Interesting idle problem...
 

Well my bike is running much better, but once it warms up, it doesn't want to idle. Just wants to slowly creep down the rpm range and die. It didn't always do this, it's a new issue. I thought it was the fuel pump I added, so I removed that and went back to the stock setup. I even went into my carbs on both sides to make sure that everything was working correctly. Everything looked fine, so I put them back together. Still happens. For those who read my other post you know I took the top of the airbox off. Well I put it back on the problem persists. Anybody have any ideas what this could be?

how fast does it go from good idle, say 1000 rpm to dying?

Man you got all sorts of problems with this bike

You're tellin me man. But, besides this new problem, I think All other problems have been fixed. And if I let it sit for say an hour. It will run for 15 minutes at good idle, then over the course of 30 seconds or so slowly drop down until it dies. No matter what the idle is set at. But it runs fine outside of idle. Revs quickly up the whole range and pulls hard.

What are ALL your jetting specs?

What are ALL the intake mods that have been done?

I know you have a fuel pump, no airbox lid, and a non-standard filter, so we need to know the exact set up you have to give you any ideas.

No, actually, I have NO fuel pump, I HAVE an airbox lid on a stock airbox, and a k&n filter. I have a single sided two bros racing exhaust and all emissions removed. I have a 190 and 195 main jet, stock slow jets, needles to the 5th clip from the top and mixture screws set to 2 1/2 turns out. All of those settings are exactly what dynojet recommended. And it was working fine. This is probably something I did... But I'm not sure what. I thought it would be some stupid mistake but I took the carbs out and apart and it is still going on.

Possibly a pvlir?

Pull a plug and take a picture, maybe we'll get some hints from there.
I'm thinking damaged needle/seats assy. or something in the fuel bowl aera.
Why did you need a pump in the first place and how much pressure ??

+1^ I had a bike that did the same thing you described it would idle fine for a few minutes than die. It was fowling the plugs on idle, but was not on cruising rpms.

Ok, with a relatively stock bike I think those mains are too big. Main jets will have an effect on the entire rev range.

DJ jets are numerically bigger than Keihin or Factory Pro for their actual size, but they still seem too big for me on a stock engine. My engine is not stock, so I am not an expert on jet sizes. But I think it is worth trying something smaller.

I agree, but it's not stock. Like I said, single sided exhaust with two brothers racing can, and a k&n filter. And with those parts, dynojet recommends 190 and 195 jets... And main jets really have nothing to do with idle. Plus, like I said, it didn't do this a week ago, so that can't be it.

I think your bike is stock enough for comparative purposes. An exhaust and aifilter is fairly common.

Factory Pro do not agree with your comment on main jet effect.

http://www.factorypro.com/tech/carbtun.html

did you check your vacuum lines to make certain they are correctly placed? did you check the TPS with a multimeter? what does it read? most are out of adjustmt.

Well I did just set my tps... it was in the 800s. and I went as low as I could without modifying anything. like 550 I think. I put it back to where it was originally tonight... I'll try it out tomorrow. I know it shouldn't cause any problems but I'm just covering all my bases.

And I see they imply the main jet affects idle... but look anywhere else, like...
http://www.dansmc.com/carbs2.htm
http://www.aircooled.net/gnrlsite/re...es/jetting.htm
http://www.geocities.com/motorcity/s...476/basics.htm
http://www.4strokes.com/tech/carbover.asp
http://www.scooterfocus.com/scooter_...rejetting.html

And they'll all say the same thing... main jets meter fuel from roughly 3/4 throttle to wot. And obviously there is some overlap, but I would not suspect main jets at all in a situation like this.

Main jets effect fueling from idle on up. True, much less at idle, but nothing you've linked, and nothing I've ever read, suggests that main jets don't matter at less than 3/4 throttle.

It's true that Dynojet instructions suggest that 195/190 would work for your set up- IF you had TWO two bros cans. ( but one two brothers can flows a lot less exhaust than two two brother's cans, as a matter of fact, one Two Bros can probably flows less than the two OEM cans). But based on my personal experience, and I believe many of the folks on the forum, the Dynojet implied jetting is overly rich, and you don't have two cans.

My personal semi educated wild ass guess about your jetting? You'd be way better off with 180/185. You're way too rich, the richest combo in the dynojet kit. When your bike warms up, it chokes on it.

You could take off the mains jets and go get your groceries without even noticing as long as the needle don't pull too far off, it will just fall on it's face when the slide needle outflows the req fuel.
The main and needle are the same circuit, nothing can go trough the mains as long as the needle is plugging the tube.
Engine health and carb synch can come into play on something like this.
On a healthy bike, the throttle blades should cover the pilot hole and pull fuel from the idle circuit. If the compression is bad due to a tight valve adjust for example, the idle is cranked up using the idle screw moving the throttle blades exposing the pilot hole to the manifold vacuum, gas drips and idle becomes erratic. Same goes if a carb is synched further than the other.
A leakdown test is a good idea.
This is worth checking

[QUOTE=maverick;210061]Well I did just set my tps... it was in the 800s. and I went as low as I could without modifying anything. like 550 I think. I put it back to where it was originally tonight... I'll try it out tomorrow. I know it shouldn't cause any problems but I'm just covering all my bases.

I think you need to go closer to 400. I just rotated mine around clockwise and drilled a hole in the back plate and screwed a self tapping screw in and wire tied the other hole which was off the backplate. later I found out the others more perceptive than I bent the arm to give them the appropriate ajustibility. The air mixture adjuster: I slotted it with a dremel and screwed out 2 1/4 turns. Do the basic shit and at least you know that you've eliminated the obvious first. then if you want you can do other: Cut the flap off the airbox, foam/oiled filter, PAIR, Plug resistors, .40" shim needle, maybe back to stock jets, etc.

keep at it. you'll get it squared away!! :flamethrower:

Well I suppose I should mention, to be clear, that there are a few other mods. Pair removed of course, +4 ignition advancer, carb cooling lines removed, I think thats it... at least that might have anything to do with this. it's got ape tensioners, race clutch springs, +2 sprocket, shift kit, and other goodies too but they're don't exatly affect idle. And like I said, this is a very new condition, so it's got to be something that changed in the last week or so. Such as tps adjustment, etc.

If Ape CCT's are adjusted too tight that will cause your bike to stall as you mention!

Chris.

I will definitely check those... Also, I forgot to mention dyna coils and wires...

Hi,
Just curious has to why if the cct's being too tight, would only cause the bike to stall when its warm?

That would depend on how over tight they were if that is the case. If they were really over tight then the problem would be there when the engine first fired up too.

If they were only slightly over tight, once the engine warms up the metal parts expand, so consequently the cam chains becomes tighter, so I was wondering if that could be maverick's problem.

I always do the final adjustment of fixed CCT's such as Ape when the engine is at full working temperature.

Do you solved the problem with bad iddling?

Good to know, mine was dying like above after the cct swap, but it was a piece of paper towel in the airbox, it still idles rough a bit when warm so I'm thinking they might be a bit tight...sucks to have to take it appart again.

Well I guess we can start this debate once again, but the bike does run better with the lines in place. Greg N. has done the dyno test and I just did the trial and error method but they are a good thing.

It just might be time to start another thread to explain how they work again.
The most common misconception is that they are to prevent carb icing which is incorrect. The purpose of the set up is to warm up the fuel in the float bowls (if the lines were for icing, they would be routed to the carb body, not the float bowl) which makes the fuel atomize easier.

Also the coolant flows to the carbs only when the thermostat is closed. When the bike warms up and the thermostat opens, the flow is by-passed from the carbs.

I disagree regarding coolant flow to the carbs. It flows to the carbs all the time. The thermostat is not a three way valve. It's either open or shut. See coolant flow pic below. We've been through this one before.

Maverick, have you checked to ensure your choke is turning off all the way. A stuck open choke will cause the plugs to quickly foul and the bike to stall. I had the same symptoms when I tried running the #50 idle jets. Also, after it stalls, pull a plug and check the condition. Black and sooty will indicate fouling which will narrow down the cause.

Well I guess we have to disagree on this. By using the diagram you provided I will explain how I see the system working.

We'll start with the thermostat, no it's not a three way valve, but it is a two stage set up.

http://fiche.ronayers.com/Index.cfm/...oup/WATER_PIPE

If you look at position #2 while its not the best pic you will see that there is a top & bottom to the thermostat (well the do run $35 and that is the reason)

When it is closed the coolant flows from the heads to the thermostat housing, then runs directly to the water pump or to the carbs (per the diagram)

When it opens the flow on the bottom is blocked and the top opens and the coolant flows to the radiators.

There are a couple of reasons why it would make no sense to leave the lower part of the thermostat open while the radiators are flowing.

First, if it was flowing, you would be taking coolant directly off of the heads and routing to the water pump, straight back into the motor. Doesn't sound like a good idea to me but by the diagram, that is what is happening if the lower circuit is always open.

Second, look at how the lines enter the water pump. Both the by-pass line enter the pump at a very bad angle to the impeller. So while the thermostat is closed the system will pump but at a reduced efficiency.

Now when the thermostat opens, you have a nice clean path to the impeller from the radiator. So the way I see things, by the angle of the impeller to the by-pass lines, the flow should reverse. If that were the case, the arrows should point both directions, but that wouldn't make much sense either because you would then be routing flow back to the radiators.

So once again, the way I see it is the coolant flows to the carbs while the thermostat is in the closed position. When it opens, the coolant is blocked from the bypass lines.