Belt Alignment

Just following up the recent thread about weight saving with a belt drive kit, the really important install issue is the alignment of the gear mainshaft to the engine crankshaft. Bob Patton identified a really neat and effective method that I followed and I hope the picture below helps to illustrate the concept. It is the gearbox mainshaft that must be adusted in parallel to the engine crankshaft, so all the adjustment following belt tension is about skewing the gearbox left or right to correct parallelism.

You must have a left side gearbox tension adjuster "lollypop" bolt fitted to align a belt drive and to retain that due to drive chain pull.


BELT TENSION - loosen the top and bottom gearbox bolts, slacken the right and left adjusters, push the gearbox forward and fit the belt, assemble the clutch and rotor, tighten the shaft nuts with only 40 Ibs torque on the clutch nut. Then use the rear wheel chain tensioner to draw back the belt to around 20-25mm up and 20-25mm down play.

With the spark plugs out, kick over the motor to witness any belt wander.

BELT ALIGNMENT - Leave the alternator stator off, use 2 set squares - a smaller one laid on the magnetic rotor against the front pulley thrust plate. A larger set square held against the clutch basket flange. Butt the 2 handles against each other. A perfect shaft alignment will show no gap between the handles. A gap toward the primary case means the right hand adjuster needs to skew the gearbox forward, a gap toward you means the left hand adjuster needs to skew the gearbox forward.

From trial and error, I found this process to be usefull : Assuming the case of the alignment gap being toward the primary case, the gearbox needs to skew forward from the right side. Gently nip up the top and bottom gear box mounting bolts. Slacken off the left lollypop adjuster forward nut a couple of threads. With a 1/2' open end spanner, turn the right adjuster forward nut clockwise (tighten) one full turn and the gearbox will move very slightly under tension with no free play in the cradle. That is why you must have the top and bottom bolts just nipped up. Check the pulley alignments again, make sure you hold the clutch set square at the middle of the clutch, to avoid bearing play giving a false reading. Turn the right forward nut again until the gap disappears.

When happy with no gap, fully tighten the bottom gearbox bolt, then the top one. Then lock both left and right lollypop aduster nuts.
Install the stator, fit up the left foot peg assembly, run the motor and check for belt wander. Go for a ride around 10Kms to get the belt hot and then re-check belt up and down tension is around 20mm. Any scuffing on the edge of the belt means alignment is not perfect so re-check and repeat.

Yes that is the way to do it. Some may find it advatagous to have a gap of 1/8" at the end of the perpendulars to compensate for the play normally found in the clutch hub.

Say What? Will your belt stay intact with detectable clutch wobble? If so how long have you run your belt with detectable clutch wobble? Can ya give a value to the detectable clutch wobble amount tolerated by your belt?

Anyone remember the tale of Comoz setting up a special ignition and couple others findings after new engine turning, just enough, till seeing oil at head before starting? Bob's squares are a cam lobe saver but so is just turning front pulley loose on its taper to verify before a run off test. As belt alignment gets close but not quite good enough it can take a dozen turns to see then an adjustment and a dozen more turns then few more dozen to verify or skip that and run it up test which needs another belt to start over if not quite right.

Hi Steeve , just some readings from BDM, plus you can scroll up and down his text.have good fun!
http://nortoncommandoclutch.zxq.net/index_111.htm

hobot said:

Say What? Will your belt stay intact with detectable clutch wobble? If so how long have you run your belt with detectable clutch wobble? Can ya give a value to the detectable clutch wobble amount tolerated by your belt?

Anyone remember the tale of Comoz setting up a special ignition and couple others findings after new engine turning, just enough, till seeing oil at head before starting? Bob's squares are a cam lobe saver but so is just turning front pulley loose on its taper to verify before a run off test. As belt alignment gets close but not quite good enough it can take a dozen turns to see then an adjustment and a dozen more turns then few more dozen to verify or skip that and run it up test which needs another belt to start over if not quite right.

Click to expand...

I never said a anything about a wobble.
But I have never seen a clutch hub without some amount of play.

Sorry if I confused who's clutch wobbled detectably, but I know they can be made very solid stable undetectable by vision or feel and only few 1000th's slack if mic'd. Nuts tends to loosen and bushes tend to wear, especially if kicking up heels in lower gears a lot and long, then wobble creeps back till belt can't take it though a chain can go on and on and on no problem. I've seen too many photo's of worn cam lobes and my own so sensitized to turn engine over much w/o it over 2000 rpm or wring out in lower gears but to reach 4th.

Martin Thanks for the reference and experience site. These Cdo's are a complex kit and puzzle that only looks lawn mower simple on the outside. Lawn mower blades usually turned by belts so perfect to adapt to Nortons. I always wonder where I will screw up next for a show stopper a long ways away.

hobot said:

Say What? Will your belt stay intact with detectable clutch wobble? If so how long have you run your belt with detectable clutch wobble? Can ya give a value to the detectable clutch wobble amount tolerated by your belt?

Click to expand...

WTF?

hobot said:

Anyone remember the tale of Comoz setting up a special ignition and couple others findings after new engine turning, just enough, till seeing oil at head before starting? Bob's squares are a cam lobe saver but so is just turning front pulley loose on its taper to verify before a run off test. As belt alignment gets close but not quite good enough it can take a dozen turns to see then an adjustment and a dozen more turns then few more dozen to verify or skip that and run it up test which needs another belt to start over if not quite right.

Click to expand...

WTF? X2

My belts didn't take very much clutch wobble to end up compacted in alternator spaces. Traced to sleeve bushes burnt up so oil grooved em and ran ATF to get some lasting bushes in lower gear blasts for miles and miles and miles and miles in 2S cam joy.

Turning engines over below 2000 rpm is bad juju on lobes and indeed Jim C and others have tales enough to back up this pensiveness any time turning and turning engine such as belt aligning or pre-oiling before a brand new start. Your dual square procedure is a great way to shorten the risk time turning to assure belt stays put.