R100R vs R100GS power?

[MattW]

Sorry guys another numpty question

I've just discovered (I think...) that the R100R had a lower power motor than the GS variant (60hp vs 70hp).

Could anyone confirm whether this is in fact true? - The GS hybrid I'm considering buying is based on a '92 R100R and as I wish to use it for two up touring, that missing 10hp could be important...

cheers
Matt

 

[John Armstrong]

One source of info: http://www.bmbikes.co.uk/bmwmodels.htm

I'm sure I've seen the specs in a table format, can't find it at the moment though

 

[Jon P]

The R100R and the R100GS are identical except for the rear silencer. I have had each model and can confirm that they both perform the same.

The 70hp motor that you refer to were the most powerful factory motors that were fitted to the older (twin shock) R100RS, R100RT and R100CS. These motors were higher compression and were last made for model year 1983. When BMW reserected the 100 airheads (monolevers) in '86 they reduced the output in an attempt to meet new emissions.

There was a book recenty published about the R100RS and in it there are several tests comparing the R100RS (twin shock 70hp) and the re-introduced R100RS (monolver 60hp) and the results were interesting. It revealed almost idential performance with the lower output later bikes having better flexibility and better mid range performance. Yet again, proof that the higher output motors only show difference at the top of the rev range.

I know over the years some people have converted their GSs to the spec of the higher output motors and one chap I knew even fitted a K1 rear ring gear set to raise the final drive ratio.

Anything is possible - I wonder if someone has confused an R100R ('91-on) with an RS, RT or CS ('81 -'83)?

 

[MattW]

Thanks for the replies guys. The information provided by both of you agrees perfectly.

The '70hp' information was from old post on here - I assume as you say Jon, that the poster must have confused the older mono GS with the para. Just shows that jumping to conclusions on the basis of what you read on forums isn't always a great idea

thanks again
Matt

 

[Rob Farmer]

Of course there's nothing stopping you fitting higher comp pistons, a high lift cam and larger inlet valves to a GS. I fitted a 70BHP engine into my Monolever g/s and scared the bejesus out of myself. The standard motor soon went back in

 

[Beemerboff]

Some of the GSs had the high compression motor, with a reputed 70 HP, and places like Moteren Israel have high compression pistons to suit if you feel the need.

But peak horsepower figures dont tell you much - it is the torque figures that count, and I can assure you that the low compression motor has plenty of that.

It pulls much better and feels more power full than the new F800GS , and BMW claim 86 hp for that.The F800 may have 86 hp somewhere, but not any place you are likley to use it in normal riding.

Handles better and has a lower wet weight than the F800GS too--------.

 

[MattW]

Rob, Boff - thanks for the input

I certainly feel no need for more power than a standard 100GS (many people have already attested that the GS is more than capable of any two up touring I may care to do) - my concern was more that the 100R had less than the GS and hence might not be as suited to two up use

thanks again
Matt

 

[Jon P]

Thanks for the replies guys. The information provided by both of you agrees perfectly.

The '70hp' information was from old post on here - I assume as you say Jon, that the poster must have confused the older mono GS with the para. Just shows that jumping to conclusions on the basis of what you read on forums isn't always a great idea

thanks again
Matt

The confusion won't be with the momo GS and paralever, as the monolever GS was only ever an 800. The 70hp motors were from the road bikes with twin rear shocks.

 

[Jon P]

Some of the GSs had the high compression motor, with a reputed 70 HP, and places like Moteren Israel have high compression pistons to suit if you feel the need.

But peak horsepower figures dont tell you much - it is the torque figures that count, and I can assure you that the low compression motor has plenty of that.

It pulls much better and feels more power full than the new F800GS , and BMW claim 86 hp for that.The F800 may have 86 hp somewhere, but not any place you are likley to use it in normal riding.

Handles better and has a lower wet weight than the F800GS too--------.

I have always said that 'numbers on paper' don't translate to 'real world power' Though, the higher quoted powere outputs do tend to show up with top speeds.......but then are we really that interested in those these days.

My recollection of the R100s that I had (including, GS, GSPD, R, RS etc) was that it was a delightful power unit with lovely flexibility (and bags of charm)and the need for no more than five gears. My current 1200GSA may be quoted as a 100hp and sure, when I wind it up it goes but it does seem to be a bit flat and in need of a couple of down changes before good overtaking power is reached.

When I get back to the UK in the next few months I am going to go and find another R100 - can't wait!

 

[Rob Farmer]

Matt,

It wasn't this old post of mine was it? http://www.ukgser.com/forums/showthread.php?t=118141&highlight=70bhp

That engine is the 70BHP one I Fitted in my Mono for a week or so. It's a 1981 engine and lives in a bike thats now owned by shapeshifter.

 

[(RIP) Proff]

Spot on Rob.
All the 70 hp engines were Heavy flywheel models[ pre 82]
My 90s is only 67 bhp
all the lighter flywheel 100's are 60 hp with very few exceptions.
[factory ride away ltd edition Black RS for instance ]

 

[MattW]

Matt,

It wasn't this old post of mine was it? http://www.ukgser.com/forums/showthread.php?t=118141&highlight=70bhp

That engine is the 70BHP one I Fitted in my Mono for a week or so. It's a 1981 engine and lives in a bike thats now owned by shapeshifter.

Nice bike

No it wasn't your post Rob.
I actually found one of 'Airfans' threads where he talkes about the building of the bike he now has for sale. In this thread he exchanged a few posts with another GS'er talking about the lower power....

cheers
Matt

 

[BillN]

The 70 brake twin shock RSs had a higher top speed, (maybe 12mph), than the monos RSs

The (later), mono RS had a different rear axle, (2.91 versus 3.00) ratio which made them VERY slightly faster, (less than one quarter of a second), over a quarter mile.

 

[smilee mark]

Matt,

It wasn't this old post of mine was it? http://www.ukgser.com/forums/showthread.php?t=118141&highlight=70bhp

That engine is the 70BHP one I Fitted in my Mono for a week or so. It's a 1981 engine and lives in a bike thats now owned by shapeshifter.

Bought back memories . I bought one of these in 83 thinkin BM are fck>>>nnn crazy to stop making this.. I thought if I buy one and look after it I will not lose any money... F,,ers started makin them again,,, it is still the nicest bike I have owned.and brings back the best memories . I took it anywhere...more to the point it went any where the gs would go.. maybe not as easy in places but a more comfotable ride to get there.. they were/are great bikes..