idle jumping

[mealexme]

Long time no speak! Mainly because I havent been on the computer much for a while, and the sad thing is I probably had more of a life when I was on the computer every day haha, but anyway, I obviously am not cut out to be a mechanic!

I decided to change the spark plugs and air filter for K&N filter and iridium plugs. No real reason for it, its not going to do anything to the power (or so I thought) with the restriction in, but I wanted to put the best in.

So, I do it all without a haynes manual (get me!) and put it all back together again but forgot to put the vacuume pipe(?) (the line that goes from the petcock to one of the carbs. The petcock has an on, reserve and a prime setting if that helps. It definitely wasn't the fuel line itself.) and started it, revved it (because im a yob) and realised after a few seconds, shut it off and reconnected the pipe. Started it up again, it was running alright as far as I could tell and didnt think anything of it.

The bike ever since has run like it does if you try and ride just after starting the bike and not putting the choke on. Or if its running out of fuel. Jerky.

I checked everything that I had done today, checked the plugs (all four have the same marks on them so one doesnt seem to be getting hotter than the others, or not working as well as the others) checked the air filter was seated correctly, pipes not blocked, pipes not pinched, clips all on correctly and have a tight seal as far as I can tell. Cleaned the carbs with carb cleaner (didnt take them apart) made sure I had enough petrol etc. Went out for a ride letting the bike warm up for a few minutes before hand, riding for about 5/10 mins and the problem persists. When I stopped I realised the idle was both low (1krpm) and inconsistent which is why it feels jerky whilst accelerating. I managed to get the idle speed higher (I found the dial to do that all on my ownsome!) as it may have been turned a few days before I did the service by a mate by accident (trying to find my petcock haha) but I didnt notice, so that problem is sorted.

However, the idle speed still jumps anywhere between 1.5k and 2.3k randomly. The needle does not want to stay still! My mate may have changed the idle speed, he may not. The two may be connected or they may not, but does anyone have any suggestions?

Could not connecting the pipe the first time cause damage to the engine?

Could it be dodgy plugs?

Anything else?

EDIT: I also have an aftermarket exhaust that has no baffle (I lost it) so could it be the aftermarket can with an aftermarket air filter means that the air is just passing through too freely (is that even possible) I dunno, this is why I need you help lol

Thanks, Alex

[Tango]

Sounds like you may have an air leak somewhere.......probably not major....so it could take a bit of tracking down. Also if you have taken the baffles out of your exhaust and put a high flow air filter in you may need to re-jet your carbs....

[Stu]

Tango Its still restricted in the carbs too so I dont think a rejet will really help to be honest

as for the idle as Tango says check for an air leak

[Tango]

Tango Its still restricted in the carbs too so I dont think a rejet will really help to be honest

as for the idle as Tango says check for an air leak

True Stu.....I guess if it's got washers between the airbox and the carbs that'll restrict the flow enough.....

[mealexme]

an air leak you say?

A how the hell do I find that, when to run, the tank has to be fitted to the bike (the fuel line is really short) and wheres it likely to be? In the vacuum pipe?

But im guessing I will need to look into rejetting in the future then, once the restrictor kit is out. I think I will have to get a garage to do that one for me, even though I HATE garages. £40 an hour? Rip off! Or is it something I can do myself (well, obviously not if I cant even change a few spark plugs without destroying the thing)

Thanks for the quick, direct replys!

[Stu]

for rejetting you dont go to a garage!!!

you go to a tuner with a dyno they will run it first to see if it needs doing then if it does it will cos around 200 notes well worth it though

to find an air leak just go over your work and check everything and use a squirt of wd40 around the inlet rubbers while its running you will soon know if its there

[eastanglianbiker]

it could just be getting to much air due to having the K&N filter in it try putting the original one back in and see what happens

[Fozzie]

I think Boothy had an issue when he fitted an K&N filter

[mealexme]

I think Boothy had an issue when he fitted an K&N filter

Oh good. I kept the old plugs, I even keep old indicators for the bulbs/wires, I still have my old broken brake lever from when I came off a while ago just incase I come off again and brake the new one even worse. The ONLY thing off the bike I have thrown away straight away was the air filter... :/ Typical

I thought K&N made products to make things better anyway so why would it make it worse? Something to do with it being restricted? But if its restricted then the air flow is restricted anyway, so it wouldnt matter what air filter I had on it surely?

[eastanglianbiker]

K&N 's generally give improved air flow into carbs so in yor case it will be making it run very weak and as fozzie said i seem to remember boothy having similar probs with filter

[mealexme]

K&N 's generally give improved air flow into carbs so in yor case it will be making it run very weak and as fozzie said i seem to remember boothy having similar probs with filter

im not trying to argue here just understand, but I thought air flow was directly linked to the amount of fuel due to it being pulled in by the vacuum, so surely if there was more air then there would bemore fuel? Also I thought the restriction worked by restricting the flow of air anyway so hympothetically it wouldnt matter if I didnt have an air filter on it, it would still take in the same amount of air due to the restriction? (and yes, I know I need an air filter so stop the dust and crap getting through )

But yea, I shall get myself another new filter. Thankies for (hopefully) sorting out my problem

[eastanglianbiker]

no totally wrong thinking alex the air filter restricts the amount of air flowing through the carbs as the air enters into the rear of the carb and not through a jet inside the carb the less restrictive the filter the weaker the engine will run.remove filter completely without rejetting it and it will just bog down when you try and accelerate

[Fozzie]

Basically you have carbs with jets... They supply fuel, from different jets at different points of the rev range. E.g. Idle jet deals with keeping the bike going with no throttle and little air flow, up to the main jet which is supplying fuel at the top end.

This corresponds to an amount of air. The filter restricts and keeps the air flow clean.

If you allow more air in you could supply too much for the amount of fuel it can draw from the carbs, and so it runs lean or very badly in easy terms.

This is why when you up the air flow you re-jet the carb for bigger jets

I think I got that right

[mealexme]

right, got it.I think lol.

Any idea how much rejetting is roughly?

[Stu]

right, got it.I think lol.

Any idea how much rejetting is roughly?

 

Read above I answered that for you!

Don't jet it yourself get it set up on a dyno as you don't know how its running! You just can't guess these things

[mattycoops43]

I'm not a fan of K&Ns for the simple reason that the airflow changes drastically as it gets dirty through use. They are designed to be cleaned obviously, but because they are wet filters needing oil, i tis much more drastic than on a standard dry filter which will provide roughly the same airflow for a lot longer before it gets clogged. I am not knocking K&N's, they do what they are meant to, but I am saying unless you're in a race situation where it will be removed and cleaned very frequently, most peoples maintenance schedule is just not up to it.

Or to put it simply, a dirty K&N is worse than a dirty paper filter.

So, you're bike will be fuelled correctly for about a week until it gets dirty, then it won't run right. I used to fit gas kits to landrovers, and we always took k&n's off as they were not reliable enough to keep a gas system running right as they are much more sensitive to mixture than petrol engines.

[mealexme]

right, got it.I think lol.

Any idea how much rejetting is roughly?

 

Read above I answered that for you!

Don't jet it yourself get it set up on a dyno as you don't know how its running! You just can't guess these things

so you did. I read every part of that post apart from the cost lol.

and it seems that k and n probably isn't the best for me then

[eastanglianbiker]

if i was you i would go back to standard lot less hassle

[Fozzie]

I'm not a fan of K&Ns for the simple reason that the airflow changes drastically as it gets dirty through use. They are designed to be cleaned obviously, but because they are wet filters needing oil, i tis much more drastic than on a standard dry filter which will provide roughly the same airflow for a lot longer before it gets clogged. I am not knocking K&N's, they do what they are meant to, but I am saying unless you're in a race situation where it will be removed and cleaned very frequently, most peoples maintenance schedule is just not up to it.

Or to put it simply, a dirty K&N is worse than a dirty paper filter.

 

 

I agree however my bike and bikes such as the Kawasaki ER6F use wet filters as standard.

I have replaced them on both though they werent that filthy, they were discoloured but nothing horrible in there.

[mattycoops43]

Yes, you're right, but on a wet filter, you'd be surprised how much difference that slight discolouration makes. I don't know if they have changed, but k&n's used to be bad for this, worse than other makes.

The best type was the old vortex oil filters on early landrovers, a big cannister full of coarse wire wool, with an inch of engine oil in the bottom. The oil wicked up onto all the wool. The air was directed into a vortex through the wool and any dust particles stuck to the oil, any big bit fell to the bottom.

Good enough for desert conditions, no loss of airflow AT ALL, and only needed engine oil topping up every few years. Only downside is they were about 18" high by 10" round and weighed a ton!

[Boothy]

Just seen this... Yep I bought a K&N filter and it just messes up your fueling best thing to do is just buy a standard Suzuki one or a pattern one. The only way to get it fueled properly with a K&N is too get it re-jetted at a dyno place and your talking a good £250+ for that so not really worth it.

And I've also tried it with the standard can and with a 350mm aftermarket one with no baffle and it made no difference still cocked up the mixture.