840 bore kit ?

[harley metisse]

Hi all, I'm new to this forum, but have rebuilt more than a few xs650's over the years, all back to standard though.
My query is this - what is the story with going up to a 840cc engine size ?
Tony Hall of Halco was the guru on this, but alas that avenue is now closed, so who else knows about these things ?
I should say, the engine to be "breathed on" is a 447 series motor if that makes a difference.
Cheers

 

[TwoManyXS1Bs]

Some old 840/860cc threads.

http://www.xs650.com/threads/crazy-840-on-ebay.933/

http://www.xs650.com/threads/want-a-860cc-xs.13477/

http://www.xs650.com/threads/too-hard-to-kickstart.2506/

http://www.xs650.com/threads/880cc-or-860cc-xs-conversion.52148/

http://www.xs650.com/threads/big-bore-sleeve-wall-thickness.23508/

An 860cc kit.
Maybe you can chase down the published web link.

 

[Signal]

In the UK the links below would be a good place to start.
http://www.smedspeed.co.uk/tech.html
https://www.heidentuning.com/

 

[harley metisse]

Thanks for the "UK" based info, i have emailed Heiden and await their reply and have had several emails from Howard at Smedspeed, who seems very wise and knowledgeable on this topic.
However, having a 447 motor, with, I understand, shorter conrods, I might have a problem.......damn.
Someone has mentioned Honda CR500 rods, has this been done before, and if so, reliable ?
Keep the advice coming chaps.

 

[Signal]

CR 500 rods are used in conjunction with special pistons for long rod conversions never heard of one bigger than 750cc though.
If you are rebuilding the crank why not use 533 rods or what ever goes with the big bore set up you intend to use.

 

[hotdog]

Installation of Yamaha XT500 pistons (87mm) with a 533 crank yields an 880cc engine.
Further information on this is available from - Old Side Car Cross it is in French, however, google translate does a good job. The site is worth a read if you intend to go big - the French and European Side Car Cross builders really were the pioneers in big bore XS Yamaha's and frequently had them built to 1000cc +

As mentioned above by Signal, Smedspeed has some excellent write ups on building an 880cc engine and other mods in there technical page.

Good Luck

 

[harley metisse]

Hi Hotdog, thanks for the message, I have to admit that I thought that the 880cc motor came from using XT500 pistons and the crank from the 533 series engine.
It would be good news if those pistons will work in the "shorter stroke" 447 engine.
I have read the french website and it is interesting I agree, but is there anywhere that gives me more detail on this up-grade ?
Any books perhaps ?
Thanks anyway.

 

[Signal]

I do not know of any books with details of engines larger than 750cc.
The XS650/750 Engine Modification Guide is worth getting.
http://650central.com/

What do you intend to use the motor for?

 

[harley metisse]

My intention is to build a bigger bore XS, but it needs to be reliable, it will be used for weekend trips and holidays as well as general use around here locally in Cornwall.
I have a standard 1975 XS650B that I have just restored so the next project is to build what I would call a "hot rod" version, something with a bit more go, more torque etc etc, just like we would have built back in the day.
I won't be racing it, just street use, but the idea of a street sleeper appeals to me that's all.
The important thing to remember though is that it must not really cost a lot more than it could be worth when finished, it will not be a money pit.
Besides when we had these bikes back in the mid seventies, the 50 bhp was more than a match for the normal cars found on the road, BMC 1100/1300's, Mini's, Cortina Mk2/3's, Moggie 1000's, Escort 1100/1300's, Hillman Imps etc etc, but now any small family hatchback is pushing around 100 bhp, hence thinking if I'm going out to pass everything on my sunday morning breakfast ride out, I will need more go !!
Or perhaps another bike altogether........lol

 

[Signal]

You may be better off going for a more common and probably cheaper 750cc set up or as you say another bike altogether.
Used sport bikes represent great value for money in terms of handling and performance far better than any tuned up XS.

 

[harley metisse]

I don't disagree with you, I'm just a little bit stubborn at times I guess.
I'm not expecting anything that fast, just something that will surprise people sometimes.
I've been through the normal VFR, GSXR 1000, R1200GS, KTM 950SM, Z1000SX etc etc and even a BMW Megamoto HP2, so new faster bikes have their uses but with bikes like that you are expected to be fast, I don't mind having something different......

 

[Signal]

I understand completely.
At one time I had an XJR 1300 and an XS 650 with a 750 kit and a few other mods, the XJR did everything it was supposed to very well but was just bland. The XS on the other hand is always fun to ride (I sold the XJR).

 

[harley metisse]

My thoughts..................as well.
I am likely to go a little soft if our summer European adventures are going to be lengthy (the last one was over 3500 miles in 15 days), so I may buy a cheap Yam Fazer 1000.........
Back to the next project though - has anybody done one of these 840 or 880 conversions to an American spec, 447, engine ?
Any pointers would be really helpful.
Cheers

 

[hotdog]

Hi Hotdog, thanks for the message, I have to admit that I thought that the 880cc motor came from using XT500 pistons and the crank from the 533 series engine.
It would be good news if those pistons will work in the "shorter stroke" 447 engine.
I have read the french website and it is interesting I agree, but is there anywhere that gives me more detail on this up-grade ?
Any books perhaps ?
Thanks anyway.

HM, you are correct. The 533 crank is required for the 880 MOD. I have amended my post above to reflect this.

 

[Gadjo fandjo]

Hi HM did you finished your project?
I am just starting mine. I bought the kit from Tony Hall some 20 years ago and never managed to get time, finance, and garage together until recently...I might need tips regarding the starter motor as I did kick bikes for 3 decades and then had wear and tear knee damaged so will prefer to avoid the kick.
Then for the Mikuni 34VM jetting...(I will consult the tech dep here as I saw a post) but just in case some quick tips or do's n don't for this type of inflated bikes.

 

[Signal]

This is from Howard Smed its for an 880 conversion. Howard has sold the business but Smed speed is still trading.
From time to time Heiden Tuning also have bigger than 750 cc pistons and other parts.
http://www.smedspeed.co.uk/tech.html
I have the parts for an 880 motor just keep getting sidetracked onto other projects.

 

[harley metisse]

Hi, yes Howard has sold the business, the new owner is Rick Forte, and he is very approachable.
Not gone down the 840 route as yet, but I have some ideas on what to do......watch this space.

 

[Gadjo fandjo]

True, I have just been in touch with Rick from SmedSpeed and he seems very helpful, plus plenty of super good advice on the website.
I am so glad to have found someone in the UK who keeps the XS spirit after Tony Hall !