Idling problem

B

Becker

New member
Location
Australia
My Jota has just been recently resurrected, running well, except when idling facing upwards. When I stop on a hill facing downwards it will idle fine . When i stop on a hill facing up it seems to starve of fuel and cut out unless i constantly keep giving the throttle a little bit of a blip. I was getting a bit of crap in the float bowls at first and thought this must be the problem but after riding and cleaning them out a few times (and puting extra filters in the lines) they seem to be pretty clean now. So I'm wondering what else it might be. I'm a bit of a novice when it comes to this stuff but thinking maybe float level height or something ?? Anyone had similar problem before?
 
I assume there is water in the tank. when you stand up hill, the water collects at the rear end where the pat-cocks are and the level of water rises beyond the point where the little tube of the pet-cocks reach to and it sucks water instead of gas. Easy check: if you go to reserve adjustment of the pet-cocks, the problem should increase.

Drain the tank completely, remove the pat-cocks, clean the mesh filter , make sure there is no liquid and no dirt left in the tank and re-fill with fresh (!) fuel. Also drain completely the float bowls and check the idle jets

If that does not fix it, spray brake cleaner around the inlet stubs and see if there is some leakage.
 
Float level.

Pilot jet is closer to the "front" of the carb and will be starved slighlty on an incline. Matters get better on decline.

Set float heights to 18mm EXACTLY (book says 18 +/-0.5mm, probably 18 +0.5 is closer to what you've got...) and all will be fine.

Anybody accustomed to carbs with side-mounted float bowls will recognise these symptoms. Especially in slow, tight corners, fuel level changes are quite dramatic, causing all sorts of strange behaviour.

piet
 
sfcpiet said:
Float level.

Pilot jet is closer to the "front" of the carb and will be starved slighlty on an incline. Matters get better on decline.

Set float heights to 18mm EXACTLY (book says 18 +/-0.5mm, probably 18 +0.5 is closer to what you've got...) and all will be fine.

Anybody accustomed to carbs with side-mounted float bowls will recognise these symptoms. Especially in slow, tight corners, fuel level changes are quite dramatic, causing all sorts of strange behaviour.

piet
Click to expand...
Hi Piet, you were pretty well spot on , were around 18.6 now around 18.1 and all fixed
cheers Greg
 
Ditch the extra filter, check and clean the filters in thevtaps and the filters on the carbs. Extra filter can cause fuel starvation. You running the later model fuel delivery pipe or hoses from the outside carbs the centre? Fuel starvation possible with the standard setup, especially when pinned trying to keep up with the QLD mob. Try and get hold of the RGS fuel rail. Check with Red.

Cherrs
Marty
 
Incorrect float heights, even minor differences, are hugely under-estimated. Just a little deviation from the vertical magnifies a small difference in height, especially at idle.

piet
 
Still, I would check the other points, too. Be it just for the peace of mind... I know that carefully adjusted carbs in all points make a huge difference. However, these were 0,1mm out of the adjustment range. Not sure this can cause the bike to actually stall. But maybe it depends what (steep) angle of uphill this happened. Piet has way, way more experience than me.
 
Had a break in the rain today and took her out for a couple of smaller runs around the burbs, problem is definitely solved with the float level , didn't cut out on me once , where before it would have for certain
 
OK, thanks for the feedback. Great to hear she runs better now; kudos to Piet once more ;-)

These carbs are quite good, but they really need to be set up perfectly. Had several bikes where the choke sliders where unevenly adjusted - something only a few people take a look at. It caused the bike to only start on 2 cylinders or stall after 20 seconds of running. Putting everything (float levels, idle mixture screws and the choke sliders) to the base setup made the bike run without cutting out, stalling or running rough. It was a fix of maybe 15 minutes really (Floats were already correct, just checked them, Choke sliders and idle mixture screws totally off...).
 
Hi Terry, if you pull the rubber boots up you will see the adjuster and lock nut. With the shorter chokes I had to remove the lock nuts and screw the adjuster all the way down on the sf2 to get some free play. Removing the lock nuts is much easier than trying to shorten the choke cable outers
 
Thanks Marty,
I was wondering if there was any special trick to making sure each plunger has the same lift.
I've measured the length of each cable where they exit the outers and they are the same.
I'll start with the middle one and make sure there is some slack on the outer and then measure the adjuster and set the two others to the same length.
Cheers from sunny Sydney? Are you at 'safe diving depth' yet?
 
Was around at Wills friday night, another submariner, after " a few" beers and looking at the forecast, we moved all the bikes out of his backyard and up to the front yard. Hasnt flooded yet but i reckon its iminent. I back onto the same creek, but higher up. Subiaco creek last flooded this time last year when i was in N Z
 
Legs said:
Thanks Marty,
I was wondering if there was any special trick to making sure each plunger has the same lift.
I've measured the length of each cable where they exit the outers and they are the same.
I'll start with the middle one and make sure there is some slack on the outer and then measure the adjuster and set the two others to the same length.
Cheers from sunny Sydney? Are you at 'safe diving depth' yet?
Click to expand...
Eyeball about the same few mm slack until you feel it starts to lift the plunger is fine. As long as the plunger can sit onto the fuel outlet with a bit of slack in the cable and they lift about the same.
 
yes, just stand right side of the bike and look into the carbs. you see the choke slider on the left side of the intake. make sure they open all at the same time and fully close.
 
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