airbox modifications? motovert

[mudskipper]

After a never ending battle with getting my motovert 160 running.
Zeus has been merciful.

Air screw out 2 turns, jet needle up a notch from centre 'lean'.
I couldn't run the bike no matter what I did.. took the airbox off the carb.

first kick, she runs.
I take it the filter is effecting the air pressure, in turn effecting the air/fuel mixture?
Idle screw is set 1/4 turn above slow idle giving enough to kick over when cold.
I don't want to put on a uni filter as that can lead to dramas with water and gunk during a good ride.

Has anyone modified an airbox for better airflow? or upgraded airfilter to find better response? I would like to keep the thoughtlessly placed airbox so I can do baby river crossings in the hope to keep fudge out of my bike.


PS. thanks to those who helped with feedback on the battle to get it running.

 

[SwapperMX]

Couple of things here, cos no air box in the world, no matter the design should affect the bike enough for it not to start. Is your air filter in the air box drowning in air filter oil?? That is one scenario that may restrict air flow enough for the bike not to start or run correctly. Besides that, the bike should at least run, air box on or off. Also, you are braver than me, wanting to do creek crossings on a motovert 160!!

 

[my67xr]

if it runs better with no airbox, then you'll need to replace the air filter, is it blocked with dirt, or too much oil ?
what sort of filter are you running now ?

i wouldn't hesitate to fit a Uni Filter to it.
and you can get the waterproof filter socks for them too, so basically no mud/water will get through and into the carby.

 

[mudskipper]

if it runs better with no airbox, then you'll need to replace the air filter, is it blocked with dirt, or too much oil ?
what sort of filter are you running now ?

i wouldn't hesitate to fit a Uni Filter to it.
and you can get the waterproof filter socks for them too, so basically no mud/water will get through and into the carby.

I might look into that sock idea, havent touched the original airfilter, nor have i taken
It in the dust or mud, ill pull it out and have a look if it
Has too much oil.

 

[GooseMan]

yep will have to agree, could only be a airflter, airbox's only effect top end performance. Run it with the airbox on but without the filter in. that will definitely varify if it is the box or filter just for interests sake.

 

[mudskipper]

yep will have to agree, could only be a airflter, airbox's only effect top end performance. Run it with the airbox on but without the filter in. that will definitely varify if it is the box or filter just for interests sake.

so even though im on crutches, ive managed to play around with the bike.
Removed the air filter, kept the airbox in place, bike would not turn over.
took the air intake hose off and bam. runs a treat.

took a closer look and I believe this is whats happening.....

it looks like the air jet gets an amount of fuel spat out as if you were to flood the carb with fuel and turn it over, you get that kick back out of the starter.
anyway..
finding some residual fuel sitting across the 2 intake points at the bottom of the air intake side of the carb.
the problem is, the intake hose causes any residue to run back to this low point, covering these points "blocking them" with fuel.

after removing the intake hose and getting a bit of fuel spat out on first kick, the bike will then turn over no dramas.

PROBLEM.
I see it being the intake hose making these jets the low point for liquid, blocking the intake of air. I may need to look at the uni filter if this is the case.

 

[GooseMan]

Have you tried without the choke on?

 

[mudskipper]

nah but can give it a crack.

thinking about it. is it not that fuel is somehow getting out the 2 jets on air intake end.. but fuel leaking into carb from slide as though im flooding it?
once this happens, these 2 jets are now blocked with fuel until I can clear them.

that a better explanation?

 

[GooseMan]

either way there is too much fuel there. The choke being off may help, but it will probably result in you having to dismantle the carby cleaning it, adjusting your float level and you may also have to big a jets. By putting the air box on this is restricting the air flow just a little causing a richer mixture, which will cause the fuel to spit out as you mentioned.

 

[mudskipper]

either way there is too much fuel there. The choke being off may help, but it will probably result in you having to dismantle the carby cleaning it, adjusting your float level and you may also have to big a jets. By putting the air box on this is restricting the air flow just a little causing a richer mixture, which will cause the fuel to spit out as you mentioned.

SPOT ON.
First run in the mud a while back found my bike had flooded and wouldn't run after, spark was oily black....
.
after putting it all back together inc filter. I couldn't get it to start without choke, even then it was a battle.

Before I look at smaller jets from current MAIN 100/ Pilot 20, I will confirm the position of the jet needle in the slide, I read if you need to go outside one of the 3 centre notches, you should be looking at jetting. (top)1!111====(bottom) position on jet needle I am referring to is where I feel it should be atm.

if I drop jetting size, should I drop a size in both Main and Pilot?

 

[GooseMan]

That depends on how it runs, main might be fine, hve you dismantled it at all? Check the centre needle as you said. Did it run alright before this? Thry cleaning you plug as well, or better yet get a new one. What bothers me is if it ran fine before then jets should not need changing, there must be another reason for the flooding. If it has bean dismantle then something might have been put back together differently.

The other thing I just though I'd ask is it spitting the fuel out right from the first kick or two? Or is it after a few kicks? If it takes a while for it to spit fuel the that will just be because the fuel going in is't getting burnt. Which could be electrical......

 

[mudskipper]

That depends on how it runs, main might be fine, hve you dismantled it at all? Check the centre needle as you said. Did it run alright before this? Thry cleaning you plug as well, or better yet get a new one. What bothers me is if it ran fine before then jets should not need changing, there must be another reason for the flooding. If it has bean dismantle then something might have been put back together differently.

The other thing I just though I'd ask is it spitting the fuel out right from the first kick or two? Or is it after a few kicks? If it takes a while for it to spit fuel the that will just be because the fuel going in is't getting burnt. Which could be electrical......

I have for ever had ongoing problems with this bike with it starting, every electrical component was swapped out inc a recent carb. which has all parts. will only spit fuel when I get a kick back out of the starter, can only tell with thee intake hose off.
tomorrow ill check the position of the jet needle and correct it if need be, I have Main 97.5/Slow 17.5 on the way to trial.

Im concerned that if its just lean enough to start with fly wide open inc no air filter, its way too rich and it will continue to run rich. only leading to the spark not firing once it is running hot for a while.
Ill try with the jetting as I want to keep the airbox, I feel it is essential to have it running more lean that I need choke on a cold start, otherwise its already rich when its cold.

 

[GooseMan]

ok then could be jets, give it a go and see what happens.

I'm the same, I would like to have an airbox on my bike.

 

[mudskipper]

current status.

Main Jet is out.
Swapped slow jet for a 17.5, down from 20.
Jet needle in centre possy.

Air screw tool just arrived for adjusting during jetting.
Cast comes off leg tomorrow so as soon as Im walking * next day I hope * I can start working with the jetting.

What I have already noticed, it has changed from too rich to now lean. Requires choke and a bit of throttle until it has warmed up. I have a jetting sequence to run through, thus the reason for the main jet being out and its too loud 3/4 rev on the stand so I need to ride it for a response.
Sitting at 2 1/2 turns out on the air screw, that's what I can work with.
Also the throttle takes an amount of time to drop to idle, I shaved the grip edge back as it rubbed on the hand guards but I believe either the cable needs some lube or the idle screw position is effecting the round slide. Mind you, metal on metal doesn't make for the smoothest surface.

Big rant done, ill post an update in a few days that may help some motovert people.. still waiting on new air filter foam.

 

[my67xr]

have you checked the valve clearances?
having them set too tight can make fuel spit back through the carby.

the pilot jet is for idle up to just over 1/4 throttle.
if it blip revs ok, then i would stay with the 20 in the pilot circuit.

another thing to look at, if your slide is sitting up a bit high, it can be drawing fuel though and making it look like the pilot jet is too big/rich

 

[mudskipper]

valve clearances, worked my way down to .003 and .004 to a stage where there is no more rattle, feels a lot better, only .0005 above was too noisy.

with the previous 20 idle, I never needed choke as it was way too rich with idle screw set out quite a way and air screw at 2 1/2.
ill test with smaller as to drop the airscrew and adjust the idle if possible. found a note that winding idle in a wee bit more can help with throttle sticking above idle..?

tried running it but fell over on my newly repaired foot, so im banned from enjoying my bike for another week.

 

[mudskipper]

Back on my feet with current setup running.
Dropped both Main and idle jets to 97.5/17.5 and jet needle a touch lean.
New air filter material and airbox is on, air screw 2 1/4 turns.

Starts first go and needs choke to warm up, big improvement. Putt around for about 10 mins each day in 1st gear to get an idea of how she holds up when shes hot.

Final dramas include:
1)takes time to kick start after stalling, unless thats normal
2)still seeing fuel spit back out of round slide, when airbox hose is on, this covers what look like air intake ports
3)spark still black, *yet to really open up the throttle

Q's.
Someone with knowledge, could you check my Off road vehicle permit Q's - regarding the engine numbers I posted?
Should I back off my carb draining screw just a touch as to allow drip of fuel out if it floods?
Any ideas on why spark is staying black?
Also, why I still get excess fuel spitting out slide?

So close, yet so far....

 

[my67xr]

the spark plug wont reach the self cleaning temperature of 450 degrees c unless you are riding in the mid - high rpms for a while
thats why you need to fit a new/clean plug and do 2 or 3 runs at wide open throttle and under load before you do a plug chop to check the colour.

why is your bike flooding ? too high float level ?

 

[mudskipper]

I am hoping to not have to touch the float, running off how it was put together stock.
Will spit fuel out intake end of carb if fails to turn over, usually after stall. At which stage
I find myself waiting a minute and giving it a hard kick to turn over. I havent read much about
any specifics when adjusting float levels as I imagine a small adjustment could have a big impact?
But this fuel spitting back out is a real pain.