Need 39mm fork cap bolts


Information and questions on GL1100 Goldwings (1980-1983)
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Dubdenny
Posts: 48
Joined: Thu Jun 18, 2020 4:13 pm
Location: Yardley, PA
Motorcycle: 1981 GL1100 Interstate

Need 39mm fork cap bolts

Post by Dubdenny »



Hello group,

I'm searching for 39mm fork cap bolts to go with my air assist delete on the front end of my 1981 GL1100i. I've been searching the internet and all I can seem to find online is aluminum Chinese crap that I don't trust and some 39mm Harley cap bolts that require a special wrench bc of their shape and dome. I'm having a hard time believing that in the last 41 years I'm the only one who's made this conversion to higher rate progressive fork springs to delete the air assist in the front end. In addition, the pneumatic fork caps are fugly and a pia to remove and install bc of their shape.

TIA for any suggestions on where to buy standard steel fork caps in 39mm size, or cross references to other motorcycle models or brands that may have been manufactured with 39mm forks with metric thread pitch. This forum rocks.


Bill in Yardley, PA
William K. Denton
Lazarus CycleWorks
“We Breathe New Life into Old Bikes”
wkdenton@verizon.net
267-980-7788 office/cell
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bruce swaybill
Posts: 151
Joined: Wed Dec 11, 2013 11:26 pm
Location: farmington, ct
Motorcycle: .
1983 honda gl1100i interstate
2009 triumph bonneville t100

Re: Need 39mm fork cap bolts

Post by bruce swaybill »

Why delete the air preload? The Progressive springs are not preloaded enough to provide all the compression travel you need. You will need the air to set the static sag properly.
Have a nice day! :)
Dubdenny
Posts: 48
Joined: Thu Jun 18, 2020 4:13 pm
Location: Yardley, PA
Motorcycle: 1981 GL1100 Interstate

Re: Need 39mm fork cap bolts

Post by Dubdenny »

Hi Bruce,

I don’t like air assist forks or shocks bc they always seem to leak. As far as insufficient preload and compression travel (i.e. too much sag), I’m not sure where you’re coming up with the information to support your comment? The Progressive Suspension information provided in the installation booklet says that the 11-1102 springs “require no air assist”. If the sag is not correct out of the box, I will add preload with the necessary lengths of pvc pipe spacers until the sag is correct, as I have done with other bikes in the past.

Thanks!
Bill in Yardley, PA
William K. Denton
Lazarus CycleWorks
“We Breathe New Life into Old Bikes”
wkdenton@verizon.net
267-980-7788 office/cell
User avatar
bruce swaybill
Posts: 151
Joined: Wed Dec 11, 2013 11:26 pm
Location: farmington, ct
Motorcycle: .
1983 honda gl1100i interstate
2009 triumph bonneville t100

Re: Need 39mm fork cap bolts

Post by bruce swaybill »

I agree that a adding a fixed length spacer can be used to adjust the sag. Preloading this way also consumes spring stroke before it goes solid. The air pressure does not. Perhaps there is enough extra stroke that it will not limit the wheel travel before the tubes bottom out or the oil level tops out.

With the Progressive springs in my Interstate, I still found the sag excessive with zero or low pressure. I keep mine at 20psi. I rebuilt my forks in 2014 with new seals and bushings and have not had leaking issues since.

Also, oil-only shocks/forks leak oil sooner or later. After enough leaking, the oil level drops below the seals and let’s the air out.

I would recommend caps with adjusters for fine tuning.

Bruce S.


Have a nice day! :)
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