Rough warm up?

[darrsi]

Over the last few days i've had to persevere with the bike to get it to warm up, mainly at the initial start up.
It's very throaty after hitting the button and i have to coax it in to life with the tiniest amount of throttle.
Once it's cleared it's throat i let it tick over for a couple of minutes then i'll warm it up by riding, but even that takes another 5 minutes.
The thing that's confusing me is that it's been fine all over winter with the really cold weather, but today for instance was way warmer than we've been used to and it's been starting like a pig.
The battery's okay, no issues there, and once it's properly warmed up it behaves absolutely fine.
Got a newish K&N fitted, and the bike's used 5 to 7 days a week so it's not sitting about.


For the record i initially started the bike today with a Moto GP end can on, but then put my old Quill race can back on and went for a spin and everything felt good.


Any thoughts please ?




Just read this on another forum:


Re: Engine Rough at Start Up

Update - funny thing....after doing a valve adjustment on my ST1100....found 2 valves were on the tight side...at the limit but not below the limit....guess what ? Two shims later they are all back in exact specs now and NO more rough start-ups. Only did it on very cold days and for very short time. Passing this on as a tip to check your valve clearances if you are having these symptoms.

[philshaq]

Hi Darrsi, can't really add any advise outside of checking the valves as your update says, I did have a question though, do you start with or without the choke? I use mine through the working week and always start it on the choke for 30 sec.

[darrsi]

I've never used the choke, never needed to.

[philshaq]

ah right. Might be worth a bash to see if it clears its throat a bit quicker.

[darrsi]

I'll try it in the morning, too much air would aim at not enough fuel or an air leak, although once it warmed up it ran perfectly well so that doesn't sound too likely in theory??
I've had an air leak before via a carb intake rubber not being refitted properly and it causes hesitation on hard acceleration, it wasn't doing that today!

[philshaq]

Yeah you're right, doesn't make much sense if its working fine when its warmed up. What makes you think its getting too much air?


If there is something a-miss then starting on the choke might just hide the problem rather than cure it and get it back to starting as you are used to, which I'm guessing you're aiming for.


I use the choke out of habit so tomorrow will try it without!


Sorry I can't be of more use.

[darrsi]

I was just explaining an air leak as an example, and what happens.
I'd imagine as soon as i touch the choke the engine will just cut out, at a guess, i'll let you know tomorrow?

[philshaq]

sounds good.

[darrsi]

Bike started on the button this morning, and it was much colder than yesterday, then it got a little bit throaty so i tried the choke and it just cut out straight away, which i expected.
It felt a tiny bit better than yesterday but i'm still not convinced that it's quite right, although again once warmed up it was fine?
Definitely way too early to even consider worrying about the K&N filter, so i'm still a bit stumped as it never used to play up in the mornings at all?

[Ebme Geek]

i tried the choke and it just cut out straight away

What I find with mine is it will fire up without choke absolutely fine, but as I put the choke on to hold an idle while it warms it will die unless I give it some teasing on the throttle, couple of gentle blips norm does it and aim straight tor 3/4 of the choke, then it will sit there warming up fine and I can back the choke off by the time I get out of the drive.

Strange how it dies as the choke is applied, I will have to see if I can find details of the choke circuit, It's fine going off the choke slowly.

[darrsi]

I've never needed to use the choke before so i wasn't really expecting that to help, mine's normally the same, a few blips then it would tick over on it's own no problem at all.
And it doesn't normally take as long to warm up which is why it's so noticeable to me.

[His Dudeness]

Just check all the basic stuff first. No harm checking the valve clearance while you're at it but I'd say if it was a valve clearance problem it would be more of a gradual problem rather than it's fine one day and then the next day it won't start properly

[red98]

semi blocked pilot jets in the carbs 

[darrsi]

@His Dudeness, i've never personally checked valve clearances myself before, is that a pig of a job to do?

@red98, if there was a blockage in the carbs would it not run roughly all the time, even after warm up?

[His Dudeness]

I don't think it's a clearance problem but if you want to check them it's handy enough. The service manual goes through it quite well so have a read of that first. Getting the cam cover off can be a bit fiddly because it hits the thermostat. You can remove the thermostat but you'll have to drain the coolant or you can just unbolt it and you might be able to get the cover out with the thermostat loose. Then take out the plugs and remove the alternator cover. Then rotate the engine and line up the marks are per the manual so you're on the compression stroke on cylinder 1. Check your clearances and rotate the engine again. It's all in the service manual. You'll need a set of feeler gauges and the engine has to be totally cold. The only place you can go wrong is when you're loosening and tightening the cam cover bolts. If you make a balls of it don't blame me :lol

[red98]

two sets of jets in the carbs,pilot jets take care of the slow running,main jets then take over at anything above tick over

hey dude...ive managed to get the cover off before without upsetting the thermostat....it is a bit tight though

[His Dudeness]

two sets of jets in the carbs,pilot jets take care of the slow running,main jets then take over at anything above tick over

hey dude...ive managed to get the cover off before without upsetting the thermostat....it is a bit tight though

bit of swearing will probably get it out :lol

[darrsi]

I don't think it's a clearance problem but if you want to check them it's handy enough. The service manual goes through it quite well so have a read of that first. Getting the cam cover off can be a bit fiddly because it hits the thermostat. You can remove the thermostat but you'll have to drain the coolant or you can just unbolt it and you might be able to get the cover out with the thermostat loose. Then take out the plugs and remove the alternator cover. Then rotate the engine and line up the marks are per the manual so you're on the compression stroke on cylinder 1. Check your clearances and rotate the engine again. It's all in the service manual. You'll need a set of feeler gauges and the engine has to be totally cold. The only place you can go wrong is when you're loosening and tightening the cam cover bolts. If you make a balls of it don't blame me :lol

Probably why i've never done it before, the problem i have is being on call for work at weekends so i can't just start taking the bike to bits in case i have to go to work straight away. I normally have to borrow a bike from my mechanic and let him do the fiddly stuff.
I just checked and the valve clearances were checked 14000 miles ago, not sure how often they should be checked.

[red98]

were they checked or adjusted 14000 miles ago 

[darrsi]

were they checked or adjusted 14000 miles ago 

Don't actually know, 'cos i had a few things done to it at the same time?
The weather's gonna warm up for a whole TWO DAYS so i'll be interested to see if that makes any difference at all in the mornings as well.  un