Engine rebuild thread

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Re: Engine rebuild thread

Postby Ozmadman » Wed Nov 08, 2017 3:24 pm

Thanks, that's put my mind at rest but I can't remember where mine came from, not club spares cos I would have fainted at the price! think it came from AMC classic spares??? will have to trawl though my mountain of receipts to see if can find it. Its the bearings with plastic cages that really worry me. I suppose the moral of the story is fi t a well known brand... My gearbox main bearing came from Simply bearings when I did my box as at the time club spares were out of stock of the original one
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Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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Re: Engine rebuild thread

Postby clanger9 » Sat Dec 16, 2017 10:00 pm

2nd set of (better quality) main bearings fitted easily: heat case to approx 150C in the oven, bearings in the the freezer for ~20 minutes. As long as you work quickly, the bearings should just drop in. Give them a gentle tap home to make sure the inner race is flush with the crankcase.
IMG_2081.jpg

Things to note:
- A small amount of Loctite 603 will help to keep things in place. I don't like 'staking' bearings (as recommended in the manual). It's brutal treatment for a delicate component and you risk distorting the bearing race.
- Make sure you fit the breather stator the right way round! ;)
- The stator can be difficult to line up with the fixing hole if it's 'nipped' between the bearings as there's no easy way to rotate it. Best to try and line it up as close as possible before you fit the inner race.
- Use threadlock on the stator retaining bolt and tighten it firmly (to 10ft-lb).

I've held off assembling the crankcases because I've made the mad decision to run the engine on Castorene. That's a castor/synthetic blend and shouldn't be mixed with mineral oil, so until the oil arrives I won't proceed further...

Meanwhile, T&L Engineering have re-sleeved the barrel for me and Cox & Turner sourced a set of new piston rings so I'm going to run with my no-name CSR 9.5:1 piston. It willl be interesting to see if the engine holds together :?
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1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: Engine rebuild thread

Postby Expat » Sun Dec 17, 2017 12:21 am

Indeed....an interesting saga so far.
Keep shiny side up.

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Re: Engine rebuild thread

Postby Ozmadman » Mon Dec 18, 2017 1:18 am

clanger9 wrote:- Make sure you fit the breather stator the right way round! ;)
- The stator can be difficult to line up with the fixing hole if it's 'nipped' between the bearings as there's no easy way to rotate it. Best to try and line it up as close as possible before you fit the inner race.
- Use threadlock on the stator retaining bolt and tighten it firmly (to 10ft-lb)
If you have the mid stator option of the 3 versions (you can use this to replace the early interference fit type) as in the picture you can line it all up before assembly as the tube screws into the stator... Actually you can even line the early one up.. all you have to do is insert the tube into the stator hole before the inner race is fitted, shouldn't be a problem but it should be a snug fit in the hole and not like in my video! https://www.youtube.com/watch?v=xux_7OUzkt4
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Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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Re: Engine rebuild thread

Postby clanger9 » Thu Jan 11, 2018 4:58 pm

Resleeve is done, courtesy of T&L Engineering. Looks good!
Next step is to hone the bore to the right clearance and get this little lot assembled...
IMG_2238.jpg

IMG_2237.jpg

IMG_2236.jpg
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1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: Engine rebuild thread

Postby Ozmadman » Fri Jan 12, 2018 1:06 am

clanger9 wrote:Resleeve is done, courtesy of T&L Engineering. Looks good!
Next step is to hone the bore to the right clearance and get this little lot assembled...
Didn't they do that for you?
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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Re: Engine rebuild thread

Postby clanger9 » Fri Jan 12, 2018 7:46 am

They wanted to, but I have the piston here. It needs a bit of thought about what clearance to run, so I'd rather get it done locally.
So it's honed "slightly tight" at the moment.
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: Engine rebuild thread

Postby Ozmadman » Fri Jan 12, 2018 4:56 pm

clanger9 wrote:They wanted to, but I have the piston here. It needs a bit of thought about what clearance to run, so I'd rather get it done locally.
So it's honed "slightly tight" at the moment.

Bet its not as tight as my Yam RD350 two stroke engine. Spec for that is 0.0014"-0.0016" any more and they will rattle like hell from new.
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed

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Re: Engine rebuild thread

Postby clanger9 » Fri Jan 12, 2018 5:27 pm

Crikey, that is tight!

Bore checked out, it turns out my (used) piston is slightly undersize on the skirt, so even with the undersize bore it'll still rattle a bit. Given that it's going to get thrashed, I'd rather have it too loose than too tight... :twisted:

Other interesting observation is that my (original) 9.5:1 piston is significantly lighter than the pattern low-compression piston I took out (280g vs. 320g). The PO must have been very worried about the excess weight, because the heavy piston has been carefully lightened by removing lot of material from the inside. :shock:

IMG_2242.jpg

IMG_2240.jpg
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1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: Engine rebuild thread

Postby clanger9 » Sat Jan 13, 2018 7:18 pm

Coming nicely together...
Most important thing: don't forget the breather rotor on the crankshaft! ;) (2nd pic...)
IMG_2244.jpg

IMG_2246.jpg

IMG_2247.jpg
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1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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