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drive belt/primary chain tension adjustment

5724 Views 4 Replies 2 Participants Last post by  OldBoy99
A few questions for the gurus...
I performed these checks recently as part of the 10,000 mile maintenance on my '98 FLHTC. I replaced the rear tire, and therefore had to reset the rear wheel alignment and the belt tension. I checked the primary chain tension but did not adjust since the free play was OK (I think, more on this below).

On Drive belt tension- I bought the HD belt tension gauge and followed my service manual procedure with my wife sitting on the bike (she's pretty close to my weight). But now I hear a "whining" noise comming from the left rear. Sounds like its comming from the rear wheel sprocket. If I turn off the motor and coast, the whining is still there. I removed the lower belt guard, but that did not solve the problem. In comparing my FLHTC belt (which I just adjusted) to my FLSTS belt (which I assume my dealer checked/adjusted 2500 miles ago at the 5000 mi service), the FLHTC belt seems much tighter. My question is: if I follow the procedure in my service manual, which states 5/16" to 3/8" deflection @ 10lbs. force, should the belt be set correctly? Maybe I should just try it again? Is there a trick to this? A book I have gives the following procedure:

"Grasp the belt with your thumb and two forefingers at about 1 1/2 inches back from where it exits the bottom of the primary case. Now twist the belt back and forth on its axis. You should feel serious resistance to this twisting at about a 45 degree angle from flat. If you can twist more like 90 degrees - too loose. If it feels tighter than a bow string at only 25-30 degrees - too tight."

Does this "trick of the trade" method seem about right?

On Primary chain tension - I followed my service manual procedure, but felt my measurement of the primary chain free play was somewhat inaccurate. The best method I could think of was to I mark off 5/8" and 7/8" on a bent metal rod, and tried to get a reading off of that as good as possible. Anybody got a more accurate method for checking this free play? Are there any special tools out there that make this check easy?

Thanks. Appreciate the advise:)
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They tend to be quite finicky, but after a while you get the hang of it. The one thing that seems to make a lot of difference is temperature. You are supposed to adjust them on a cold bike, but you might want to recheck it with a moderate amount of temperature in the bike if the weather is on the cold side (not a hot bike).

Recheck the alignment, make yourself a little tool with a bent welding rod and measure from the center of the swingarm pivot shaft to the center of the axle, on both sides. You have to pop the two little chrome caps off. I usually twist the belt in the center of the lower run and it should go past 45 degrees easy but take significant effort to get to 90 degrees just before you get there, with no one on the bike but the weight of the bike has to be on the ground. If there is any doubt in your mind it's better to run it slightly on the loose side then on the tight side. Loose eats belts and tight eats up more power then you would ever believe and eats gearbox and axle bearings. Just one or two flats on the adjuster nuts makes a significant difference.

The primary chain you can check with a little machinists ruler. Push up with it until you just make contact with the chain and then push up as far as it goes. You can read the measurement on the ruler using the upper edge of the inspection hole as a reference. Same thing applies, better loose then tight. One tooth in the adjustment makes quite a difference and sometimes you just can't get it spot on.
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Forgot, it's usually best to check the adjustments at 3 or 4 spots, ie turn the wheel a little, and adjust at the tightest spot. Also adjust with the bike in neutral, it might be possible to get a bad reading with the bike in gear.
'mornin HIPPO,
Yep, I made that welding rod tool as described in my manual, and was real careful to get the alignment spot on. I think I just set the belt too tight. I'll try the method you described, and check in several places as I turn the wheel.

I think the primary tension was OK, if anything it was on the loose side. But that machinists ruler sounds like the right way to go, I'll have to pick one up.

Thanks HIPPO

Finally got around to adjusting belt. Backed off adjuster nuts 3 flats on each side and re-checked alignment like you suggested. Like magic...no more belt whine:D

Thanks again!
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