GPZ1100 B1/2 is it just a Z1000j?

[malmojoe]

just trying to get the model differences a bit clearer in my mind. Is the GPZ1100 (b1-2) built from the Z1000J? Are the frames the same, engine interchangeable etc.
What about the tanks/panels/tail?
Could you put a unitrack engine in a J and is the unitrack the best engine for a street special?

thanks for input.

[ADRIAN H]

Shamelessly pinched from another forum.

The GPz1100B1/B2 tank is pretty much the same as the Z1000J, Z1000R and Z1100R tanks, same goes for the side panels seat and seat unit. The later GPZ1100 unitrak motor has 18mm pins instead of 17mm pins, larger valves and different valve angles, the combustion chamber is a different shape, you can fit a unitrak head onto an early motor but you can't fit an early head on a late motor as the pistons will kiss the head as the later pistons are a different shape on the crown. fitting the late head on the early motor will also lower the compression, and the valve cutouts on the piston crown will also need looking at, especially using high lift cams.
The Unitrak cams are the highest lift of all the J series engines. The clutch on the late motor is a 6 spring job whereas the earlier are still 5 springs, as the earlier Z1000A motors. Gearbox bearings are different, you can swap boxes but it's not a straight drop in and requires work. The Z1100 shafty is the same basic motor as the GPz1100B1/2 just the outputshaft and bevel box need swapping to convert from shaft to chaindrive.
I've got a later 18mm pin crank and 1170 pistons and head on my Z1000J motor.
You can convert the later motors to run a Dyna S ignition system but you need to use the ignition housing from the earlier motor, and the mechanical advance assembly of the earlier motor.
Injection systems on the GPz1100, and GPZ1100 can be problematic, but many have been swapped out for carbs, from the Z1000J or flatslides.
I'm building an 1170cc draw through turbo GPZ1100A motor for someone at the moment.

[tlc]

There are a few extra brackets on the GP frame for oil cooler etc.
The GP tank is slightly wider at the front mounting point and has a little less capacity? but otherwise fits no problem.
The Uni motor goes straight in.

For the best special use a J frame and tank with Uni motor. (Incidentally, what I am doing)

[Ginger Bear]

My old 'J' framed Uni-trak engined special.

Motor goes straight in, you just need to modify the sprocket cover, or fit one from a 'J' or B1/2.

[malmojoe]

All good news, thanks oh great ones. LOve your bike Steve.
So here is what I'm thinking - from excess parts around my junkyard - sorry - workshop.
Ive got a MkII engine, Z1R tank, panels and screen,. Have found a cheap B2 frame with a log book - not bought yet. Throw it all together and see how it looks

[Ginger Bear]

MKII motor will need new engine mounts. Top rear is the same, so bolt it in there & work out the rest.

[big green bus]

THE Z1R tank will not fit without a hammer and has different mounting points the B1 tanks petrol tap is in a different place to the others

[malmojoe]

so that's not gonna fly. If I buy the frame I'll need a new engine and tanks

[Big Fluff]

Chris (TLC) is doing the same as I have done... Z1000J frame and GP engine.
Though my engine is only a B1, it's got unitrak cams in.
Complete front end is ZR750, Metmachex swinger and ZR rear wheel.