unknown bike problem need help.

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Jammo

Jammo

Well-Known Member
Joined
Sep 20, 2011
Messages
317
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1
Location
Newcastle, NSW
Hey guys,
I have a 125cc thumpstar that i bought locally from Marshall Motorsports, ( one of the sites sponsors)
not very happy with it paid $750, it is absolute junk, not much torque pretty gutless,

but now i have a new problem,
when i get to half throttle it starts dropping power every second or so, i have to either ride full throtttle or hardly any at all,
i recently put 800ml of oil into the engine and it blows some smoke when started for possibly 10 seconds, other than that a little bit of smoke now and then,

I know my valves are probably off,
oil is leaking from front of engine, 1-2 drops here and there, chinese crap bike, so i tightened those bolts and i dont think it is leaking anymore..




ONE IMPORTANT THING :
on the top of the engine there is a thick black tube going just near the wheel off the engine, and oil drips out of it, whats the go with this? never noticed it dripping before,
has ruined my driveway ahah so not too happy.

also have a little hole in my exhaust, ( probably about 4mm circular) air comes out of it obviously when riding, should i leave this or get it soldered over? or any of you guys have a spare thumpstar exhaust you'd sell for cheap, ill buy it newcastle region.

thanks guys, much appreciated.
 
is it blue smoke or black smoke ?

oil out of the head bolt.. well thats the cooper washer not seated most likely, one of the head bolts is used as a oil feed line to head itself.

tube on the back of the motor near the rear wheel is a breather tube if you have over filled the motor you might get some oil out there, or if you have been giving the bike a hard time but it will be generally minimal amount of oil coming out that tube.

how much oil come out prior to topping it up ? was it smoking before the top up ?
 
you might want to mention how old the bike is and how many hours of run time it has on it..

might pay to throw a little video up of it running with this smoke problem.. it could be related to the power problem..
 
Have you contacted Marshall's about your issues? First thing i can see, is you have recently bought a bike and probably have done very little set up or pre ride maintenance and have posted here saying the bike is crap..not happy with it...so many issues blah blah blah. This dont sit well with most members and to me is a kick in the teeth to the sponsors. The guys that pay sponsorship which in turn keeps this awesome site running.

After looking at your threads, im not sure how to take this one? you have multiple threads stating your buying a DHZ, building a crf50 and a thread saying you bought a 2nd hand "Thumpstar" off a mate thats been sitting for 7 months? Is this the same bike this thread is about? If so, you really have no grounds to even mention Marshals name.

Back to your problems.. firstly, its a 125, not exactly a torque monster regardless how much you weigh. The surging could be due to the fact your valve clearances are not properly set (as stated above) and your carb more than likely needs adjusting. Crappy carbs you say? maybe, but correctly adjusted are more than fine (temperamental, yes) but fine for a stock engine.

Where exactly is the oil leaking at the front? From the square plate? have you had it off?
If you have, you've probably put the washers back on incorrectly. There should be 3 steel washers and on the bottom left there should be a copper washer.

Wheres the exhaust hole? you need to be a bit more specific, maybe even post a pic.

If you need help, ask for it just dont come on here with the whole Chinese crap BS story.
 
yeah didnt mean disregards to marshall's the guy is quite nice, just saying i have a few of the exact same bikes if great condition, but run like crap.

exhaust hole : near the head maybe 15-20cm away from the engine, near the curve.
retightened front bolts, not leaking anymore,
re did my oil , smokes a lot less now, is a greyish smoke, but never smoked before, since i put fresh oil in it smokes.

if i clean the carby and re do the airfilter could that possibly stop the engine problems?

when i slowly use the throttle to gain speed, it gets to a certain amount and goes ; braaaaaaaaaaap burp burp burp ( sorry, trying to explain in words,) i will probably post a video, and a picture of the exhaust and front end of the engine,

thanks guys for the help, again i did not mean disrespect to anyone..
 
i reckon clean carbie and check ya valves.. theres are threar in the how to section on how to fix stuff yaself mate... and how old ya fuel also?? with the hole weld it up or silver solder a patch.. most sheety shops can do and most likely someone will do a cashie.. you might also wanna check out the thread on pre ride maintance etc.. like running period do's and dnts yeh..
 
1. check valves.
2. clean carby.
3. clean air filter.
4. check earthing (the electicals, make sure all connected and not dirty or wet.)
5. tighten every bolt on the bike and loctite most of them.
6. check spark plug is all ok or even replace to an ngk if it doesn't have one.
http://www.miniriders.com/motor-tutorials/24965-how-set-valve-clearances-horizontal-engines.html
http://www.miniriders.com/carby-tuning/25033-carb-jetting-tuning-dummies.html
http://www.miniriders.com/bike-setup/24239-achtung-noobs-your-new-pitbike-you-set-up-tips.html
http://www.miniriders.com/bike-setup/12274-tricks-trade.html
 
i will clean carby and air filter,
i do not have the correct feeler guages, does anyone have any?
and does anyone have ;
feeler guages and a 125cc exhaust i could buy?
i will buy of you if you have
 
Jammo said:
i will clean carby and air filter,
i do not have the correct feeler guages, does anyone have any?
and does anyone have ;
feeler guages and a 125cc exhaust i could buy?
i will buy of you if you have
Click to expand...

Classic Honda 50's Australia - DRP Valve Adjust Tool Set
Classic Honda 50's Australia - Feeler Gauge - 0.002 and 0.003
Classic Honda 50's Australia - Feeler Gauge - 0.004 - 0.005

0,003 for inlet and 0.004 for exhaust for valve adjustment

and if its crf style

Big Bore Alloy Performance Exhaust System 125cc 140cc CRF50
 
can i buy feeler guages at bunnings? just ask for feeler guages and they will know what i talkn bout?
 
thanks guys, does anyone have a spare exhaust laying around theyd sell me?
i will pick it up or arramnge to meet somewhere:)
 
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