45 Engine/Gearbox Alignment

Method for aligning engine and clutch sprockets.

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old man emu
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45 Engine/Gearbox Alignment

#1

Post by old man emu » Thu Jan 10, 2019 8:28 pm

I have to pull my gearbox out of the bike to replace a broken bottom stud (Part # 2318-26), after which I'll need to align the engine and clutch sprockets. I know the job requires the use of a straight edge.

Could someone post some pictures of how the straight edge is used to set the alignment?

Thanks,
Old Man Emu



Mark44
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Re: 45 Engine/Gearbox Alignment

#2

Post by Mark44 » Thu Jan 10, 2019 11:45 pm

No doubt someone will correct me if I'm wrong, but I don't think you need to align the transmission and engine. The transmission can be adjusted fore and aft, but unless the trans plate is wallowed out, it's not adjustable left and right. The straight edge is to align the rear wheel with the trans drive sprocket.

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Re: 45 Engine/Gearbox Alignment

#3

Post by kitabel » Fri Jan 11, 2019 2:55 am

A long ruler should touch the teeth on both sprockets simultaneously with no visible gap indicating an angle. If it looks good, try the other side, there may be a gap but it will be the same width on both.
I agree, there is no adjustment provision built in. The lateral (left-right) alignment should be really close if all the parts are in good shape, no bent studs, elongated holes etc.
Most of the alignment errors I've seen:
1. sprocket not original quality, the taper may not be correctly located in the hub
2. the sprocket isn't fully seated, typically a burr on either mating surface, wrong key, or the key didn't fully seat in the shaft
3. bent frame, repaired front motor mount etc.
The transmission itself would be difficult as all of its attachment points are fixed.
Normally, if a small error is detected (chain from the engine does not accurately align with the clutch drum tooth row on both sides) it's possible to make a small adjustment using the condition of the buffer plate.
If the engine sprocket teeth are outboard (too far left) of the clutch teeth, insert a thin shim (brass or steel preferred, although aluminum has been used, roughly equal to the error) between the buffer and the clutch shell and re-attach. If need not be a continuous circle as long as all of the rivets are included and the entire width is covered, making 3 smaller pieces may be easier. Make sure they're flat.
If the engine sprocket teeth are inboard (too far right) of the clutch teeth, thin the buffer on a large piece of glass, surface plate etc. with fine paper and re-attach.

old man emu
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Re: 45 Engine/Gearbox Alignment

#4

Post by old man emu » Fri Jan 25, 2019 12:00 pm

I've been delayed getting onto this job, but it is "Go!" for this weekend.

In response to Kitabel:
  • The engine sprocket is NOS
    The sprocket might not be fully seated. I'll check that as I re-assemble things.
    The frame doesn't show signs of having been bent. I've been riding it for nearly 6 years. It tracks true and tyre wear is even.
I think that I will have enough jiggle room to align the clutch sprocket and engine sprocket by moving the gearbox. You have to remember that things were all OK until I snapped the front left gearbox bottom stud.

old man emu
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Re: 45 Engine/Gearbox Alignment

#5

Post by old man emu » Sat Jan 26, 2019 12:01 pm

When I lifted the gearbox out, I noticed that the block in the middle of one of the gearbox bottom studs which fits into the frame was slightly off parallel. That could cause the fore/aft adjustment of the gearbox to be affected by binding.

old man emu
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Re: 45 Engine/Gearbox Alignment

#6

Post by old man emu » Sat Jan 26, 2019 11:02 pm

Hopefully some good news. Last night, I put some WD-40 on the top of the broken stud in the gearbox body. This morning it seems that the WD-40 has soaked down the threads. I hope that this means the threads on the stud aren't frozen into the body, and will come out easily with an EZY-Out.

It's Sunday morning, so please attend the church of your choice and pray to SAINT ELIGIUS, PATRON SAINT OF ARMY MECHANICS that my efforts will be successful.

OME

old man emu
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Re: 45 Engine/Gearbox Alignment

#7

Post by old man emu » Sun Jan 27, 2019 12:38 am

All praise be to St Eligius

I've just finished my celebration dance after successfully removing the broken stud.

For the first time in ages, I was able to free-hand drill a hole in the centre of the stud without skidding the drill off to the side so I could insert an Ezy-Out. As I started to wind the Ezy-Out into the stud, the stud began to unscrew. It came out soooo easily. Even better is the fact that the threads in the gearbox body are undamaged.

The other stud that I said earlier was a bit off centre unscrewed easily, too. So I'll refit both studs and make sure they are properly aligned.

OME

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Re: 45 Engine/Gearbox Alignment

#8

Post by old man emu » Sun Feb 17, 2019 10:31 am

Finally got everything bolted back on the bike and was able to do a road test. The ride is so much smoother now, and there is less noise.

Autumn is around the corner with weather just made for rides in the country. Maybe I can get some enjoyment out of this bike!

ccislander
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Re: 45 Engine/Gearbox Alignment

#9

Post by ccislander » Tue Mar 05, 2019 5:07 am

Happy motoring!
Springtime around the corner here - finally! I’ve been putting a 45 together for a while now and am just getting ready to mount the motor sprocket and clutch.

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