How much?

How much would it cost me for a new engine that is reliable?
What is the largest size possible that will fit on my ST70 frame without any modifications? (I know it's been asked a million times before but I'm an admin and allowed to ask again)

Reason I ask is that I quite fancy using my bike as transport to keep petrol costs down...

I don't have the time or skill to fix my current engine!

Comeon waynus???????? whats the best and cheapest???? i was going to put a 125 or 140 lifan engine in my lady dax dont think you have to alter frame, let me know too as my frame has come back so next thing to buy is an engine ! leexx

Hi James
Your first problem is the electrics yours is a 6 volt like mine, there are some engines on Ebay at the moment but you have to look under Monkey bike again these are 12 volt, I was told today by Adrian at OORACING that a 140cc charger engine will fit my 69 ST50 frame because they slot one of the mountings also there is a chance that the swing arm might catch but that is easily sorted.
The Charger engine gives between 14 and 18 BHP so your Lady would be no slouch.
But I feel your money and time would be better put into your original engine.
Merry Christmas to you guys and lets see more ST's in the New Year
Regards Tufty AKA Clive

Thanks for the replies guys. Yeah I kinda agree with you that putting the effort into my current engine would be the best thing to do but I think it has something seriously wrong with it, big end bearing?!?!
It starts easily enough, but once some revs are applied it sounds like a box of spanners being thrown about!

Just stripping the engine down is going to be a hassle in itself, let alone diagnosing the problem and putting it all back together again. A couple of the screws are rounded off and will need to be drilled out, or have a socket welded on to get them out!

I was simply hoping I could pick up a cheap engine that is reliable and attach it to the bike! My bike is near perfect apart from the engine (which sounds knackered) and the seat condition although I will be changing it for a black one! (and sorry everyone, the flower seat isn't for sale - I'm going to put it in the loft!)

timing chain noise?????????

Hi James
dont put the seat in the loft it will deteriate quickly due the heat in the summer and the cold in the winter put it under the bed.
As I see it you have not got a lot to loose if you strip the motor down as you already suspect it is knackered, at least by taking it apart you will gain in experience and you might be pleasently surprised and as you can get hold of workshop manuals for ST's either a copy from David Silver or the Clymer manual I personnaly found the David Silver version better, your description sounds like cam chain tensioner.
You do not have to split the engine case, just remove the head and barrel and topend cam gear (this is where a manual is a must) and then you will probably find a knackered tensioner gear.
You will then be able to check the piston and conrod more easily and then decide to replace the motor or rebuild it, this way you will keep the originality I.E the air box etc.
Regards Tufty

I have got an electronic copy of the manual on disk if you want a copy I will try to email it to you if you send me your email address if that does not work I will copy it and send it by post.
I had never stripped one of these engines before and when i did it was easy. I could strip one in a few hours now and once you have done it once you dont need the manual again.
Regards
Dom.

Thanks for the offer of the manual, I think I do have one already but will double check.

I hope it is the timing chain as I don't fancy splitting the case however I will need to get it apart to take a look. Cheers for the advice about the seat!

The bike is in a secure shed that is snowed in at the moment, hopefully over the coming weeks I will get chance to take a look at it, unfortunately I have nowhere to work on it so will have to brave the cold! I'm very jealous of you guys who have garages etc!

James, first of all, if you're about to complete check and repair your engine, I'll do my very best to talk you trough this lovely job.

Second, as far as the possibilities for another engine go, there are really endless possibilities.
So let's see what you're after first.
- reliability? Go for a Japanese or good quality Chinese / Thai copy. There's a lot of junk on the market, so watch out.
- Performance? Are you after a +100cc engine? Or just a quicker 72cc-88cc engine?
- Looks? Would you like to stick with the semi clutch? Don't mind having a big completely re-styled engine? ...
- Costs? A complete new engine will set you back anywhere between 200€ and +5000€. All depending on what you're looking after.
- Condition? Are you only looking for brand new replacement engines, or will a low mileage or even a good runner suit your needs?
- Type of clutch, crank,...? Manual, semi or auto clutch? On crank or gearbox? Long or original stroke crank? Number of gears?
...
Anyway, keep in mind that several other parts could need replacement, depending on the type of engine you choose.
Exhaust, carb set, throttle, electrics,...

My opinion?
Go with an original low mileage Honda engine.
These babies will last you forever when bought or brought back to good condition, especially the 12v engines are really bullet proof.
85cc for that extra juice whilst retaining the original looks.

Cheap but still reliable?
Zongcheng 72cc, Jingcheng DX90 (85cc on long stroke, a 6v non-Hitachi ignition fits),...

Super reliable but more expensive?
Honda Nice, Honda Wave, Honda Monkey AB27 + bore-up,...

leeandaly wrote:I was going to put a 125 or 140 lifan engine in my lady dax dont think you have to alter frame, let me know too as my frame has come back so next thing to buy is an engine ! leexx

The only things that might need minor adjustments:
- Space bewteen the mounting brackets of the frame.
Sometimes you need to widen this a bit. (Only a few mm's)
- Mounting of the clutch cable can need some smaal adjustments.

Keep in mind that:
- the 125cc version is somewhat more reliable as the 140cc.
- you should change the original exhaust
- original throttle system shouldn't be used
- the wiring should be changed to 12v
- the performance is really not that great for such a "large" engine