Bonneville America Forums Forums Technical Forums Performance Mods Erratic Idle?

My idle seems to wander a lot. Everything else seems fine and I have
adjusted the pilot screws and still no good. I set it blip the
throttle a couple times let it settle everything is good
then it runs up fast at the next stop, adjust it down blip the throttle
everything is good then next time it stalls. If I am
stopped for any length of time the idle is always a little
faster at first then it will slow down. Any ideas?

throttle cables sticking?

Erratic Idle was a member of Monty Python....

But seriously, mine does the same thing. I think it is the nature of the beast. It seems to get better with age and miles and mods. I now keep my idle set around 1100-1200 rpm and it will still rise and fall sometimes but it never stalls. Synch'ing the carbs seems to help a bit. If you want to borrow my Carbtune, let me know.....

Mine is dong exactly the same thing and I am a bit baffled. Additionally during downshift I throttle down and I hear the carbs spitting (for lack of a better term). I have played with the carbs to no avail. I just did a big bore and cams and starting to think I may be off a tooth especially since there does not seem to be a way to advance or retard timing. I had a fair amount of play in the chain and in playing I did try another tooth and the mark was still just about where the manual says. Any thoughts on this possibility.

could it be carb ballance?

c

The CVKs are just like that it seems. I don't think there is any real fix for them. Mine has always done it, unless I had the Mikunis on, then the idle was rock solid.
I have RTV'd the suckers on, new vacuum caps, not much good. It will idle just fine but ocassionally it will just idle about 100-150 rpm higherf for no apparent reason. I will live with ti as it runs fine throughout the entire throttle range.

Jang0,
Don't you have the fancy CR carbs on now? If so it appears it may be a vacuum issue with the vacuum assisted type carbs. The Mikunis were the flatside ones and worked differently. Maybe the new 39mm FCRs will help?

Pat, I have stock carbs and left the set up exactly like I had before big bore and cams. I had to go out to 4.5 turns on air mix to stop the chatter on decel. I have yet to put the Truxton needles but will once I get these little issues sorted out. By the way have you put in the Truxtons? And if so what is your set up and how is it performing? Except for idle issues the bike just screams with power. I take that back, I am hunting an oil leak but minor right now.

Check all the plastic caps on your vacuum fittings for cracks and pin holes. Also, make sure the manifold boots are OK and clamped right. Too tight is almost as bad as too loose.

I have checked once but maybe your right. This weekend I'll tear into it and make sure everything is sealed. Thanks
Jango

I have checked once but maybe your right. This weekend I'll tear into it and make sure everything is sealed. Thanks
Jango

I looked for vaccuum leaks and found one bad cap and I
did sync the carbs and I figured for sure that would fix the
problem but NOOOOO still the same. I guess I'll just set the
idle abou 1150rpm and live with it. Sound like the nature of
the beast. Besides I got better things to do like chase
strippers and other assorted scantily clad women!

Hi John,
Sounds like it's time for larger pilot jets. I bet both you and Pat have to really hang on now, operating the throttle in a more refined manner, as you both focus on managing wheel loft!

jango,
My current setup is 904cc, stock carbs, with 160mains, 42pilots, ~3 turns on screws, TBS needles, no airbox, K&N filters/freak and the wonderful looking and sounding Thunderbike pipes.
And as I was cleaning every nook and cranny yesterday while it rained, I have yet to find even the slightest leak or drip. This baby's tighter than a drum. I changed the oil and filter again at 250 miles, still on the dino oil, I'll put synthetic back in at 500 miles. The oil I drained was nice a clean, as was the filter I chopped open to inspect for metal chunks, none found. So far so good. I took my daughter for a 50 mile ride the other day and it was amazing that the motor didn't even care that she was on the back, way more torque.

The spark plugs look just like this picture (perfect brown color):

I have the thruxton needles, but haven't tried them yet, maybe later this week.

Pat, This wekend I will try the Truxton needles and search out this leak of mine. I may even change the oil like you did. Not a bad idea. Yup tweak some more. Moe, you are about right on hanging on. The torque is amazing, then too I through that cam in there for good measure. A few more nice weekends, a little tweaking and she goes under the dyno. So who is anxious to know the results??? Pat you may be doing a lot more tech support once the dynos come out. By the way great write up. people will need it and appreciate it as I did. Oh and do not forget making sure you have plenty of patience and beverage of choice.

Jango

Try running a piece of tubing from one port to the other. My idle seems to remain constant since doing this.

OK you guys. Next time you post something like this at least do me the favor of knocking on some wood. Vera has always wandered a bit at idle, but after this post she wandered a bit more. I had a new air filter on my shelf so I looked at my notes and thought, yeah, 10 thousand miles ago back in June '04 I last replaced it. I installed the new one last Monday and the idle wandering seems to have narrowed back to a normal wander...Go figure.

My old filter didn't look dirty until I held it up to the sunlight vis-a-vis the new one. A big difference in light penetration existed.

PS: Something else I did that I never paid attention to in the past. The metal cage overlap on the oem filter was placed towards the rear of the air box. Thought this might give the intake rubber snorkels a better air flow. Yes, I'm going to go to the Uni filter eventually...

anyone see a fuel injection set up for the beast?

These carbs and air box sucks

I ran a piece of tubing from one carb to the other tying
together the two unused vacuum ports and it does seem to
keep the idle more constant.