125H Clutch, carburettor & gearing?

Lambertini era singles (125 and 250 - half v-twins)

125H Clutch, carburettor & gearing?

Postby themoudie » 21 Sep 2015 13:07


Purchased a 125H in 2006 that then 'sat' until earlier this year. 23,000Km on the clock and doesn't appear to have been thrashed or dropped, so far!

I've had the forks chromed by HCP, paint attacked on tank and mudguards by 'metal worm', so refinished with 2 pack and red stripes applied as paint rather than tape. Rear shocks devoid of damping , so a pair of NJB shocks installed. The exhaust pipe is still sound, but the chrome is rubbish. The silencer has been emptied of all the loose bits :roll: patched and then painted with VHT black exhaust paint. The wee hole at the front end prevented drainage of the condensation. New Hidenau tyres and tubes, the old ones had plenty of tread but were cracked and perishing in the tread.

Carburettor rebuilt with new float needle, choke plunger, 'O' rings & gaskets (Eurocarb). The main jet was changed from the 82 that was installed, to the 72 listed in the 'blue' manual as "standard". Unable to check plug colour until after MoT, so will take it for a run afore checking the colour.

Slipping clutch even after cleaning and de-glazing all working surfaces, so purchased (NLM) new half friction and 5 full friction plates. "Thank you!" to Paul Compton for the kickstart installation video on UTube, it was driving me crackers! :shock: Still occaisionaly get a 'skirling noise when sitting in neutral and ticking over from the clutch area? Have I missed something when tightening up the clutch spring retaining nuts? Done up 'tight' at present and of 33.15mm average spring length. Plain metal plates 1.8mm thickness. Oil was the familiar oxtail soup colour, so the breather has been extended to the rear mudguard and the 2 baffles removed from the engine end of the breather pipe, the condensation just runs straight back all over the gears, kickstart then into the sump. Not nice. Changed the oil twice so far.

Passed the MoT today, but after riding an SRX 600 single or a Ducati 450, the top speed of 60Kph and lack of any real 'get up and go' was disappointing. :roll: Yes, I know it is a 125, but, the motor feels strong even though 'tick over' is vague, it pulls cleanly, and yet it is almost as though the clutch still slips or the gearing is way "off"! I was expecting cruising speed of ~80Kph.

I realise there are not many of these about and experience/knowledge is lacking, so any ownership experience would be gratefully recieved.

Thank you for your time.

My regards, Bill
Ready for MoT, 1979 Morini 125H
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Re: 125H Clutch, carburettor & gearing?

Postby MarkB » 21 Sep 2015 15:28

I've no experience of the 125s, but I'm sure that Mr Guru will be able to give you more definitive answers. One thing is that the breather tube needs the baffles where it comes out of the crankcase to provide sufficient pressure to push oil mist up to the valve gear.
"I'll have a V please, Bob."
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Re: 125H Clutch, carburettor & gearing?

Postby EVguru » 21 Sep 2015 16:13

Mine will keep up with traffic on 60mph roads, but you do have to rev it all the way out to make progress. It did the MRC trackday a couple of years ago with my generously proportioned friend Roy on board.

I've done very little mechanical work on the wet clutch engines, so I can't be of much help there.

Modern fuel tends to cause a rich idle mixture and a leaner idle jet can help.

Mark is quite correct about the baffles, they're there for a reason. Excessive condensation suggests you might be getting blow-by on the rings.
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Re: 125H Clutch, carburettor & gearing?

Postby themoudie » 21 Sep 2015 22:35

Aye Mark and Paul,

Thank you both for your comments and advice.

I must rectify a couple of errors I made with the dimensions I gave in my initial post. The length of the springs in the clutch are 34.0mm not the 33.15mm quoted and the plain steel clutch plates are 1.2mm thick, not the 1.8mm quoted. :oops:

I will replace the baffles in the breather as you both advise, so that the 'top end' gets it's oil mist.

The mechanical rev counter has failed, I've checked the drive and it is all working, so at present I have no idea of the 'RPM' the engine is running at. Your ability to keep up with 60mph traffic, Paul, was what I was anticipating, but at present 60Kph on the flat and 70Kph downhill with a following wind are the maximum. There is more travel on the throttle, but no response and twisting it open further produces a dull, flat engine note and no response. I have checked the plug again after a 30 mile run around minor roads and some A roads and the colour on the insulator looks a nice tan colour, but the side electrode looks very 'clean', almost a bit weak. Maybe the 82 main jet was in for a reason, but after conversation with NLM it was thought to be on the rich side.

When adjusting the idle mixture after fitting a new idle mixture adjustment needle, it appears not to be very sensitive to alteration, but using a Gunson 500 and viewing the blue colour seems to have made that better, but maybe not perfect. I am only ~¾ of a turn out from seating and this would suggest that going down 2 on the idle jet size might be benificial.

When renewing the timing belt, for safety sake, I lined the stator up before tightening, but don't have a strobe to check the ignition timing and wondered if this could be another reason for the lack of power. How sensitive are these beasties? I know a Duke 450 has to be set at TDC, even a degree out either way makes a large difference to the running and performance of the engine. Do you have a preferred strobe?

Thank you for your time.

My regards, Bill
Plug after a 30 mile run.
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Re: 125H Clutch, carburettor & gearing?

Postby hendre » 22 Sep 2015 06:14

Hi Bill,
I got a complete 125H clutch lying around, I'll measure the springs/plates to see if they are usable. Maybe we can work out a deal
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Re: 125H Clutch, carburettor & gearing?

Postby themoudie » 02 Oct 2015 17:15

Aye Andre,
Thank you for your offer. However, after fitting a new set of fibre plates and a half fibre plate the 'slip' appears to have been cured.
My regards, Bill.
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