250 carbs onto 200

[HomerDodd]

Just wondering if dual '84-85 XR 250 carbs will work for better performance on the smaller XR200?  I don't want them to be too big as that could negatively affect performance. Thanks.

[Chuck.]

Which year XR200R?

[HomerDodd]

30 minutes ago, Chuck. said:

Which year XR200R?

'85 XR200 RFVC. I think the 250 carb set would mount directly, but have larger throats, slides and jets. Thanks !

[Chuck.]

Yes they should fit, don't know about the bell size so may need the 250 air boot. And jetting is different.

[zrxer]

Yes, they'll bolt on and run. I did the swap about 10 years ago. The 200 carbs had some superficial damage so I threw on a set of ebay 250 carbs. Didn't spend any time jetting them, just put them on as-is. Seemed to run fine but I know it probably would have benefited from some jetting and tuning.

[HomerDodd]

5 hours ago, zrxer said:

Yes, they'll bolt on and run. I did the swap about 10 years ago. The 200 carbs had some superficial damage so I threw on a set of ebay 250 carbs. Didn't spend any time jetting them, just put them on as-is. Seemed to run fine but I know it probably would have benefited from some jetting and tuning.

THanks !! Any low or mid range power increase that you recall?

[Chuck.]

The last time I rode a twin carb back to back with an equivalent single carb bike was back in the nineties for the 250Rs and back in the eighties for the 200Rs.

[zrxer]

1 hour ago, HomerDodd said:

THanks !! Any low or mid range power increase that you recall?

Unfortunately I can't really give you a comparison because I never really put any time on the bike with the stock carbs. I just remember thinking it was pretty fast for a 200cc 4-stroke.

[Chuck.]

4 minutes ago, Chuck. said:

The last time I rode a twin carb back to back with an equivalent single carb bike was back in the nineties for the 250Rs and back in the eighties for the 200Rs.

Have said that I owned a 87 XR250R with a 84 twin carb engine, and rode RFVC 200Rs belonging to a friend. The twin carbs provided smoother throttle response at low speeds and lots of top end power, just like a four barrel carb on a car. The RFVC 200 had more power than a 2 valve 200, and a broader power band, but was a bit softer on the bottom.  The RFVC 200 was a better bike for climbing mining tailing piles because of its more and broader power.  However for trail riding I preferred the 2 valve motor. My XR250R was way faster than my 200 but weighed a lot more.  At that time I also had a RM Full Floater chassis with a modded XR200R engine, and it was a far superior bike for Enduro competition, mountain trail riding, and hill climbing; we called them Billy Goats. The twin carb models do need non stock jetting for best performance and engine life.  But time marches on and I prefer today's bikes.