300cc Kit

[sqwert]

210 miles on the 300cc today.

Starts as easy as the 250.
EFI self adjusts with a few minutes of riding up to 6000rpm, as fast as I went during break-in.
Better throttle response idle through 6000rpm.
More power idle through 6000rpm.
Throttle less open speeds up to 65mph.
More compression breaking when throttle is closed.
68.57mpg, previous best 66mpg, past average about 62mpg.
Less shifting on curvy and hilly roads or in traffic.

So far very happy with improved performance on the paved back roads. Can't wait to complete break-in as performance is still improving with miles as parts break in.
Jump in fuel efficiency may be a fluke, but maybe not. Nice surprise.

Ride to breakfast in the morning, then fresh dino oil to complete break in. Then another couple hundred miles on the back roads. Looking forward to full synthetic Mobil 1 going back in. Mobil 1 was worth 3mpg over dino Valvoline way back when. A similar improvement over dino Valvoline this time will make 71-72mpg a reality. Sweet, what with the price of gasoline going up again.

[2LZ]

Originally Posted by ChondaChondaChonda

2LZ- I just recently purchased a GPX that has the NC250 with a carburetor. I have not even put gas in it yet - It's identical to the one in the picture above. I will be converting it to EFI and I will give you the carb if you'd like.

I'd love to try it but I'm afraid what wouldn't work if I tried the swap. Thanks tho!
My main concern with the EFI is that it seems to lean out in the high R's that jetting would handle easily.....
I can't remember the last time I saw a real trials tire on a bike other than the ones rotting on my old Yamaha.

[NzBrakelathes]

Originally Posted by ChondaChondaChonda

2LZ- I just recently purchased a GPX that has the NC250 with a carburetor. I have not even put gas in it yet - It's identical to the one in the picture above. I will be converting it to EFI and I will give you the carb if you'd like.

What EFI are you fitting? What is the cost etc?

[ChondaChondaChonda]

Hammered my big bore for 9 hours yesterday and 4 hours this morning. Absolutely flawless and it pulled everything I aimed it at. Lots of 2nd gear singletrack.


Lots of places it was bouncing off the rev limiter.



EFI is awesome when you ride lots of big elevation changes. This section of transfer road took us to 9818 today.

[NzBrakelathes]

I am off to the farmer bike flee market today - add some KM on the bike (FARK nose what you boys call MILES) the places is miles away so will ad around 65km today

[2LZ]

I'm not worried about chain life with our type of roads. I am defnitiely thinking of going back to the stock gearing all the way around tho. It would be nice to have a little longer legs now that it can pull from a stop without overly slipping the clutch.

[sqwert]

Originally Posted by 2LZ

I'm not worried about chain life with our type of roads. I am defnitiely thinking of going back to the stock gearing all the way around tho. It would be nice to have a little longer legs now that it can pull from a stop without overly slipping the clutch.

Good choice since you live right in the middle of millions of acres of awesome paved, desert, and forest roads. Those of us who are somewhat light weight and ride from home can get away with the stock ratio, and especially enjoy the midrange boost from the 300 kit out on the paved roads as long as you are careful about the single track.

When I ride that way I have to take home with me. Between altitude, luggage, and bones, even with the 300 kit I expect a couple more teeth will help.

Stock is borderline for startups on the nearly flat roads of home when loaded for travel. Once rolling, ratios are choice! Kind of like a sport bike.

You make a very good point about clutch life when rolling out of parking with a heavy load, big bones, and a steep grade. The 300 will help by reducing rpm at roll out, thus less slipping, but I'll still be planning ahead for the most gentle roll out before parking. The RX3 trans is very different from the TW stroker engines with XT transmissions that I am used to, so I stall a lot. Old habits.

[NzBrakelathes]

Yesterday I did a trip to the Meishan/ a county of that city DMV to transfer my bike to Shuangliu an area of Chengdu and all went well.
300 kit really has little need to rev the living shit out of it, just roll on some gas and away you go etc.

I do have no charging on my bike and few other issues to iron out but at least the bike is in my legal (Be it my Chinese) name etc

was 90Km to the Meishan DMV then 90KM to Shuanliu DMV then 15KM home.

I have the 14 tooth front sprocket and I am sure stock rear, so stock gearing and pulls just fine and in fact maybe a slightly taller gearing wouldn't be a bad thing to reduce the 100KM/PH RPM from around 6000RPM to a little less.

There are only a handful of non Chinese with legal bikes and licenses here and I hate that as all things with effort can be done correctly and with good reason
But that is another story

[sqwert]

Roll on and go pretty much sums up bm impression of the 300 kit, too. When first installed it seemed the 300 kit with no break in, with dyno oil, behaved about the same as the 250cc with a good break in with Mobil 1 synthetic. Now, with a few hundred miles (~685km) break in the 300kit is definitely stronger up to 6000rpm. That is what I wanted. I expected the lack of low and mid range with the OEM displacement was due to a well-flowing air/fuel mix in the top end. That is the price one pays for a 25hp 250. Only turned it faster once and was too concerned avoiding speeding compensatory trucks to note how high it pulled. Pulled well enough to keep me out from under a pipe bumper/grille guard.

Note that the horsepower and torque peaks claimed for the 250 are 9000 and 8000 rpm respectively. I noticed the engine at 250cc did not quit pulling at 9000rpm, but kept right on going a bit more. That is why I chose not to mess with the ports when installing the 300 kit--the power peaks would be more useful for me if they were a bit lower, and so far things seem right. After a few hundred more miles (800km) break in, and a switch to Mobil 1 synthetic, I'll reevaluate the power band and decide what, if anything, I'll do next. If anything, probably just free horsepower mods like a low restriction intake as such mods increase efficiency AND power at no costs. Maybe a final drive adjustment. Too early to tell.

[2LZ]

Originally Posted by sqwert

Now, with a few hundred miles (~685km) break in the 300kit is definitely stronger up to 6000rpm. That is what I wanted. I expected the lack of low and mid range with the OEM displacement was due to a well-flowing air/fuel mix in the top end. That is the price one pays for a 25hp 250.

That is also exactly what I was hoping for. What was very disappointing to me with the OEM 250 (as I've said here a million times) was the utter lack of low end and mid range. It's a four stroke for Christ's sake! If I wanted peaky power, I'd bust out a two stroke and get far more peaky power for the CC's.
Even my old Honda XL250 felt like it had more low end and mid range than the RX3. Four strokes are supposed to be torquey. If they're not, it's like decaf coffee. What's the point?

[Weldangrind]

Interesting! I have a CB250 in pieces that I've never ridden; I just assumed it was a five speed like a CG motor. When I find it, I'll check into the ratios.

[franque]

Jerry - I don't know 100% if it will work, but I've had this one on the back burner in terms of something I want to get: https://item.taobao.com/item.htm?id=...A%22item%22%7D (sorry about the long URL).

[JerryHawk250]

Originally Posted by franque

Jerry - I don't know 100% if it will work, but I've had this one on the back burner in terms of something I want to get: https://item.taobao.com/item.htm?id=...A%22item%22%7D (sorry about the long URL).

Thanks, would just have to verify all the dimensions.
Opps, Sorry for getting off topic. Thought I was on a different thread.

[Juanro]

Hi,

My kit has just arrived. I haven't installed yet.
Here there are some pictures and the unboxing video:



Regards

Juanro

[Juanro]

Pics