Inconsistant idle speed

[Brian Bethell]

Hi, I have an RD07 1998 with only 2000K's (it been stored and not stored correctly so had a few fuel probs) Finally everything was running sweet, steady tick over at 1200rpm, no hesitations or flat spots and I was happy.
Got caught up in traffic in 30C+ temperature and the fans cut in and then after that I had problems with the tickover staying at around 2000 (it varied) and then slowly (after 5 to 20 secs) coming back to 1200rpm. Its not the throttle sticking or the chokes I've blanked them off as I dont need them in Indonesia. I have adjusted the air screws (again) and it appears to have cured it (not 100% but getting there) I'm not convinced its the air mixture as it was running so nicely. I think its an air leak but where? I have renewed the carbs to head rubbers - the originals had been poorly fitted and had damage to the edges. New fuel pump, fuel filter and fuel cock. My next move is to fit a Dynojet kit and replace the carb gaskets and "O" rings in case there is an air leak there. I have to wait until I can get a balancing kit before I can checke the carb synch: Whew!
Any ideas or experiences appreciated. I can get the carbs off in less than 20 minutes now. Cheers Brian

[StumpyFingers]

Did you clean out the Carbs?
If they got residue caught in the jets they may give similar symptoms.

[BobA]

Brian

I don't think carb balance will be the idling problem, but correcting it, if it's wrong will give you a smoother engine. Symptoms are usually vibration around 4500-5500rpm.

Idling wise, I wonder if it was evaporation or an air lock? Check the fuel filter and possibly the pump, and if you're running in high temeperatures like that a lot, it may be worth trying to wrap some insulation around them possibly to see if that changes anything. Make sure the fuel lines are following their original routes and aren't in contact with heat sources.

Also check the rubbers between the carbs and airbox, if they're done up too tight they are inclined to slip off and cause an air leak.

If the temperature was 30deg, I'm pretty sure it would have been a lot higher in close confines of the engine.


Good Luck


Bob

[futter]

Air filter?Is it clean/dirty/old etc?

[Brian Bethell]

Thanks for the quick replies and advice. I didn't want to write war and peace but there is more info. Yes to new air filter. I have rechecked the rubbers from the carbs to the head and they "appear" to be still in place although to be sure I'll have to remove the tank, and airbox ...again. The vapour lock might have been an issue but it stayed the same after it cooled down and after I changed the fuel filter (for the second time in about 2 months - as the tank had quite a bit of crud in there). If I can get the dynajet kit soon, I'll do it all again and fit the dynajet kit at the same time. The jets were "partially blocked" when I first got the bike but I blew them through and cleaned the varnish off with clean petrol and it ran well. This is not to say a bit more crud has been disturbed and is now blocking a jet. I might be an expert by the time I have finished?? I also fitted a Leo Vince slip on pipe and it has made a noticable difference to the power spread and the torque at lower revs. There are many variables here but I'm hopefully working through them logically. Fortunately I still love the bike!! Thanks again.

[doglegdon]

Hi mate, I'm over your neck of the woods(Philippines). I had the same problem recently, but put it down to water in contaminated fuel, have you filled up at petrol station you don't normally use, especially after heavy rain/humidity? After using up the tank full I had and refilling at my usual station, my problem seems to have gone away. Just a thought.

[Brian Bethell]

Doglegdon,
Along with the other dozen or so variables I have (I think the previous owners car mechanic had fiddled with various things to get it to run smoothly when the root cause was "a paper cup full" of rust in the tank and the filter and pump full of varnish from stale old fuel" I think you might be right. I was thinking about the level of fuel in the tank as a few people have had those problems when they are having fuel filter/fuel pump problems; but not the contaminated fuel. I always get the best fuel and its RED and if you spill any its "thicker" than petrol I'm used to, greasy almost. The tank is full right now as I'm checking the fuel consumption as I still think its running a little rich. So I will monitor where I get fuel and if I have any problems. The "coming back to 1200RPM idle speed" problem is a fixed as I have experimented leaning the air mixture, but now I have uneven running when on constant revs, particularly at lower revs. Ride it harder and its not noticable. I'm determined to get it right and it stay right - maybe I'm expecting too much? Cheers Brian. PS where are you in Pinoy land? I'm interested to here.

[doglegdon]

PS where are you in Pinoy land? I'm interested to here.

I'm in Negros, the sock/boot shaped island, in south central Philippines to the south west of Cebu island. Barry Neves is in Cebu City, Ned H is up in "Tagalog-land"(Manila), so XRV.UK.ORG is well represented over here!
Great to hear you're leading a hard life, out here in the tropics too!

[Brian Bethell]

Doglegdon,
I'm thinking of moving to the Phillipines and I was going to visit Mindoro, if you have any advice or comments could you please let me know on bdbethell@yahoo.com.sg cheers. Brian

[Austin]

Did you check the valve clearances? Tight valves give inconsistent idling and a slow fall to tick over.