Topic: Re: 650 overbore/550 engine hybrid underway...final stages

[paulages]

pinhead: i haven't taken measurements, but both tapered ends of the crankshaftes appear to be the same, indicating that the 550 alternator could fit on a 650 crank.

[paulages]

okay, here's an update:

i've done a lot of swapping parts around, and it appears that i'll have several options here.

1) all 650 innards with 550 covers. this will require machining the tapered end of the crankshaft to accept the 550 stator, and using     the 550 clutch basket on the 650 primary and clutch gear drives.

2) all 550 behind the crank, sans kickstart.

either way, i can keep the nice look of the 550 engine except for the kickstart (haven't totally given p on that one yet, though).

now to figure out which one is better... (new thread on the way)

[Tommy Neimeyer]

You will be running the 550 valve cover on the 650 head?

[paulages]

haven't had a chance to experiment with that yet tom, though i know i said i would soon. i promise i'll check it out this week. i lost the thread you started about it. i take it you never turned up a definitive answer? by the way, do you have any idea what gearing was inside that 550 race bike?

[Tommy Neimeyer]

Yes I have the info someplace.  As I remember, he combined the 550/650 and ended up with a very close ratio trans.  Once I find the details, I will post.  It did require some simple machining to make it work.

After looking at te head/valve cover issue, I do not think it will seal.  Somebody else also commented that it would not work stock but they were going to add some metal via welding to allow it to work.

Cheers, Tom

[Pinhead]

The 550/650 alternators aren't swappable. The 550's cover is larger and the 650's crank is larger. The 550 rotor has a larger OD and a smaller ID. The stator on the 650 is smaller than the 550's, too.

[bill440cars]

The 550/650 alternators aren't swappable. The 550's cover is larger and the 650's crank is larger. The 550 rotor has a larger OD and a smaller ID. The stator on the 650 is smaller than the 550's, too.

            They just had to go and make things complicated, didn't they? Ya might know it.

[paulages]

pinhead-

i'm just gonna have my machine shop mill my crank end to accept the 550 alternator when they balance the crank/rotor. the 650 has a larger diameter, so this should be no problem.

[Pinhead]

You'll still have to use the 550 cover, rotor, stator, and field coil. The diameter of the 650's stator is smaller than the 550's, and likewise the 550's casing is a bit bigger. It won't really look good on the 650 lower end... The bolt holes line up but that's pretty much it.

[paulages]

pinhead,
i was planning on using all of the 550 charging components. the entire point is to be able to use the 550 covers. i have no problems whatsoever with my 550 charging system, so i have no issues with using it. i'll double check the mating of the covers, but i believe you're wrong about the cases being larger on the 650. i have both cases sitting on my workbench, and they look identical. if can make the rotor fit on the crank end, then the cover, field coil, etc. should work fine.

tell you what, i'm headed there now. i'll try the 550 crank in the 650 cases (just to mimic the taper needed on the end of the 650 crank) and see how it all lines up.

tom, i'll look at that valve cover for myself too.

[Pinhead]

pinhead,
i was planning on using all of the 550 charging components. the entire point is to be able to use the 550 covers. i have no problems whatsoever with my 550 charging system, so i have no issues with using it. i'll double check the mating of the covers, but i believe you're wrong about the cases being larger on the 650. i have both cases sitting on my workbench, and they look identical. if can make the rotor fit on the crank end, then the cover, field coil, etc. should work fine.

tell you what, i'm headed there now. i'll try the 550 crank in the 650 cases (just to mimic the taper needed on the end of the 650 crank) and see how it all lines up.

tom, i'll look at that valve cover for myself too.

It's not the crank position, it's the actual mating of the 550 covers to the 650 block. The bolt holes line up but the covers themselves don't fit perfectly. The 550's covers have a larger diameter than the 650s. It will bolt up but it won't look good without a lot of metal work.

[paulages]

yeah, you sure are right pinhead. eric (mr. blasty) and i sat there and looked at the two sets of cases right beside each other after i tried the 550 cover on the 650 cases, and i swear they look exactly the same. but as you stated, the 650 cases are slightly smaller on the rear half of the alternator area.

so, back to plan A.

550 cases, alternator, and clutch basket. 650 crank and top end, and a mish mash of clutch and transmission parts.

i figured out tonight that i should be able to swap out whatever gears i want from the 650 or the 550. if i keep the primary gearing of the 650, i'll have the supposed benefit of it's better clutch. i'm actually thinking about using the 650 transmission with the 550 1st gear, so i can keep the kickstart, but i still want to figure out what the best combination of gears is from both bikes.

it seems that the easiest solution to keeping the gearing i'm familiar with in the 550 and still have the better clutch would be to use the 650 primary, full 550 gearbox, and then just adjust at the final drive to compensate for the lower primary ratio.

[cafe75-550]

Ive been toying with the idea of a 550/650 hybrid also, and have finally gotten to the point where Im doing measurements. My plan is to stay primarily 550, with a 550 bottom end and cylinders but using 750 liners and pistons with a 650 head (to keep compression somewhat normal). I started thinking that there was no way to put the 750 liners in the 550 cylinders without changing the oil system, especially since I saw Dr. Tom's hybrid. But the 750 liners I have come in at 69.6 mm OD, and with the 550 cases at 66.4mm and 2.5 mm to work with before getting into the oil passage (thats to the o-ring indent not the actual oil passage), it seems like it should work out...1.6 mm increase in radius with .9mm left to the oil o-ring detent. Not much to play with, but its a press fit anyway, so the bore on the cylinder should also be 69.6 (letting the machine shop worry about the hundredths for the fit).That would allow for a 836 kit with the liners, giving 672cc. I also bought one of those henry abe kits, the liners on that are at 69mm, so that for sure stays out of the oilway. Push comes to shove you could probably take the .6mm off of the 750 liners and not go with that big of an overbore....

[paulages]

i measured my 550 cylinders up as well, and found what you did. I'm still planning on running the oil lines externally. my machine shop said it would be no problem making the necessary restrictors for the oil flow.

have you mocked up the 836 pistons yet? I'm not sure the valve cutaways will work with the 650 head. the valve placement is different in the 650's. I'm looking into some custom pistons myself. 65mm like the 836 kit (which my math gave me a 740cc...maybe i calculated wrong?).

keep me filled in on your progress...

[cafe75-550]

I havent mocked up with the pistons yet, I think it slipped my mind  that the 750 uses offset valves...on the other hand the 750 valves look to be larger than the 650's ( I dont have those specs) so it might be a wash, I'll have to check that out tomorrow. Any reason why you're leaning to the external oil lines? Not that it would be difficult to block the internal lines, but if they remain intact wouldn't that be the better solution? Unless maybe the increased temp would make them ineffective 

[cafe75-550]

Oh and your math is fine I think, I'm planning on running the 550 crank so no increased stroke, the only 650 parts Im planning to use is the head and camshaft.

[paulages]

honestly, i was just initially blown away by the old brit bike look of the external lines on the bike you referenced that tom posted pictures of. when i measured everything up, my sleeves were gonna come damn close to those oil passageways, so i just decided it was a good enough reason to do it. i'm not sure what effect the oil lines being so close to the cylinders would have, but even if it didn't heat the oil up more, external lines would seem to have a cooling benefit.

[bwaller]

Re external oil lines, an attractive benefit might be eliminating the typical oil weeping problem, hmm might look at that too. Paulages how are you determining the amount of restriction needed re top end oil flow? I have a 500 Interceptor and the external oil line attaches at each head with a special banjo bolt that appears to have been designed to do just this.

[paulages]

the restrictor in the heads is basically just a plug with a tiny hole in it. my machine shop said it would be easy to just make a fitting for the line with the same sized orifice.

[Tommy Neimeyer]

Having worked with Dr Tom and his 500 big bore a little, one of the biggest problems I have seen is keeping oil from seeping at the base of the cylinders.  Remember Honda designed a certain amount of contact area between the case and cylinder block.  The big bore sleeves take up a lot of this "designed" contact area.  With less sealing area, it becomes harder to keep oil in.  Not trying to be a wet blanket just pointing out a ongoing problem I have seen. 

[paulages]

by the way cafe75-550, nice bike. the lines look quite familiar. are your electrics and battery under your tailpiece?

[cafe75-550]

Thanks! Ive been working on it for about a year now, most of the work happened over last winter when I tore it down to the frame, polished the frame,removed all the tabs and gusseted the frame, replaced all the bearings, rebuilt the forks, switched the dual front set up from a parts bike to it, and did the work on the tank (knee dents and early cap) which is a 750 SS. This winter the original engine is being reworked, and hopefully final bodywork and paint on the tank. The battery is under the rear bump, the electrics are mounted to the bottom of the seat awaiting me to fabricate a cover. Its primarily inspired by one of Carpy's bikes, but I cleaned it up to look more like the british cafe's (of course they can run sans battery making it easier...)

[markymark]

Hey all, I am pretty new to this forum and have in the last 4 months aquired a 76' cb550.  I am having so much fun.  When I got it i put 750 carbs on almost emediatly and noticed a big power gain.  My bike runs great with 30k miles and I ride it every day and sometimes I beat the hell out of the excelleration. It seaps oil but still runs amazing for a 30 year od bike.   

My question is this........   I want to put an 80' cb650 engine into my classic looking 76'.  Is this an easy swap?  I was at the bike junk yard and did some measuring and everything looks the same. "I'm not great at measuring".  But like I said it looks the same.  So has hanyone done this?  Will this be an easy swap?  I don't care much about the kick start as long as the bike starts. 

Will an 80' cb650 fit my cb550 frame and match up?  Will I have to change the ECU?  Help:)

[Chris Liston]

Hey all, I am pretty new to this forum and have in the last 4 months aquired a 76' cb550.  I am having so much fun.  When I got it i put 750 carbs on almost emediatly and noticed a big power gain.  My bike runs great with 30k miles and I ride it every day and sometimes I beat the hell out of the excelleration. It seaps oil but still runs amazing for a 30 year od bike.   

My question is this........   I want to put an 80' cb650 engine into my classic looking 76'.  Is this an easy swap?  I was at the bike junk yard and did some measuring and everything looks the same. "I'm not great at measuring".  But like I said it looks the same.  So has hanyone done this?  Will this be an easy swap?  I don't care much about the kick start as long as the bike starts. 

Will an 80' cb650 fit my cb550 frame and match up?  Will I have to change the ECU?  Help:)

I believe this has already been done and the 650 motor will fit in the 550 frame no issues.  I'd imagine you should swap electrics and harness though.

[Ibsen]

Will an 80' cb650 fit my cb550 frame and match up?  Will I have to change the ECU?  Help:)

The 650 engine will fit. And if you can get the complete 650 electronic ignition system, use that as well.And from my humble experience from riding a 550, the difference will be quite noticeable.