How to Wake Up a 1975 r90/6?

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Eatinbugs
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How to Wake Up a 1975 r90/6?

Post by Eatinbugs » Fri Jan 05, 2018 10:10 am

Hi,
I just bought a 1975 BMW r90/6. Original owner, 28,000 miles, very nice shape. But it's only been driven 15 miles during the past 25 years. Stored in a heated garage in Michigan with stabil in the gas, it has been started semi-regularly over that time and only driven around the owners yard and down his gravel road. When we put in his lawn tractor battery, it started in just 3 tries, then settled into a smooth idle (with choke on). We ran it only a couple minutes, but I'm very encouraged. I know sitting, not driving is never good for a vehicle, but I'm not certain what to do to properly bring her back to riding form.

What do you experienced souls suggest to properly re-awaken this sleeping beauty??

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Zombie Master
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Location: Vancouver Island BC Canada

Re: How to Wake Up a 1975 r90/6?

Post by Zombie Master » Fri Jan 05, 2018 11:52 am

Look inside the gas tank. Rust. It could run good for a shot time and then rust will start to block up. Personally I would not run the bike until I've checked the fuel system. I'd drop (all) the oil and filter cold (check the check valve in the filter housing) and refill with inexpensive oil for a short run, then change both again. Inspect! Service the front brake. Expect seal leakage. Do not remove the front engine cover without removing the battery ground! Lovely bike! Post a pic.
Last edited by Zombie Master on Fri Jan 05, 2018 8:11 pm, edited 1 time in total.
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jagarra
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Re: How to Wake Up a 1975 r90/6?

Post by jagarra » Fri Jan 05, 2018 12:23 pm

I agree with ZM, having resurrected vehicles that have sat for a long period, the fuel system and brakes seem to be the most vulnerable units. I would plan on a carburetor rebuild, to include floats, and a complete brake system flush. As mentioned, I would expect to find some weeping on the M/C.
1974 R90/6 built 9/73
1994 BMW R1100RS
1964 T100SR Triumph
1986 Kawasaki Concours

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George Ryals
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Re: How to Wake Up a 1975 r90/6?

Post by George Ryals » Fri Jan 05, 2018 12:23 pm

I would suggest dropping the oil pan to clean out sediment before running the engine up to operating temperature.

Cranking and running the engine for 5-10 minutes doesn't evaporate moisture from the oil, so it has been accumulating for 25 years making goop in the pan.
Smile it's contagious!
'74 R90S, '67 /2 Conv w/sc, '66 R50/2
'74 Harley FXE, '72 Harley FLH w/HD sc
'69 BSA 441 Victor Special, '74 R90/6 Basket case
'85 R80RT wreck for parts

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Steve in Golden
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Re: How to Wake Up a 1975 r90/6?

Post by Steve in Golden » Fri Jan 05, 2018 1:20 pm

What they said.

Welcome aboard Eatinbugs!

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Zombie Master
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Re: How to Wake Up a 1975 r90/6?

Post by Zombie Master » Fri Jan 05, 2018 8:12 pm

George Ryals wrote:
Fri Jan 05, 2018 12:23 pm
I would suggest dropping the oil pan to clean out sediment before running the engine up to operating temperature.

Cranking and running the engine for 5-10 minutes doesn't evaporate moisture from the oil, so it has been accumulating for 25 years making goop in the pan.
Best practice!

Check sump screen while you're in there.
Last edited by Zombie Master on Fri Jan 05, 2018 10:29 pm, edited 1 time in total.
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SteveD
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Re: How to Wake Up a 1975 r90/6?

Post by SteveD » Fri Jan 05, 2018 9:55 pm

Willkommen.
The pan bolts require just a tad of torque past finger tight.
Cheers, Steve
Victoria, S.E.Oz.


1982 R100RSR100RS supergallery. https://boxerboy81.smugmug.com/
2006 K1200R.

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Zombie Master
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Re: How to Wake Up a 1975 r90/6?

Post by Zombie Master » Fri Jan 05, 2018 10:29 pm

SteveD wrote:
Fri Jan 05, 2018 9:55 pm
Willkommen.
The pan bolts require just a tad of torque past finger tight.
This true, and just use grease to seal the gasket.
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Rob
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Re: How to Wake Up a 1975 r90/6?

Post by Rob » Fri Jan 05, 2018 11:18 pm

And the new gasket will compress and you will need to recheck the torque.
Rob V

Wobbly
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Re: How to Wake Up a 1975 r90/6?

Post by Wobbly » Sat Jan 06, 2018 7:08 am

Welcome to Airheads !! No clue as to what your location might be, so it's not clear if you have another 3 months sitting around and tinkering (Michigan), or seriously ready to ride right now (Arizona) ?

In the intervening time some things have drastically changed... fuel for the worse, and oil for the better. These are changes akin to "night and day", and are going to drive some rather mandatory maintenance items....

• Fuel and the effects of leaving old fuel in the system is going to be your Number 1 issue. You're going to want to dump ALL the fuel in the tank and carbs ASAP. The bike may start, but it's not going to run very well without new high octane fuel. Not just any fuel, you're going to want to research Top Tier fuels ( http://www.toptiergas.com/ ).

• Run time on the older fuel has probably damaged the spark plugs. Having a new, spare set of NGK BP7ES around would be wise.

• You'll also need an additional fuel cleaner and conditioner for at least the first year. I highly recommend Star-Tron. ( http://www.starbrite.com/item/star-tron ... e-additive )

• Oils have vastly improved, but most oils are not suited for older engines, so you need to study before you leap to buy. You should be running a 20W50 oil in the engine, API rated SF or SG, like Valvoline VR-1. If it's cold, or for short term use (like your first ride), you can use 15W40 API rated CJ-4 diesel oil. The dipstick is NOT screwed into take the level reading. I seriously doubt you need to drop the oil pan, just drain the sump and refill. Due to the age of the oil seals, it's always best to use non-synthetic oils at first.

• The gearbox, drive shaft and final drive all use the same type "gear oil". Any name brand, non-synthetic oil will be fine, such as Valvoline 80W90. You may wish to buy a baby bottle or other small marked container to measure the 150cc for the drive shaft.

• DOT4 brake fluid has a maximum life of about 5 years, and ideally should be replaced annually. Therefore your front brake system (about 70% of your total stopping power) will need extensive inspection and fluid flush before hitting the road. Your front brake master cylinder and reservoir are tucked under the fuel tank. Even after the bike is being ridden (and brakes heated), due to the extended storage, I would highly advise at least 2 more complete fluid changes.

• Your tires are not going to be road worthy after such an extended storage. Consider new tires and tubes on both wheels before riding. You can use the "vintage" tire sizes of 3.25-19 front/ 4.00-18 rear, or the newer metric sizing of 100/90-19 and 120/90-18. There are numerous brands that offer excellent tires in these sizes. The minimum tire is probably the Bridgestone Spitfire S11. Avoid Shinko.

• Mice have a long history of nesting in BMW air filter housings. "BMW" is German for Bivouac Mice over Winter, or something to that effect. Anyway, at some point for a performance improvement, you'll want to pull the LH air filter cover and remove all the straw and chewed up paper.

Hope this helps.
After 20 years as a professional bike mechanic and 30 years as an engineer I know just enough to be dangerous !

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