Curvy won't idle without choke, won't do mid throttle, will rev
 

Oh yeah, hello Org- it's that annual post I do where I remember I own a bike. How are we all?

Actually decided to do some work on it this winter though, and first things first, it starts but it won't idle even when warm without choke, and as soon as you add throttle it stalls. But if you just blast it open it'll run happily, it's only low revs and idle that it's trouble. Filter in or out makes no difference.

So I am thinking, fuel or vacuum basically, some of the hoses look pretty dubious but fuel has to be the number one suspect since it's probably full of varnish. Anything else I should think about before I get into the carbs themselves? I may do the vac and fuel hoses on general principles.

Oh yeah, these Yuasa YTZ12S batteries are flippin amazing- it's been dead for years, stuck it on the optimate for a day, and it's as strong as ever.

Also, I was taking it to bits tonight and thinking "I remember nothing" but my hands totally remember how to get the carbs off. Now i just need to figure out what all this apparently random extra wiring I added is for.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Your bike is registering its displeasure at having been left in a dark corner, unloved and ignored for yonks. As a penance you are required to strip down the carbs and remove carp from very small spaces.:(

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Buy a bottle of RedX fuel treatment.Stick half a bottle into half a tank of fuel and give the bike a good run.See if that clears it out :)

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

i'll say blocked primary jets in the crabs. once the choke is off then the primary jet takes over as far as i can remember.

give this a try first. using a can of compressed air or brake cleaner with the straw attached blast some down the two jets you can see at the top of the carbs making sure that the straw is making a seal between jet. only use small bursts till it clears.

start bike and warm up then turn tickover up a little then shut choke off and do the same as above.

redx wont shift gum in blocked emulsion tubes or jets. it requires a strip and blast with compressed air.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Blocked crabs, got it.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

I will second that, worked like a charm for me with bikes that had stood for a while, then I took to adding it to fuel before laying them up, that prevented it happening at all, also worked on motor mowers, start second pull after 6 month winter layup and idle well straight away.

For me it is a no brainer not to try a good dose (in a case like yours tip 500 mil in - don't mess about with reading dosage on bottle) you would be amazed the effect it has.

At £5 or so it is cheapest option.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

WINDY! How are you, you old stick? Frankly Redex is mindless optimism, but who says it won't work, it'd be easier than spannering. Sounds like a blocked pilot jet or two, it's a faff but after this long the crabs could do with a bit of attention.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

I have seen the effect sploshing a bit of redex around in a dirty lacquered up carb has, the gunge disappears like snow during an 'H' bomb explosion. It is mainly kerosene but has other stuff in as well.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Agreed. My dad has a rarely used curvy and it suffers from this problem almost every time it's dragged out. An old trick that can sometimes provide a quick fix is to remove the airbox, start it up and rev the engine and then stick your hand (or some other flat object) over the end of the carb for a few seconds. The sudden high vacuum helps to drag any blockages out of the jets, though it will splutter a bit as it will run very rich whilst you are blocking the carb.

Obviously repeat this on both carbs in the case of the SV. Don't try this using your hand on large capacity engines either...

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

I have successfully treated a number of carbed bikes (and lawnmowers and generators) displaying exactly the symptoms you describe, when carbs are left unused the Dinosaur Juice evaporates and leaves gum and lacquer from long dead trees and plants behind to glue things together and block jets, this is easily removed with a good glug of good ol redex (without using any tools other than the key to the fuel cap). After it has sorted this problem I would put some in before you leave it unattended in a lonely dark garage or shed again. £5 to try it WTF! are you delaying for ?

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Also worth noting is that Ethanol isn't particularly friendly to your bike, especially when you leave it in there for protracted periods of time. Some brands of Super Unleaded used to be Ethanol free but I think they all pretty much have 5% now, although maybe Shell and BP Ultimate might still be holding out (I gave up trying to avoid Ethanol eventually and now just use additives as has been discussed).

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

+1

Ethanol attracts water which will cause corrosion in fuel systems not specifically designed to handle it.

https://auto.howstuffworks.com/fuel-...age-engine.htm

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

yes alcohol does attract water like brake fluid (hygroscopic) but it actually helps emulsify the water that usually sits in the bottom of the tank so is actually helping to stop the tank rust.

the big problem facing carbed bikes that use fuel with alcohol is the lack of lubrication in the float bowl chamber resulting in sticky floats and shut off needles/valves resulting in the carbs flooding. adding a tiny bit (a few ml per tank) of say 2t or indeed any oil to the tank will help in stopping the above (do not add to FI bikes). the good news is that the alcohol helps with winter carb freezing.

alcohol will not rot rubber or plastic components any quicker or slower than petrol.

the gel like substance that is left in the carbs after prolonged periods is emulsified petrol as the carbs are open to the atmosphere.

there is no need to put any fuel additives in modern FI bikes.

modern fuels are designed with additives to help keep the combustion chamber and associated components clean so there is no need to put any more in such as redex, your just throwing your money away.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

We will just have to disagree on that, after I started using a bit of redex every so often and over winter, I have never had a problem with fuel system on bikes, and still glug a bit in cars every so often and never had any fuel system problem with them either. Makers will put minimum additives they can in fuel, and if you buy Ultimate or such 97RON it actually costs you more than redex taken over a period. I have seen Redex bring engines back from the dead, no-one ever saw J3sus do the same, but millions still believe in him LOL

We are not talking about a lot of money here, a quick trip to Halfords or local motor shop (or even Asda etc.) - it either cures it or it won't, but it won't cure itself by talking about it and recommending stripping carbs down ultrasonic cleaning etc.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

I've been doing a bit of reading up and apparently Supermarket chains don't put as many additives in the fuel as the Branded stations.Also it's not commonly known but Oil companies change the fuel mix for Winter and Summer.

Since using RedX in my Carby bike the last two days longish ride-outs out my Reserve light didn't even come on at 150 miles.Which for a sit-up-and-beg is cool for me and as good if not better than my old Honda CX500s :)

There's a lot of decent reviews around on Fuel Injection additives as well,

https://www.amazon.com/Liqui-Moly-20...ustomerReviews

As these things have done me no harm I think even if I had an FI Motorcycle I'd give them one big glug and then see how they went.For me it's fuel stabilization effect I want as well as my bikes can get left for some periods of time and I've had issues before with,"Stale Fuel" :(

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Speaking as someone who owns several bikes that only get run once or twice a year I'm going to have to disagree with you on that one. I'm not privy to the technical reasoning behind it but I sure know from experience that if I leave some of them with old untreated fuel in the fuel system I'm going to have issues when I try and start them.

Edit: in fairness Bibio I think there are two issues here, one is do we need to add anything to modern fuels to improve performance or maintain the engine, in which case I'm inclined to agree with you, the other is do we need to add anything to modern fuel to stop it going stale and potentially causing issues, and my view is you do.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

I always refer to petrol or diesel as Dinosaur Juice because they are not as clean as they look and when they evaporate they leave gummy lacquer residue behind, both inside carbs and on injector nozzles - this is the remains of old plants and trees, dead sabre toothed tigers, mammoths etc. in fact whatever was there to decay and turn into crude oil.

Petrol that is left untreated in bikes (or even stored in cans for a while) can lose its more volatile compounds which are the ones that explode most easily, so this makes engine harder to start, but the same evaporation leaves residues behind that can block things up and stick things together inside the fuel system, neither of which are helpful.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Its not the dinosaur juice that evaporates it is the additives that are used instead of lead. The lovely carcinogenic things like toluene and benzene. These are very volatile and evaporate out of the fuel which is why old petrol stops your bike from starting. If you could get the bike warm the dinosaur juice would start to evaporate and everything would be fine.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Lead tetraethyl in petrol was used to improve octane rating (ie make it harder to ignite petrol in cylinder and reduce compression induced self-ignition allowing higher compression ratios to be used improving efficiency of engines). That is why other octane improvers you mention are are used, if they evaporate it would lower the octane rating and make fuel easier to ignite.

Leaded petrol used to degrade when stored as well, was this caused by the lead evaporating ?

The availability of 100 octane plus fuel from USA was one of the reasons our aircraft outperformed the Jerries later in WW2, allowing higher boost pressures to be used in our aircraft engines (and other engines like MTB's as well).

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Bibio is right on every point. As said above, old fuel makes starting hard because the lighter stuff has evaporated and left the heavier stuff behind, almost regardless of octane ratings. Also leave it long enough and it does leave some muck behind that needs cleaning out. Some of you guys have had far more success with Redex than the rest of us. Back in the days when I worked in fuel additives it was a generation behind what even Tesco were putting in their 95 RON, it was basically mineral oil (for cleaning the backs of inlet valves) with no dispersants or anything else unless you count redness. I'm sure they've moved with the times so I don't know about now. TBH unless you're on commission I'm not sure why you're getting so aerated about it all.

Unless you've exhumed your bike then ultrasonic cleaning isn't necessary, the usual whizz round with a toothbrush and WD40 or whatever your spray of choice will be sufficient. Redex or anything else won't shift particles of rust, hairs, spiders, water droplets etc. like a blast through a straw.

Windy, you still with us?

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Redex is not mineral oil, it is mainly kerosene with other active stuff, it is for cleaning injectors, carbs and fuel system these days - not an 'upper cylinder lubricant' any more, and has not been for decades. Gone are the days of tipping redex in through carb and filling whole street with oily white smoke.

It really is a no-brainer to try it, it is the least effort and for a fiver even if it does not work it ain't the end of the world. And yes I have had a lot of success with it, and no I don't work for the company.

As for Redex shifting hair, spiders and water - you need Mr Muscle drain cleaner for that. Never found hair or dead spiders in my fuel system, but have found gum and lacquer - which is what Redex really loves.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

When I put my curvy away for winter I use a Draper fuel syphon to easily draw all the fuel left out to put in the car/other bike for commuting. I give the tank a light spray round with WD40 then mix half a litre bottle of Aspen fuel (ethanol free, available from garden centres/garden machinery specialists) with a drop of two stroke oil to pour in the tank and shake around. When spring comes I fill the tank full with fresh fuel which waters the two stroke mix to almost nothing then away we go.

You have to treat all modern fuel like milk, use it don't store it as it has a fairly short shelf life.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

kerosene (paraffin) is heating oil so its mineral. it comes from the same process of making petrol, diesel, tar etc.etc from crude oil.

btw, my bike gets kept outside without a cover all winter, most of the time i dont even take the battery out and i never drain the tank. come the start of the season it fires up first or second push of the button. the bike has only ever let me down once with electrical problems and that was the connectors on the RR. i have only been through one battery in the 7 years 37k i have owned it. oohhh and it only ever gets used once a week on a sunday apart from my annual tour up north which is a long weekend.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Same thing but difference class, jet fuel being a heavier distillate. Redex is sold containing 60%+ of the stuff :p

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Well that stayed impressively ontopic :rolleyes:

In proper Northwind form, I've derusted the subframe, removed all the plastics and started refurbing my spare petrol tank, and not actually looked at the crabs. Oh and ordered about 6 different sets of indicators from aliexpress because I couldn't decide which ones looked nicest, and my Buell ones have dissolved and fallen off. And taken the front brake lever off, for reasons I'm not clear on.

Thing about additives is while they can work if you put them in before you park it, once things are blocked up they generally don't get to where you want them. It has bp ultimate in which is generally pretty stable but, it is about 7 years old soooooooo

In the name of keeping myself on target for fixing the fuelling, I am now looking at 3D printing some brackets for a headlight. That'll sort it.

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Classic Windy

Re: Curvy won't idle without choke, won't do mid throttle, will rev
 

Yep sounds about right lol