Topic: Where do you get your machine work done?

[Scott S]

 I'm looking for a shop that's familiar with the Gentleman's Express piston modifications. This is to run the 750 pistons in a 550.
 Are there any SOHC knowledgeable machine shops out there? The forum member who used to offer this service hasn't been around for about six months.

[Big Jay]

I was the one who first did that mod, but now, I don't remember and have no specs.

[mick7504]

Here is a link to an article about that mod.
http://forums.sohc4.net/index.php?topic=20601.0

[Scott S]

 Big Jay, the Gentleman's Express article has the measurements, etc. Are you still capable of doing it?

[Big Jay]

We had fixtures, etc. for doing those. We don't have that stuff anymore. I also don't think the specs in the article are complete.

[Scott S]

 Well, shoot. If anyone knows of a sop that can do it, let me know. I think I'd rather go that route instead of modifying the aftermarket "605" kits, upgrading rings, gaskets, etc.

[754]

 Soos is the guy that was modding pistons on here..

 is he MIA ...

[MidnightLamp]

I have a pair of CNC lathes at home and can come up with a jig to cut the skirts and crowns. I can give a try to a set of my toasted K4 pistons on Saturday (tomorrow is Canada day).  I do have a piston vise, so can flycut the valve reliefs, but have no cluse on how deep they need to be, as I don't have a 550... If someone in Canada has a 550 and could send me a junked piston I can figure out a baseline and increase it from there?

I'd be down to make a set or two to try out for free if someone is willing to risk a set of CB750 pistons for the cause.

[Scott S]

 754.... Yes, Soos seems to be MIA. He hasn't been active here since December. I sent him a PM anyway, but no reply. According to his services offered thread, he had some family stuff come up and was taking a break.

 MidnightLamp....That would be great. If you get it figured out, please let me know. I'm sure I'm not the only one that is looking to have this mod done.

[MidnightLamp]

Well, good news and bad news. I only have one 750 piston kicking around that is not an F2 piston or a big bore piston. I guess i tossed the rest of the k4 pistons because they were completely unusable. Anyone in Canada willing to donate a set to the cause? Since these are for test cuts, I'd gladly take a scrapped set.

[Tintop]

PM sent

[MidnightLamp]

Thanks tintop!

Here's one I cut as a sample from the blown K4 pistons. It's pretty....messed on the sides, so I only cut the top half of the piston as a sample. Specs are as per the gentlemens express article, and the cut specs are:

23mm compression height (above wrist pin centreline).
15 degree taper, starting 6mm inwards from compression deck.
pop up of 3.18 mm.



seems like the remanants of the original valve cutouts are still there 

Cheers

[MRieck]

I don't want to be a buzz kill BUT you can get good, 61mm aftermarket pistons for the 550. Why go through all that work...and it is a bunch of work....to still have an old, used , cast piston? I did a ton of work for a fella that made a set of those pistons. He, or somebody, did nice work but it was still an old, used, cast piston. I say start fresh with new, forged,much more modern components. The cost of new parts will certainly be offset by machining costs unless somebody is doing it for basically nothing. That's their business the BUT new parts are now available. I have the 550 Kibblewhite valvetrain parts in stock too.
  The thing to keep in mind is that type of work was done at that time because there were no good aftermarket parts. Jay started out with the CB350 pistons for the 750 because no one made big pistons.

[MidnightLamp]

Mike, I think it's mainly the entry price of a 550 big bore. Isn't buzz the only one making big bore pistons for the 550 right now? At $600, it's a damn steal for a set of forged pistons for a bike that does not have a big aftermarket following. At the same time though, $600-800 will buy you a CB550 round my parts that is in decent shape. I figured i'd hook up a few people here in canada with some pistons on my off time with my new lathe (built it myself from a manual lathe), and it gives me some practice time 

I wouldn't be charging anything for a the first few, and probably would stop after that, considering Soos only wanted $50 for a set. It would take me about half an hour per set (considering I now have the tooling and finally found my piston vise). The concern is duly noted and appreciated, because I definitely wouldn't want to be cutting pistons all day and trying to turn a profit... I'll leave that to piston makers   

And I know the pain of the NEED to build parts like this, the enfield was a nightmare to fix. I ended up making: the oil pumps, the piston, the connecting rod, and the cylinder sleeve because nothing of that sort was available. 

[Tintop]

+1 Mike on going with new.  Dynoman has 61mm JE pistons for 550's (& 550/650 hybrids).  For the price I wouldn't consider recutting used 750's anymore.

[Scott S]

 Mike, once you start "upgrading" the aftermarket kits, they're not so cost effective anymore. Everyone says to not use the oil rings that come with the kit, so factor in new CB750 rings and machine work on the oil ring groove. Then, upgrade the head gasket, which is something else many people recommend.
 At that point, I can buy a set of NOS CB750 pistons from ebay, rings and gaskets (which I was going to have to spring for anyway), and machine work to do the Gentleman's Express mod, and I come out to the better and I'm using genuine Honda parts (and not used pistons) and quality aftermarket gaskets.

 The only thing is, at that point, the Dynoman kits are dangerously close in price and, as you pointed out, are new, forged and don't need any additional work or upgrades. Decisions, decisions.

 Does anyone even make 1st over pistons/rings for the 550? I have a suspected broken ring (haven't torn it down yet) and would be happy with just an overbore.

[Tintop]

........ Does anyone even make 1st over pistons/rings for the 550? I have a suspected broken ring (haven't torn it down yet) and would be happy with just an overbore.

Honda , that's what is in my 550, for just that reason.