big bore kits with rephased crank

Jungle_Biker

I just got my first 447 XS 650 engine. I haven't torn into it yet, but I will be doing so before too long and I have plans to go with a 277 degree rephased crank at some point. What I want to know is, has anybody run a really big bore kit with a rephased crank and how did it do? I'm mostly curious about wether or not the Halco 970 kit would work with a rephased cran and cams.

Cooltouch

Doesn't that big Halco kit require stroking the crank? Also possibly making modifications to the case?

I don't see why it wouldn't work with the rephased crank and cams. The dimensions don't change for the rephase, just the timing.

Best,

ichael

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

As far as I know that massive Halco engine used a massive crank and lots of case mods. Not just bolt on big bores.

I you rephase its just an engine timing change, so it doesnt effect the bottom end.

But if you want a big bore motor that large you are going to have to mod the bottom end big fashion!

And you do know that Halco no longer exists. Tony Hall the owner passed away and is well missed I can tell you!

Jungle_Biker

Yeah, thanks Jake68, I had heard about Tony Hall passing away--I understand Palma Tuning will be doing a lot of the same sort of things he did, but as of yesterday, their website was still in design phase.

In the end I will most likely go with one of the 750 kits, but I would sure like to know more about some of the 840, 900, 970, 1023 and 1078 kits I've heard about. I read an article about some Swiss-made 1023 kit and the tester wrote about how terrible the vibration was at idle and I wondered if a rephased crank might not have helped to cure that problem. Surely I can't be the first to have thought of that idea.

jayel

Ah yes, the Moko/Yamaha 1023XS, made their own cases, moved out the clutch (went to dry clutch?) only 4 speed said it shook the filling out of your teeth but would out torque a dump truck, think it was originally designed for sidecar racing

xs1961

Jungle_B , I can tell you anything you want about the 840 motor as Ive built/owned/run quite a few over the years , You'll need a 533 rodded crank to start with mate, machine the cases & camchain tensioner & find yourself a couple of Suzuki SP370 pistons and some 85mm liners(Ive used Audi car liners). .
Ive also had a couple of Wiseco 750's which are definitely the cheaper/easier way to go.

Jungle_Biker

Thanks XS1961--I may be picking your brain at some point in the future, as your 840 engine sounds like just the sort of thing I like to do. (I also like putting XL500S pistons in 1978 and earlier XL 350's to make a killer 440!)

What's reliability like on the 840's? I found one guy who claims that his Halco 970 now has 30,000 miles on it and is still going strong. Is he for real? How far can you take an XS 650 engine before reliability takes a nose-dive?

xs1961

My recent 840 covered approx 20,000 miles (including several drag sessions in the Ramsey sprint on the Isle of Man)without a problem.
They run a little hot cos the oversize liners (sleeves in U.S. speak) fill in the airway between the cylinders so an oil cooler is reccomended.
Only composite head gaskets seem to work (cant get 'em here in the UK anymore)
Anything bigger than 840 needs the crank 'stroking'
All the best Mate

cscarroll · Full Member Joined: Oct 08, 2006 Posts: 112

J_B,

You're making me jealous! If only $$ were no limitation. I guess we can't all be "Kings in Exile".

p.s. My heads are going back to the machine shop, could be building the motor up as early as this sunday...

Jungle_Biker

Hey! CS, great to hear from you. Listen, at this point I'm still doing research to find out what has been done and what can be done, what works and what doesn't. Anyway, don't count on me to be spending loads of cash on this. However, since I do have free access to a machine shop, there's lots of stuff that I reckon I'll be doing myself. I can handle the crank rebuild/rephase and the cylinder boring myself and I think I can manage the camshaft rephase as well, so that will bring my costs down considerably. Cool about your engine coming together. Why are your heads going BACK to the machine shop?? Did they mess up your valve job? Did you decided to bead blast the head after all? I was just thinking how cool it'd be to recast the head in bronze like an old Excelsior Manxman, but that might be going a bit over the top...

XS1961, thanks for the good info on 840 longevity. I think 20,000 miles is pretty respectable for an air-cooled hot rod engine. Did you ever try a copper head gasket? I think I can make my own copper head gasket and could even manage to do the copper o-ring seal if I needed to.

xs1961

I never tried the copper gaskets Jb, i got pissed-off with them blowing on my ol' Triumphs & BSA's !
I do know someone who machined a groove in the barrel top mating face & likewise in the head , he swears it never blew again...

What Happened to 650rider.com?

Yamaha xs650