New Zongshen RX3 (ZS250GY-3) Dual Sport

[Weldangrind]

Oldqwerty, you continue to tease us about your awesome TW's, but you never show us pics. Can you provide links to build threads on the TW forums?

I'm planning on a TW special, and I'm currently gathering parts for it. It will be in addition to my trusty TW dual sport.

[oldqwerty]

Originally Posted by Weldangrind

Oldqwerty, you continue to tease us about your awesome TW's, but you never show us pics. Can you provide links to build threads on the TW forums?

I'm planning on a TW special, and I'm currently gathering parts for it. It will be in addition to my trusty TW dual sport.

1) I don't do pics. I carry an ancient phone with no camera because it fits in my pocket and hasn't broken. I've bought 20 or more digital cameras over the years and they just get destroyed, lost, or stolen.

2) I'm very limited on upload speed and bandwidth with this wireless ISP in the truck. It usually takes an hour or more to upload a single picture to photobucket, IF I can get photobucket to load before timing out. I only get 10 hours between work days, and I sleep 8 of those.

3) I have ADHD, a very severe case. I get hyperfocused on a project, say, building an engine, and I block out every distraction, say, taking pictures. I work alone in a closed up shop with the mp3 player knocking techno instrumentals to drown out audio distractions. I intended to let my daughter take pictures while I worked--she was really good about staying out of my way and staying quiet while I worked--then sit down after each work session and let her type up the captions. No daughter, no pictures.

4) The TW builds ended up being therapy mourning my wife and daughter. Taking pictures for others' pleasure was at the bottom of my list of priorities. So much so I actually bought a camera and accessories to take pictures of the 267 build, then gave the camera, still unopened, to my son for Christmas two years later. I didn't even document the part numbers and sources I used so if anything ever breaks, I'm screwed. Due to the mental state of mourning I can't even remember the basics of what I did, like the bores and strokes of the engines or the tooth count of the sprockets.

5) Almost every mod on both bikes was stolen from someone else's ideas on the internet. The rest was just common sense and basic engine building. There are no secrets. Asian markets have a booming population of well built TWs. How many how-tos for 6-speed conversion, retrofitting the kicker, stroke, bore, headwork, etc., do we need? No need for me to create another. The only secret about finding out how to do these mods is to realize most anything done to a XT225 or TT230R engine can also be done to a TW. Lots of XT225 stroker builds at adv. xr100.com actually built TT230R engines up to 250cc and ~30hp and a carb and exhaust could be had with the kit. The 276's top end is VERY similar to the maxed out 250 engine from XR100.com because I bought a TT230R xr100.com engine off eBay and reverse engineered it, then added a tweek or two of my own., like a stroker crank and reverse cone megaphone exhaust.

5) The only trick parts are the EFI on the 267 ( http://www.useasydocs.com/index.html ) and the exhausts, which use the same tuning technologies as stock but are sized to cooperate with the other engine components that are carefully matched to insure everything works together to:

A) provide on the 267 a broad powerband that matches stock output at idle and enhances that TW puttability. You can be chugging along below idle in 6th gear (about 9mph), whack the throttle wide open, and the bike will smoothly accelerate to a top speed of 84mph. You see, the whole purpose of this build was to improve upon the highway capabilities of a loaded TW without ruining the stock TW character. At most any given road speed you can be in any of three different gears and it won't make much difference.

B) provide on the 276 all the peak power that can be had from a TW200 engine, the heck with the low speed and mid range. The powerband is so narrow I doubt the 4-5 shift of the stock TW trans would stay in it. If you are not in THE right gear when you whack the throttle, you aren't going anywhere. 91 octane (R+M)/2 required.

None of this is secret, even the exhaust tuning math can found on the internet. Fifty years experience building engines makes it a little easier for me, but EVERYTHING one needs to know is out there, free for the taking.

Just an FYI, I used a DT350 spark arrester to keep the 267 legal in national forests. No spark arrester on the 276. It's street only.

I've had all three of my TWs on a number of dynos. The stock bike properly jetted makes 12.7 to 15.0 hp and 9.8+ft/pounds. The 267 makes 19.9 to 23.5 hp and 15.3+ ft/lbs. The 276 makes 26.8 to 30.1 hp and 19.1+ ft/lbs. Depends on the dyno, ambient conditions, fuel quality, who is operating the dyno, how much air is in the rear tire, etc. E10 will cost you 15-20%.

Word of advice: Do not expect a ~25+hp engine to actually work with the wide ratios of the stock TW trans. Ain't gonna happen. Use the TT-R trans on a remachined TW countershaft. The 2-3 gap of the TT-R trans is a lot smaller than the 2-3 gap of the XT trans, about 4/5 the rpm drop. All the other gaps are about the same. In fact, 3rd through 6th are the same parts on both.

Also, don't do either engine build without sorting the brakes and suspension first. With so much more power and speed the stock brakes and suspension are inadequate.

There! I've given you all my sources. Happy hunting!