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Discussion Starter · #1 ·
So, I got a 2004 linhai duster 300 from my grandparents.
I've got it to start, and eventually rev up...
But for about 2 minutes after being started, it won't rev up... It just barely stays running, after that 2 minutes it will rev up fine ..
What could the problem be??
If the carburettor diaphragm has some cracks in it could that cause the problem...
It's also running very rough... I need to tune it this afternoon...
Thanks
Matthew
 

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I don't think the diaphragm is the problem. It wouldn't fix itself when warm. Have you cleaned the carb?
It sounds like it could have a partially plugged pilot jet and is running lean on cold start.
If its been sitting , that's where I'd start.

Mad
 

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Discussion Starter · #3 ·
I don't think the diaphragm is the problem. It wouldn't fix itself when warm. Have you cleaned the carb?
It sounds like it could have a partially plugged pilot jet and is running lean on cold start.
If its been sitting , that's where I'd start.

Mad
Yes it has been sitting for quite a long time.
I've just replaced the diaphragm, and there is no difference.
I've run quite a bit of carb cleaner through it, no difference.
I'll look into cleaning the jets.
Matthew
 

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Yeah you have to remove all the jets, clean them AND make sure the holes they sit in are clear. For example,
if you shoot some carb cleaner in the pilot jet hole, you should see a small stream in the carb throat.

Mad
 

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Discussion Starter · #5 ·
Yeah you have to remove all the jets, clean them AND make sure the holes they sit in are clear. For example,
if you shoot some carb cleaner in the pilot jet hole, you should see a small stream in the carb throat.

Mad
Hmmm. I checked the jets.. but didn't check the jet holders...
Now last night I ran it a bit, and then it stalled now I haven't gotten it to start again....
There is a spark, and there might be petrol ...
But I can't get it to fire.
 

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Try shooting some starter fluid into the intake. If it fires up it's probably a fuel issue.
If it doesn't, try a new spark plug and check for spark.

Mad
 

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Discussion Starter · #8 ·
Try shooting some starter fluid into the intake. If it fires up it's probably a fuel issue.
If it doesn't, try a new spark plug and check for spark.

Mad
So, we got the quad running...
The engine is running so rough that the spark plug gets coated in carbon after 30 or so starts... And then it won't start.
Cleaned the plug , and it starts up....
But still not revving up properly...
So far it has started up properly twice, but then when turning it off and on again, it won't run properly again...
First time, was totally random... We did nothing to it....
Second time was after we had opened the carb an rechecked the jets.
Then we tried starting it without auto choke plugged into carb, and with fuel line closed...
Nothing ( obviously (
Then we opened the fuel valve...
Nothing
Plug the auto choke in...
Starts up fine , revvs up fine.....
....

Now 2 things....
When the engine was running correctly, I noticed that smoke was leaking out of the exhaust...
Why would it do that... Unless the exhaust was blocked???
When I checked the pilot valve... I sprayed some carb cleaner through it... And I saw some appear in the throat of the carb .. but no where near the amount I was spraying in it.... Does this mean it was blocked???
The actual little screw in jet is all clear, I was spraying into the section where the little jet head screws in... The jet seat??
 

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Yeah, you're only going to get a small spray in the carb throat. If the plug is turning black it indicates a
rich fuel mixture. My suspicion is that your auto choke may have been stuck open causing a really
rich fuel mixture. Maybe try a new one if you can buy one. As for smoke out the exhaust, where
are we talking ? Right at the cylinder head ? Do you feel strong pulses coming out of the muffler ?

Mad
 

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Discussion Starter · #10 ·
Yeah, you're only going to get a small spray in the carb throat. If the plug is turning black it indicates a
rich fuel mixture. My suspicion is that your auto choke may have been stuck open causing a really
rich fuel mixture. Maybe try a new one if you can buy one. As for smoke out the exhaust, where
are we talking ? Right at the cylinder head ? Do you feel strong pulses coming out of the muffler ?

Mad
Ok cool ... Will see if I can get a new Choke unit....
Where the exhaust attached to the engine head ..
Basically where your foot would be... when seated on the quad.
The pipe runs all the way to the back above the rear tyre ..
That pipe is made up of 3 pieces held together by springs.
At the first spring held join is where it is leaking... (First from where it attaches to the engine head).
 

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Ok, as long as you feel good airflow out of the muffler, the pipe should be ok. However, if the internal baffle has broken loose, I could obstruct the exhaust and cause it to run bad. Best idea is to remove the entire exhaust pipe and check it
over. Use some PB Blaster on any bolts for a few days before trying to remove it. If the pipe is clear, get a new
exhaust flange gasket that goes right at the cylinder head.

Mad
 

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Discussion Starter · #12 ·
I checked the pipe...
All clear... Looked like the one join wasn't put together properly..... No more leak now .....

Now to find a new auto choke unit...
Although I'll first test this one .....
 

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Discussion Starter · #13 ·
I checked the pipe...
All clear... Looked like the one join wasn't put together properly..... No more leak now .....

Now to find a new auto choke unit...
Although I'll first test this one .....
 

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Discussion Starter · #16 ·
Whoops ! One Chinese quad for another. Probably a lot of stuff is the same.

Mad
Well if it had been a Honda or a Yamaha....
I would have known it the minute Iaid eyes on it😂....
The big brands like branding all of their stuff....
But yea it is still very similar...
I think this weekend I'll give the carb a very good clean....
Ive seen guys soak the carburettor pieces in fuel I think?? Is this ok for the parts??
And maybe I'll also check the valve clearance...
Along with checking the e choke....
 

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I think using gas works but it's kinda risky. Contact cleaner or an ultrasonic cleaner better.
Valve adjustment is really important to have it run properly.

Mad
 

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Get some carb cleaner or Contact cleaner. You want to make sure the passages in the carb body are clear.
Air alone may not clear any blockages. When everything is clear, then use air to get everything dry.

Mad
 
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