Kind of strange, I've got 220 miles on mine and haven't done any of the exhaust/air mods yet, except for a new iridium spark plug. I was able to hit 55 with no problem (before new spark plug, still had some left in it too, wasn't going for top speed). I weigh 192 lbs. Also keep in mind the speedo is a few mph below your actual speed.

In general, weight has nothing to do with top speed. weight affects acceleration. Drag coeffecient affects top speed.

If I had $0.05 for everytime I have heard (or read): "I modded my airbox and exhaust, and now my bike runs like sh*t"

Odd. I've had much success with these mods.

The main reason even a 'small 120lb person' such as myself still has to go into 'Full Tuck' to reach 65 - 83 mph on a 197cc China Bike :hehe: weight isn't holding you back at high speeds, it's the crap aerodynamics mixed with the low(er) HP/Torque these engines produce in the higher RPM range :D

Haha I think it's because there are so many who change a whole bunch of stuff at once then don't know how to dial it in once they've got the mods in place. I've heard of a lot of folks who've had success because they methodically changed things one thing at a time or had an idea of where they were going to begin with. On the other hand, I've known plenty of people who don't put in the time and thought required to change things to a better option.

Well, I decided to ride up to the Bingham Canyon Mine overlook Tuesday, and I finally got around to posting the pictures online. Here is the link to the gallery where I posted all of the pictures I took. It's really annoying to upload them to this site, so I'll just direct you there. After that trip and commuting yesterday, I am up around 579 km (360 miles) and the bike is still doing well. I don't think I mentioned on here that when I adjusted the valves a while back, the intake was very tight. Both are adjusted now and the combination of valve adjustment and 17T sprocket on the front has me running a bit quicker now than I was. I've noticed the difference a lot more on the low end. My first and second gears stretch a lot further now than they did with the 15 tooth countershaft sprocket.

My top speed so far, downhill, has been 64 mph (GPS). I'm hoping I can raise that a bit, but the motor seems to be the problem rather than the gearing when I'm heading uphill. I am not opposed to trying a 47 or 43 tooth sprocket, but it feels to me like the engine can't keep up at 55 mph up the hill near my home. Maybe with a 47 or 43T rear, I could gear down and make it happen anyway. We'll see. I'm still planning on waiting until at least 500 miles before making any substantive changes to the engine itself. Of course, that's only 2 days commuting! :D If I do feel like I need to modify the bike to get better performance out of it, I plan to follow the "Mrs. 2LZ Phoenix" method. ;)

So far, the only problem that wasn't my fault was my speedometer cable breaking at 341 km. I pulled it when I first got the bike, greased it, rerouted it, but it still didn't last. I'll probably replace the speedometer/odometer with the mjstef model once that's out. I want a tach anyway, since I like to have more evidence than just my finely calibrated ears can provide. ;) Other things I've encountered was a drop on the right side that broke the front brake lever mount/front brake reservoir ($30 with the new lever) and a drop on the left side that broke the clutch lever ($10). I've thought about picking up a few extras (top case, saddlebags, tank bag, heated grips, quick drain oil plug, etc) but haven't yet done so. This bike has been just what I wanted so far, even if it is a little slower than I hoped.

Thanks for the report, oddthought! On Mrs. 2LZ TT, I noticed a definite increase in mid-range and the ability to sustain better speed up hills between 4-500 kilomiles, in stock form. Every evening I took it out on the exact same route for exercise and there was a noticeable improvement every evening, especially toward the end of that kilomileage.

Yeah, it's definitely improved quite a bit over the time I've had it. If I can maintain 65, that'd be enough for me to take the faster roads as I commute to work, but if it doesn't work out that way... well, maybe I'll just have to get a street-oriented bike!

Back roads, man....back roads. Why rush? It's only work. ;-)

:lmao:

My wife and kids might get mad if I up my commute from my normal 2 hours a day to 3+. That ride up Butterfield Canyon made it a 4 hour ride! :D

Actually it runs great, just won'tdo over 50.
Never has. Edit: other than a steep downhill section.
The exhaust and airbox were both done in the past few days, after going through other steps one at a time.

Once it hit 200 miles I changed the plug and oil, then ordered new jets, becausethe 108 is lean at my elevation.
I went to 110.
Ran fine, minor improvement in acceleration, but main thing was that it was no longer lean.

Adjusted valves that were way too tight.
Then removeded airbox lid after talking to Gerry at csc.
Had to go to 112 jet for that.
Feels nicer. No top end improvement.

Just added the exhaust and went to 115 jet within the past two days.
Not expecting any top end improvement. Hopefully once it loosens up after 500 miles or so. It just sucks trying to get around to ride it when I have traffic backed up behind me.

This wasn't a " I made changes and broke shit" post.
It was a "My bike has yet to go above 50, even though everything seems ok and I've made improvements" post.

Where most people say there bikes struggle from 50-60, mine has always struggled from 40-50.
Although that has improved a bit now.

I wonder if something is going on tithe throttle and not allowing wot.

As far as I can tell, the slide on the carb is working fine and the bike is at WOT.
I have not used GPS to verify top speed yet, I will soon.
I do know that at up to 40 everything is mostly accurate.

I have a tach and register about 8k Rpms at 50.
I've seen a top of 8.5k Rpms.

I keep hoping I'd find something wrong. I even triple checked the sprockets hoping I misread them.
I even plan on double checking my valve adjustment.

But so far I haven't found anything wrong.
So, time will tell.
It runs fine otherwise.

I did seem to have an issue with the gas tank having a venting issue. I clipped a small bit of the orange rubber piece under the gas tank lid and that seemed to solve it.
Seems it was building a vacuum in the tank.
Was something else Gerry had mentioned to me to check.

That is the definition of "runs like sh*t".