erratic idling

[tmb99]

I'm having trouble with my idle, here are some details.

Bike won't idle when cold, needs throttle, starts easy but can't use enricher that kills the bike straightaway. When hot the bike seems to either idle high or low never seems to find sweet spot.

Not sure of the jetting, going to pull that in the next day or two. However when I swapped the pipes it fouled some plugs, friend who is a mechanic applied a "cheap fix" by dropping the needle and putting a hotter plug in it: BP5ES. since then it's run pretty good, appart from the idle.

Bike details - round slide VM34's, pods, GS drags with homemade internal baffles, standard points ignition and charging.

Pulled the plugs which were black. Put fresh ones in and did a block lap, killed it open throttle and pulled the plug.

Looks rich? I've heard it would be running rich at idle due to open pipes?
Apart from that anyone got any suggestions what to do?

 

[CDNTX650]

That is too rich...bp5 is already 2 steps hotter...waaay to hot. Unsteady an inconsistant idle is a sign of rich. There is guys on here who can pretty much tell you exactly what needles, and jets to run. Insulator should be a light tan, and hve a small ring at the bottom of it, where its hard to see. I wouldnt even drive it with bp5 in.

 

[tmb99]

Cheers - thanks for the advice. Anyone able to point me in the direction of jetting for that setup? I've been doing a lot of reading but most posted 'perfect' setups are for stock airbox and pipes.

 

[tmb99]

So it seems the carb wizards are fiery bastards - most likely from absorbing too much petrol over yrs of pulling carbs apart. Most threads I've read offer little insight, just claims of "not this again" and general scorn... so I delved deeper and discovered some of their earlier transcripts... I've pulled my jets, got a magnifying glass out! and it seems I'm rich! however not a good rich.

240 main
50 pilot
6DP17 Needle
159-P6 needle seat
2.5 slide

wisdom seems to state 180-200 main and 20-25 pilot. I will keep hunting answers cause buying a heap of jets doesn't sound like fun.

 

[ippytattoo]

This is a common baseline I have seen around a few times. Hope it helps.

Main - 180
Pilot - 25
Needle 6F9 - clip - 3rd slot
Needle Jet- P-6
Slide Cut Away - 2.5
Air Jet - None
Float Height - 25

And you are right buying a heap of jets isn't fun but sometimes it is a necessary evil. I went through it with the CVK's and I think I ended up with more in jets than I had in the original carbs.

 

[grizld1]

That's a common baseline alright--for the fuel we get in the US. tmb, here's news for ya--nobody jets VM carbies for a stock airbox, and few run 'em with stock exhaust.

Although fuel differences may account for some difference, your jetting is crazy rich. Read the VM section of the Carb Guide. I won't write it again just for you. You'll find a link in the Tech section.

 

[tmb99]

Cheers grizld1 your carb guide was my starting point of research. Most went over my head first few times I read it. After that I've been trying to find baseline for pods and straights, but the more I read the more I think that baseline is pretty damn adaptable.

Thanks a lot for that guide it has been invaluable.

Anyone know; as the needle I have (6DP17) is fatter I should run a larger main? Or is it best to ditch that needle for a 6F9? I've ordered a range of jets from local source however I can't find that needle.

 

[grizld1]

Your MJ is already big enough to drive a truck through it. You don't correct a lean needle by fattening the main. You do it by installing the right needle. BTW there is no 6DP17 Mikuni needle. What you have is the 6DP1, which is the generic item. You need the 6F9, and the sooner you stop second-guessing and trying to muddle through with the bits you have on hand, the sooner you're going to have your carbs straightened out.

Trying to compensate for too much fuel with hot plugs to prevent fouling is a recipe for disaster. The XS650 Club of Australia has some of the most knowledgeable hands in the world. You'd be well advised to get in touch with them; Google for the URL.

 

[CDNTX650]

That thing is so rich you are probably washing oil off the cylinders and walls like crazy.

 

[5twins]

Remember, pull the air jets right out and run without them, or you'll still be too rich even with the recommended jetting and needle. In fact, pull them out right now, it may help some.

 

[grizld1]

Actually it probably won't help. A change in the pilot air jet (fixed in VM carbies) will make a difference in the pilot mixture; but the function of the main air jet is to control atomization at high RPM (usually unnecessary, given the demand characteristics of the XS650 motor). I doubt that he'll be able to turn high enough RPM in current state of tune to tell the difference between the OE 2.0 MAJ and an open hole. I'm surprised that motor even runs with a #50 PJ and #240 MJ!

Ain't it grand when you've given the advice, the OP says he's read it, admits hasn't followed it, and starts fishing around for ways to make the mess he has work anyway? Here's a starting point, Bud--stop looking for short cuts and DO WHAT I TOLD YOU TO DO.

 

[tmb99]

Wow, I was right, his a fiery bastard the one who know about carbs.... ahhh thanks? for the help buried somewhere throughout the scathing criticism and scorn... I tried to be overly thankful for the guide (which is awesome) but seriously your attitude can go eat a dick.

I came here guessing my jetting was a bit off and looking to learn about the topic. I did some research and started reading, but thought I'd throw it out to the "community" for a baseline on my setup - what I thought was a reasonable question. A day of research later I bit the bullet and spent a fair bit on money on a range of jets. Having trouble finding the needle, I asked what I again thought was a reasonable question - could they be worked with. At least two 6DP17 needles do exist, I have them sitting here.

I didn't install the current jets, needle or plugs. I'm trying to make it better, and trying to learn something new in the process. Ain't that grand...

5twins, thanks for the heads up, I checked that when I first pulled the carbs and the air jet area appears empty.

So, now to just scuttle off and order the 6F9 needles.... peace out

 

[grizld1]

The "community" has peer reviewed that material six ways from Sunday. Since you've taken the opportunity to name call, I'll just point out that reading a bunch of drama from self-absorbed twits who don't follow directions and think that information has no value unless it's directed to them individually gets tiresome. Here's a tip. The world will look and smell better and you'll learn much more if you pull your head out where the light can shine on it.

 

[tmb99]

Most carb threads I've read you're the one bringing the drama. You were never asked directly for information. You choose to jump in and be patronising to people learning. Part of a cohesive learning process is asking questions. Just prior to your involvement in this thread, my question was answered.

Anyway enough days of our lives, the jets and needles are ordered, I'll start the tuning process and try to never ask any questions about carbs again...