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550 to 650 questions

  • Thread starter Thread starter musicman
  • Start date Start date
M

musicman

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I've been pondering this, haven't made a move yet since I still think I'm going to sell the 550 in a few weeks, but if I don't I need more umph out of this thing, so I have some basic questions.

My bike being a '79, what year 650 jugs should I be looking for? I know the 650 and 550 cams are different, but can I just use my head on the 650 bottom end, or are the chambers different? If I did this I'd get a set of cams from MegaCycle, really mild ones, also would port the head, fairly familiar with that side of the world. Also curious about sleeves, I take it since grinding is needed the 650 sleeves have a larger OD than the 550 ones by a fair bit, how far can the 650 be punched though before (being a street bike) I have heat issues? Would be nice to make it to 700cc roughly, I want to work within the limits of the stock sleeves. Also curious if the 550 and 650 have the same stroke. And some really basic questions, are our wrist pins press fit? Any cam chain tensioner upgrades? Anyone done an oil cooler on a 550?

That's it for now, kinda just dreaming at the moment, though I'm into sleepers and a mildly built 700 in a 550 chassis would be fun I think :cool: I'm not having any luck finding a bike locally in my ridiculously low price range, so kind of thinking just keep toying with what I have, with the seat I built my 6'3" frame actually fits this thing half decent, though I hate to think about what I look like sitting on it :eek::lol:
 
Stroke is the same, 699 ccs is doable, there are more than enough cooling fins, you need the 650 head as the pistons have a more efficient shape than those of the 550, the 650 head works better.

The 550 cams give more top end, the 650 more grunt, watch out the sprockets are different. The wrist pins usually push out with a finger, you may need to push a little harder than that.

This is all from other members who have written up threads on this mod, I have not assembled mine yet.
 
So the chambers and domes are different, that's good to know. Curious on years of parts to use, basically through 81 right? Not too worried about the cams since I'd go to Megacycle and send them 550 cams for cores, not a fan of stock I guess. And then carbs, I'm a fuel injection guy and NOT in any way shape or form a carb guy, so I've been learning a lot these last few months :o I'm starting to understand my VM carbs, can I use them on the 650 head too? Would save me a couple dollars since I have a pile of jets now, new boots, k&n filters, etc. Just for the sake of knowledge I guess too, I'm not sure I'd want to change horses mid race and go to CV carbs, and buy all new parts and learn to adjust/tune all over again, though I guess the VM carbs will be a restriction on the build, not sure. Though if I can't use them on the 650 head then I guess I need to suck it up. I miss my laptop, tuning software, and sensors, this whole doing manual labor thing to make the engine run good is irritating :lol: :p

Lots of good info there, thanks! For a few years I've been wanting to build an odd engine, the only reason I'm stewing on this is I've never built a cycle engine before and I think it'd be fun to do something different.
 
Parts bin engineering is IMO, not odd.If a 650 engine/parts bike could be found it'd make an interesting project,for sure.
 
musicman said:
My bike being a '79, what year 650 jugs should I be looking for?
Click to expand...
Easy one there, the 650 was only available '81-'83.

musicman said:
Any cam chain tensioner upgrades? Anyone done an oil cooler on a 550?
Click to expand...
Personally, I would not consider it an "upgrade", but there are manual tensioners available. There is nothing wrong with a properly-working stock tensioner.


musicman said:
Curious on years of parts to use, basically through 81 right?
Click to expand...
No, as I mentioned earlier, you start with '81, go through '83.



musicman said:
I'm starting to understand my VM carbs, can I use them on the 650 head too?
Click to expand...
You would have to make adapters. All of the GS bikes had the CV-type carbs by 1980, so that is what the intake ports on the 650 would be sized for.



musicman said:
I miss my laptop, tuning software, and sensors, this whole doing manual labor thing to make the engine run good is irritating
Click to expand...
Sorry about your luck. :p

If you want fuel injection, why not get a system off an XN85? That was Suzuki's turbocharged 650 that had fuel injection from the factory. :D
Or you could order up a Megasquirt setup, which would probably be a LOT cheaper.

.
 
Hmmm.... now you have me thinking, a fuel injection swap is up my ally, man what a frankenbike that would be, lol. Could just build a manifold and run some tiny injectors, like 15lb ones or something, haha. WOT it would still probably only see 50% duty cycle. And why not turbo it?

This has some gears turning in my head now, time to do some reading, heehee
 
You only need a 1mm over bore to reach the magic 700cc mark.

I have done this conversion and it works. If you have any questions just ask. Best to send me a PM as I don't frequent this site as much as I used to. Other projects going on in my shed presently, VX and Guzzi are keeping me busy.
 
Don, a Guzzi build thread in the projects/rebuilds section would be most welcome. ;)

Eric
 
Get on it musicman. I too come from the world of laptop tuning turbo'd vehicles... Whole new world here. I'd love to watch that build if you ever decide to swap to fuel injection and slap a little turbo on there. Ive got alot more learning to do with this type of ballgame but a tiny turbo on my 550 has crossed my mind.
 
What's funny is I was thinking about a turbo long before I even owned the bike, go figure.

But pricing stuff out, if it doesn't sell then I'll just do the punched out 650 conversion, port the head, and call it good. Too much money to throw at this thing, if it were a bigger bike I think I'd have a turbo already.
 
Any links to info you've come up with on the 650 conversion would be appreciated

Thanks
 
7981GS said:
Don, a Guzzi build thread in the projects/rebuilds section would be most welcome. ;)

Eric
Click to expand...

Eric, not sure a Guzzi build on the site would be appreciated.

Anyway I picked the Guzzi up a couple of days ago and it is in much better nick than I thought it would be. So Don't really intend to do much to it at this time. Maybe an external oil filter added later on -- as you need to drop the sump to change the filter on the early 850s. And some of the 750s didn't even have an oil filter or air filters for that matter.

The motor is pretty cammy and a bit hard to get off the line but once moving it has really brisk power. A few pics for you Eric.

P1050008.jpg


P1050011.jpg




P1050010.jpg



P1050009.jpg


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