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

[paulages]

jimmy..  I'll have to write a better reply when i can, but i think using 550 pistons or any other flat top pistons with the 650 head would result in a fairly low compression ratio. The 650 pistons are very domed to match the hemi head.

[hymodyne]

not to hijack, but in response to my own question on this thread about the 650 gasket on an overbored 500, I'll never find out; a single 650 head gasket was 67 bucks at my honda dealership. the cometic gasket was 45

hym

[FunJimmy]

I think using 550 pistons or any other flat top pistons with the 650 head would result in a fairly low compression ratio.

Sorry to miss lead you Paul.

I'm wondering about using a 650 crank and rods with my 555 (59mm) flat top pistons and the 550 head.

Thanks
Jimmy

[paulages]

gotcha jimmy. I'm checking email etc. on my mobile phone in the van on tour.. Doesn't make replying or even reading threads very easy. Plenty of time to kill though..

[paulages]

making some progress...

trans and crank assembled:



cases sealed:

[Soos]

Hey paul,


From what you have seen of the 550 and 650 cases, do you think it would be possible to mod. a 650 case to accept a 550 kick-starter?


just curious..... 

l8r

[paulages]

Hey paul,


From what you have seen of the 550 and 650 cases, do you think it would be possible to mod. a 650 case to accept a 550 kick-starter?


just curious..... 

l8r

if you're a proficient welder, yes. you'd have to fabricate a pretty strong sleeve for the shaft to reside in, and brace it similar to the 550 case. i would imagine locating it perfectly to be difficult.

another incompatible part i discovered: the shift shaft.

[bill440cars]

         Well Paul, I call myself keeping up with this 650/550 build and next thing I know, I've missed some of the posts you've made. Sure am glad it doesn't take much for me to catch up. I know that it's got to feel good to get the case put together and on it's way.  

[paulages]

         Well Paul, I call myself keeping up with this 650/550 build and next thing I know, I've missed some of the posts you've made. Sure am glad it doesn't take much for me to catch up. I know that it's got to feel good to get the case put together and on it's way.  

thanks bill-- not totally sure the cases are closed for good... the main bearing clearances ended up being a little tight after all.. likely related to the mismatch of the crank and cases. it actually takes both hands to start the crank turning with the stator. once it "breaks" it'll spin freely with one hand, but i worry that's a but too tight. i've never had that happen before, but i've also never measured bearings so painstakingly and had such tight selection.

got my 520 sprockets in at least. anyone want to guess a starting point for jetting?  that'll be fun....

[mlinder]

With pods and open exhaust?
122.5 mains

[Soos]

What carbs are you running?


With my overbore(61mm 650cc's) stocker airbox, 4-1 "superflow" exhaust and cb750 carbs('73) i'm running with 107.5's.
Today I went to a local shop and had them check the exhaust and it's almost perfect mix. a tad on the rich side, but it's good.

If you are running with 650 carbs....
I'd guess in the neighborhood of 112's to 120's

If you are running 750 carbs, 115's - 125's

But i'm guessing. Or at least thats the range i would start in.

l8r

[paulages]

guess i should have given the specs:

718cc bore with 10.5/1 CR
megacycle 126-20 cam
mike reick stage 1 (i think) porting
K&N pod filters
early cb750K carbs
MAC 4-1 with glasspacked muffler (relatively open)

the '79 cb650 carbs ran 90 mains.    i thought i'd start somewhere around stock cb750 jetting. i'll be using an autometer to dial in the a/f ratios, but i gotta start somewhere, right?

[paulages]

     

i bent an oil rail installing the cylinders yesterday. goddammit. i've never seen oil rings so hard to compress. we had to re-chamfer the bottom of the sleeves three times, until they were almost sharp on the edges. i got them all in, then apparently the bottom rail on #3 jumped out at the last minute.

the bent rail isn't the end of the world, as i have to leave town again for couple weeks anyway and can order another from hastings, but it did score the cylinder wall a little bit. that sucks big time. 

[paulages]

okay, so i'm back in town only to discover bad news. dan took the scored cylinder out another half thou, and it was still bad. another half and it was still there. guess i have to make another sleeve.    anyone have a cb750 cylinder sleeve laying around they'd let go for cheap?

[paulages]

okay, pulled apart a top end from an F engine billy (billdramp) had laying around and dropped the liner off at dan hall's this morning. hopefully he won't take forever to make the new liner and re-bore it.

[Muk]

good luck paul i'm anxious to see how this beast turns out

[paulages]

good luck paul i'm anxious to see how this beast turns out

yeah, me too. it's been long enough...

[Pinhead]

Just for your info, the '79 CB650 came stock with 90 main's. A very common upgrade is going to 98 or 100 mains without any other upgrades.

I went to 102.5's, removed the airbox lid, and opened the exhaust and it's probably running a short-hair lean. I would think 115's would be a bit rich, though.

Then again I've never worked on anything other than my stock motorcycle. I'd say that'd be a starting point, though.

[bill440cars]

       Hey Paul.  Sure hated to hear about your problems with the engine assembly and all. I can well imagine your wanting to get that one together successfully and take it our for a run to see all that work pay off.
              You take care and I'll catch you later on,  Bill

[paulages]

       Hey Paul.  Sure hated to hear about your problems with the engine assembly and all. I can well imagine your wanting to get that one together successfully and take it our for a run to see all that work pay off.
              You take care and I'll catch you later on,  Bill

thanks bill. it'll get there eventually... tons of other projects at the same time don't help either. 

[bill440cars]

       Hey Paul.  Sure hated to hear about your problems with the engine assembly and all. I can well imagine your wanting to get that one together successfully and take it our for a run to see all that work pay off.
              You take care and I'll catch you later on,  Bill

thanks bill. it'll get there eventually... tons of other projects at the same time don't help either. 

          Oh yeah, I hear ya Paul. Still trying to kinda dwindle my list of "Project Bikes" down to a workable size, while taking care of everything else. You take care,  Bill


          Great work BTW!

[paulages]

small update: finally got the cylinders back after having to manufacture a new sleeve to replace the one i scored with the bent oil ring, and have successfully installed them tonight. i can't believe how difficult those oil rings were to install. we had to chamfer the bottoms of the sleeves so much they were almost sharp on the edges.

dan (the machinist i have worked with this whole time) has been going through some serious medical problems recently, so i have been patient. he has cancer, and he is in the hospital right now with kidney failure. i don't feel comfortable saying much more in respect of his privacy, but suffice to say i've had no problem being patient here.

there is only one small detail left to work out with the oil lines in the head, and i should have it back next week. assuming i can squeeze in some time somehow, this means i might finally have this thing buttoned up soon...

[bwaller]

Good of you to exercise patience in light of everything Dan is going through, sounds like he has been a real partner in your project.

We in turn can be patient too...............but hurry-up will ya!! 

[paulages]

Good of you to exercise patience in light of everything Dan is going through, sounds like he has been a real partner in your project.

We in turn can be patient too...............but hurry-up will ya!! 

being patient doesn't necessarily relieve frustration. 

[paulages]

ok- cam installed and timed. the card called for the following numbers:

          INTAKE            EXHAUST
 open   25 BTC            54 BBC
close    54 ABC            25 ATC
lobe
center   104.5             104.5
----------------------------------

i now have:
open    27 BTC            51 BBC
close    57 ABC            22 ATC
lobe
center   105                104.5

i also measured intake duration at .379", despite the card claiming .363". i tried my hardest to make sure the angle of the dial indicator was parallel to the valve stem, but the measured difference could be due difference in angle of the indicator causing slightly more travel than the actual valve stem. there was quite a bit of variation at "zero" lift, which i found interesting, and i'll never do this again without an enormous timing wheel. the ability to read an 8" wheel and get the accuracy necessary is too difficult. i'll probably print a huge (24" or so) one off of the one i bought and mount it on card stock. still, i'm happy enought with a .5 degree ballpark for my lobe center.

now all i have to do is assemble the clutch, the rest of the rocker assembly, and make the oil lines...