750 triples with 850 frame?

Is it ok to use 750 triples with an 850 frame?

It appears that is what my project bike has, although I'm not really sure about the frame. The part numbers on the yokes (NM 061916 lower, NM 061917 upper) would seem to indicate they are from a 750, although my parts book gives the numbers as 061916 and 061915 respectively. I'm not sure why the upper number doesn't quite match or what the NM prefix is doing there. But the 850 numbers are totally different.

I recall reading that a steering geometry change was made on the 850 frame and that there was a corresponding change to the yokes. IIRC, using 850 triples on a 750 frame yields undesirably quick steering.

And is there a quick visual way to tell whether the frame is a 750 or 850 model? I couldn't find any part numbers on it. It has the late style sidestand mount but does not have the Mk3 seat mounting bracket so it seems to be pre-Mk3. But that's about all I can tell.

Onward into the fog,
Debby

debby said:

Is it ok to use 750 triples with an 850 frame?

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I think the general recommendation is no (NOC Service Notes etc.), for the reasons you have mentioned, all 850 yokes (triple trees) have *ANG* casting marks.

debby said:

And is there a quick visual way to tell whether the frame is a 750 or 850 model? I couldn't find any part numbers on it.

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You should be able to identify the frame type from the frame/VIN number? 850 models starting from 300000.

There should be a frame part number on the front face of the left-hand fuel tank mounting bracket? But these numbers are rather small and faint so could easily be missed or have been painted over. Is that where you looked?

I read the Notes as saying 'The factory said no, but we say 750 triples in 850 should be OK'. I have the same setup in bits so will be trying it out when I get round to restoring the bike.

kommando said:

I read the Notes as saying 'The factory said no, but we say 750 triples in 850 should be OK'.

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Debby,
The 74 (so *850*) frames also had shock absorber mounting plates that extended further back to strengthen the rear seat frame loop , so that would be one possibility as a visual check.

No ID plate and no numbers visible anywhere. The shock plates are not the extended ones, so that makes me think it's actually a 750 frame. So the 750 triples should be fine. Got lucky on that one I think.

Debby

Only the MK3's had the extended shock mount brackets, so an early 850 is difficult to identify.

Some late Mk11As had the extended gussets as well (late 1974 on) so that still leaves 1973 and early '74 850s.

I had an idea that the steering lock abutments changed but I can't find any documentation about it.

One possible clue (although it might have been changed as well) is the swinging arm. 750s up to 1973 just had a cross tube but this gained two triangulating gussets for the Mkv 750s and the 850s (Mk111 850 was of course different again).

kommando said:

Only the MK3's had the extended shock mount brackets

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The MkIII shock gusset plates are different again to both earlier types, in their shape and due to the MkIII frames having a mounting plate for the MkIII seat hinge, so a MkIII frame can be easily identified.

79x100 said:

Some late Mk11As had the extended gussets as well (late 1974 on) so that still leaves 1973 and early '74 850s.

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I'm not sure it was as late as that (1974 frames have a different part number).

Sorry L.A.B., we're slightly at cross-purposes here. I hadn't picked up on an earlier 850 gusset change and the frame numbers seem to have changed from year to year.

What I have seen are Mk11As with known provenance from the last few months of production carrying Mk111 rear gussets complete with hinge mounts. Presumably they changed over earlier than the motors !

79x100 said:

What I have seen are Mk11As with known provenance from the last few months of production carrying Mk111 rear gussets complete with hinge mounts. Presumably they changed over earlier than the motors !

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I certainly don't disagree with that at all.

Well, here's some more detail on my situation. As is often the case with me, it's a bit complicated :lol:

The project bike is a bitsa, and the frame appears to be from a 750, judging by the 750 triples and the unbraced swinging arm. But I'm replacing that frame. It was in poor condition - rear fender loop bent, sloppily repaired, and bent again, broken steering stop, thoroughly butchered sidestand mount. Nice powdercoating though :roll:

So I traded off the Kuhn bodywork for a new frame. A friend with a large parts stash had an NOS frame hanging from the rafters collecting dust. The guy he got it from told him it was a factory replacement frame of the 850 variety, NOS and never used and all that. I have no idea if that's really true - the guy was kind of a sleazebag - but it's a very nice frame. It sounds like it could be either an 850 frame or a late 750 frame. In any case I think it should work well for me. It's just the basic frame so I'll use the swinging arm, cradle, and triples that came with the project bike. Those parts seem to be in good condition.

One thing I noticed about the new frame - the mounting holes for the coil bracket are slotted. I've never seen that before. I don't know if that means anything though.

Debby and the mystery bitsa

debby said:

It sounds like it could be either an 850 frame or a late 750 frame. In any case I think it should work well for me. It's just the basic frame so I'll use the swinging arm, cradle, and triples that came with the project bike. Those parts seem to be in good condition.

One thing I noticed about the new frame - the mounting holes for the coil bracket are slotted. I've never seen that before. I don't know if that means anything though.

Debby and the mystery bitsa

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Debby, do you have this bike going yet?
Are you still planning to use/using the '750' triples with the ‘850’ frame?
I am interested as I have what is supposed to be an original 1974 850 (VIN 312XXX) with triples that do not have the ANG cast in the bottom.
I’d be interested how it handles. I rode my 850 bike for ~3yrs around 1989-1992 but did NOT have handling problems, EVER.
Other problems came from the DPO on the other hand...
so it became a basket case.
This frame is a ’74, but the frame part number is 06-4140, a narrow frame loop and with a braced swingarm. I need to dig out the original VIN plate (took it off years ago for frame painting) and check that stamp.
Also, years ago I picked up a spare frame at a car swap meet. It is definitely a 1975 850 (VIN 328XXX date stamp 2 75) with ‘extended’ shock brackets, a wide rear loop but round ign coil mount holes.
Go figure..

teeb said:

Debby, do you have this bike going yet?
Are you still planning to use/using the '750' triples with the ‘850’ frame?

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It's currently in the early stages of reassembly. I didn't get a lot done on it over the summer, and there were some complications as always, but I've started working on it again. It will be a winter project.

I am planning to use the 750 triples with that frame. There would be one degree of extra rake, but I don't think that will be a problem. It might make the steering a little slower but that should be ok.

I have a lot of work to do before the bike goes out on the road, but I'm planning to have it running by spring, or maybe a little earlier if all goes well.

Debby

Got the same problem

The other day I pulled the fork gaiters up and found wear and rust on both stanchions, so while waiting for new stanchions, bushes seals etc. to arrive I decided to paint the triple clamps and check the steering head bearings. I found that I have a 750 top clamp and stem and a "ANG" 850 bottom clamp. I have found so far, parts from at least five different models in this bike. I just ordered a new 750 bottom clamp, while I am waiting for it to arrive I want to remove the steering lock and strip and re-panit the top clamp, can anyone tell me how to remove the lock from the top clamp.

Thanks
Graeme

On my bike the lock just pushed out with a socket of the proper diameter. It was stuck in with some loktite type stuff. To replace I just tapped it back in. It's like a taper fit.

Thanks Irutt, I tried that and it came out pretty easy.

Graeme

Yup, mine came out easily too.

Since this old thread came back to life, I might as well post an update about the 850. I'm calling it the Anti-Cafe Project. Lots of guys buy standard bikes and turn them into cafe racers. I'm doing the opposite - I bought a cafe and I'm putting it back to stock!

It's currently in the final stages of assembly. The last major task remaining is wiring, and there are also a number of small jobs remaining to be done. Progress has been slow because I haven't had much time to work on it, usually only four or five hours per week. Still, I'm hoping to have it snortin this month, possibly at our club's Spring Tech Day, which is just two weeks away.

I'll try to post some photos when I get a chance.

Debby

Drive the lock out from the underside with solid drift. It helps to soak it in a good penetrant like Kroil first.

Re: Got the same problem

graeme-in-oz said:

I found that I have a 750 top clamp and stem and a "ANG" 850 bottom clamp.

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I'm slightly surprised the forks actually fitted both yokes due to the dimensional differences between the parts? With the fork stanchions fitted to the 850 lower yoke the stanchion tops ought to be out of square with the tapers in the 750 upper yoke, I would have thought?