Topic: 605cc questions

[Scott S]

 Thanks, that's the kind of info I'm looking for.

 I'd prefer to do the Gentleman's Express mod if I can find someone that is knowledgeable about the machine work for the piston mods.
 By the time I bought the 605 kit, swapped gaskets, rings, machine the ring land, etc., I'd be far better off to use the genuine 750 pistons OR the Dynoman stuff, don't you agree?
 How's the quality on the Dynoman stuff? Is it pretty much ready to go or does it need upgrading in any area?

[bwaller]

Contact Buzz, but sure it's a bolt on, plus the pistons are brand new. They'll be machined with plenty of margin to run any cam.  So many people buy old, used, worn out slugs the owner doesn't want anymore to start a new project....sheeeese.

By the way Buzz will sell you a cam for less than you can buy them from Web. Mike Rieck can do the same with Megacycle stuff.

[Pain]

my pistons will be here early next week.. i'll put some pics up on my build thread if u want to check them out.

[Scott S]

 I take it Buzz is at Dynoman? His stuff is starting to look more and more attractive, especially when you start nickel and diming your way through "correcting" this and that from the various other options.
 I'l have to look into the MegaCycle stuff, too.

 On the same subject, let's say I just want to fix and engine with a broken ring on one cylinder. Are 1st or 2nd overbore pistons available for the 550? Or do you have to go on up to the "big bore" kits? I haven't seen 1st overbore stuff in my searches.

[Pain]

yeah buzz is at dynoman.. if u email them he's the guy that emails you back. i was in your place not so long ago.. i had the 605 kit.. got frustrated with everything i needed to do with it and then realized all i would get out of it... then i started looking into the 750 pistons mod.. got more frustrated... around this time dynoman released those new pistons and then when they offered the $100 store credit with purchase i was sold.

don't know about the overbore pistons.. i never saw any.

[crazypj]

If spigots are 1.62mm, boring an extra .25mm will make them 1.495mm (you only take 'half' off each 'side')
 The liner inside block is at least 2mm larger diameter than the spigot so I think I would go for 61.25mm.n

[Scott S]

 That makes the 61.25mm piston set a good deal....IF I could find someone that can do the Gentleman's Express piston mods. Which, at this time, I cannot.

 I'd be happy with a 0.25mm overbore of stock CB550 pistons if I could find them.

[RAFster122s]

Scott,
APE can't do it if you supply the specifications you want?  They have said they have done it in the past. If you tell them what you want (from Gentleman's Express article) I would imagine they can do it. Question then becomes is it affordable. 
Have you asked local machine shops if they would do the piston modifications?

Are you doing these mods to your cb500?

If so, you would need the 605cc kit to go to 61mm, if you have 550 cylinders you can bore them to 61 safely, beyond that becomes a gamble.
I believe that is what bwaller has indicated.  He's knowledgeable.

Going larger than stock 750 pistons and you might need new liners (750 liners) for overbores.
paulages did the 718cc 550/650 hybrid write up and used 750 liners in his 550 cylinders to overbore for the larger 750 pistons. I forget what size he went with.

Aren't the dynoman pistons are forged pistons as opposed to cast pistons.

David

[Scott S]

 I have not looked into APE yet. This is the first time the name has come up in this thread. I haven't asked any local shops yet because I was hoping there was someone in the SOHC4.net world that is set up to do this and has experience.

 The mods are not to the CB500. I recently picked up a CB550 and the engine mods will be done on that one (for the better bottom end, transmission, etc., as well as no need to change liners).

 The Dynoman kit keeps looking more and more affordable when you factor in all the incidentals that go along with the other options.

[Scott S]

 What about these overbore kits? I can get them in .25 and .50. How is their reputation as far as rings, etc.?  Can I use a stock gasket set with these? Should I upgrade to copper or ?

[RAFster122s]

The henry abe kit isn't known for high quality.  Not sure about the other kits you are referring to.
The dynoman stuff is good and it's pricey.
But you'll spend quite a bit on heavy upgrades to the motor.

Have some head work done, drop a '79 650 SOHC4 cam or a good perf Webcam camshaft in it (58a or 58b) and it will wake up and be stronger across the band.

The dynoman kit is like the Gentleman's Express but using a nice forged piston.

Don't use copper gaskets unless you have special needs. They are hard to get to seal without leaking and you'll have to live with some oil leaks using them. Just go with a standard composite gasket properly sized for the bore and compression you are going for...

If you go with having someone modify pistons, then go with NEW Honda 750 pistons (61mm) instead of used.
Price a set of Honda OEM pistons and then the work to have them modified. You might come out cheaper going with Dynoman stuff.  I don't know which would be cheaper.
592cc pistons and parts are available from Dynoman for a price...is it worth it to you to go that route or would the extra work of sourcing and having the work done yourself be better. What's the rpm band for the performance mods versus what you want from the bike. Your cam selection will determine this to a certain extent.

Then there's the subjects of piston coatings and other higher tech stuff you'll want to research.

If you are going to do a rebuild, then spend the money to have it done right and done well.  Some things you don't want to skimp on, that's parts quality.  A motor rebuild isn't something that is inexpensive or real quick to have happen unless everything is off the shelf or is on a timetable you can deal with.

David

[crazypj]

I much prefer copper gaskets, as long as oil passage to head is counter bored for dowel and 'o' ring.
I've used them for 30+ years without issues (actually, the same one on my 550  )
 Even completely stock, the 'o' ring hardens and leaks, not sure if a square section 'o' ring would last longer (I think Suzuki makes one, don't remember bike/model though)

[TwoTired]

Even completely stock, the 'o' ring hardens and leaks, not sure if a square section 'o' ring would last longer (I think Suzuki makes one, don't remember bike/model though)

Can you think of a reason why a Teflon oring with it's higher temperature withstand characteristics wouldn't be a viable improvement?

Cheers,

[crazypj]

Only problem I could see with a Teflon ring is compressibility?
Maybe silicon with 400deg + capability would work?
There is a lot of stuff available now that didn't exist (AFAIK) 30+ yrs ago.
 The o ring still isn't supported though so any distortion will cause a leak