My bike won't start/run...... Fixed.

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nvd20l

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Hey guys,

Having some problems with my 110cc dirt bike (chinese bike). It is annoying the #^%@ out of me. I have been using it for hours without any real dramas. The other week, I changed the oil (I used Shell VSX4), let it warm up and rode it about 10m down the street. It started to break-up/misfire badly upon opening the throttle. When I brought it back home, it cut out and died.

I started it back up last week, let it idle for a few minutes, then gave it a little throttle (choke open) to warm it up further. It started to break-up then died (this has always happened).

I went to start the bike up just now, tried both electric and kick start, it wont kick over. Checked the spark plug, cleaned it and fuel is OK. When it does start up, it will die if trying to idle and will break-up then die after a few seconds when using a little throttle. When trying to start, what appears to be white smoke is exiting the exhaust and thick black oil is seeping/spraying from the exhaust pipe (where it connects to the muffler).

I know it's a long winded explanation.......

Has anyone experienced this problem before and how should I go about getting it fixed so I can ride it again?

Thanks guys.
 
No no no way hozay. I dont know a great deal about bike or mechanics, but I know not to do that. Straight VSX4 in the oil and ULP in the petrol.
Thats not the problem....
 
a bad crank seal will leak gearbox oil into the cylinder causing the oil in the exhaust and smoke it will be fouling your plug aswell do u see the oil level in the gearbox dropping?
 
I checked the oil level (not sure how to check the gearbox oil) and it seems to be OK. The plug did have a small amount of oil on it when I pulled it out though.
 
i just took this picture for you it has been slightly sanded to get some carbon deposits of it not the best picture but u can see the difference to a normal spark plug if your crank seal is gone the plug will be black,wet,carbon deposits with this plug my gearbox oil was leaking into my cylinder causing everything u described above... but no stalling
Picture025.jpg
 
The plug was the same as you have just described. We did sand it a little. I will check the gearbox oil.

This bike is fairly new and I have ridden it only a few times. Is this normal for these types of bikes and so soon?
 
In that case, I think I will have to get in touch with the guy I bought the bike off.......
I might have a chat with my local motorbike shop as well and see what we can do.

Is it a big job (and expensive) trying to fix it, do you know?

Thanks heaps for your help. I appreciate it.
 
it depends it'll be a big job if u need to split the casing some motors u dont need to split the cases to remove the crank oil seal but you will need to get the new seal pressed into the case
 
Before we go pulling the motor down check a few thing first.
Was the problem there before you changed the oil?
If not something has happened when you changed the oil.
Check that you didnt overfill the motor with oil. Was the bike tipped over for any length of time? These were the 2 most common causes of your problem that I encounted when I had my shop. It sound like oil has found its way into the combustion chamber and these are 2 causes.
 
No, this particular problem was not there before I changed my oil. It ran for a few minutes then carked it.

I put under a litre of oil in and it was around the right amount as per the dipstick/manual.
The bike has always stayed either on its stand or on a crate and has never been layed on its side.
 
It is highly unlikely that there is any mechanical damage. I still think that oil has found its way into the combustion chamber & is related to something that happened during the oil change. Anything else is a pretty big co-incedense as your motor was fine upto this point. from my experience these engines hold around 1/2 lt oil, but without knowing your motor that might not be 100% correct. Do you remember how much came out?
Ok, what I would do is this- drain about 1/2 the oil that you put in leaving about 1/2 lt in, remove and clean sparkplug or replace if badly fouled. While the plug is out kick the motor over fast several times to expel any oil in the cylinder. Replace plug start motor and run at fast idle until the smoke clears(this can take quite a while).
I have 2 of these motors (1 in a pitbike, 1 in a quad) & because of the difference in the angle the motor is mounted one takes a lot more oil to fill than the other. If i filled the bike to full on the dipstick it would be way over full. The quad motor is mounted dead level and takes 600ml to fill.

The gearbox & engine oil share the same oil. As your bike is a 4 stroke if you had bad c/case seals it would only leak oil to some point outside the motor. On a 2 stroke if your seals are bad oil can be sucked into the engine and cause excessive smoke. Just thought I'd clear that up :wink:

These motors are normally very reliable if you keep the service up.

Hope this helps.
 
That helps heaps. When I get a chance, I will empty some of the oil out and remove the plug and see how that goes. I will let you know.

Thanks again guys.....
 
wtf? dont empty half of your oil these bikes take around 900mls to fill them up your only putting in 600mls? you will fry the clutch and run the gearbox dry :shock: tgr61 i was talking about the crank oil seal not the case cover gaskets
nvd20l, it could also be a faulty oil pump take the motor to a shop let them tell you what is wrong with it probably cost u around $30 for them to check over it
 
Gazza- with all due respect mate I've been a qualified m'cycle mechanic for close to 30 years & have also been race preping 2 & 4 stroke engines for most of that time. Running the amount of oil (600ml)I suggested will not damage the clutch or gearbox as if you add that to the amount of oil that is always left in the engine you are pretty close. Just as it won't be a faulty oil pump. This problem has only occured since the oil change so it is a 99.9% chance that the problem is related to that. While it is possible, it is highly unlikely that the bike suffered some mechanical failure at the exact same time as the oil was changed.
The honda xr 70etc engine which these engines are closely related to hold from empty around 800ml. If you were to pull the motor down drain every last drop of oil out you might just get 8-900ml of oil to fill it if the engine is sitting level. In reality you don't get that much out. What happens is that some of these pitbikes mount the engine slanted well forward and if you fill it up by using the dipstick (Which is toward the rear ) as a guide you will overfill the engine as it is the same as checking the oil with the bike facing downhill. Some of these bikes also have a sight glass towards the front on the same side as the dipstick and if you use that as a guide it only takes 300ml of oil to cover the glass! This is a fairly common problem with these motors and you will find that when you drain your oil you will only get about 600ml out. If you then put 1lt in your engine will be well overful.
On a 4 stroke m'cycle engine the crankshaft and the gearbox are together in the crankcase with no seal or division between them in the case. In a 2 stroke m'cycle engine the crankcase is sealed from the gearbox.
 
here is a 4 stroke motor doesnt look like the gearbox oil free flows into the crank looks like both crank halfs fully seal the crank and gearbox seprate page 46-47
http://glacoinc.brinkster.net/christemple/ktm/Engine_4Stroke_250_525(00-03).pdf
Picture026.jpg
no oil lessons needed here mate... this is the dipstick of our 110cc dirt bike when we fist got the bike the oil was filled to the yellow line as u can see well over the full mark the motor was hot when the check was made... my little nephew didnt want to wait untill i drain the oil so he rode the bike he didnt care what happen to it that was about 6-7 months ago and about 750k's on the motor not a problem he has dropped the bike a number of times never have we had any problems also i dont judge your experience but you could always update your profile its showing junior member?

nvd20l, the link above will show u the crank seal on page 47 number 5 take the bike to a shop they can do pressure test for u and tell u what is wrong with your bike
 
Gazza are you saying that the gearbox & engine on the honda xr50/70 or any chinese copy are separate from each other with no way for the oil to flow between them? If so can you please tell me where you fill the engine and gearbox separately? Both obviously require lubrication. Just to help you understand have a look at this page
http://houseofmotorcycles.bikebandit.com/partsbandit/showschematic~dept_id~1133124.asp

This is a crankcase schematic for a xr/crf70. you can see that the gearbox and engine do share the same case area with no division between them.

The link you posted is for a KTM with a DRY SUMP style engine that in this case uses the gearbox part of the case as an oil sump. They still share the same oil. The pitbike engines we are talking about here are WET SUMP - 2 different things. The seal that you are talking about has nothing to do with the problem. 4 stroke crankcases are not pressurized you are getting confused with 2 stroke engines.
 
alright i stand corrected i cant really tell from the view need to see inside the left case there looks to be some type of gear that devides the gap and how does the oil get filtered in this case?
 
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