Speed and power has decreased about 50%

GoldenMotor.com
V

VTHokie

New Member
Dec 18, 2012
42
0
0
Virginia
Hey all,

I've been enjoying my kit trouble free for a couple months now. After a few long trips on the thing, I decided to remount the engine with some thick rubber to reduce vibration yesterday.
After remounting the engine, the bike only gets up to about 20 mph. I used to enjoy 34 mph consistently. The bike starts up perfectly, is peppy and goes 0-15mph just like it used to, but once it hits about 20, the bike sounds like it is just giving up. Then after about a minute of driving it, the bike starts surging forward, then slowing, surging, then slowing.

It's soooooo frusterating. What I've troubleshooted so far:

1) I made sure all the bolts on the intake, case head, exhaust, etc were tight
2) I took off the carb and looked for any problems - didn't notice any
3) I removed the air-filter (the one thing I had to re-attach after re-mounting the engine), and replaced the spark plug with a new one

After this, bike still acted the same way, so I....

4) Replaced the carb with another NT that I had
5) I replaced the fuel line (was worried the in-line filter was causing it to flood)

The bike took off and flew perfectly like it used to. I got it up to 32 mph, I slowed down, rounded a corner, and then the bike started chugging like it was before. It started doing it all over again, same exact symptoms!! Maxxing out at 20 mph for a minute, then surging, slowing, surging, slowing, and so on until I turn it off. So I believe it's safe to say, it isn't the carb.

What's going on here fellas? Any ideas?
 
Last edited:
Desert Rat

Desert Rat

New Member
Jul 30, 2012
565
9
0
Apache Junctoin Az
VTHokie said:
Hey all,

I've been enjoying my kit trouble free for a couple months now. After a few long trips on the thing, I decided to remount the engine with some thick rubber to reduce vibration yesterday.
After remounting the engine, the bike only gets up to about 20 mph. I used to enjoy 34 mph consistently. The bike starts up perfectly, is peppy and goes 0-15mph just like it used to, but once it hits about 20, the bike sounds like it is just giving up. Then after about a minute of driving it, the bike starts surging forward, then slowing, surging, then slowing.

It's soooooo frusterating. What I've troubleshooted so far:

1) I made sure all the bolts on the intake, case head, exhaust, etc were tight
2) I took off the carb and looked for any problems - didn't notice any
3) I removed the air-filter (the one thing I had to re-attach after re-mounting the engine), and replaced the spark plug with a new one

After this, bike still acted the same way, so I....

4) Replaced the carb with another NT that I had
5) I replaced the fuel line (was worried the in-line filter was causing it to flood)

The bike took off and flew perfectly like it used to. I got it up to 32 mph, I slowed down, rounded a corner, and then the bike started chugging like it was before. It started doing it all over again, same exact symptoms!! Maxxing out at 20 mph for a minute, then surging, slowing, surging, slowing, and so on until I turn it off. So I believe it's safe to say, it isn't the carb.

What's going on here fellas? Any ideas?
Click to expand...
Look it up here, popular consensus is NEVER use rubber as engine mounts
these motors were made for a hard mount NO RUBBER
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
I concur 100%. Do not use rubber or any resilient material in the engine mounts. You can not eliminate vibrations, only transfer them to the engine mounts and the fasteners.
Several reasons why you're loosing power. All of them can be traced to the rubber in your mounts.
The engine must be mounted solidly to the frame. My guess is you're foaming the fuel in the carburetor and causing a lean condition. Get rid of the rubber.

This subject has been discussed here often. A 2 stroke, single cylinder engine will produce vibrations. It is not, as generally said, because of "cheap Chinese manufacturing" but is caused by a single cylinder engine 2 stroke design that produces power pulses unopposed by another cylinder. It is not actually vibration, although it is felt as such, but instead the power pulses from one cylinder.
You will not eliminate them unless you shut the engine down and coast with the clutch disengaged. Transfering the pulses to other parts isn't eliminating them but only moving them to someplace that will eventually cause you problems.

Tom
 
V

VTHokie

New Member
Dec 18, 2012
42
0
0
Virginia
That's reassuring, glad to hear it might be that easy. I'll remove the rubber and let ya know tomorrow how it turns out. thanks guys
 
V

VTHokie

New Member
Dec 18, 2012
42
0
0
Virginia
Sorry for the delay, I just got around to removing the rubber today. I mounted it like it used to be - directly to the frame, and the problem persists!
One could even argue that the problem has gotten worse.
What other possibilities could there be for this significant reduction in performance?
I used to be able to drive this thing anywhere without any problems what-so-ever, but now I can't get it above 20mph and it sounds funky.
Did I blow a ring somewhere? Did I get some gunk up in something?
Should I replace the engine?

Any advice would be greatly appreciated
 
N

nightcruiser

New Member
Mar 25, 2011
1,180
2
0
USA
Are you still running the stock spark plug wire and boot? They suck, could be a problem, replace with automotive wire and boot, or at least try the spare. Are you sure the carb jet isn't clogged? I guess trying a second carb would eliminate that, but you never know. Is the fuel filter (in the top of the fuel valve) clean? Best bet is to remove this filter and let the fuel flow right into an inline filter instead. Is your air filter clean? Is your head torqued down properly? Is your choke vibrating on? What about your fuel mix? Is it fresh and accurately mixed? Is your gas cap venting? Is your coil or magneto loose? Wiring solid?
Just rattling off a bunch of stuff off the top of my head since you have determined the rubber isn't the source of your problem.
 
577-Jersey

577-Jersey

New Member
Mar 23, 2013
293
1
0
central western nj
I would do a compression test,,and pop the head and jug off to have a look just to rule that out.If it still does it make sure everything is sealed up around carb.
When it happen is it loading up or leaning out?
If its leaning out could be a float adjust.but since you said you swapped carbs with a known working one my bet is the jug or crankcase.

Just for giggles test the coil and mag with a DVM,,could have a bad winding there that gets hot and quits from high resistance.

Good times :)
 
V

VTHokie

New Member
Dec 18, 2012
42
0
0
Virginia
Thanks for the suggestions - suggestions like these are much appreciated.

Air filter is clean because I tried two different filters and even removed the air filter and tried it. Choke is fine and staying put. Gas cap is venting (a little too much in fact - it's custom and leaks at the cap a little but this hasn't been a problem ever before). Fuel mix is 20-30:1 as always, and it's fresh.
So I'm gonna check two things right now: first I'm gonna check the fuel filter in the gas tank peacock - it's a custom tank I bought on ebay for a moped, and I bought a brand new peacock for it but the filter might be clogged w/ some old stuff so it's worth checking out. (but when I've drained fuel into a cup, it runs smoothly so I doubt that's a problem).
I'm also gonna switch out the CDI and magneto with a spare I have.

If these don't work - I'm gonna look up instructions on doing a compression test and give that a go - that's unchartered territory for me, so it may be a little tricky

Thanks for the suggestions and I'll get back to you
 
Last edited:
577-Jersey

577-Jersey

New Member
Mar 23, 2013
293
1
0
central western nj
Your welcome,,
Always good to have more heads in the pie.I have a slow running petcock on my bike,,almost too slow but the bike still runs fine,,if yours is running out nice and steady I would rule that out.

When you do a compression test anything between 105 and 130 psi is acceptable,,lower than 100 psi you will start to have troubles.

Harbor Freight has a decent compression tester for a reasonable price,,you will remove the plug and screw in the correct fitting,,then without ripping the hose and meter apart with your cranks pedal down the road and crank over the motor 15 or 20x,,then look at the gauge...if its below 100 psi,,put a few drops of motor oil in the plug hole,,then do the test again,,if you psi comes up,,something is wrong with the jug and or its internals.

Good times :)
 
T

TomT52

New Member
Mar 1, 2013
12
0
1
71
Michigan
Check to see if the jet has vibrated loose in the carb, will make it run badly and four stroke from running to rich. Just an idea.
 
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
another problem we see sometimes is a clogged muffler - take it off & see if you can blow thru it with no resistance
 
577-Jersey

577-Jersey

New Member
Mar 23, 2013
293
1
0
central western nj
crassius said:
another problem we see sometimes is a clogged muffler - take it off & see if you can blow thru it with no resistance
Click to expand...
Thats a great point,,
I see that all the time with 2 cycle motors,,first thing I remove is the spark arrester screen from my muffler on my chainsaws and stuff.Does a china girl muffler have a spark arrester in it,,i never opened one up yet?
 
N

nightcruiser

New Member
Mar 25, 2011
1,180
2
0
USA
crassius said:
another problem we see sometimes is a clogged muffler - take it off & see if you can blow thru it with no resistance
Click to expand...
Good point, was going to mention that as well but I guess I forgot. If the muffler gets loaded up it can cause you troubles....
 
CTripps

CTripps

Active Member
Aug 22, 2011
1,310
1
38
Vancouver, B.C.
577-Jersey said:
Thats a great point,,
I see that all the time with 2 cycle motors,,first thing I remove is the spark arrester screen from my muffler on my chainsaws and stuff.Does a china girl muffler have a spark arrester in it,,i never opened one up yet?
Click to expand...
I think I've seen three different style interal set ups on four of the 'stock' J-pipes that come with the kit. Some had holes full of burrs and crap. When the holes were cleaned out it seemed to help, and reduced/improved the noise a little too.
 
577-Jersey

577-Jersey

New Member
Mar 23, 2013
293
1
0
central western nj
CTripps said:
I think I've seen three different style interal set ups on four of the 'stock' J-pipes that come with the kit. Some had holes full of burrs and crap. When the holes were cleaned out it seemed to help, and reduced/improved the noise a little too.
Click to expand...
Yeah,,
The pipe on my grubee from a few years ago doesn't even have a cap on it,,its a sealed unit,,guess if it gives me trouble Ill have to clean it out by soaking it in a solvent for a day,,or cut the bottom out then just weld it back together,,might be easier to just get a new pipe..lol

Good times..

Tom :)
 
CTripps

CTripps

Active Member
Aug 22, 2011
1,310
1
38
Vancouver, B.C.
577-Jersey said:
Yeah,,
The pipe on my grubee from a few years ago doesn't even have a cap on it,,its a sealed unit,,guess if it gives me trouble Ill have to clean it out by soaking it in a solvent for a day,,or cut the bottom out then just weld it back together,,might be easier to just get a new pipe..lol

Good times..

Tom :)
Click to expand...
Brake cleaner works well for cleaning out the pipes too. I grab an old margarine tub or something, half fill it with kitty litter, and hold the pipe over it while I spray into the top end. The litter will absorb some of the gunk that drips/dribbles/pours out the end and make for easier clean up of your workspace. When done, slap the lid on the tub and lob it in the trash (or on the shelf for next time, if it's not saturated.) If you don't have something like that to catch the gunk, the same idea works with sand or dirt, or even paper towels. Wear a pair of (safety) glasses though, that stuff stings if you get it in your eyes, trust me. A pair of disposable gloves will keep the worst of the goo off of your hands, too.
 
You must log in or register to reply here.
Top Bottom