Crank end float mystery

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Ozmadman
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Re: Crank end float mystery

Post by Ozmadman »

Thanks for the update
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
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clanger9
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Location: Chester, UK

Re: Crank end float mystery

Post by clanger9 »

OK, mystery solved: I spoke to Les at Russell Motors (who seems to be the fount of all knowledge on these things). He said: "the manual's wrong, the parts list is right, you need part 041703 for your bike". Fair enough!

Luckily they had one left in stock, so I've got a spare to replace the (slightly bent) mainshaft in my box. Les also commented that "we've been selling loads of Lightweight bits lately. Especially late-model CSRs..." Maybe lots of Lightweight restoration going on? I can only hope so!
1989 Moto Morini Dart 350
1993 Ducati 750SS
Steve S
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Re: Crank end float mystery

Post by Steve S »

I'm now at this stage of re-assembly and think that my crank sprocket had been on the wrong way round. It was fitted (without any spacer or shims between it and the crankcase) with the shorter end facing the rotor which had chain marks on it identical to Clangers!

It also had a washer between the sprocket and the rotor, this washer fits snugly on the shaft and would be too large for the one which should go under the nut and which was missing from mine.

Steve S.
Steve S
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Re: Crank end float mystery

Post by Steve S »

Got it sorted now, it had definitely been assembled the wrong way round, when I tried it the primary chain was quite askew, so reversed it to the way Clanger and Ozmadman recommended and it is straight as a die!

I found no shim behind the sprocket and a tiny amount of end play which disappeared when I tightened it all up. I did put the washer back between the sprocket and the rotor as it was such a perfect fit I thought it could be a correct part for once!

I found a slightly over the top spring washer for the rotor nut and tightened it up against the braked rear wheel.

Pleased with my new gear indicator as well!

Steve S.
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clanger9
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Re: Crank end float mystery

Post by clanger9 »

That looks really good Steve! It seems the "reversed sprocket " issue is really common. Understandable really as it does look odd when you put the front sprocket on...

I think it's normal for there to be no spacer or shim under the sprocket. My bike is clearly unusual here - no doubt I will discover the reason for this when I get round to rebuilding the bottom end.

As for the washer under the rotor: this would only be needed to align the rotor with the stator. It's tricky to measure, but I'd check that the rotor is properly in line with the stator, just in case there's something amiss here.
1989 Moto Morini Dart 350
1993 Ducati 750SS
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Ozmadman
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Re: Crank end float mystery

Post by Ozmadman »

I wonder how many lightweights are running around carving up the rotor unbeknown to the owner. The problem is, you think it is going to hit the casing when it is fitted the correct way round but actually it doesn't. The 0.020" end float (now just a gap) ends up at the other side (timing side) of the crank as you pull up that nut presumably to allow for any expansion in the timing side bush? You never know what had been done by all those years of previous ownership. When I stripped my engine my sprocket was the wrong way round with washers to space the rotor (obviously not enough though) and it had shims up against the LH side of the flywheel presumably to get rid of the end float and unbelievably, NO BREATHER ROTOR AT ALL on the crank just the ally stator that fits in the case between the two bearings on that side!! How the engine never destroyed itself I don't know as that rotor provides the load on the two LH side bearings inner races as you pull up that crank sprocket nut!! The Woodruff key on the crank that holds the rotor in place was also sheared of level with the crank and it took close examination to actually find where it was and much drilling with minute drills to get it out. So, when you take your engines apart, check carefully as you never know who has had their hands on it before!!
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
Steve S
Posts: 123
Joined: Fri Sep 30, 2016 12:03 pm
Location: Hertfordshire United Kingdom

Re: Crank end float mystery

Post by Steve S »

Yes good thought Paul, I hope lightweight owners read these threads regularly so they can pick up on the "reverse engine sprocket" issue.

Bike now road tested and as sweet as a nut!

I can hear you say, "remember to keep that gearbox topped up with 3 pints of oil!"


Steve S.
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Ozmadman
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Re: Crank end float mystery

Post by Ozmadman »

Ha, ha... Think you are far too clued up to miss that one!
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
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