70s (he still builds for the formula 160 guys up here, and makes tons of cool #$%*). he said he put lots of 650 heads on 550 bikes back in the day. as a matter of fact, i think he's done just about every combo possible here. i wish i had met him prior to my build, as he's done pretty much the exact same thing, but it was fun having to figure it all out anyway. he has lots of great tips on these bikes i'll try to share here.

OK, I have a hard enough time shutting down the PC and you post that teaser?



Thanks.

[paulages]

i talked to les barker a couple weeks ago, who built my race bike in the 70s (he still builds for the formula 160 guys up here, and makes tons of cool #$%*). he said he put lots of 650 heads on 550 bikes back in the day. as a matter of fact, i think he's done just about every combo possible here. i wish i had met him prior to my build, as he's done pretty much the exact same thing, but it was fun having to figure it all out anyway. he has lots of great tips on these bikes i'll try to share here.

OK, I have a hard enough time shutting down the PC and you post that teaser?



Thanks.

i have to dig a little more. for example, the oil pump from the racer produces 60 PSI at idle, 70 under revs. an 1/8" shim under the pressure relief valve spring did the trick. he knows lots of great stuff, just gotta get it from him.

[bill440cars]

i talked to les barker a couple weeks ago, who built my race bike in the 70s (he still builds for the formula 160 guys up here, and makes tons of cool #$%*). he said he put lots of 650 heads on 550 bikes back in the day. as a matter of fact, i think he's done just about every combo possible here. i wish i had met him prior to my build, as he's done pretty much the exact same thing, but it was fun having to figure it all out anyway. he has lots of great tips on these bikes i'll try to share here.

OK, I have a hard enough time shutting down the PC and you post that teaser?



Thanks.

i have to dig a little more. for example, the oil pump from the racer produces 60 PSI at idle, 70 under revs. an 1/8" shim under the pressure relief valve spring did the trick. he knows lots of great stuff, just gotta get it from him.

            Whoa!!!   Seems like this Hybrid Engine is opening up an whole "Treasure" of great info Paul!   Carry on buddy, please carry on.

[olds-cool]

Great details.  I'm interested to see what else you can share.  I'm starting to second guess my future purchase of a 750 for my next project bike.

[jason teamshralp]

Is this engine in the bike in your avatar? I saw you ride around the corner I was standing on and then you just took off like a bat out of hell. You left me looking like a little kid. It was in north portland near the St. Johns Skatepark.

[paulages]

Is this engine in the bike in your avatar? I saw you ride around the corner I was standing on and then you just took off like a bat out of hell. You left me looking like a little kid. It was in north portland near the St. Johns Skatepark.

yeah, that's the bike. funny, a sighting!  it feels like a bat out of hell... i was probably headed back over the st johns bridge and up germantown for skyline blvd. i love that ride so much.

[bill440cars]

        Really glad that you are getting to take the "718" out for a spin now and then. Get it feels good to have it in ONE piece and in the frame, so you can enjoy it too!

[paulages]

        Really glad that you are getting to take the "718" out for a spin now and then. Get it feels good to have it in ONE piece and in the frame, so you can enjoy it too!

hell yeah it does. i haven't even cared to get around to fine tuning it yet... it runs like a champ and i figure i'll have plenty of time once the rain rolls around to get it totally dialed in. 

[bill440cars]

        Really glad that you are getting to take the "718" out for a spin now and then. Get it feels good to have it in ONE piece and in the frame, so you can enjoy it too!

hell yeah it does. i haven't even cared to get around to fine tuning it yet... it runs like a champ and i figure i'll have plenty of time once the rain rolls around to get it totally dialed in. 

        I can understand that, just seems to be too hard to stop and take care of, what seems like at the time, such a trivial thing (when you can be out and rolling on! I can only umagine how well that "Mixture" runs flies.

                          Enjoy Paul, you've deserved it!

[CrisPDuk]

On the strength of this thread I'v just gone and bought a complete but seized 650 motor

Think I'm going on another learning curve over winter

[paulages]

On the strength of this thread I'v just gone and bought a complete but seized 650 motor

Think I'm going on another learning curve over winter

HELL YEAH!

[dragon79]

hey just joined and been checking out all the info on this. was just curious as to which cb750 pistons you used? were they a 750 high compression piston. and what is the oil line on the right lower side going to?

[paulages]

i used aftermarket 811cc pistons, which would have yielded a 10.5/1 CR in a cb750 cylinder. anything you use will have to be modified anyway, so you'll decide the CR. given that i didn't have to reduce the dome at all, i'd recommend high CR pistons to begin with though. i ended up at 10.6/1 after removing material from the shoulder and sides of the dome.

the oil lines you see are feeding the top end, bypassing the stock lines that run through the cylinder block outside of cylinders 1 and 4.

[Pinhead]

With 10.6:1 compression ratio, are you having any trouble with pinging, overheating, or any other type of engine misbehavior? Have you figured gas mileage?

[billybobobrain]

Is this engine in the bike in your avatar? I saw you ride around the corner I was standing on and then you just took off like a bat out of hell. You left me looking like a little kid. It was in north portland near the St. Johns Skatepark.

yeah, that's the bike. funny, a sighting!  it feels like a bat out of hell... i was probably headed back over the st johns bridge and up germantown for skyline blvd. i love that ride so much.

I miss Portland, I used to tear up skyline in a 2000 Mazda protege.

I am under the impression for some reason or another that the CB500 engine is the same as the 550 on the bottom.in theory could this be done to a 500, or am I mistaken.

[dragon79]

was the oil line nesessary or just a precaution.? is the 811cc kit still available, i see more 836 kits around.  its awsome what you have done and hope you don't mind the questions. there are so many cool things that have been done or being to these bikes its great!!

dr79

[paulages]

With 10.6:1 compression ratio, are you having any trouble with pinging, overheating, or any other type of engine misbehavior? Have you figured gas mileage?

i've had no problems with pinging, once i installed the oil cooler. i need to hook up a speedometer and figure out the gas mileage...

Is this engine in the bike in your avatar? I saw you ride around the corner I was standing on and then you just took off like a bat out of hell. You left me looking like a little kid. It was in north portland near the St. Johns Skatepark.

yeah, that's the bike. funny, a sighting!  it feels like a bat out of hell... i was probably headed back over the st johns bridge and up germantown for skyline blvd. i love that ride so much.

I miss Portland, I used to tear up skyline in a 2000 Mazda protege.

I am under the impression for some reason or another that the CB500 engine is the same as the 550 on the bottom.in theory could this be done to a 500, or am I mistaken.

it is true that you could use 500 cases, but the trans is actually different between the 550 and 550. the 550 and 650 transmissions are more similar.

was the oil line nesessary or just a precaution.? is the 811cc kit still available, i see more 836 kits around.  its awsome what you have done and hope you don't mind the questions. there are so many cool things that have been done or being to these bikes its great!!

dr79

i got the 811 kit, because it was cheap as hell on ebay ($65 if i remember right). i wanted to go with 836 pistons, because it would yield 740ccs, which would be 4ccs over a stock cb750. oh well, it'll still burn one with a quickness.  i ran the oil lines externally as a precaution. i managed to fit the sleeves without interfering with the stock passages, but i thought the extra precaution against heat (due to increased proximity to the cylinders) would be a good idea.

[billybobobrain]

it is true that you could use 500 cases, but the trans is actually different between the 550 and 550. the 550 and 650 transmissions are more similar.

So not to sound ignorant but, what affect is this going to have on converting a 500.

[paulages]

it is true that you could use 500 cases, but the trans is actually different between the 550 and 550. the 550 and 650 transmissions are more similar.

So not to sound ignorant but, what affect is this going to have on converting a 500.

i don't imagine it'd be all that different, but the deficiencies of the 500 engine (i'm probably going to piss off some 500 guys here) would make it less desirable in my opinion. not sure how the 500 trans and clutch would hold up.

[pdxPope]

Watch it you elitist bastard! 

The 500 trans would probably be ok (it would depend on the shape it was in before the mods, of course)

But the CB500 clutch is garbage on a good day, so I wouldn't recommend it.


-JP