Minton Mod on front forks

[YAM277]

 

[YAM277]

Thought I would add a pic showing the stock and mod next to each other. The mod has the 1/4" bit on one of the four lower holes and a 3/32 bit drilled through the newly drilled top two holes.

 

[5twins]

I think you meant to say 3/32" for the top drill bit size? 5/32" would be slightly more than half the size of the 1/4" bit and not much smaller than the original lower holes. Obviously, the small drill in your pic isn't that big. For anyone finding this thread in the future, here's a chart showing stock and modded hole sizes for the 35mm fork damper rods. Being that these old forks weren't cutting edge by any means, "rocket science" so to speak, I'm sure any of the inch size bits near to the numbered ones would work OK if you didn't have the numbered ones .....

But, if you did want numbered ones, HF has a pretty nice set that's not too expensive. Or, if the top #45 is all you need, here's a lifetime supply for $5 .....

http://www.ebay.com/itm/371545072565?_trksid=p2060778.m1438.l2649&ssPageName=STRK:MEBIDX:IT

 

[YAM277]

Thanks for the chart and clarification 5T, hope the pics can help anyone giving this a try.

 

[5twins]

Yes, they should, they are very good. Something else I do is bevel the holes. An engineer buddy of mine told me they will flow more/better that way. Yamaha actually did bevel them on the first year 35mm damper rods ('77) .....

 

[YAM277]

Thanks for your pics and additional input. I think I also read that you use 7mm of fork oil?

 

[5twins]

7 ounces. Stock amount is just under 6 ounces but these forks just plain work better with a little more oil in them. It helps reduce the dive on braking quite a bit.

 

[XS650D]

5twins nailed it.I did this mod to my 77 and never looked back.Playing with preload and fork oil weight also makes a difference
but the Minton/5Twins Mod it the deal breaker.I found that 10 weight and approx 1inch preload spacer under the cap was the ticket.
But i weight 150 lbs.Probably 15 weight fork oil if u are bigger in the waist line. Worth noting,i also run the fork springs out off a xs 500 strait rate
which i prefer over progressive.Just my own personal observations.Is it summer yet?

 

[YAM277]

As always, 5T's input can help many of us, but going up to a 15 wt. oil might not flow as easily as the 10 wt? I appreciate you factoring in the possible extra weight ratio's of us huskier riders, but I would still suggest the 10 wt. fork oil. Also as 5T suggested, going up to 7 ounces instead of 6 oz., when filling up the tubes. As you mentioned "D", the results were a game changer! Thanks for your input.

 

[azman857]

I read 5twins thread on the Minton mod and did it when I replaced the fork seals on the SG. Way better ride. Not saying USD forks good, but better than before.

 

[YAM277]

It's great to have this mountain of information at our fingertips! Appreciate the feedback of all, on the mod, we can see how this change in the forks can better the ride. The support on this site always amazes me. Just plenty of good karma, with everyone ready to pay it forward!

 

[jetmechmarty]

Probably 15 weight fork oil if u are bigger in the waist line.

Uh....No! Oil viscosity has nothing to do with the weight of the rider. If you're too heavy for the springs, you need more spring.

 

[arcticXS]

Not saying USD forks good, but better than before.

Not sure if fork orientation (USD vs RWU) has much to do with damping performance, it really comes down to the valving. USD forks have weight/stiffness advantages, and allow more overlap between inner and outer tubes.
Some USD forks are actually piss poor designs with regards to damping, like the stock USD Marzocchi on some Ducatis. Very basic valving, and difficult to modify as well.....

 

[arcticXS]

Uh....No! Oil viscosity has nothing to do with the weight of the rider. If you're too heavy for the springs, you need more spring.

And a heavier spring then requires more rebound damping, which is what you get with thicker oil......

 

[vr3506]

@YAM277

Can you tell, what's the effect on demping?

 

[pcoumbe]

I did the same with my forks and added Race Tech emulators from 650central. Made a big difference to the ride and handling

 

[YAM277]

For me it was a major rebuild on everything in the forks. Seals,springs,fork brace, oil, doing the Mod and cleaning out 38 years of gunk and build up. I think any bike would have less dive after doing this much to it VR, I would back up the recommendation of 5T and others who support this Mod. Just Do It!

 

[motorbikerx]

Very Interesting!

 

[drgonzo]

Yes, this is interesting. When the AMA had the old 883 twinsport road racing class, tuners used 40wt motor oil to increase damping in the stock forks and most of those guys were in the 130ish range. Just saying.

 

[motorbikerx]

there wouldnt be too many bumps or undulations on a racetrack though so stiffening the forks with 40 weight may be a great idea for that type of riding.
On my Victory I upgraded the front end with a thorough clean out (they tend to collect a lot of gunk at bottom of forks) drilling and chamfering the damper rods as well as fitting Gold Valves and Progressive springs weight rated a 10kgs heavier than my actual weight.
New seals too of course...I did accidentally make the spacers above the forks too long as I didnt think of the cap recessing into the thread.
This made my modded forks way too hard, just over the top, on dissasembly I figured out my mistake.
Forks worked really well for hard riding, though earlier this year I scored a great deal on brand new 2011 Kingpin front end , chrome and complete Upside Down forks, They handle just as good stock as my modded standard forks yet have a more supple ride over bumps, the best of both worlds, bonus is they look really good too, combined with a valanced Kingpin front fender and wide 18" Hammer wheel, in place of the skinny 21"er
The old upgraded entire front may make it onto the XS650, only time will tell.