1976 R 75/6

[Bfish]

I have an opportunity to purchase a restored '76 R75/6 from a person I know and trust. Bike is being ridden. I've never owned a "vintage" moto before but am excited to get into them and become semi-proficient at keeping them running. Any advice, etc for this particular model I should be aware of? Thanks:D

[BIG AL]

Add fuel and oil as needed, don't be afraid to ask for maintenance advice, and ride, ride, ride.
I had 220,000 miles on my R75 motor before an unfortunate over-revving-at-the-racetrack-incident left me with a spun rod bearing. These things are tough.

[Bfish]

great answer! i can handle that.

[rocketman]

Not knowing what your ride now,I'd say one of the most important things to remember with an airhead, they LOVE RPM's, like the oilheads, below 3000 is lugging the engine. Above 3 grand and they are happy as a clam, plus it helps to keep the battery well charged since at below 1500-1300 rpm the alt. is not charging the battery, you'll notice the red gen. light come on, long as it goes out by 1500 everything is as it should be, but it still takes to around 2000-2200 before it is fully charging the battery.

Oh, and they just LOVE being ridden all day long, as often as you can spare, with plenty of revs!

RM
diehard airhead rider.....

[Bfish]

i ride a 2004 r1150rt currently. soundsl iek same rpm deal.

[sgborgstrom]

30 years of design between your R1150 and the R75 mean there will be some getting used to. Those 70's airheads are more...shall we say "agricultural" than the oilheads, a bit stiffer and clunkier and they have that (in)famous rubber-cow effect in corners. That said, I have a bunch of money invested in restoring the /6 in our garage just 'cause its so much fun to ride. You can also tinker with it in a way that your 2004 ride just doesn't allow.

One of the beauties of riding an old bike is how much more exciting riding within the speed limits can be. They just don't handle high speed as well as the modern stuff.

This could be start of the "dreaded" Multi-Bike-Syndrome. Not that there is anything wrong with that, just make sure you have space to expand the garage when the time comes.

Steve
4 bikes in the "old" garage
prepping to pour the slab on an 1100 sq foot garage addition....

[James.A]

I have difficulty thinking of an R75/6 as vintage. It does have an electric starter. I helped a friend fix up an R75/6 earlier this year. A bike that I sold 14 years ago when I had a kid on the way. It had been subjected to several years of neglect, and it is astounding just how tough and forgiving those bikes are. He uses it as his daily rider and he has a total of about $2000 in it. A good investment in the context of $2.00 gasoline. He restores vintage Indians and I've seen him drop $2000 on a box of parts at swapmeets. BTW, it's the first bike he ever owned with electric start.

[flash412]

Originally posted by Bfish I have an opportunity to purchase a restored '76 R75/6 from a person I know and trust. ... Any advice, etc for this particular model I should be aware of? Don't believe the manual. The valves should be adjusted at 0.006" on the intake and 0.008" on the exhaust. You MIGHT go to 0.004" on the intake.

You need to check the valves every 1500 miles or so. This only takes about twenty minutes to do. For certain torque the heads and adjust them every 3000. That bike does NOT have hardened seats. When you find that the exhaust valves are tightening up every time you check it, drop to 1k. When you find them tightening up at 1k... pull the heads and get hardened exhaust seats installed (and new exhaust valves). That's LOTS better than dropping a valve.

[lkchris]

Originally posted by Bfish
i ride a 2004 r1150rt currently. soundsl iek same rpm deal.

Yes, same "old wives tale." Makes you manly, though.

Run it like any engine.

[James.A]

Kent, does it hurt an airhead motor to observe that 3000 rev floor for operating RPM?

Steve, I'd add on to my garage if I wasn't up against a zoning limit. Currently, I am looking at a somewhat distressed commercial building in town.

[sgborgstrom]

>Steve, I'd add on to my garage if I wasn't up against a zoning l>imit. Currently, I am looking at a somewhat distressed >commercial building in town.

I had to amend the deed to my house, swearing that nobody would ever use the space as "living quarters"- might have something to do with the actual house being slightly smaller than the finished garage/shop space will be.

As for the whole RPM thing, I just run it in the "sweet" zone and don't worry too much about the actual RPM.

Steve

[rocketman]

Originally posted by sgborgstrom
>Steve, I'd add on to my garage if I wasn't up against a zoning l>imit. Currently, I am looking at a somewhat distressed >commercial building in town.

I had to amend the deed to my house, swearing that nobody would ever use the space as "living quarters"- might have something to do with the actual house being slightly smaller than the finished garage/shop space will be.

As for the whole RPM thing, I just run it in the "sweet" zone and don't worry too much about the actual RPM.

Steve

Then most likely you never run below 3000 once moving, (cept maybe in stop and go, when you can't avoid it) as the sweet spot is deffinately above 3K!

RM

[James.A]

I gotta tell ya fellas, I have 3 bikes but only 1 working tach.

[lkchris]

Originally posted by woodnsteel
Kent, does it hurt an airhead motor to observe that 3000 rev floor for operating RPM?


That "floor" is realistically more like 2000 rpm, and even then only in higher gears.

OTOH, this is not to recommend 2000 rpm before letting out clutch to start from a stop.

Engines are like tires, i.e. the more miles the more wear. Revolutions are "miles" to an engine. A bike with 50K on the odometer at an average 5000 rpm has a motor twice as worn out as a bike with 50K on the odo at an average 2500 rpm. Yes, it hurts. PS: the first bike consumed a lot more fuel to go the same distance, too.

The point is, "dont' lug it." Or any motor. "Rev the bejeezus out of it" is NOT the opposite of lugging it.

[rocketman]

Originally posted by lkchris
That "floor" is realistically more like 2000 rpm, and even then only in higher gears.

OTOH, this is not to recommend 2000 rpm before letting out clutch to start from a stop.

Engines are like tires, i.e. the more miles the more wear. Revolutions are "miles" to an engine. A bike with 50K on the odometer at an average 5000 rpm has a motor twice as worn out as a bike with 50K on the odo at an average 2500 rpm. Yes, it hurts. PS: the first bike consumed a lot more fuel to go the same distance, too.

The point is, "dont' lug it." Or any motor. "Rev the bejeezus out of it" is NOT the opposite of lugging it.

I kinda doubt that there is a one to one ratio in so far as RPM's are concerned, and in the case of airhead motors you prob do more damage averaging 2500 RPM's than running it at avg. of 5000. I know of very few folks (if any) who would recomemd running an air head at 2500, not to mention at that RPM, even in top gear you'd prob never get over 45 mph! And consider that at 2500 they don't have much pulling power compaired to say 4000. Again running between 4 and 5 K will not hurt these bikes in the least, you can still get well over 100K with ease, asuming you do general maintenance on regular basis.

Most folks I know would say 2500 is lugging these motors.

RM

[James.A]

....and I think I am responsible. Let's hope Bfish is joining the ranks of airheads. The first I ever heard of the high rev boxer concept was from I guy I used to have work on my bikes. His theory was that low rev loading of a boxer motor promoted bottom end wear because of the opposed cylinders pushing back and forth on the horizontal plane. I think that there may be merit to the argument, but my thinking is that the relatively heavy flywheel mitigates the effect. I have re-trained myself to keep my bikes(airheads) in lower gear in town and saving high gear for highway use. The sweet spot on my bikes seems to be between 3k and 5k. High revving my R27 single only seems to extend the coast time between gears. My cage is a Subaru(4 cyl boxer) with an automatic transmission. At 55mph, the tach registers 2100 rpm, and just under 3k at 70 mph. Those motors can go 200,000 with proper care.

[bprigge]

Getting back to the original topic of 'what about those R75/6s?',
I would like to add my 2 cents worth.

I bought a 1976 R75/6 down in Los Angeles in July of this year.
The bike had 42K showing on the odometer and ran well, needed
cleaning up though. Two days later I set off on a 2700 mile
interstate trip to Minnesota via the northern route. The bike
had NO problems, in fact I set a personal one day distance record of 946 miles on the 3rd day out. I ran the motor between 4500
and 5000 rpm for three and a half long days.

Feeling very confident in the reliability of the bike I set off
from Minnesota to Olahoma City and back two weeks later.
The R75/6 ran great again going down and back EXCEPT that
it developed a valve seat recession problem on the way south.
The only symptom it had of the problem was that it would not idle
without a little throttle cranked in. The left exhaust valve had
lost all of its .008 clearance. I reset the clearance in Oklahoma
City and headed back WITH a normal idle but lost the clearance
again in southern Minnesota, this time the left exhaust valve
clearance was completely gone and the right side was down to
about .005 on the exhaust valve. Reset them again when I got
home and the idle was once again normal. That was the sum total of the bikes problems since purchasing it in July and
riding the heck out of it until two weeks ago when it got cold
up here. I'm planning on installing hardened valve seats this
winter after I'm really positive the riding seasons is over (deep
snow, frozen lakes) So I would say those R75/6 machines are
pretty sound bikes. Its a real treat to have a 'classic' as a
daily rider and not have to tinker with it every weekend to keep
it on the road.

Also, on the 'high revs' issue, I think lugging any
motor way down under load is poor practice because you get
minimum oil pressure and flow at low rpms, unless the motor
was designed to be 'lugged', as in old farm tractors. My Beemer
is happy as a clam at 5000 rpm, all day long.

Bruce from Minnesota