Mine of information

Hi all, I've recently found this forum and I must say it's a brilliant mine of information!
I've recently got back into Dax's having bought one by chance last year whilst looking for CG125 for my girlfriend (I had a ST70 in my teens back in the 70s)
My Dax is a 90 ST50 with C90 engine(+ upgrade exhaust, carb etc). I got it cheap as it had a sheered off kick start shaft when I found it and didn't run, the mechanic who rebuilt it for me told me the camshaft wasn't standard also, as it needed a longer replacement chain. Does this sound right?
I've got very limited tech knowledge so this site is a great help and I've really enjoyed reading back all the way though past posts and now feel a lot more confident reaching for the spanners! Next time it needs to come apart I'm going to do it myself!
Keep up the good work.Thanks to all, Andrew.
PS Its great to find a forum where threads aren't hijacked all the time but are quickly answered with detailed KNOWLEDGE.

Welcome to the site!

I don't post very often but just wanted to say thanks for the kind words!

The site is very lucky to have lots of knowledgeable members who help each other on a daily basis. I have lost count of the times that people on here have helped me, from being able to answer my questions within hours, to even a member sending me some parts to help fix a problem!

I have lots of plans to improve the site and over the coming months I will be introducing a number of new features which will benefit all members

Thanks,
James

angektep1s wrote:the mechanic who rebuilt it for me told me the camshaft wasn't standard also, as it needed a longer replacement chain. Does this sound right?

Yes and no.
The crank is different. It's stroke is 49,5mm instead of the 41,4mm of the ST50/70 engines.
That means the cilinder is a higher type, 69mm instead of the 63mm.
The old style heads (OT70, Kitaco Ultra, Takegawa R-stage,... for 6v) can be used, with the same normal camshafts.
So that's where the mechanic went wrong.
The distribution chain needs to be longer because the LENGTH (not the stroke) of the crank is longer, and thus the cilinder needs to be higher,... so you need a longer chain.
(example: there are 50mm-52mm strokers that uses the 63mm short cilinders)

The C90 engine is used by Jingcheng for it's DX90 engine.
One of the very few reliable Chinese engines.

The length of the crank compared to the height of the cilinder is the same as all 6v engines, so you'll need to keep that in mind if you would ever need to shop for a new piston.

Hi

I just wanted to say that I am also a new member to this site but I think its fab - have always liked ST50/70's and the tech help ur members provide to each other on this site is really amazing and quite warming really! Am glad I found this site. Am useless mechanically-speaking but the boyfriend is trying to get my 89 ST50 Dax going for me, so I do all the research/part finding!