Atomik Reign, Lifan 150, Big Foot questions

[my67xr]

unscrewing it makes it leaner, doing it up makes it richer.

it might make it easier to tune if you fitted a manifold spinner between the manifold and head.
that way you can leave the carby fitted, but have it turned out to the side of the engine to make it easier to access the mixture screw.

then once you have it adjusted and running nice you can undo the screws at the spinner and turn the carby back around to where it was.

26mm Carby Carburetor Manifold Spinner Adaptor PIT PRO Dirt Quad Bike ATV Buggy | eBay

another thing that would help your engine run better is a slightly bigger Pilot Jet a #20
DHZ sell them pretty cheap $5ea
Mikuni Carburetor Slow / Main Jets

 

[user 21036]

Thanks, I might buy a #20 jet...
How much difference will turning the air/fuel out 1/2 of a turn make?
I'll take a photo of the carby and the condition and how much it's been turned in

 

[my67xr]

try turning it a 1/4 turn at a time, then take it for a ride to see what difference it makes
listen for a hesitation as you pull the throttle on.
and listen for popping as you back off decelerate.

 

[user 21036]

Here are some pictures:

Spark plug is fully 100% black, sorry the picture is so out of focus


Also some pics of the carby (how unclean it is, and also how much the air/fuel screw is in)

And lastly please watch this video of my front sprocket and how loose it is














Please click this image to view the video

 

[my67xr]

the carby does look pretty dirty inside.
must have been filled from a dirty jerry can, and sat around not being used for a while too.

you could try giving it a thorough clean out with carby cleaner etc, but it could take a while.and carby cleaner at $10 a can.
just be careful when taking it apart too, don't bend the tab in the middle of the floats or it will change the float height.
and pull all the jets/screws out and blow it out well with compressed air, replace the Pilot jet while you are at it? (the smaller o/d long thin one)


or for about $45 you could replace the whole carby with a new one.
26mm Mikuni Racing Carby 110cc 125cc 140cc 150cc Bike Dirt ATV PIT Trail Quad | eBay

sprocket movement looks ok, then wont sit there firm when new, but they are cheap to replace anyway.

 

[user 21036]

When I had the carby out I looked on the small one and it had a weird square thing on it and the number 20... So I presume I already have a 20 jet.
I cleaned it out with methylated spirits and brake cleaner, I got a fair bit of it out and scrubbed it with a tooth brush so I presume the stuff I couldn't get out won't really harm anything will it?


I had a look down at the head while it was idling and realised I saw smoke coming out from the exhaust port, I just assumed it was the gasket so I undid the two nuts holding the exhaust pipe on. The first one came off fine but the second one's stud keeps spinning (nut stays there the whole stud spins)

Now I ended up not mucking around with it and came straight to here, Does the exhaust stud need to be welded, or is it actually threaded into the engine?



Also I undid the fuel/air screw half a turn and in the 15 second squirt around the backyard it is shaking a lot less in low revs!
I also redid the valves properly, as in I got them on 0.003 and 0.004 exactly so I can't blame anything on the valves anymore


Edit: Just test it then and if I rev it quickly (probably around 1/2throttle) it just bogs down/stalls. Could this be due to a block jet or is it because of the air/fuel screw?

 

[Blender]

the studs are threaded into the engine. if the stud keeps spinning, just let it come out with the nut still attached, and take the nut off once the stud is out. you'll need to buy a new copper exhaust gasket too, they are a crush fit, so once its fitted and sealed, once its taken off it wont seal, and you'll have a leaky exhaust.

are the exhaust studs rusty at all?

 

[my67xr]

if it has a #20 then i guess you are ok for the Pilot Jet.

for it to stall at 1/2 throttle, there is still a blockage in the Needle Jet maybe?
the brass threaded tube that is where the Main Jet screws into, the holes that goes across it, from the middle section and down to the threaded end, are for 1/2 to full throttle
they all should be open/clear
while it is out check that the hole where it fits into the carby is free of dirt too.
it looks like this when you take it out-

the nut may be locked onto the studs' thread too and be undoing the stud out the head
if it is this, then you can keep undoing it (with the other nut completely off)
and then the exhaust should drop down and come off.

the other thing it could be is if that nut was done up too tight, it might have stripped the thread out of the nut
you could buy another nut, and to get the old one off, you can put a big flat screwdriver in between the flange plate and head, and try levering it away from the head as you undo it.
you might get the nut off without too much effort.


otherwise you could use some of these stainless steel nuts with the serrated face so they don't come loose,
and wont rust
Flange NUT Stainless Steel M6 HEX Serrated 10PCE Washer G304 | eBay

 

[user 21036]

Hmm okay, I just took off the carby again, blew through all of the jets and it still stalls when I rev it quickly, and it feels as if it doesn't have any compression except at TDC...


I had a look through all of those small holes and they all looked 100% clear, Is it possible that it has to do with the valves?

 

[user 21036]

EDIT: Not the air filter, not the mixture screw.
Either valves or possible a blocked jet (even though i've checked twice)

I'm leaning towards the valves because I feel hardly any compression until I get to TDC


Any other ideas on what it could be or do you think it is more likely to be one rather than the other?

 

[my67xr]

it would take a lot of oil to restrict it
can you try and squeeze most of it out with a doubled up paper towel or similar on both sides ?

it only need a light spray across it to be able to pick up any dust etc.


so it stalls when you blip rev it ?
if so it is the Pilot Jet or idle circuit

maybe try richening up the idle mixture, screw it back in the half a turn you turned it out, then go in another 1/4 turn and try it.

 

[user 21036]

It still does it without the air filter...

I guess it would be the pilot jet or the mixture screw.... but I always thought it was running rich?


No chance it could be the valves could it?

 

[my67xr]

when you removed and cleaned the jets did you do the side holes in the Pilot Jet?
and where it screws into the carby base, look into the bottom of the threaded section of the carb, can you see light though the end of the hole ?

 

[my67xr]

you have done the clearances on the valves a couple of times now.
did the cam gear mark line up close on the mark in the head at 9 o'clock ? (within a couple of mm's)
and did the T mark(or straight line) on the flywheel line up with the mark in the case at 12 o'clock? (within a couple of mm's)

 

[my67xr]

the only other thing that could be restricted is the Pilot Jet port, or the tip of the mixture screw might have some dirt there ?
but you'd need to get the carby apart again and blow compressed air through the air filter side small ports
and check that it is coming out through the pilot jet hole in the carby base.


another trick you can try, is take the air filter off, hold the palm of your hand across the filer side of the carby to block it off.
then kick it over a couple of times, this can put a load of suction through the ports and sometimes dislodges a blockage.

then try kicking it over and trying to start it again,
it will take a few kicks to fire and run properly after doing it

 

[user 21036]

I'll try that last trick, It's really hard to get the feeler gauges into the exhaust valve, Because the bash plate it in the way, And the angle that the feeler gauge is on when it is in there it's hard to tell how tight is.


I'll try the air filter trick tomorrow morning and then i'll just try turning the air mixture screw a full turn in or something just to see if it does work

 

[my67xr]

the bash plate only has 4 bolts holding it on, just remove it to do the exhaust

 

[user 21036]

Ohh I thought the engine was actually bolted onto the bashplate, Because there are 4 bolts down the bottom, 2 on onto the sides of the engine

^^ I think that's correct, I always thought they were there to hold the engine in place

 

[my67xr]

yeah 2x 8mm headed bolts into the bottom sides of the head, and 2x 10mm headed bolts under the engine(they go through the foot peg mounts too)

 

[zwebx]

most of us, undo the front two bolts from the bash plate and bend it down a little.. then after bend it back up