Scooterotica

I have a 1964 LI 125 which has been subject to a local " restoration" here in Malaysia. I'm currently re re-restoring the bodywork, and doing some suspension/ brake upgrades, inboard disc with hydraulic conversion, dampers, MB progressive for springs, 12v conversion, LED tail light etc so that its at least its sound and safe.
In the long term my goal is for this to be reliable and fun to ride in modern traffic whilst looking fairly stock. As the engine runs, and I have other projects to work on, my intention is to leave the engine as is for the moment and then do a complete engine upgrade at a later date.
However although the engine runs its pretty slow and couldn't pull the skin off a rice pudding. Its been fitted with a series 2 exhaust for some strange reason.

Questions I have:
1. Is the series 2 exhaust affecting performance? If so would it be worth an upgrade now to say an MB Superclubman or AF Copy Clubman which is available at low cost here? If I did this I would want the exhaust to be Ok to be used when I upgrade the engine later.
2. If I did change the exhaust now, any point in making a carb change now as well? Again would only want to do this if same carb could be used later.
If I could get a noticeable increase in current performance now and use the parts for the "final" engine build then this would be a good result, otherwise I can just leave as is and do a full engine upgrade later.

3. Last question and I realise this is a tricky one. For the final engine upgrade I want something very reliable, easy to start, fun to ride in modern traffic and I would prefer not to have to spend many hrs doing plug chops and "dialing" everything in. There seem to be a bewildering range of options on on the market at a wide range of costs and all with their die hard fans and detractors. I don't mind spending money so long as it really gives value. At one end of the scale I've looked at something like a Beedspeed ported SR alloy 195 kit, GP crank, Scootrs flatslide carb, copy AF clubman, at the other end of the scale looked at the full MB Racetour along with all the other MB kit, crank, carb , ignition , Superclubman etc. In know this is subjective and everyone has their opinion but is there a " sweetspot" combination which would give me what I want at most reasonable cost?

Thanks in advance.

Cheers

Tippo

You could get a lot of different answers to an engine upgrade. For what it's worth I would suggest you put a sil gp crank with upgraded bearing in. Electronic ignition up grade the chain guides replace seals etc and add a clubman. These are all fairly cheap upgrades compared to the top end which could be done at a later date.

Me personally would add a gt186 kit

Me personally, if I had a small block engine like yours. I'd get a decent standard crank, 26mm carb, BGM clubman pipe & a GT186 kit. Fairly decent turn of speed and reliability. But regardless of your choice, you'll have to get it set up correctly, be it plug chops or a dyno.

Originally I hadn't planned to pull the engine apart for a while and was just thinking of carb and pipe . However keep finding more to do on the body and frame so am thinking will do a full rebuild.
Don't really want to spend 600 quid plus on the cylinder and carb now so was thinking of building a strong bottom end maybe MEC race crank with 110 rod so that down the road when bring bike back to UK can fit a GT kit or similar.
Here in Malaysia I can pick up a SR 185 kit, PKW carb, atomic reed block and clubman exhaust for 250 quid total. Was thinking about putting this on in the meantime to see how it goes . Or is this just madness ?



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What I've decided to do is to build a strong bottom end using a Gp crank with Yamaha rod, top quality bearings etc. and put a cleaned up SR 185 top end on it. The idea being that if this meets my goals with regards to performance etc. then great but if not at a later date can always simply change the top end.
Have a question with regards to porting and potentially matching the casing ports to the cylinder. If I use the 3 mm MB base packing plate as a template if I put this on the case it doesn't cover any of the port area but if I put it on the cylinder base then it does cover some of the ported area ie the ports on the cylinder are bigger than the ports in the case. Photos attached.
Should I open up the ports on the cases to match the cylinder? I'm a bit reluctant to do this and take metal off the cases when I may end up with a different cylinder down the road but if this will have a big effect on performance then I guess I should.
Thanks in advance for any advice.



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personally I'd leave as is- the difference if any, is likely to be minimal IMO. Good idea re the bottom end by having it as strong and reliable as possible with good quality bearings etc.

I'd bolt together and see how it runs with the new top end subject to correct timing/ jetting etc.

You can always change the top end later if needs be.

What piston to bore clearance have you got there on the kit?

Chris

Chris, thanks again! Will measure the bore clearance tonight but with no rings on the piston is close fit and slides up and down with no noticeable play.


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measure the ring gap as well please.

Chris ,
Probably need to replace my old vernier calipers with some nice digital ones but beast I can tell the cylinder is 63.9 mm and piston is 63.5 mm .
On the ring gap the ends of the rings are notched and when I put them in the cylinder the ends of the notches are too close for me to get anything in to measure. See photos.
On a slightly different subject although the cylinder porting has been cleaned up by local dealer the transfer ports still not seem to be open for about half of the window cut in the steel liner so am assuming this needs further work? See blurry photos.
Thanks!


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cylinder size vs bore size does tend to be a compromise- too tight and it will seize (albeit with an alloy or alloy/ steel lined cylinder there are more forgiving), and too loose it will rattle and be down on power.

I tend to give my new piston and old cylinder to a guy I use in Bristol (Steve at "Piston Broke"), and tell him to rebore giving me "three thou" in old money (not metric). As long as the running in is done correctly (I use lots of short sharp hot/ cold cycles of around 2 miles each), I've not had a problem. I'd be inclined to get the piston and bore measured accurately at a machine shop to see whats what..

As regards ring gaps, I go for around 8 thou, but you won't be able to measure this until you are happy with the bore clearance as outlined above.

Can't really see the porting in the pix, but invariably they will need tidying.

Chris