Anyone tell me the difference between

Flatbutt1 · 12-30-2005, 10:11 AM

these two V belts for a '99?

04 12 31 1 341 779 ribbed v-belt
04 12 31 7 681 841 ribbed v-belt (4PK592)

captainasty · 12-30-2005, 10:21 AM

The 04 12 31 7 681 841 ribbed v-belt (4PK592) is for racing and HP models.

Good for .3hp gain but the spin up is knocked down by 5ms.

JonyRR · 12-30-2005, 12:02 PM

FB;
I intend to visit the local import auto parts store this weekend with both an OEM belt and the 'tribal knowledge' goodyear gatorback belt that's in reality 1/4" too long for an S. (the goodyear belt takes up all the adjustment room for the alternator brand new) in an attempt to find the perfect belt. progress or lack thereof to follow...

Dale Flowers · 12-30-2005, 02:09 PM

It would be nice if someone would clear up issues concerning the best choice of belts. It has been debated for some time and most of us are in need of a new one. Let us know what you find out.

wswartzwel · 07:04 PM

I have heard panty hose can be used for a road side fix... somebody should investigate that option too.

on2wheels52 · on2wheels52's Garage

Gus Wilson from Model Garage used that trick in the 60's, was in the pre-pantyhose days.
Jim

jweicht · 04:07 AM

Flatbutt - May not be the answer you're looking for but from what I've seen there is only one belt suitable for your '99 (like mine) - the P/N that ends in -779. I don't know the physical differences between the two, but the Bob's BMW catalog shows the -779 P/N applicable for Oilheads up to 6/03, then the other belt for subsequent models. It also shows the upper (alternator) pulley changed P/Ns at the same time, but the bottom (crankshaft) pulley stayed the same for all models. Logic tells me the two different upper pulleys may be of slightly different diameter, which would change the belt length, but unless you've changed to a newer upper alternator and/or pulley, you still need the -779 for your '99. I was at Bob's and bought a new belt a couple of weeks ago for my upcoming 36k service, and they sold me the -779 without asking any further questions other than what year my bike was.

Wish I would have thought about this yesterday, I was at Bob's again and would have asked to see both belts side by side for comparison. Next time....

Flatbutt1 · 12-31-2005, 04:34 AM

jweicht ; thanks thats good info

Bill; i hardly ever wear underpants let alone pantyhose!

cap; good tech info

Thanks all!

brad black · 12-31-2005, 01:35 PM

from memory, the belt from 6/03 on is a 'stretch fit' belt, where the alternator is not moveable and you wind the new belt on using a special tool. i could be wrong, maybe it was introduced later. there's a service bulletin on it anyway.

island_dude · 01-01-2006, 06:43 AM

I guess removing the pantyhose from the donor passenger would be the best part of that roadside repair.

Dale Flowers · 01-01-2006, 07:36 AM

Briefs or boxers... elastic band would be a better alternative including the stretch-to-fit feature. Another reason to wear clean underwear.

jweicht,
How much was the new belt?

jweicht · 01-08-2006, 12:03 PM

Dale - Sorry for the delayed response, the -779 belt was $15.39.

Also, I just changed my bike's belt and confirmed that old belt was also the -779 part number.

Sideshow_S · 01-08-2006, 08:42 PM

Quote:

Originally posted by jweicht
Dale - Sorry for the delayed response, the -779 belt was $15.39.

Also, I just changed my bike's belt and confirmed that old belt was also the -779 part number.

So what is the proper installation? Do you need a special tool? I have to do this before 'the season' starts. Was nice enough to ride today. Salt sucks.

jweicht · 01-09-2006, 02:32 AM

The most time consuming part of this process was getting the alternator cover off. Of course, I already had the gas tank off for other maintenance. Remove the four plastic cover bolts and pull the cover. From the right side of the bike I loosened the three nuts at the front of the alternator and squeezed the belt, which brought the pulleys closer together. Remove the old belt and slip the new one on. Go to the left side of the bike and, using a long extension with a universal joint and the proper size Allen wrench bit (4mm, I think), come in from behind the alternator's lower left side and put the bit into the bolt head and turn it counterclockwise. This will raise the alternator and tension the belt. Holding the proper tension, tighten the three front nuts and you're done. The belt is tensioned properly when you grab it with your fingers at a central point between both pulleys and can just twist it 90 degrees using your fingers. If you can twist it past 90, it's too loose.

Oh, and then you can pop open a brew and admire your work.