Author Topic: scan or info on the sc500 story think it was in an early VMX mag ?  (Read 4546 times)

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Offline Freakshow

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Hey people, want to drag out the Sc500 and have another bash at getting them to run properly.  Word is someone in WA got one working OK or maklins, anyhow article in VMX was also mentioned soe any one have a copy that can scan to me ? or put me in touch with someone who has specs ?  also heard they sleaved back the ports ?  anyway, like to have another shot at these bangers.

cheers Freaky
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Offline Rossvickicampbell

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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #1 on: April 19, 2010, 01:48:07 pm »
Freaky - Pee Lawson has an awesome quick beasty.  I will try and dig up some details for you as to his address etc.

cheers

Rossco
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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #2 on: April 19, 2010, 02:39:46 pm »
IIRC use the 5 speed box and put the heavy DT flywheel ign on - and then they are a 'good thing'.

Offline Rossvickicampbell

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Offline jerry

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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #4 on: April 19, 2010, 04:52:01 pm »
Issue 2 page 43 everthing you need to know. Cheers Jerry

Offline Tossa

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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #5 on: April 19, 2010, 05:01:42 pm »
Hey Rosco, just read the link.  It also has a test on the MX360, and yep there a couple of things in it that have happened to me, the back brake sticking on when riding in mud(Manji) last yr.  The front brake cable not being in the holder and sticking on (Bunbury) and it goes on. 

The SC500 there is also a new membe believe the surname is Cooper, him and his son have an SC500 as well.

Peter Lawson stuck his 500 motor in a YZ frame, Bill Davis (USA) rode it at Wandering 2yrs ago and we put him in hospital, I saw Brooke riding it at narrogin last yr
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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #6 on: April 19, 2010, 08:13:44 pm »
Extending the swingarm length 25+mm is a common suggestion to improve the handling of MX and YZ 250/360's. Haven't tried it but if it's good for a 250 it should be compulsory for the SC ;).

If I went for the 5 speed I would probably run the DT rear hub for the cush drive - take some of the impact off the gears. The heavier mag would help here as well.


Offline Freakshow

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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #7 on: April 19, 2010, 09:04:53 pm »
Can anyone hook me up with the info in issue 2,

Put the word on your mate Ross, i just need the specs, im thinking of borrowing the motor from one of my Sc's and putting it in my champion frame for the Dirt track nats, like to get the low down before i waste time on it.

but if it got potential would like to make a start on it so i can test if it works. or not
74 Yamaha YZ's - 75 Yamaha YZ's
74 Yamaha  flattracker's
70  Jawa 2 valve speedway's

For sale -  PRE 75 Yamaha MX stuff, frame, motors and parts also some YAM DT1,2,A and Suzi TS bikes and stuff

Offline jerry

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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #8 on: April 19, 2010, 09:50:23 pm »
Im not able to scan but I can photocopy and send it to you if you like. Jerry

Offline Tim754

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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #9 on: April 19, 2010, 10:09:36 pm »
Hope you get permission to do that ;)
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Offline Nathan S

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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #10 on: April 19, 2010, 10:34:03 pm »
The article won't give you anything new, Freaky.
It was basically a list of the bike's evils, and then "fit the right gearbox and ignition and its a lot better".

The good thing about telling the truth is that you don't have to remember what you said.

Offline Rossvickicampbell

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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #11 on: April 19, 2010, 10:51:44 pm »
Freaky - as Tossa has said - Pete put an sc500 motor into a 250B frame.  I know he took the decomp off it but the thing fair flies.  I have ridden it a few times and whilst not having ridden a true SC500 (the so called monster etc) this thing fair flies and everybody I know loves it.  it doesn't have a powerband just pulls and pulls and pulls and..........  I love it - really is a good combination.  Was contemplating it myself (based on having funds I haven't done anything) but I beleive Pete is adding a sidecar to it!!!

Will get back to you when I hear from him but he also works away freaky.

cheers

Rossco
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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #12 on: April 19, 2010, 11:04:07 pm »
I raced an SC500 powered Champion flat tracker in the early vintage days and managed to get it running OK but it never really grabbed me as being right. I added did a few home remedies like using DT360 heavy external flywheel points ignition, an extra head gasket and welding the cutaways in the gudgeon area on the piston to help prevent the pistons cracking in that area and therefore mishaping and causing the piston to go oval and possibly sieze. I made a mod to the ignition involving an extra relay and a switch to automatically advance the ignition to make it easier to start but can't remember the details.

My fellow 'good 'ol boy'  Fast Eddie Phipps bought the bike from me and fitted his trick ex Brian Clarkson road race SC500 engine which has the sam piston mod as I did (I did it), 5 speed MX250 transmission, and YZ400 ignition and it hoots. Best of all though are the mods he's since done to my old engine. Ed's a bit of a thinker and figured that one of the problems with the SC500 is that the bore is too big in relation to the stroke. Add to that the poorly designed piston that goes out of shape so easily and you have the main reason the SC wasn't as successful as it could have been. What Ed's done is to machine up a new sleeve to reduce the bore from 96mm down to 89mm using a Honda CR500 piston. While the bike hasn't been ridden all that much for other reasons, the early tests showed it to be quicker than the original and shows less tendency to nip up.

Freaky, one thing I do remember is that the SC500 used to torque twist the flimsy Champion swingarm which didn't help the handling all that well. Phippsy's welded some pretty substantial braces to the arm in a bid to prevent the twisting.
« Last Edit: April 19, 2010, 11:08:12 pm by firko »

Offline JC

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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #13 on: April 20, 2010, 10:41:41 am »
I'm lead to believe (from a mate who had it done) that Small Coil Rewinds in Vic can rewind the coils of the std ignition to work wonders w more appropriate advance curve etc, if you want to go that way.

Offline Freakshow

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Re: scan or info on the sc500 story think it was in an early VMX mag ?
« Reply #14 on: April 20, 2010, 03:34:48 pm »
See i thought the guys on the 360 put the whole staors on them from the 500 to get the slow trun from the motors on the flat track ?

anyhow i have ran a stock Sc500 on the FT on an open day and it was a non event it was nothing more than a wet blanket and it just putted around, hence im surprised all the ho har on them, so im guessing it needs some set up to even get back to arm bending and we might find it to be somthing worth looking into a little more.

I have a few 500 i could work into a progect, not keen to use one on MX but i think the Track could be fun if you can just leave it in 2/3rd gear, cant see the point of moving to 5 ? 

anyhow it was more around the jetting and bore i was after.  Someone told me the article had the MODs in it so i was going to not reinvent the wheel.  But willing to look at bigger improvments if they are exactly thatand actually work on a bette rmore responsive and reliable unit.

Im not the fasted guy out there so i dont need a killer weapon, i just like something that works when i get on it.  I think the champion i have earmarked for it will be fine, its got a 360 in it ATM and it traks along just fine for me, be interested to see if it can get a little more drift out of a few more horses.

be interested in hearing from both these guys as to what they did, part number preferred and lets see if we cant get these on the mombo.  alway looking for something differant to take to the track and have a play with.   I did hear of guys dropping the sleeves to shut of a few ports ( not required) and they became more Yz 400 based, plus would help with the lack of pistong out there over 90mm...............  report back guys if you can get the heads up or pass on my number for a chat if you can.

cheers freaky.
« Last Edit: April 20, 2010, 03:55:05 pm by Freakshow »
74 Yamaha YZ's - 75 Yamaha YZ's
74 Yamaha  flattracker's
70  Jawa 2 valve speedway's

For sale -  PRE 75 Yamaha MX stuff, frame, motors and parts also some YAM DT1,2,A and Suzi TS bikes and stuff