Slow top end on first build.

J

Joshua

New Member
I have about 150-200 miles on my new build and I just don't have much power and I can only get up to about 20 mph on a flat. I ran a 20:1 mixture on the first gallon of gas and then went up to a 28:1 on the second gallon, which I'm about done with. I know they run better after the first 200-300 miles but mine has not improved and I think it has gotten worst. here are a few details:

-new plug and wire.
-synthetic blend on the first 2 gallons going to full synthetic with a 32:1 from here on out.
-adjusted the e-clip because I fouled the first plug but then went back to the second from the top when I switched to the 28:1, plug looks good.
-checked the float and jet, looked good.
-cleaned the filter in the tank after the first gallon and changed the inline filter after the first 1 1/2 gallons.
-I had to add a extension tube on the carb with a 45 deg bend so it would fit around the seat post. the extension is 3-4 inches. could this be my problem with power.
-I've checked for air leaks with carb cleaner and its sealed up tight.
-new gaskets around the exhaust, carb bowl and manifold.

I was riding it the other day and it just didn't seem to have as much power as it did the last time I rode it, it won't pull hills as fast and it is just slower all around, and it never was that fast. this is when I checked the jets to make sure they didn't have any junk stuck in there, it looked clear. It has alway had a rough spot when you are riding it, it will run good until you get the rpm's up and then it gets rough. it will be rough going up a hill until it has to start working a little harder then it will smooth out some and sound good. The engine gets just a little bit of oil build up after a fair amount of riding, its on the front part of the engine I'm not sure where it is coming from. I know this is probably a little confusing but it is hard to describe what it is doing exactly. I kinda hope someone else has had this problem and will know what I'm talking about. If I left anything out you can just let me know. Thank you guys in advance.
 

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I haven't changed the bolts on the head yet but they are tight. what size studs are they and I will go get some today. I have checked for air leads around the adapter with carb cleaner and the engine idle doesn't change, I will use some rvt and seal the weld just to make sure. Also I'm not sure why it felt like it lost power from one ride to the next. Thank you guys.
 
it may be a optical illusion on the second pic , but I dont see your front mount bracket!
mine broke one time and it run really rough and had to limp it home. does it idle well?
 
Pull the baffles out of your muffler and give them a good cleaning, try drilling the holes out a bit bigger while you're at it. Too much back pressure from the muffler and it doesn't matter what else you do to the engine, you're still not going to go very fast. They do tend to collect quite a bit of gunk while you're running heavy on the oil for break in which could also explain a loss in power.
 
filestyle1 yeah the front mounting bracket is there its hard to see in these pics, It idles smooth as far as I can tell. this is my first chinese motor and I've never been around another one so I don't have anything to judge it against. if I rev it up with out a load it is smooth as silk all the way through the rmp range.

Jakylpops I will pull the baffles out right now and check them out, I've never looked at them that might be the prob. Thank you guys for the help, I'll let you know what I find.
 
filestyle1 sorry I was wrong I looked at the pic and remembered when I took this pic I didn't have the front backet on, I was doing some adjustments. Good eye.
 
I pulled the baffles out of my exhaust! it took some digging but pulled all three out and it give me a little more power on the top end! but the chengine does need some back pressure to run good!
 
so you just pull them out? I just took the end cap off and took it for a short spin and it ran way better, it was loud but man it ran good. what do you pull out that round tube up inside or the flat pieces of metal with the holes in them?
 
if it were that easy ! its actually the plates , there tacked to the silencer tube inside the pipe. I took a big screw driver , clamped my pipe into a vice (upside down) so you can look into the pipe and then with a big hammer knocked off the tacks connecting to the silencer. and then used my needle nose pliars to pull them out. I pulled one plate at a time out , so if I can tell the difference or not. and right now I'am not even using my stock pipe , I went to a tuned pipe instead.
 
ok thanks, I went ahead and drilled the holes bigger on the first plate and then added another hole. then I got to thinking about how it ran better with the end cap off so I took the bolt out that holds it in place. I was thinking this might let off some of the pressure, well it did and it ran a lot better. So what I did was put the bolt back in and drilled a hole in the cap beside the bolt and wow it runs better. It is a little louder but really not that bad. it still feels like it is starving for fuel sometimes but that is something else I have to figure out. thanks for all your help.
 
Have you checked to see blown head gasket, check head bolt tension when cold, run until hot, allow to cool then check tension again, the increased length of the manifold will affect the performance, the shorter the run the better
 
The reason it won't run right is the mod you did on the intake tube, sorry to say. There is nothing wrong with your engine. I've had several run-ins with customers at my shop doing similar things to their ATV's and Dirtbikes.
When you extend the length or bend the intake in any way,shape or form, the engine can't pull the required amount of air/fuel mixture. It will run like it's starving or staggering because the distance from the carb to the cylinder is too great. That's why you'll notice on all engines 2 or 4 stroke, the carbs are mounted very close to the heads or cylinders, some are mounted directly to the cylinders or with very short "rubber boots".
Actually, if you can even shorten the stock intake tube to fit the carb into your frame, you'll be better off.
Definitely pre-mix 50:1!!! The scare tactics of mixing rich are not true. I've built many race engines and have only used a ratio of 50:1 (even for break-in) with Maxima Castor 927 Racing Oil. Never had a meltdown or any failures. Customers are constantly freaked out about it.
My 48cc bike engine ran awesome out of the box with all the mods I did to it and a mix of 50:1.
Hope this helps.
 
motorhedz thank you very much, I was pretty much sure that was the problem. I have a trek bike I am going to switch the motor over to so I will have plenty of room for the correct length intake. Thank you for your help.
 
Hello,
Found your comments about 50to 1 mix interesting. So you are saying these chinese motors will not sieze up or get damaged using 50 to 1. All I've seen about them was going to 32 to 1. Heck if I can go to 50 to 1 that will be great,less fouling,less oil burning.Have you ran a motor long term at this ratio? I'm not challenging you, just want to be sure not to do damage. About time to mix more fuel , had to ask.
 
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