Author Topic: 550/650 hybrid or 650 big bore HOW TO (Read 110855 times)

turboguzzi · « **Reply #150 on:** July 04, 2011, 09:55:14 am »

will post some pics and measurements later paul ( if i manage to fight the compulsive need to go down and play with the 88' GSXR i've just brought in

)

TG

turboguzzi · « **Reply #151 on:** July 05, 2011, 03:38:34 am »

there you go

66'ers

17 is edge of pin hole to piston edge

would be 24,5 pin CL to edge

crown curve goes almost edge to edge.

TG

paulages · « **Reply #152 on:** July 05, 2011, 10:58:09 am »

These look perfect for the RC181 project. PM me price details, please.

turboguzzi · « **Reply #153 on:** July 05, 2011, 04:13:53 pm »

They are yours and there's no secret price paul, you'll only have to serve as my posting address to get me stuff from the USA for the next few years..... a deal?

and still, would check ebay before shipping across them ocean,

TG

paulages · « **Reply #154 on:** July 09, 2011, 01:55:54 pm »

Quote from: turboguzzi on July 05, 2011, 04:13:53 pm

They are yours and there's no secret price paul, you'll only have to serve as my posting address to get me stuff from the USA for the next few years..... a deal?

and still, would check ebay before shipping across them ocean,

TG

I'd have gladly done that Anyway Yossef... so, I'll agree to your terms.

Hey, if we're lucky and the timing is right I may even be able to deliver parts to you in person.

turboguzzi · « **Reply #155 on:** July 10, 2011, 12:19:47 am »

check your pm's

mickey6 · « **Reply #156 on:** July 28, 2011, 10:33:40 am »

gonna try this with a 500 case and see what happens.

paulages · « **Reply #157 on:** July 28, 2011, 10:58:18 am »

Quote from: mickey6 on July 28, 2011, 10:33:40 am

gonna try this with a 500 case and see what happens.

I'm in the process of doing the same. It won't be any different than with a 550.

mickey6 · « **Reply #158 on:** July 31, 2011, 10:16:15 pm »

cool beans. Then I should more or less be able to follow the methods in this thread

.

sinister902 · « **Reply #159 on:** August 15, 2011, 02:57:50 pm »

I just got ahold of a 1980 CB650 engine in running condition. I am now on the hunt for cb750 liners and I'm planning on using an 836cc kit for pistons. I beleive I understand all of the how-to besides ONE detail....

you mention what specs you STARTED at for modifying the pistons, and stated that after some more work you got clearance that was acceptable..... does that mean the specs you listed as where you started are too tight and the "more work" means different specs for machining the domes?

paulages · « **Reply #160 on:** August 16, 2011, 12:07:35 am »

Quote from: sinister902 on August 15, 2011, 02:57:50 pm

I just got ahold of a 1980 CB650 engine in running condition. I am now on the hunt for cb750 liners and I'm planning on using an 836cc kit for pistons. I beleive I understand all of the how-to besides ONE detail....

you mention what specs you STARTED at for modifying the pistons, and stated that after some more work you got clearance that was acceptable..... does that mean the specs you listed as where you started are too tight and the "more work" means different specs for machining the domes?

Yes, the clearances were too tight. Bear in mind that the shoulder height and valve reliefs are going to be different for every manufacturer, at least by a few thousandths. You'll have to measure yours and calculate how much squish you want, etc before machining. It's too bad Soos disappeared, because he machined several sets of overbore pistons for a 650, including the 64.75mm pistons in my engine now. He could surely help out with general parameters.

sinister902 · « **Reply #161 on:** August 16, 2011, 05:00:48 am »

Quote from: paulages on August 16, 2011, 12:07:35 am

Yes, the clearances were too tight. Bear in mind that the shoulder height and valve reliefs are going to be different for every manufacturer, at least by a few thousandths. You'll have to measure yours and calculate how much squish you want, etc before machining. It's too bad Soos disappeared, because he machined several sets of overbore pistons for a 650, including the 64.75mm pistons in my engine now. He could surely help out with general parameters.

Yeah, I really wish Soos was around.....I have no idea how to go about calculating all of that mumbo-jumbo and was hoping it would be as simple as going to a local machinist with specs and having it done. Guess not haha.

paulages · « **Reply #162 on:** August 16, 2011, 11:05:13 am »

Quote from: sinister902 on August 16, 2011, 05:00:48 am

Quote from: paulages on August 16, 2011, 12:07:35 am
Yes, the clearances were too tight. Bear in mind that the shoulder height and valve reliefs are going to be different for every manufacturer, at least by a few thousandths. You'll have to measure yours and calculate how much squish you want, etc before machining. It's too bad Soos disappeared, because he machined several sets of overbore pistons for a 650, including the 64.75mm pistons in my engine now. He could surely help out with general parameters.

Yeah, I really wish Soos was around.....I have no idea how to go about calculating all of that mumbo-jumbo and was hoping it would be as simple as going to a local machinist with specs and having it done. Guess not haha.

Start by having your cylinders bored out to fit the pistons, then fit one up and measure how far the piston stands above the deck. Make sure the base gasket is in place and use spacers to bolt the cylinder block down tight. Measure along the pin axis, as the piston will rock against it and will make it harder to know how far above the deck you are. I'd recommend machining the shoulder even with the deck, as you can adjust your squish with the thickness of the head gasket. That said, you're stuck using a copper gasket if you want more then .043" squish though, as that's the thinnest composite gasket you can get.

sinister902 · « **Reply #163 on:** August 16, 2011, 11:41:23 am »

I think I'll be making a thread in the coming months as I aquire the parts....hopefully it will become helpful to others as well as a place for me to ask the specific questions on how to do things so people such as yourself can hop in and help me out with advice....

65Ch3v3LL3 · « **Reply #164 on:** August 30, 2011, 11:19:55 pm »

paulages,

I'm sourcing parts right now for my 79 CB650. What did you use for head studs? All I can seem to find are larger ones for the CB750. Will they work or will the stock ones be fine?

Also is there any special bearings that I need for the 06 GSXR 1000 rods? It seems they would be stronger since that's a high horsepower engine to start with.

paulages · « **Reply #165 on:** August 31, 2011, 10:37:51 am »

Quote from: 65Ch3v3LL3 on August 30, 2011, 11:19:55 pm

paulages,

I'm sourcing parts right now for my 79 CB650. What did you use for head studs? All I can seem to find are larger ones for the CB750. Will they work or will the stock ones be fine?

Also is there any special bearings that I need for the 06 GSXR 1000 rods? It seems they would be stronger since that's a high horsepower engine to start with.

You'll have to use stock 650 head bolts, but the torque specs are the same as the heavy duty aftermarket versions offered by APE, etc. I don't have any experience with the GSX-R rods, but as I understand it you just need to measure the clearances and size them the same as you would with OEM rods.

KC3 · « **Reply #166 on:** September 06, 2011, 08:03:21 am »

Hi All,

I am definitely a noob when it comes to this forum, so sorry if this is in the wrong section. I have a 1976 cb550f (almost bone stock). I'm running 4 into 1 with a hand made muffler (glass packed). Stock carbs (the kind off a cb750a I think) with uni pod filters covered in outerwears to keep rain out. I bumped up the jet size to a 100 main and left the rest stock. It runs great, and has around 20K miles on it. I am wanting to throw a cb650 cam in it (which I have already purchased) and I am wondering if this will potentially harm my valves. Is it going to present the potential to burn them up? Thanks in advance for the help.

KC

kayaker43 · « **Reply #167 on:** September 06, 2011, 08:49:23 am »

KC3,.. It won't hurt a thing and probably won't need rejetting either? You'll use the 550 cam sprocket and install as normal. The tachometer won't work so you will have to use a 650 tach and drive gear or an electronic one.

Do a search for more info,.. its all spelled out in more detail in other threads.

Scott S · « **Reply #168 on:** September 10, 2011, 02:00:28 pm »

I'm guessing that a 650 header would be too big on a 550 unless you had headwork and a big cam, right? It looks like the o.d. of the pipes are ~5mm larger than the 550 pipes.
I'd probably lose a lot of low end torque, huh?

paulages · « **Reply #169 on:** September 11, 2011, 05:09:53 pm »

The 650 pipes won't even fit in the 550 head, at least not the ones I've had on hand.

Scott S · « **Reply #170 on:** September 11, 2011, 05:29:37 pm »

Well, I tried it, sorta, by sticking a pipe in a port at the junkyard. It fits but is very tight. Guess I'll offer it up for sale to fund my ongoing projects.

65Ch3v3LL3 · « **Reply #171 on:** September 12, 2011, 02:27:47 am »

Paul,

If I remember correctly I think I read that Soos recommended the 77-78 F2 pistons so the CR didn't drop so much. Do you think the Cycle-X domed F2 836 pistons would work in the 650 chamber?

paulages · « **Reply #172 on:** September 12, 2011, 10:14:55 am »

They look like they'd work well, still needing some machining of course.

65Ch3v3LL3 · « **Reply #173 on:** September 12, 2011, 10:37:25 am »

Thanks Paul. Yeah I knew I would still need to machine the edges for the smaller combustion chamber I was mostly concerned if these had too much of a dome to fit in the chamber. However the valve reliefs look really deep so I'm assuming there is plenty of material there in case I need to remove a bit.

I emailed the guy in Japan that's selling the cheap 836 kits to see if he had any of the 77-78 high dome pistons. I figured its worth a shot. If not the Cycle-X ones aren't too pricey.

Thanks for your help.
Tim

Pinhead · « **Reply #174 on:** September 12, 2011, 12:12:54 pm »

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.

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Author Topic: 550/650 hybrid or 650 big bore HOW TO (Read 110855 times)