Alternative rods and pistons

[crazypj22]

Hi Otto.
The CM400 pistons are too small (70.5mm dia)
You need CM450 pistons (75mm dia)
The crowns need shortening slightly, about 2.5mm, just around the edge to fit into XS combustion chamber.
It's easier to do it on a lathe than a milling machine.
With the CR rods you can pretty much button it up. Don't know the CR but it will be slightly lower than stock.
If you can get a set of XV pistons/cylinders and a spare XS cylinder its not just a case of switching cylinders, the case has to be bored for clearance of the bigger liners (of course you could do his while you have bottom end apart) It shouldn be a problem to get measurements and give it about 0.5mm clearance, about 32mm deep.
PJ

PS
could someone ask moderator to make this a 'sticky' its had nearly 3,500 views, almost as much as porting,so I guess its pretty popular.

[otto]

Thanks PJ!
DOH!
Yah, I meant 450. I think 70.5 might have a little compression problem.
I'll need to get an idea from some local shops on cost of boring the jugs and case to decide. How did you go about shortening the xv750 sleeves? seems like they'd be awkward in a lathe. (I haven't used one in 20 years).
Thanks
otto

[crazypj22]

Hi otto,
just hold the flange area in a 3 jaw chuck and slowly part off the bit you don't need. I made a bull nose centre for the first few I did to support the spigot area but now I just go straight in (slowly ;D)
Then reduce the diameter to the original size for the amount that sticks out of the block.
You don't need a massive lathe to do this. I use a table top 7x10 from ENCO, same as the Harbour Freight one. It takes up very little space and it works for piston mods as well (and I've made valve guides and various other stuff on it) Doesn't have power I'm used to but it gets the job done (slowly)
I'd like a bigger machine ( I used to have a 10"x48", actually too big for most of the stuff I made) but have neither the space to put it or cash to get one.
A medium sized milling machine will be ok for the case opening, it doesn't have to be high precision, closest 0.25mm is more than good enough. (I've done cases on the big machine I had, bolt case to cross slide and use boring bar in chuck, got pictures somewhere ;D)
Are there any evening classes in your area doing this sort of thing or any model engineering clubs?
Maybe something to check out, learn some new stuff and save some cash
PJ

[jack]

So PJ,when do your evening classes start? ;D...........Jack

[otto]

I've thought along those lines many times PJ! Never have found anything workable though. I'm with Jack, think I'll just hop a quick flight to the opposite corner of the country.

Think its all moot at this point anyhow. The accountant is backing down on this project anyways, so I may just be in milk it out another season or two mode. The plus side is things are looking better than first glance indicated on the crankshaft. You're right, this should be a sticky. Someday I will go this route...... someday. I can hear my wife now... And pigs may fly out of my a$$.

[crazypj22]

jack said:

So PJ,when do your evening classes start? ;D...........Jack

5.50pm until 11.00pm. you get a 20 min break at 9.50 - 10.10 ;D
I've been lecturing almost 7 years at MMI in Orlando, its not as easy as people think, particularly as I'm British and have a bad attitude to management (I can do your job, you cant do mine so leave me alone type of thing ;D)
They do run tours of the school though if your down his way for Bike Week or Biketoberfest, call in and say hello ( or any other time , just call ahead for tour times)
PJ
BTW, I had over 30 yrs experience in Britain before I started here, its pretty much the same working in a shop and kids have bad attitudes all over

[crazypj22]

otto said:

I've thought along those lines many times PJ! Never have found anything workable though. I'm with Jack, think I'll just hop a quick flight to the opposite corner of the country.

Think its all moot at this point anyhow. The accountant is backing down on this project anyways, so I may just be in milk it out another season or two mode. The plus side is things are looking better than first glance indicated on the crankshaft. You're right, this should be a sticky. Someday I will go this route...... someday. I can hear my wife now... And pigs may fly out of my a$$.

I wouldn't worry too much about time scale, when I started mine I put a 6 yr limit on it as I knew here would be other things that needed my time and money. (and other projects that get started) Its been over 4 yrs so far, I keep coming up with new idea's to try out (some of them actually work as well ;D)
I'm doing a big bore kit on a XS400 DOHC motor at present, for a friend (i.e. free) using Suzuki GS500 pistons. It has to be done by Dec 23rd as friend is leaving Florida.
Just at found this on SOHC.net, CM 450 being parted out, they may let pistons go cheap, e-mail
[e-mail]
PJ

[hsi88]

Hi Guys, I bought Bigg Matt's project bike. He already rephased the crank to 277 degrees and included LA liners and XV750 pistons along with the CR500 rods. I am shipping out the cam to Megacycle and will be getting the Newtronics ignition which is already set up for 277 degrees. Matt also hand crafted a monoshock setup with a slightly longer swing arm and the rake was steepened. I will be fitting 36mm Lectrons to this one. I plan to do the same to another "Tracker" that I bought cheap but will be installing a turbo on that bike. I have a stable of Norton Commando's as well and enjoy the "vibes" of a big parallel twin.

[50gary]

Welcome, and that's quite a first post. I would say the 277(s) will vibrate quite a bit less than the Nortons? The Lectrons will also be interesting. keep the updates coming.
Cheers, 50gary

[otto]

Well that's a bummer, I'd always thought Matt had finished that bike. That was more or less the direction I wanted to go for the engine, make sure to let us know how it turns out.

[mercurymorse]

A few points. As a rule, long rod XSs make more power. They are particularly advantageous in dirtack racing, as the short rods make for a more explosive mid-range, and coupled with the lack of flywheel, forces one to compromise midrange performance, typically by using Mikuni round slides and 1 3/4" head pipes, to get the bike to hook up out of the turns, or you just go up in wheel spin. Although this is necessary in the dirt, it makes for less than optimum performance on the pavement. Heavier pistons and rods are plus in a re phase, as it improves the balance factor for a quarter fire motor, which needs to be substantially less. That is, more like 50%, compared to about 65% for a stock 360. This why 750 re phases are smoother than 650 re phases.

[hsi88]

Hi PJ, you mentioned using a lathe and milling machines. I would like to be able to machine some of my own parts. Certainly reworking XV750 pistons come to mind, including valve pockets. Also regrinding cams would probably save me some money as almost every bike I build gets a new cam grind. I also have a constant need to bore cylinders and install larger valve seats. Is there one or two machines I could buy to get me started. I have a little experience and I am a quick learner. I want to ulitmately work up to cranks as the old Nortons I work on have a great need in this area with their "explosive" cranks anytime they get beyond 7-8k RPM. Anyone can respond.

[crazypj22]

If you eventually want to move up to Norton sized cranks your going to need some reasonably large sized machines.
I'm guessing the flywheels will be around 8~10" dia but relatively short so you could get by with a smaller lathe as long as it has a removable 'gap' at headstock (a section of lathe bed is removable for larger diameters.) I've done almost all my turning on the Mini Machines available from Harbour Freight, Grizzly, et.al.
I burned out the speed controller on mini mill as its too small for almost everything I was making (but good for practice as I hadn't done much milling)
I ended up with the $899.00 Mill from HF, not exactly what I wanted, but, didn't take up too much space and fitted into what I could afford. It has 5" quill travel which will be enough to bore blocks/cylinders (wouldn't work on a long cyl like the Norton one)
The Lathe I want is about $3,500 (still a cheapy )
I have neither cash or space for it so I'm still using the mini lathe, 7x10.
I may eventually end up with a bigger machine though if I can figure out how to finance and where to put it, then I can bore longer cylinders.
There is a 7x14 advertised sometimes. (around $499.00) Its great for smaller stuff, up to about 4" diameter or so, pistons are easily modified and I've made Aluminum bronze valve guides for about $3.00 each instead of $18.00 plus (material was only $1.00 per inch) You can also make them oversize to salvage worn heads.
I don't know how you could re-profile/grind cams without a cam grinder though, its possible to make some sort of attachment to fit lathe but I've never seen one so wouldnt know how to go about it.
All for now,
PJ

[hsi88]

Thanks for the info. I have 6 XS650's and except for the 72, they all came pretty cheap. I have 3 tracker projects in various stages of completion. I want to go with larger bores on all of them and have been buying Virago cylinders and pistons (in very nice shape) for as low as $10 plus about $25 in shipping. I plan on using both the cylinders and pistons and will need to bore and press the trimmed virago sleeves and will need to cut down the pistons. A little bit of labor, but we are talking $35 (plus $100 for two rods) for an 800cc bike compared to $400+ for a 750. Granted, these aren't high performance parts, but they look adequate. I am only doing the one 277 degree bike because of the high cost of the cam and ignition. The others will be real "thumpers" with the original 360 degree crank. I bought a whole batch of XS650 Branch oversize valves and have a valve cutting kit from Neway that I use on my Nortons. For starters, I will probably just need to bore cylinders and adjust pistons. I am looking at some combination machines from HF to see what I can get for cheap.

[Cooltouch]

When I was in the market for a decent combination machine a few years ago, I gave it a long, hard amount of thought and decided instead to go with a separate lathe and mill. Cost was about the same as a large combo machine, but functionality was way better.

I bought an HF 9x20 lathe, which is a nice little unit once it's dialed in. Plus there's a large support group for this machine over at Yahoo groups, so just about any question I've had about it, I've been able to get answered pretty promptly by the folks over there.

For the mill, since my eventual idea was to convert it to CNC (and still is -- one of these days), I went with a dovetail column machine rather than a round post one (you have to retram the head with a round-post machine every time the head is moved, not so with a dovetail column machine). I bought the mill from Wholesale Tool: www.wttool.com/product-exec/product_id/14840/nm/Geared_Head_Mill_Drill_Machine_w_Dovetail_Column

Like the lathe, it's a decent unit as long as you respect its limitations. A Bridgeport it ain't, but it gets the job done quite well for the tasks I've used it on.

Best,

Michael