Loose Primary Chain

[swooshdave]

So it's suppose to be 3/8in? That seems so tight. But I think I have it too loose. I went for tight enough it won't hit the case. But it's noisy.

Primary Chain Adjustment

Please tell me if I am understanding this correctly. Is the primary chain to be adjusted so there is slack of 3/8" movement with little to no force? Not that It can be moved only 3/8" by forcing it up or down. I bought my 73 commando in 2000 and it has been an on and off again affair. It...

www.accessnorton.com

Here they say 3/8in sag.

Manual says tighten to "dead tight" then loosen to 3/8in.

I think I should tighten it a bit more and see if it gets quieter.

 

[marshg246]

As long as there is 3/8" checked at the location of the inspection hole and you've turned the engine and rechecked several times, you're good. IMHO, you have it too loose in the video.

 

[gortnipper]

With a 10mm wrench thru the inspection window, it should deflect that between distance up/down. Measure at the pin, brace the wrench against primary cover for stability.

If it is hard to get in/out of neutral it is too tight.

 

[baz]

If you are concerned about it being too tight give it a quick check when the engine is fully warmed up

 

[maylar]

Dead tight to take up the slop in the adjuster, then back until there's 3/8" total up-down in the center.

 

[jbruney]

That's much more loose than I run mine. I know it's kind of hard to keep the centerline image in mine when you check. A nice magnetic straight edge to lay along the centers of the top links, or just holding one in place, would make seeing the deflection easier since the outer is off anyway. After that going by feel is easier. 3/16" one way is hard to judge the way our brains are wired and misled by angles, dissimilar sizes and center distance rolled into one loaf.... Mine is so I have to force a reference point. String works too but not as steady.

 

[swooshdave]

If you are concerned about it being too tight give it a quick check when the engine is fully warmed up

No spec given for a warm engine.

 

[swooshdave]

As long as there is 3/8" checked at the location of the inspection hole and you've turned the engine and rechecked several times, you're good. IMHO, you have it too loose in the video.

I think so too. I went to err on the loose side but I think I need to snug it up a little.

 

[Fast Eddie]

No spec given for a warm engine.

Correct. Because the ‘book spec‘ has been calculated to give the required slackness to ensure the chain is running correctly, ie not tight, when up to temp.

So his point is, if you are concerned that the ‘book spec’ might be too tight when things heat up, then checking when hot should put your mind at rest. You don’t need a figure, you’re just checking it’s not ‘tight’.

 

[swooshdave]

So obviously there should be some determination of what is too tight when hot. Zero deflection? 1/8in?

Do we assume “dead tight” mean you can’t deflect the chain regardless of force?

 

[maylar]

Do we assume “dead tight” mean you can’t deflect the chain regardless of force?

I always interpreted that as no movement with normal finger tension. The point of that exercise is to insure that the locking bolt is against the rear of the gear case hole so that returning the other way takes up the small clearance between the bolt and the hole. Otherwise the rear chain could pull the gearbox back and tighten the chain. Something you're acutely aware of.

 

[Fast Eddie]

So obviously there should be some determination of what is too tight when hot. Zero deflection? 1/8in?

Do we assume “dead tight” mean you can’t deflect the chain regardless of force?

If you’re gonna go down that rabbit hole Dave, then with respect, why don’t you just trust Norton and go with the book spec ??

 

[DogT]

Well, for sure if it's too tight you most likely will experience difficult or strange shifting. I'd rather be on the loose side than tight.

 

[jbruney]

Careful with your perception of tight.... Remember how old these things are and God only knows what they've endured.

 

[EstuaryBoy]

Careful with your perception of tight.... Remember how old these things are and God only knows what they've endured.

She told me she was a virgin!!

 

[jbruney]

Mine told me I'm the only one.

 

[swooshdave]

Careful with your perception of tight.... Remember how old these things are and God only knows what they've endured.

This is actually my biggest worry. The manual assumes no wear.

I’ve now got it set at 1/2” which is more than the 3/8” but I think it’s reasonable. It’s definitely tighter than it was. Both gearbox bolts good and tight. Rear chain adjusted.

 

[worntorn]

Have you considered switching to a belt drive?
They are really quite good nowadays.
Kidding!
Glen

 

[jbruney]

Ooooh! That hurt.

I like chains because I carry spare connectors and my chain tool to get me out of trouble. Belts appear to be a bit too much for roadside repairs.... Thinking out loud there.

 

[RoadScholar]

Looking at the video, nice job on that, the chain appears to be a bit loose. What I didn't see is turning the engine and rechecking at multiple other locations. When I adjust primary chains I use a piece of black tape to mark the center of the loose sections and blue tape to mark the tight sections. When you have gone around to verify your marks you'll have a good image of the "big picture". I also suggest that you mark the chain plate at the center of the tightest spot because, as you already know, you may well be doing it again after you have run some torque through the drivetrain. Belts have similar characteristics, but, in my experience, not to the same degree.

I have often wondered how much the engine sprocket and the clutch basket participate in the tight vs. loose saga?? Same wonderment for the final drive chain.

BTW, with "tongue-in-cheek" if you can hear the primary chain your exhaust is too restrictive...

Best.