Shock oil for old Mulholland/Boge shocks.

Last week, I dismantled the Mulholland shocks that came off my Matchless scrambler to see what was inside and maybe re-use them at some point. Of course the oil was black and thin like water from deterioration. They looked OK inside so I put some Bel-Ray 7wt in one and 10wt in the other and exercised them a few times and gave the pull test. Couldn't tell the difference. But, compared to some factory, Girling, Commando shocks I saved, there is a huge difference, those are more like performance car shocks. You really have to pull.

So, my thinking is that since I don't know what oil was in them as they'd never been apart since new, I should go to a heavier oil, maybe 20 or even 30 as with vintage front forks. I've even seen people suggest using hydraulic jack oil but what viscosity is that? I know various brands and specs of ATF vary all over the map, somewhere in the vicinity of 15wt, I believe, but I have no way to test it.

But there is the balance between spring-weight ratings and damping to consider. This is the same discussion as about roadholder forks but applied to shocks. When they were on the G80cs it was particularly rough on washboards, all but un-rideable by my old bones. OK on bumpy forest roads if I kept the speed down. This is the setup I used for scrambles back in the day and also for trail riding but I was a lot tougher then and lighter. Also memory fades and details of the setup have faded with it. So I'm starting almost from scratch.

I'm setting it up to be desert sled for a winter trip to find the footprints of folks in the movie "On Any Sunday," California desert, if you haven't seen the movie. As originally set up with progressive 60ish/110 springs (close as I can measure) they were a little stiff, forcing me to stand on the pegs more than I like. I think 110 pound springs are OK for the road and while the bike is lightish, I am not (190 lbs), they seem too stiff for the dirt.Maybe, given the washboard pain I should go with lighter springs and lighter oil. I have some lighter springs.

I replaced the Mulollands with Hagon repro factory shocks using the aluminum bottom pieces that screw onto the body. They came with 110 pound springs. They are shorter than the Mulhollands by 1-1/2 inch. They are fine on the road now they're broken in but maybe a little stiff as I'm used to progressive springs. So I'm thinking of putting the Mulholland shocks on again. I can't test them here because winter has come and it's too effing cold to ride and the cross-country skiers get all exercised if you ride in the groomed ski tracks. They have separate tracks for fat-tire bikes but I wouldn't attempt that either. Maybe now I'm old I should just buy an electric fat bike and give up trying to chase Steve McQueen across the desert.

I ran SS1300 Boge-Mulholland shocks on my Commando PR for several years. I used 80-100 springs for road racing. I did rebuild the shocks at least once, but I just used the factory "Hydro-Damp Fluid" and parts, and have no idea what weight the oil was. I had a partial sponsorship from the company at the time, giving me shocks and parts for free, so I never tried any other brand of oil. FYI, the oil capacity is 110 cc per shock.

Some info on these shocks here:


Ken

I think Steve McQueen and Malcolm Smith were young bucks in On Any Sunday. Real hard to turn back the clock. I try every day and it does not work.

My suggestion would be leave the antique scrambler in the garage and get a modern dual sport bike so you don't beat yourself to death.

Schwany said:

I think Steve McQueen and Malcolm Smith were young bucks in On Any Sunday. Real hard to turn back the clock. I try every day and it does not work.

My suggestion would be leave the antique scrambler in the garage and get a modern dual sport bike so you don't beat yourself to death.

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Ah but I could put around in the warm sun while thinking of snow back home and not have to go bike shopping over the next month.

Good attitude. I wouldn't do it on an antique. Fear it would break.

I rode dual sport events in the Neveda desert in the 90's, but not on a Norton. Not enough suspension, and too heavy for me. I did have the P11 then, but it has always been set up as a street bike.

The guys that rode Norton P11's, Triumphs, and whatever big British twins Barstow to Vegas in the late 60's were a lot tougher than I am.

If you go, have a safe ride out there.

Schwany: Even with lights the G80cs is less than 350 lbs. I ride it around town and on gravel back roads enough to have some confidence in it's reliability, and I've kept up the maintenance. These were tough bikes bred of chair-pulling and off-road racing -- scrambles, trials and desert racing. Desert racing is what gave birth to the Typhoon, G15 then the G85 and P11, as I'm sure you know.

The story goes that the factory wouldn't address the need for more power in the desert and Berliner, the US distributor, ordered 50 or some number of N15s and they sold right away. Poke (owner of Pokes Cycle) claimed to have gotten several from the first batch. He was heavily involved in hill climbs and off-road racing in the 50s and 60s. For a couple decades there was his Indian 80" hill climber parked in the showroom with its rear wheel chained up. When looking at my G80cs at the Tacoma Ducks off-road event (scrambles, flat track, woods and road riding all in one weekend) he said, "That's a Big Bear Special that I ordered from Berliner and sold to (some name I can't remember) in 1960. His memory was always that good, right up to the end. He was pretty deaf by that time but listening to my bike run after the A-main event he said, "I can hear that timing-side main bearing growl. You'd better check it out." He was right! I managed to find a guy in the UK, Ken de Groom, who modified modern ball bearings for the timing side of a G80. I bought five, used one and sold the rest through the shop. Word got around and they were gone in a month.

A G80 in motocross trim of the day weighed ~325 lbs and the G85 was lighter than that. The Boss (Ross) at Pokes raced a G85 complete with Amal GP carb and aluminum sheet-metal primary cover. I was insufficiently in awe of that bike at the time. Riders bashed these bikes unmercifully. Our shop kept a five-pound lead hammer for straightening steel rims. My bike still shows hammer marks from where I did that to it.

My great fear would be that I'd drop it and dent some priceless sheet metal. That would keep me on the baby trails where fathers lead little kids on wee little dirt bikes. I tell myself that I'd just go for the scenery that I can't get to with my pickup camper. I tell my wife that too. Plus, when boondocking in the desert I need some transportation more than a bicycle to fetch groceries. That said, I may have to resort to a push bike in Quartzite to go to the various tent shows. I hear the traffic is horrendous.

lcrken said:

I ran SS1300 Boge-Mulholland shocks on my Commando PR for several years. I used 80-100 springs for road racing. I did rebuild the shocks at least once, but I just used the factory "Hydro-Damp Fluid" and parts, and have no idea what weight the oil was. I had a partial sponsorship from the company at the time, giving me shocks and parts for free, so I never tried any other brand of oil. FYI, the oil capacity is 110 cc per shock.

Some info on these shocks here:

Boge Mulholland

Information about vintage Boge Mulholland shocks. Includes specs and pictures as well as application information

www.thejunkmanadv.com

Ken

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Thanks for the link. I must have run across a similar page in the past because I have one page but not the one with various specs. I have the MX version, of course.

Talking single thumpers... My ATK 604 dual sport was fun in the desert. Whole lot of motor with a Rotax. A lot easier to pick up an ATK than a Norton, plus not much to worry about when dropping one. Body work and tank was all polypropylene.

Schwany said:

Talking single thumpers... My ATK 604 dual sport was fun in the desert. Whole lot of motor with a Rotax. A lot easier to pick up an ATK than a Norton, plus not much to worry about when dropping one. Body work and tank was all polypropylene.

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The big ATK was my dream bike in high school, (late 1980's). Rare, though! I've never actually even seen one "in the flesh" so to speak. I eventually picked up an Armstrong MT500 ex-UK Army bike and I have a CCM 604 sourced Rotax to go into it to replace the original low output army engine (going from 28 to 53 hp). Not the same of course, but I do like the Armstrong/Harley/Rotax/SWM mongrel that the army bike is.

Junglebiker said:

The big ATK was my dream bike in high school, (late 1980's). Rare, though! I've never actually even seen one "in the flesh" so to speak. I eventually picked up an Armstrong MT500 ex-UK Army bike and I have a CCM 604 sourced Rotax to go into it to replace the original low output army engine (going from 28 to 53 hp). Not the same of course, but I do like the Armstrong/Harley/Rotax/SWM mongrel that the army bike is.

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Wow the UK army really had their finger on the pulse of the troops! On my return from Vietnam in '69 I went looking for a bike to replace the Honda 90 I left with my GF in Saigon. I quickly discovered they wouldn't even allow motorcycles on post. They had to park at the service station across the street from the Main gate.

Regarding shock oil for the Mulhollands: I ended up mixing up some 15wt and using that. The "pull test" puts the rebound somewhere between the anemic result with 7w and the stock Girling, Commando shock I'm comparing them to. I still haven't road tested them and may not be able to till I get to Arizona so I'm taking some oil and a set of 60/100 springs in case the light ones that I used when I first got the bike prove to be too light for my now increased weight. The heavier set are pretty stiff off road. In a month or so I'll let you know how it worked out, just in case someone else is mucking around with period shocks.

Like you, I would like to ride my P11 off-road, but I'm not talking about serious riding. Most of the motorcycle trails I've been on in the US have been pretty tame, tame enough that a person going slow on an old bike could probably still ride them. I'd like to ride sections of the Trans America Trail on my P11, just to be able to say I did it. I won't be trying to set any speed records, just riding dirt roads on a bike I like. I'll leave the Erzberg Rodeo stuff to the Power Rangers on the CRF's, though I still think it would be cool to ride (not compete!) a bit of desert, just to see what Mike Patrick and those guys were up against when our bikes were made.

Thomasa, I just saw this one for Hydro-Damp fluid on eBay. It says it is medium weight, so I assume there were probably other weights available from Boge Mulholland. You could always buy this one and then compare viscosities to find an alternate. But you can probably do just as well by continuing to experiment.


Ken

Junglebiker said:

The big ATK was my dream bike in high school, (late 1980's). Rare, though! I've never actually even seen one "in the flesh" so to speak. I eventually picked up an Armstrong MT500 ex-UK Army bike and I have a CCM 604 sourced Rotax to go into it to replace the original low output army engine (going from 28 to 53 hp). Not the same of course, but I do like the Armstrong/Harley/Rotax/SWM mongrel that the army bike is.

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I believe my ATK was a 90 or 91. Can't remember. I was probably 43 when I bought it used. Harry Lillie ported the head, sold me a Rotax race cam (can't remember the cam number), and bored out a 36mm Mikuni TM to 39mm for that motor. (I ended up putting a Dellorto pumper on it, but still have that old TM carburetor) The bike was quick. I did have an '86 ATK 560 for a while as well.

Thing about going fast in the desert is it is difficult to see big Mini Cooper size holes in the desert floor when everything looks like sand and sage brush at high speed. I couldn't ride it off road today like I rode it then, and would not want to try. Nowhere near in good enough shape. I used to lament not converting it into a Supermoto for the street. It went to a good home where it was raced. New much younger than I owner really liked it.

Am I far enough off topic yet?

Seem like everything is collectable

lcrken said:

Thomasa, I just saw this one for Hydro-Damp fluid on eBay. It says it is medium weight, so I assume there were probably other weights available from Boge Mulholland. You could always buy this one and then compare viscosities to find an alternate. But you can probably do just as well by continuing to experiment.

Vintage Mulholland Shock Medium Hydro-Damp Fluid Shock And Fork Oil 8 Ounces | eBay

Still Full.

www.ebay.com

Ken

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these days, even vintage shock oil. Saw some NOS Boge-Mulholland 12 inch shocks for $129 on flea bay. I wonder how they stack up against, say, new new stock Hagon shocks. No parts available for the Boge so far as I know but at least you can change the oil.

Link to fork-oil chart

Schwany said:

Talking single thumpers... My ATK 604 dual sport was fun in the desert. Whole lot of motor with a Rotax. A lot easier to pick up an ATK than a Norton, plus not much to worry about when dropping one. Body work and tank was all polypropylene.

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Schwany, I see what looks like a Supertrapp muffler lurking under the number plate panel. Do you or anyone else know if these are considered a legal spark arrester by the US Forest service, BLM, etc. ? I have believed their vendor's website that says yes but I never went to the FS office to ask.

Thomasa said:

Link to fork-oil chart

Suspension Fluid - Pvdwiki

www.peterverdone.com

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That's a great resource, Thomas. I had seen that earlier, but lost track of the source. Too bad they didnt include Boge Mulholland in the list.

Ken

Thomasa said:

Schwany, I see what looks like a Supertrapp muffler lurking under the number plate panel. Do you or anyone else know if these are considered a legal spark arrester by the US Forest service, BLM, etc. ? I have believed their vendor's website that says yes but I never went to the FS office to ask.

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Lots of Supertrapps out there on BLM land when I was riding that thing. They were required on 4 strokes in OHV parks. It would be impossible for a spark to get past the discs. The 2 into 1 setup on my P11 terminates with a Supertrapp arrangement, but it is not legal on or off road because it has an open center. Race only, but I am not worried about running it. Not worse than opened up peashooters.