Roketa 200 top speed over 70 mph? How to go faster tips

[truthfriend7]

[b]EDITED 1/12/08


How can you get a Roketa 200cc to break 70 mph top speed?



I started this thread for new people like myself. Info on this topic is scattered everywhere, so I'm trying to organize the highlights in one place. Here it is...



I weigh 195 lbs. Based off of several hours of research on these forums, here's what I did:



1. Moved the "C" clip on the carb needle down to the lowest position. (see "Tech Info")
2. I took about 1/6" drill bit and drilled several holes inside and outside the exhaust/muffler. Tried to puncture the inner baffle as many times as possible and then drilled about 8 holes around the outer hole. Noise level increased.
3. Replaced the air box with a cone (K/N) style filter. Dirt cheap off ebay. (see "Parts Parts Parts Parts" sticky)
4. Backed out the fuel mixture screw on the carb (Picured here: http://www.chinariders.net/gallery2/...g2_itemId=1092) about 3 1/2 turns.
5. Put on a smaller rear sprocket.


THE RESULTS:


Great on startup, even without choking
Better low end power
Hit 71 mph on the highway with me sitting up, 75 mph crouched down!


So can anything else be done very cheaply (or free) that will increase your power and top end speed?


OTHER COMMENTS/IDEAS/SUGGESTIONS:


CAUTIONS:
• These bikes weren't designed for high speeds. Be careful.
• The 200cc motor is not capable of doing much over 70 mph


OTHER IDEAS:
• Increase the size of your Main Jet to about 110-120 (pictured here: http://www.dansmc.com/carb_mainjet.jpg). These can be purchased from ejcycles. Buy one designed for the Keihin styled carburetor.
• Add NOS and blow the bike up. (whoever does this please report in)
• A slight timing advance (see this thread: http://chinariders.net/modules.php?n...ewtopic&t=3048)
• Upgrade tires to a slightly larger size.



MY NOTES:
Speed is a tricky thing to gauge. I did 75 one way but going the other only got 60. Wind makes a huge difference. Also, at this point I am not certain that my uni-pod air filter made much of a difference on top speed. ALSO make sure to go for a fast ride, cut the engine and check your spark plug to see if you are running too lean or too rich. Lean gives more power but will wear out the engine much faster. To see what the plug should look like go here: http://www.dansmc.com/Spark_Plugs/Sp...s_catalog.html

I'll try to keep this somewhat updated for all you beginners like me. Thanks to everyone for their input.

[ejcycles]

.....Nitrous..... add it, blow it up, then buy another one. :wink:

You don't... How fast do you expect a 200cc engine to go?.

[red2003]

Well for starters, that's not the main jet in your pic, that's the fuel screw. Anyway, 70 mph is already faster then these bikes are made to run. Have you ever really looked over the welds on the frame closely? 8O At 70 your braking distance is gonna be huge as these have minimal stopping power. Wind resistance at that speed is what's keeping you there. Be happy with 70 and buy a sport bike if you wanna ride faster.

[katoranger]

70mph or slightly more is just all you are going to get. There is not enough power to be had to go any faster. If you put to high a gear the engine won't be able to pull it in fifth and you will be suffering on take-off.

You only real solution is to get a larger bike.

I have travelled on the freeway for about 45 miles in the right lane. I got behind a truck going 65MPH and stayed there.

Allen

[AZ200cc]

70 mph is not to shabby at all for one of these bikes . I was maxed out at about 55-59. I wouldn't trust it over that speed anyways, Because it was not designed for it.

[truthfriend7]

Thanks for you input guys. I don't expect to go over 70 mph. I was just hoping there was a way to maintain 70 mph. I can barely get up to 65 and it takes quite a while for me to do so. Does anyone have a pic of the main jet since I apparently was totally off. Maybe that's my adjustment problem.

[IronFist]

If you ride your bike out the back end of an airplane at 20,000 feet you will break 70MPH, and a few other things. You'll be fine till the ride comes to a complete stop. 8O
My bike went 60 and that's about as fast as was safe. A bigger engine doesn't mean a safer bike. Faster means better brakes, better tires, better steering, better frame and more money. Just another opinion to concider.

[katoranger]

I can maintain 70 on the flat with no wind, but I have 50 less pounds to haul then you too.

The main jet is inside the carb and requires dissassembly to change. It is a brass insert that threads into the carb.

[katoranger]

Also you usually buy a set in a range. Probably in your case 100-110. If you open up the exhaust more or install a different pipe then 110-120 might be needed.

Here is a good basic explanation of how a carb works.

http://justkdx.dirtrider.net/printcarbtuning.html

Allen

[truthfriend7]

Allen thanks so much. That is invaluable information. According to your carb info link, the main jet in the center of the carb (just below the big needle) regulates fuel from 3/4 throttle to WOT. So where can I get a 100-110? Ebay maybe? Also, what is the danger of running to rich? I know lean is bad. I appreciate everyone's patience. I've still got much to learn.

[katoranger]

Rich will foul your sparkplug. Bruce sells the jets. I would order from him and you will have them in a couple of days. They are not expensive. Tell him what mods you have done too and he can help you pick out the best ones to try.

Allen

[culcune]

The "standard" of these bikes, as far as street geared GY200's go, is the Lifan LF200GY-5 which has a 17 tooth front sprocket and 46 tooth rear sprocket. I think those, stock, will hit 65 mph and up to 70 mph in short bursts, but if I remember, most who own them said 60 mph is a more likely maintained cruising speed.

If you went with the 17 tooth front, you might try a 44 tooth rear (you can buy stock Lifan 46 t rears from Bruce at Endless Journey Cycles, but 44 t rear are the more common aftermarket, non-Lifan, part you will find out there).

The size is simply counting the "teeth" on both the front sprocket and the rear sprocket. There is one member here who bought a stock Roketa with a 17 t front/46 t rear, but was the exception rather than the rule. Most of the Roketas seem to come with 14 t front/56 t rear which max out at about 50-55, and that is screeeeeaaaaming!

[fatboy250]

Originally Posted by culcune

There is one member here who bought a stock Roketa with a 17 t front/46 t rear, but was the exception rather than the rule. Most of the Roketas seem to come with 14 t front/56 t rear which max out at about 50-55, and that is screeeeeaaaaming!

I am that member. I order two DB-07A's and they both came with OHC engines and 46 rear sprockets. The next order I got two DB-07B's and they both came with a push rod engine and a 56 rear sprocket. Top speed about 59mph with me on it.

The OHC is the way to go for long duration high speed/high rpm. You can also get an incremental increase in top speed with the slightly larger diameter rear tire like the 120/90-18 that we have on the OHC bikes. We are able to hold 70mph fairly well with a top speed around 77mph with me on it at 250lbs. Dad's a little faster at 185lbs. This is measured with the digital speedo.

[katoranger]

The OHC engines have a little better topend power than the the OHV engines.

I have a 17/45 sprockets and stock size rear tire. OHV engine. I have done 71 MPH according to GPS. That is about it, but I can maintain 65 easily.

Allen

[truthfriend7]

Allen you've been a real help. How to I get in touch with Bruce. What's his username?
I've done of bunch of testing today. I've been backing out the fuel screw on the front (what I mistakenly called the "main jet") and then riding. I believe I have it at almost 4 turns out now and it seems to be running much better. I had it at 3 but the spark plug looked a little lean. Then of course 5 made it look too rich. It got me up to about 67 mph while I was sitting up. This might be about all I need. Maybe add the bigger main jet and then I'll be pretty well at the max.
I saw a site that sells mikuni 110 jets. Will that work for these bike carbs?
http://www.psep.biz/store/mikuni_main_jet.htm#ADHJ110