G2 removing crank gear

[mn757]

Hi all,

I'm in the middle of stripping the engine down on my G2. I've ordered a workshop manual, but i've not received it as yet. Can someone tell me how the crank gear is removed from the crank ? There doesnt appear to be any space to get a puller behind it.

Also, does the gearbox need removing or loosening if I'm just stripping the oil tank side of the engine ?

I'm stripping it because the conrod snapped, although not quite in two pieces - there's an inch of metal missing on one part of it even though it still ran.

many thanks

Martin North

[paul knapp]

quote: there's an inch of metal missing on one part of it even though it still ran

I would like to see that!!

Paul

[mn757]

Not sure how this happened - was riding along fine and then just made an almighty rattling noise. The conrod is floating around the crank - there's about an inch of play. I guess the bearing must have fell apart?

Anyway, here's a picture http://www.martin-north.co.uk/matchless/rod.jpg

[pto]

From my own experience of working on this engine, you can either take it out of the frame as one unit or take the gearbox out first. I don't think you can take the engine out on it's own, but which ever way you do it the crankcase halves will have to be split to remove the crankshaft. I don't remember having any trouble removing the gear. I seem to remember you had to be carefull with the oil pump, but it's a few years since I did mine, maybe someone can remember better than me!. Alpha Bearings can overhaul the crankshaft.

[chris kelly]

Hi,

It may be that the Roy Bacon book would be a good supplement to the workshop manual when you get it.

I took my lightweight engine out whole as it where. Someone in the club took it apart and put it back together. Which means I'm interested but not gifted practically !

Alpha Bearing did the work on the bearings
and small end etc That was about 300 quid in 2003 .

Bacon writes in his book by having a subject heading '' Crankshafts '' and then differentiates into ''singles'', light singles, ( your bike,) twins and so on. Therefore you need time to study and work through it but just focussing on one paragraph he states, ''The light singles had the main shafts keyed and pressed into the flywheels but the heavy singles retained them with nuts as well. Early models of the latter had a taper fit but this was changed for a parallel one to improve rigidity'' That's how he writes so his''Post War Restoration etc ,covers a lot of detail. He states '' The singles will, with few exceptions, need a press to assemble them as well as dismantling,'' etc . Mind you I can't quite see what he states about the light singles in this res pect. Anyway, on and on and into the''Big end'' and he states, ''The light singles had two types of big end, each with its own pin, cage and either 20 or 28 rollers of the quarter by quarter inch size. The first went in the basic 250 model, the S and the CS for 1959 --- 60. The second was used by the CS for 1961 on, the CSR and the 350. In either case the crankpin was located by a key and this and the second cage were common to the heavy singles post 1957 parts.

Oh, on your question about removing the engine he states.

''Light singles dismantling.

The engine is similar to the heavier and larger singles but with quite a number of detail differences including having the oil tank built into the right crancase.

The work begins by removing the right outer cover and the whole of the primary transmission. This releases the inner chaincase which in turn allows the gear box to be unstrapped from the back of the crankcase.

This leaves the basic engine and the top half as for the singles.The bottom half has a right inner cover which carries the points plate and retains the camshaft and its followers .Below is the outer part of the oil tank and the right crankcase half also carries the oil pump and its details,

These all need to come away first, after which the crankcase halves can be parted to release the crankcase and the bearings and distance pieces associated with it.''
Bacon states his book is to be used alongside the workshop manual etc.

i've got a ''Motor Cycle 2nd January 1964, Service shop lore on the AJS and Matchless 250's and under

''Plunger,

Removal of the pump plunger can be effected after undoing the cap at the rear of the crankcase on the right, having first taken out the guide pin.
The plunger is hollow and if suction is making it difficult to withdraw, here is the dodge.

A wheel spoke bent at right angles one eigth inch from one end is inserted up the middle of the pump plunger and the bent end engaged in a recess A second spoke with the end straight is then inserted to hold the first in place while the plunger is pulled out of its housing.

No attempt should be made to separate the crankcase halves without first withdrawing the plunger, otherwise the worm drive will be damaged.

When refitting the pump plunger, note that the relieved end of the guide pin goes into the hollow retaining screw.
Turn the screw very gently until slight pressure can be felt. Then rotate the engine slowly until you can feel the guide pin drop in the profiled groove. At the factory they put a drop of oil in the retaining screw before inserting the guide pin. This acts as a hydraulic cushion and minimizes the risk of damaging the edges of the profiled groove. ''
There are two pictures. Caption, ''Wear on the end of the guide pin which engages in the profiled groove of the pump plunger will cause loss of efficiency.''

and caption '' Right '' (the picture that is ) ..''.When dismantling the oil pump there is no need to disturb this stud which merely retains a blanking cap. ''

When my engine was in bits I think my guide pin was replaced simply because the engine was in bits, as good practice.

Hope this helps. There are not lots of lightweight owners but further comments will come no doubt.

If you join the club, the club has a ''Helpliner'' and you can phone him up. I seem to remember in his ''profile'' that he has restored a lightweight. Most peoples experience, i believe, is on the heavyweights

That's it. Got to go to bed. We are one hour in front in Sweden and I have to go to school to learn Swedish in the morning !

Best wishes, Chris..

[mn757]

Hi Chris, (and others who replied)

thanks for such a detailed and informative reply. I was hoping the crankcase could be separated without touching the gearbox, but it's looking like that's not the case. I'll be removing the entire unit this weekend and following the advice you suggested. I'll also get a copy of the Roy Bacon book.

I've joined the club and the spares scheme as that will no doubt come in handy!

thanks again for all your help

Martin.