Gearbox Question

After putting a new Andover o/haul kit through my Commando gearbox two things ive noticed that concern me..

I understand the layshaft end play need to be .005 and shimming is required to acheive this... The end play that i have measured (push pull kickstart ) is .040+ with dry gasket fitted and 4 nuts pinched up.... Seems a lot to need shimming, So is this a normal amount (.040) that needs to be shimmed.. Is this OK to shim down to .005...?????

Secondly, having fitted new main shaft and new bushes, i have found that rotating main shaft and drive sprocket by two oily hand (externally on the sprocket side) very firm. I can do it, just, by holding sprocket by hand and with a rag over mainshaft turn M/Shaft. So it seem to have mosr resistance than i would have expected.. I think when fitting bronze bushes one or both may have "distorted" when fitting................. If so will this "settle in" once the box is in service ?????

Thanks

olChris said:

I understand the layshaft end play need to be .005 and shimming is required to acheive this... The end play that i have measured (push pull kickstart ) is .040+ with dry gasket fitted and 4 nuts pinched up.... Seems a lot to need shimming, So is this a normal amount (.040) that needs to be shimmed.. Is this OK to shim down to .005...?????


Thanks

Click to expand...

Check it with the gasket out. The gasket is optional for many. hylomar blue, yamabond or hondabond and the like will be just fine. May save you from that shimming bullshit.

I can't say about your second issue.

I assembled my gearbox using an RGM Motors overhaul kit. I set the layshaft end play according to RGM's suggestion by assembling the gearbox without the inner gasket and then shimming the layshaft until there is just zero end play. Then I reassembled the gearbox using a new gasket. That should give you the correct end play. The reason for doing all of this is so that first gear engages more completely and if your bike tends to jump out of first gear this shimming could help.

One thing you need to check with the Commando gearbox is that the main shafts tend to bend. This should have been checked before the gearbox was assembled. If you have a lathe it is a quick and easy thing to check. The runout should be negligible. So it is possible that the main shaft is bent inside the sleeve gear.

The sleeve gear bushings are sintered bronze which is fairly brittle. They should be pressed into the sleeve gear using a mandrel. Once again a lathe is handy for making a mandrel. I would think that either the bushings would go in fine or they would just simply collapse and buckle in. But to know for sure you need to measure the bearing bores with a ball gauge and micrometer.

After I overhauled the gearbox and got my bike running, the rear wheel spun at a fairly high rpm when the bike was on the center stand and in neutral. It took about 50 or so miles before the rear wheel turned at its normal low rpm while the bike was in neutral. So apparently the bearings need to "settle in". However, the sleeve gear bearings I used were the extra long ones supplied by RGM Motors which of course would cause a little more friction than the standard bearings.

Hehe ole mis-led yet grinning hot shot big single carb Pete is in my camp following the British based old timers instructions that AMC gaskets are optional spacers if needed to avoid shimming and better off w/o them with just Hylomar. If ya really care to know what's going on with the break in wearing in, take it apart again and see. Also good to change the lube soon after it free's up well.

I had to shim .025", no problem. The reason it's so much, it was just "clearance" when a ball bearing was used, now that clearance must be taken up using the shouldered roller. Don't forget opening up the I.D. on those shims, to clear the radius on the kicker shaft.

I had about that when I started, I took .030 out using isolastic shims, that left about .008 when everything was torqued down. Doing it over, I would probably just leave the gasket out, maybe still need a .010 shim. If you use the isolastic shims be sure and open the id up slightly. I used a grindstone in my Dremel tool. It's hard to see but there is a shoulder on the kickstarter shaft that keeps the shim from seating fully. Will give you no freeplay if you don't open it up slightly.

Yes i have found a hard steel shim of .035, reducing endplay to .005/6.. So all good..

I experienced some binding as indicated in first post from the mainshaft bushes which has now reduced for no apparent reason other that me twisting, pulling, poking (and swearing cos i split my beer) You may guesstimate that during my rebuild process, i may have rotated the mainshaft 40-50 time which has obviously "smoothed out" any distortion that may have occured in mainshaft bushing...
So happy with all that and packed away. Now for my next learning curve.. Lacing wheels to suit cradle and frame.