Monark Fork Repair

[sportscarpat]

I think everyone agrees that Monark springer forks look great. The originals are rare and expensive. I think everyone would also agree that the new reproduction Monark forks are somewhat underbuilt and lacking in quality control. I looked into the problems and figured out how to properly fix them, making the new Monark fork a safer and stronger option. I use them on motor bikes that cruise at over 30 mph, so I could not accept anything less than completely reliable springer forks. By disassembling a few sets I found consistant problems. The forks are not fully welded and the steer tube does not have a flared area to press on a crown race. If you can't press this race into place you will always have movement under braking and when hitting bumps. Here is what I found under the polished fork crown cover.

What you'll notice is the two fork blades enter into the three crown plates from below, and the steer tube enters into these plates from above. Notice the complete lack of welding through this area. The fork blades were only welded to the bottom plate so the forks could tear lose from the upper plate and cause a complete failure. Also, the steer tube was only welded to the bottom plate and all three crown plates were only tacked welded together. So, how to fix them? Basically four things need to happen.
1. Weld the fork tubes to the upper crown plates, effectively joining the upper and lower crown plates and removing the ability of the tubes from tearing loose of the upper crown plates.
2. Weld all three crown plates together wherever they meet so that no flexing can occur between these plates.
3. Weld the steer tube all the way around where it passes through the upper crown plate, removing any flexing or movement in this area.
4. Place the properly welded fork into a lathe by the steer tube and then turn down the steer tube weld within .020" of the steer tube diameter, giving a press fit for a crown race.
Here is a picture of the fully tig welded fork before machining.

 

[sportscarpat]

These next couple pictures show the fork after machining and then with the crown race pressed into place.

The complete process takes about an hour and the results give me the confidence to ride hard without worry of complete failure. I have worked out this process with Norm at Venice Beach Motorbikes. He likes the look of these forks as much as I I do and also runs them on his motor bikes.

 

[sportscarpat]

I certainly like the look of these forks mounted up to my latest motorbike build.

 

[user 135]

Nice job explaining the problem with detailed pictures. This has been brought up before but always good to have more input.

That bike is great. I am not much on motored bikes ,but yours I do like. Did you fabricate those tanks?

 

[B607]

Finally! Someone does the good fix on a product that is very popular but poorly made. sportscarpat, few of us have TIG welding equipment and skills and even less have access to a lathe. You should consider offering this upgrade service to those who have or want to run these repop Monark springers. Very nice motorbike as well. Gary

 

[sportscarpat]

Thanks for the comments, guys. Fortunately I have a nice tig welding machine in my shop at home. I have been building tanks for a few months now and I am also expanding into a few other areas like these forks. I have access to a couple machine shops so the machining part of this process does not pose a problem. I would consider helping others with their current Monark forks. I would hate to see someone get hurt running around on a set of forks that can easily be made much stronger.
Pat

 

[karfer67]

thank you so much for this post nice welds too

 

[Joeskustoms]

Thanks for the comments, guys. Fortunately I have a nice tig welding machine in my shop at home. I have been building tanks for a few months now and I am also expanding into a few other areas like these forks. I have access to a couple machine shops so the machining part of this process does not pose a problem. I would consider helping others with their current Monark forks. I would hate to see someone get hurt running around on a set of forks that can easily be made much stronger.
Pat

I might take you up on that offer as I'm looking at buying a couple pairs of forks for my current two builds

 

[American Vintage Bicycle Supply]

yes this is a very helpful post thanks...

 

[Joeskustoms]

how do these forks ride?

 

[sportscarpat]

how do these forks ride?

Now that I have riden on these forks I can say they feel good. Upon reassembly I lubed all the pivot points, tightened all the pivot bolts completely and then backed them off a 1/2 turn. At this point the spring rate feels good with my 200 lbs and I have not bottomed them out yet. This was all under pedal power so can't say what will happen when I hit a pot hole at 30 mph.

 

[azbill]

Excerllent how-to !!! 8)
Thanks Pat

 

[Joeskustoms]

how do these forks ride?

Now that I have riden on these forks I can say they feel good. Upon reassembly I lubed all the pivot points, tightened all the pivot bolts completely and then backed them off a 1/2 turn. At this point the spring rate feels good with my 200 lbs and I have not bottomed them out yet. This was all under pedal power so can't say what will happen when I hit a pot hole at 30 mph.

Nice! cant wait till i get my project rolling

 

[siberian]

maybe somebody can write how-to place monark with wide rims and 3" tires?

 

[eccles]

would you ship a set to australia?

 

[sportscarpat]

would you ship a set to australia?

Sure, if you don't mind the hassle and shipping costs.

 

[sportscarpat]

Thread bump with a quick update. I have been remanufacturing the Monark forks for some time now and have never really liked the drop-out that comes with them. They just seemed cheap to me. They are very thin and distort when tightened. I also have to open the slot up for the axle as they have a 5/16" slot opening and all modern axles are more like 3/8". So instead of reworking a lame part I just made my own out of much thicker stainless plate and included the wider slot. Nice little laser cut part.

DSC06214 by Sportsman Flyer, on Flickr

Stock version on the right, Sportsman version on the left.

DSC06218 by Sportsman Flyer, on Flickr

Here is a shot with the forks all set up on a Sportsman Racer chassis with the modification for the drum brake mounting like Norm uses.

DSC06220 by Sportsman Flyer, on Flickr

 

[axsepul]

i'm liking this. here is my version of that fork

viewtopic.php?f=1&t=37225&p=377472#p377472

 

[axsepul]

Thread bump with a quick update. I have been remanufacturing the Monark forks for some time now and have never really liked the drop-out that comes with them. They just seemed cheap to me. They are very thin and distort when tightened. I also have to open the slot up for the axle as they have a 5/16" slot opening and all modern axles are more like 3/8". So instead of reworking a lame part I just made my own out of much thicker stainless plate and included the wider slot. Nice little laser cut part.

DSC06214 by Sportsman Flyer, on Flickr

Stock version on the right, Sportsman version on the left.

DSC06218 by Sportsman Flyer, on Flickr

Here is a shot with the forks all set up on a Sportsman Racer chassis with the modification for the drum brake mounting like Norm uses.

DSC06220 by Sportsman Flyer, on Flickr

PM SENT

 

[DougC]

Thread bump with a quick update. I have been remanufacturing the Monark forks for some time now and have never really liked the drop-out that comes with them. They just seemed cheap to me. They are very thin and distort when tightened. I also have to open the slot up for the axle as they have a 5/16" slot opening and all modern axles are more like 3/8". So instead of reworking a lame part I just made my own out of much thicker stainless plate and included the wider slot. Nice little laser cut part. ....

I was one of the earlier buyers of the repro Monark fork when it came out, and have seen the problems it had.
I never asked the manufacturer, but have long suspected that they were built to be a drop-in replacement for the vintage forks.

This would have been just fine if they would have explained that in the web page on them, but they didn't, and a lot of people bought them to put on modern cruisers and found out they were "made wrong".
Among the problems I recall:
--no lower bearing race at all (modern headset bearing sizes were all a bit too large diameter)
--dropout slots too small (5/16" instead of 3/8" axles)
--dropout width too narrow (around 80mm with the plates on the INSIDE, which was how the original Monark fork plates were assembled,,, instead of 100mm, which is the modern standard for front wheel widths)
--I also saw that the original dropout plate bolts would not stay tight, as they came. I switched to using hardware store bolts with nylon stop nuts instead, but that was a hassle because the original bolt was an odd thin-head shouldered metric bolt that you could not simply flip around to mount the dropout plates on the outside of the fork blades.

If you had a metal lathe and a milling machine, all this stuff was annoying to fix, but fixable. If you didn't, it was a much larger problem to deal with.

If they were really built to the vintage specs, then they may have been built 100% correct. Standard bicycle part dimensions today are not the same as ~75 years ago.
It would have been interesting to see the vintage fork parts side-by-side with the repros to see the differences, but nobody ever managed to make that happen.