Recurring motovert pain

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mudskipper

mudskipper

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As some of you may have spotted my Q'n'A threads regarding never ending dramas with my 160.:microwave:

After many hours spent reading, adjusting, changing etc.. I got the bike to run mint.
Would start first kick and even start first kick after stalling.

Over the weekend I was chugging around, then what felt like running out of fuel, the bike stalled as I was 1/8 throttle. Figured ill make it back to the house and slowing to the road opposite the house it started to idle low, so I shut it off.
Tried to start it again but no hope.. Next day got some fresh 95 *always ran premium on my 250, its ok to run it on smaller engines yeh?* and filled the tank, would not start. no matter what.
Cleaned up the spark, cleaned out the carb and jets incase of a blockage, order inline fuel filter, *none on bike*, adjusted idle screw, removed airbox.. even adjusted airscrew just to get it going. But all too often it would just spit fuel back out the intake end, covering the air ports for main and slow jet.*does your carb slope backward or is it mounted level?* If I did get it running, the exhaust had a deep thumping noise and needed 1/8-1/4 throttle to stay alive :deadhorse:

Valves are set 0.003/0.004 if its any help.

I am all out of ideas on this... please combine brain power to create some possible solutions.
 
Could you try a spare CDI box ?? I had one that failed and it started to cut in and out for a while. Also take the plugs off and clean them all out.

Also you could have a leak where the carbie meets the intake. Get some sealer around that.
 
check the coil on the stator....... also (its sounds dumb but it happens to the best of us make sure the killswitch is off :D) ..... also try roll starting
 
to me it sounds like the Pilot jet circuit is blocked up somewhere still.
 
What would i do?
adjust valves.
inspect spark
already cleaned carb
check mounting straightness (FOR AIR LEAKS) and blow through the carby.. yes with your mouth (its awkward but works and check for air leaks that way too)
after that then replace coil, down to stator but my64xr will be able to tell you more on the electrics side of stuff
 
when you say you've cleaned the carby out again.
is that stripped right down,
and cleaned the needle and seat out, the Pilot jet hole, and the cross holes in that jet
also, the port where it screw into, the port on the air filter side where it gets its air from?
then blown through all the holes with compressed air, and checked none are blocked ??
taken the mixture screw out, cleaned it, blown through the idle mixture screw ports etc

with it needing you to hold the throttle at 1/8 - 1/4, there is definately a carby idle circuit problem
 
quick responses guys
drop jets in clean r carb, run compressed air through all ports etc..
ill have a look at the gasket seals and see if anything is loose.
ill go back over the carb with a fine tooth comb, if there is no improvement I may adjust the valves out by
0.001
 
the carby cleaner by itself wont clean any gum etc out from the ports.
get a strand of wire off a wire brush and poke it through, spin the jet on it etc to clean it out.
if you get any tiny bits of gum that look like clear/yellowish paint flakes, then it will take a fair bit of cleaning to get rid of it all.

i wouldn't think 1 thou would make any difference on the valves clearances.
 
ok ill give that a go, seems more legit. Would having an inline fuel filter be a logical choice?
I seemed to have almost the same problem not long after I ran it in, then once I got it to perth, had bike shop clean out the carb pointing out it was mighty dirty.. I thought carb cleaner did the trick but obviously not good enough.
If its dirty I don't know how to manage the fuel, I have been running it daily to power through the fuel.
CDI box replacement is no fix.
wont touch valves.
 
have you ever flushed the tank out ?
although most pitbikes use a fuel tap with a filter in it inside the tank.
sometimes the rubber fuel line can become old and deteriorate,
then when you refit it back onto your carby, a tiny piece comes off and can get stuck in your needle and seat, not letting enough fuel in.
replace the hoses too if you fit a filter, and flush your tank at the same time.
 
went through the carb with some tea strainer wire and found nothing.
Tried running it again with no success, it tried to turn over a couple of times but other than that...:deadhorse:
Whats the best recommended method to flush the tank?
ill dump the tank of fuel in the misses car and I thought maybe remove it completely, clean the pet****, put some fuel in and shake it around then dump it out the pet**** hole?
air compressor to top it off.
the fuel tap seems to be working okay as the float bowl is filling.
 
when you blow through the inlet port on the airfilter side of the carby with compressed air,
can you feel it coming out the pilot jet hole (with the jet removed) ?
also when the Pilot jet is out, can you look into the hole and see through into the bore of the carby ?

yeah take the tank off the bike, flushing the tank out with petrol is fine, put the fuel cap on, make sure the fuel tap is turned off, and shake it well.
then give it a good blow out with compressed air, until you can see it's dry inside.

some petrol taps have a plastic filter on them, that sit inside the tank, these can clog up with dirt etc
 
...sigh..
I have installed the inline filter, drained and cleaned the tank, topped with new 95.
After a few kicks and winding in the idle 1/4 turn I can get it started but need to keep the throttle on to maintain a high idle.
Opening choke and still needing to maintain at least 1/4 throttle to keep the bike running, if I let it drop back slightly to rely on idle jet it poops out.

thoughts.
It looks like a simple case of block idle circuit somewhere, whether it be the air intake or within the carb ports, I couldn't find any type of blockage. can someone recommend a source of fine wire, stiff enough to reach the tiny ports at the end of the idle screw seat?
From memory, theres 2 tiny ports which im sure my flimsy tea strainer wire didn't reach.
that's all I can think of.

progress stage = :deadhorse: still
 
mudskipper said:
...sigh..
I have installed the inline filter, drained and cleaned the tank, topped with new 95.
After a few kicks and winding in the idle 1/4 turn I can get it started but need to keep the throttle on to maintain a high idle.
Opening choke and still needing to maintain at least 1/4 throttle to keep the bike running, if I let it drop back slightly to rely on idle jet it poops out.

thoughts.
It looks like a simple case of block idle circuit somewhere, whether it be the air intake or within the carb ports, I couldn't find any type of blockage. can someone recommend a source of fine wire, stiff enough to reach the tiny ports at the end of the idle screw seat?
From memory, theres 2 tiny ports which im sure my flimsy tea strainer wire didn't reach.
that's all I can think of.

progress stage = :deadhorse: still
Click to expand...

I have seen this problem before. Are you sure the idle screw hasn't been over wound? Also what clip is the needle on?

Really sounds like a carb jetting issue more than a fuel flow issue as the bike runs if you hold the throttle on.


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motorman said:
I have seen this problem before. Are you sure the idle screw hasn't been over wound? Also what clip is the needle on?

Really sounds like a carb jetting issue more than a fuel flow issue as the bike runs if you hold the throttle on.


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Click to expand...

Idle screw just seated, clip is 1 notch rich from centre as through my pain of getting it right, this worked the best.. for a while.
Im sure it is jetting, I had a similar problem before I dropped both jets a size, but found the 17.5 idle allowed the need for choke on start up and could adjust air and idle screws to suit.

prox666 is hooking me up with a real mikuni that's tested running. "ive got my fingers ccroosssssed"
 
UPDATE.

Was recently hooked up with a genuine 28mm Mikuni carb to swap out with the origami replica. The quality of the design and parts is so obvious!
super impressed with it.

Still with some concerns though..

Still takes 1/4+ throttle to fire up and hold high idle, the sound of the exhaust is not a smooth combustion sound, almost as if it misses or is relying purely on Main jet and above.
That being said, I had cleaned out the carb prior and had flushed the fuel already, spark is clean. With a matching problem to the last carby, I feel I should be looking at the bike... eg Valves
it has a larger stator and magneto than stock if that is of any relevance, also seems to only output 9VDC to rectifier.
 
I had played with the setup on the previous carb for it to run perfect... until I came across this problem.
Swapping out to this carb that was running perfect on his I think they were 125 + 170, from memory.
at which point some fine tuning would be done.

yet I find the exact problem with this carb replaced. to me that doesn't say, problem with idle circuit.
yet the symptoms point at that.
I have a spare idle jet and 2 spare mains, tried the idle but didn't help.
Im not sure how the mixture effects the main jet but I cant really tell if its rich or lean.
In thee mean time ill do some reading and see if I find something.
Valves are 0.003/0.004, not sure if that is ideal for 160 but was ok in the past.
 
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