Questions about correct twin turbo+carb set up '85 GL1200

[robin1731]

Wrong part. The shaft that comes out of the engine, that the propshaft slides on to. That is the one that needs changed.

[gearhead4207]

sorry just got back here robin knows a lot more about that then I do the person you really need to ask is kinda under the weather right now cyborg has done one or to of these I think. robin is good

[robin1731]

ericheath has done the 1200 swap too. So he'll know exactly what needs done.

[ericheath]

I've posted this before and somehow it didn't come on the site. The 1200 will slide in pretty easily, but it may hit the rear frame near the stator. Front cover may hit the frame on the right side. The shaft that is protruding from the rear cover needs to be swapped in order to mate with the 1000 shaft. The carbs are very tight fitting in the frame.

However, if I had a 1200 I would not put it in a 1000. The 1200 as good gearing, sits lower and is longer. With the 1000 rear end, it is very tricky taking off as it is geared very very low. Mine has a 140/80/18 rear tire and it revs about 3500 at 60 mph. I did it because I picked up a 1200 for $120, and to experiment with putting the 1000 heads and cams and carbs on the bike to see what it would be like. As stated, I believe it has increased upper RPM horsepower. With 75 to 77 cams and valves, I think it is safer to let it rev a little higher than a stock 1200 it seems like it wants to do that.

If you want a little more power from a stock 1200, just swapping the heads and cams and a carb swap of some type, will probably give you a good but different kind of bump in performance. Some feel performance on the bottom end and torque in particular may suffer from the swap, but I feel it has tons of torque still. It does have the longer stroke. That I think is where the extra bottom end torque is from.

Joe Drum did the same swap and has slowly put a 1200 final drive back on his 1000. Like me, he felt it had too much jerky response in first gear. It was fun, but when I took my wife along, I used second gear to take off.

I have another 1200 to play with someday, and I think I will put it in an 83 1100 frame and use the 83 1100 heads and cams, probably not carbs. The gearing is more in the middle of the two other bikes, and the 1100 cams are designed for more low-end torque. It has the same size valves. I am curious as to whether it might make a better overall performing machine. Maybe this winter I will get to it.

[wingrider]

Sorry to cut in here, but Eric, we know you have to change the output shaft when going to a 1200 in a 1000 frame....do you need to change anything going to a 1200 into an 1100 frame? I have the 1200 ready to drop into my 77, but thinking of using the 1200 EFI in an 1100 frame instead.

[ericheath]

Since the 1100 has a circlip on the output like the 1000, I would think it does. When guys put 1100's into 1000's I think it's a straight swap. The drive shafts will go on the 1200 output shaft, but won't stay without the circlip. Joedrum tried using the 1200 without the circlip and said it will come off on you. Iirc. If you could come up with a different way to hold it??? Swapping the output isn't bad and gives you a chance to check the clutch out.

[wingrider]

Very true...gives you a good look at everything back there. Haven't yet gotten into an 1100, so I didn't know what to expect.

[ericheath]

I'm curious how the somewhat tamed cams of the 1100 will do on a 1200. I think the 11 and 1200 each had beefier u joints. The gearing of the 1100 might be well suited for it.

[wingrider]

The gearing would be a happy medium...the 1000's ran a 3.40 stock, the 1100's have a 3.10, and the 1200's have 2.83.

I am going to run the stock heads on the EFI engine, but go with 1000 heads on the 77.

[ericheath]

You also have to factor in that the 1000 had a 17" tire, the 1100's had 17" and 16", and the 1200 had 15" tires. So the actual ratios are closer than you might think. They also played around with the secondary gear reductions as well.

[wingrider]

Yes they did play with secondary gear reduction. What I failed to do when I parted out the 1200, was to measure total tire height to see if they played with rim size, but overal tire height was similar. Guess I could look up tire sizes and figure it out.

[ericheath]

83 had 140/90/16, while 1200's had 150/90/15. Pretty close. 25.92" to 25.63"

[wingrider]

I figured that 1200 wheel I pulled off and sent to Gord was about the same height as the Lester I have on the back of my 77...being I used the same box to have both shipped. . Will say the Lester was a lot heavier!

[gearhead4207]

I put 77 cams in my 83 1100 and it ran good but my stock 82 would out run it . I think this is because the 83 was higher geared I know tire size was different on the rear.

[ericheath]

Lesters were 16" and 18" for rears. I don't think they made a 15" or 17".