91 Xr600r Q

Does the 90 XR600R have a single carb or the dual carb setup?

What is involved in putting a rear dics brake on a 90 XR600R?

Do I have to swap to a rear disc XR swingarm?

Is the 90 drum rear brake XR600R a steel or alumiminum swing arm?

What is a good jetting setup for a stock 90 XR600R with the airbox opened up? Sea level riding.

91 has a single carb, it comes from Honda with a rear disc brake, aluminum swingarm. The 91 also has the cartrigde forks. If the bike your looking at does not have all these items, its not a 91 XR. Might be a XL?

The 1990 has an alloy swing arm, mine is a 1990, im not sure of the jetting but man it goes hard, the water cooled 650 struggle to match its grunt. Great old thumper, i hate the susspension on it but i will be going for a 450 soon.

i thought 91s had the old non cartridge forks with the different diameter axle, then in 92 they switch to the newer style until they quit making them, but i am not positive,

What follows is not mine, I copied and pasted it from the web site at the bottom of the post. The link would only take you to the site, not this article. Thats why I did it this way.

Anyhow I think its accurate

Here's a brief chronology of the big XR's. It seems that they only make

significant changes every 3-4 years:

1979 (or '78?) - XR500 introduced. Dual shocks on rear. 7-9" travel

each end. Honda's first pure dirt 4-stroke. Somewhat heavy, but

good handling with stiffer springs. Drum brakes at both ends.

Funky 23" front wheel for the first couple of years.

1983 - Single shock rear suspension. Front disk brake. Approx 11"

travel both ends. Dual carb setup. I owned a 1983 for about 6 years

and really liked it. A little heavy, but stiffer fork springs made

it a nice handling bike.

1985 - Displacement increased to 600cc. Little else changed.

Bigger displacement added quite a bit more torque. '85/86 models

had some problems with 3rd gear breakage.

1988 - Nickasil cylinder, single carb, and stainless steel exhaust.

Weight decreased about 10 pounds over the '87. Rear wheel changed

from 17" to 18". The decompression mechanism was changed from a

kick starter actuated system to a cam speed actuated system to

prevent the nasty kickback of earlier XR's.

1991 - Cartridge front forks (still too soft) and disk rear brake.

1992 - Unchanged except for larger diameter front axle

1993-97, little or no changes.

http://www.justxr.com/justxr.html

"What is involved in putting a rear dics brake on a 90 XR600R?

Do I have to swap to a rear disc XR swingarm?"

Obviously if you find a complete rear swingarm assembly from a 91 or later that would be the easiest way. The 91 frame has a welded on tab where the rear master cylinder mounts. Your 90 won't have that.

The pivot point for the rear brake pedal is different also.

If you decide to go through with the swap, I have a frame from a 91 XR6. You could swap all your stuff on to it. Or rob the master cylinder bracket and measure the pedal pivot point. $50 bucks, you pay shipping.

I also have a complete rear brake assembly from a 91 CR250 (pedal, master cylinder, hose, rear caliper and caliper bracket) $75, plus shipping.

The CR pedal is made of alum. where the XR had steel. Other than that I believe they are very similiar.

All this is of course you do buy it, and want to convert it.

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