Idle increases after 5-10mins riding

[nathaniel2910]

Hey guys and gals.
I have just build my gs back up after finding my other gs had engine problems,
Now the bike is a k3 with maybe 10-15,000 miles on(didn't come with clocks so unsure of exact millage as of yet).
The main problem I'm having is the bike seems to idle at about 4,000rpm at idle after 5-10mons of riding,
Now the bike starts perfectly with the choke and I can turn the choke off after less than 30 seconds and it will idle at about 12-1500 rpm, is a little lumpy but not bad, nice warm it seems to make a little pfff noise every now and again kind of like it's missing but you can only hear it if you stand behind the bike and can hear the exhaust, the engine sounds fine.
I have left the choke on for 5 mins in the attempt to heat the bike up enough to reproduce the high rpm idle but haven't been able to so far, for the first few mins of riding it will return to idle fine, after about 5 mins it will start taking a few seconds to return back and will idle about 1500 that I have set it to, then after that as the minutes pass it will resist returning to idle more until, it will not do it by itself so I have to use the clutch to stop the 4k rpm idle at traffic lights, but using the clutch to bring the revs back down it is very lumpy and makes faint clunking noises and seems to miss every 2-3 seconds, but once bringing the revs back down to 1500 it will stay there,afew minutes later doing the same thing with the clutch will work for a second before the revs rise back up.

No I have been reading other threads of similar problems and there have been suggestions of a air leak, carbs need balancing, throttle cables or choke may be sticking and the throttle slides may be sticking.

Now I will soon be balancing the carbs using the pull suppressor cap off each sparkplugs technique and checking for any air leaks, I will likely use some heat resistant silicone to reseal the manifold ends and the airbox side too just to be on the safe side.

Also I have stripped the carbs and given them a though clean over 2 days, nothing was lost and the slides and diaphragms looked to be in good condition, the only thing I did notice was the fuel screws were set differently, I can't remember exactly but I noted the turns before stripping the carbs and I also checked they still had a sharp point.
I believe the carbs were roughly 2 3/4 turns and 3 /1/4 turns roughly, now I know now they aren't right but I'm unsure what is roughly the correct setting as the bike is currently restricted due to uk licensing laws to 33bhp, this is in the form of smaller main and middle jet along with a shim on the needle and the throttle slide has I believe 3 holes in as the stock one should have 1 or could be the other way round.

So if I reset the fuel screws equally and try to roughly sync the carbs after making sure there aren't any leaks what would be the next steps, I would think valve clearances, I'm unsure about bucket shims as I have only ever worked on nut adjuster ones but I will give it a go if absolutely nessecary I think I will also try and retrieve the last mot for the bike to find a rough millage, which I doubt is much as the frame and running gear were in such good condition and it was still on original rubber.

Any help or hints would be greatly appreciated guys,
Sorry about such a long winded question

[nathaniel2910]

Also on a separate note the rev cable is leaking oil so I'm going to try and use some plumbing joint tape on the threads if not some heat resistant silicone or instant gasket but I'd prefer not to have to use that stuff

[nathaniel2910]

Also after having another think, the left vac nipple didn't have a cap on it, just a bit of degraded hose lime 3-4mm of it like the hose had snapped, I simply removed it and pushed on some clear brake bleeding hose from a bleed kit,cut it short and twisted a bilt into the hose, I'm thinking that might be causing a slight air leak, will seal it aswell while I'm at it, as I haven't come across any vac hose caps other than off eBay and thinking the hose would do the same job I've left it :/

[007brendan]

When's the last time you checked the valve clearance?  I've had similar behavior with very tight exhaust valves.  When the engine was cold, I would have to turn the idle screw up pretty high so that it didn't stall out at stop lights or when rolling off the throttle.  But when it got warm, I would have to turn the idle screw back down.

[The Buddha]

Hovering idle = lean.
If its sucking air, you can try to find it via wd40 spray when idling.
Valves being tight will make the bike want to stall right after startup unless revved.
Cool.
Buddha.

[nathaniel2910]

Cheers guys, the bike doesn't want to stall, from cold the idle is strong, once the engines hot it seems to be less smooth at idle, would it be best to do a compression test to rule out a tight valve?
Also noticed when sat on the motorway a loss of power and a mild jerking happened

[system32]

i had the same problem.
the problem was tighten exhaust valve.
check the valve clearance

[gsJack]

A tight valve is loose within a minute or so after starting as engine warms.  Check anyway, tight exhaust valves have a much shorter life.  A cold compression check will confirm if they are tight or not, thumb over the hole, crank, and pop will tell you.  Only takes a minute when plugs are out and good to do every time they are out.

I had the fast idle, commonly referred to as hovering idle, on my 97 first GS bought new a few miles after summer warm up, a too lean problem, and adjusted it out with the idle speed adjustment knob.  I'd stop and very slowly adjust idle speed down until it dropped to normal.  Repeated a few times and it was gone and didn't come back for the 4 years and 80k miles I rode it.  Never touched the carbs on either my 97 or my current 02 with 100k on it so far.

[nathaniel2910]

Right guys I've checked the clearances and the were
Exhaust L 0.04 R0.05.
Intake   L 0.04 R less than 0.03.
What was in the bike was 270 exhausts and
258 intake.
So swapped out for 265 exhaust and 255 intake.
It's a little Tappy but I'd sooner have that than no noise and a loss of power, I also cleaned and sealed the intake rubbers to rule out any air leaks.
Runs a lot better but idle still rises, after riding for 5 mins, it's back upto 4k.
If I use clutch to bring revs back down its stays at 1500  there's a clear misfire.

The last things to do is reset fuel screw, check float height and balance carbs.
Don't know what else to do after that any ideas

[nathaniel2910]

Hey guys rather than make a new thread I'm posting here first,
I've moved onto the tacho oil leak now I used ptfe tape on the thread of the cable and it didn't make any difference so I have undone the bolt holding the adaptor if you will, what the cable screws into and that slits into the head, well it's broken, when I undid the bolt it simply pulled off the head with what goes in the head still there
Now I'm trying to get what's stuck out of the head but it doesn't seem to want to budge, is there any sort of temp fix for it that anyone's found to work, as I won't be able to get hold of one for atleast a week and I new to use the bike without it spraying oil everywere, I think I'm going to try instant gasket first to see if that will do anything.
Any advice would be greatly apreciated guys and gals

[nathaniel2910]

Sorted it now guys just put on a liberal amount of gasket maker then put some around the seam just to be in the safe side.

I reset the fuel screws to 2.5 turns out which helped a lot, when warm I also turned the idle down to 1.5 from 2k then when hot I turned down to 1.2-1.3k rpm and all seems to be fine now exept if I slowly bring the revs up to 1.8k rpm there's a slap sound like when you run over a crushed drinks can, I think it might be the slides in the carbs. I'm unsure what to do about it other than strip the carbs again but it's can anything actually be done.
I still need to balance the carbs but was unable to as I used 10w40 oil in the make shift balancer(3m long 6mm pipe) and the oil wouldn't sit level and air free in the bottom of the U bend so I'm going to go get some 2 stroke oil in the morning and try that.

[The Buddha]

The intake boots sorta cant be fixed by silicone ... temporarily it works but not long term
Cool.
Buddha.