ADVrider

Go Back   ADVrider > Bikes > Thumpers
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 01-09-2013, 04:59 PM   #72706
motolab
Beastly Adventurer
 
motolab's Avatar
 
Joined: Feb 2006
Oddometer: 2,044
Quote:
Originally Posted by opium89 View Post
So, the problem is basically on off-idle hesitation. It's not present while the bike is sitting and rev'd, but very obvious when riding it. Any acceleration off idle in any gear and there is a noticeable "bog" before it starts moving along.
Quote:
What I can't determine however is if the pilot jet, or perhaps the needle are suspect.
Put some tape on the throttle housing and the edge of the grip. Mark zero throttle with a sharpie. This is best done with the engine idling, so you can tell when the slack in the cable has just been taken up. Turn off the engine and mark wide open. Now take a tape measure (metric works best in my opinion) and measure the length of the arc. Put a mark at the mid point. Duplicate this procedure to mark the mid-point between here and zero throttle opening to get 1/4 open. Repeat for 1/8 and 1/16 openings.With the help of the marks, determine precisely during what throttle opening(s) it misbehaves. Don't have an accident trying to look at the marks while riding. If you do, I'm not responsible!

Correspondences on CV carbs:

Low rpm all throttle positions: float height, needle base diameter, emulsion tube outlet size
WOT operation overall: main jet
WOT operation between HP peak and red line: main air corrector
WOT operation below red line: jet needle shape
1/4 throttle opening: jet needle clip position
1/8 throttle opening: pilot jet size
1/16 throttle opening: pilot jet size
idle: mixture screw adjustment

Note that tuning should always be done from the top down, although the idle mixture screw should be adjusted at each change.
Quote:
Does anyone know where these two items can be acquired on the cheap? I've tried calling Sudco on the pilot jet, but they were far less than useful on the phone and are completely unable to determine which pilot get I need. Procycle of course sells the needle in a kit, but as you probably know, it's a little pricey, and I only really want/need the needle and not the rest of the parts included.
See http://www.advrider.com/forums/showthread.php?t=528038.

Regards,

Derek
motolab is offline   Reply With Quote
Old 01-09-2013, 05:05 PM   #72707
motolab
Beastly Adventurer
 
motolab's Avatar
 
Joined: Feb 2006
Oddometer: 2,044
Quote:
Originally Posted by Feelers View Post
I would get this needle: #584310346-G5. I think that is the right part number for the KTM LC4.... Don't forget the circlip.
I would recommend installing an adjustable non-USA OEM needle, part number 13383-32E00.
Quote:
I would keep the stock size pilot jet, though. Putting in a new one would eliminate that though as a problem source.
I agree that a fresh pilot jet should be installed to start.

Regards,

Derek
motolab is offline   Reply With Quote
Old 01-09-2013, 05:29 PM   #72708
motolab
Beastly Adventurer
 
motolab's Avatar
 
Joined: Feb 2006
Oddometer: 2,044
Quote:
Originally Posted by opium89 View Post
Do you know if the jets are stamped with their respective sizes?
They are, but I would also make sure that they are genuine Mikuni items.
Quote:
There'a also a couple other things to note. The idle on this bike seems a little high to me. This is with the idle adjustment backed all the way down. The second thing of note is there is a little bit of a "backfire" immediately after the bike is shut off.
I recommend checking for vacuum leaks.
Quote:
I use the term "backfire" loosely, as it's more like a muffled "boom" sound, as opposed to the "pop pop pop" I get when the bike is running noticeably lean when cranking the air/fuel screw down. The sweet spot for the air/fuel mixture screw seems to be between about 1 1/2 and 2 1/2 open.
The most proper way to refer to the idle mixture screw (aka pilot screw) on a BST carb is as a fuel screw, as it does not adjust air and fuel simultaneously. There are things called air screws on carbs where you adjust the idle mixture by changing the quantity of air being bled into the pilot circuit. The reason this is important is that a fuel screw makes the idle mixture richer by screwing out and leaner by screwing in, whereas an air screw makes the idle mixture richer by screwing in, and leaner by screwing out. Fuel screws are usually on the downstream side of the slide, and air screws are usually on the upstream side (although I have seen occasional exceptions).
Quote:
Get past 3 turns or so, and the idle speed starts to creep upwards.
That's likely to be happening because you're adding fuel to match the extra air that is coming in as a result of a vacuum leak.

Regards,

Derek
motolab is offline   Reply With Quote
Old 01-09-2013, 05:31 PM   #72709
motolab
Beastly Adventurer
 
motolab's Avatar
 
Joined: Feb 2006
Oddometer: 2,044
Quote:
Originally Posted by procycle View Post
Most expect a bigger pilot jet will cure a lean hesitation which is actually due to the needle. They end up with a rich bog off idle followed by the same lean hesitation they started out with.
The validity of these statements depends upon whether the hesitation is in the 1/16-1/8 or the 1/4 opening range.

Regards,

Derek
motolab is offline   Reply With Quote
Old 01-09-2013, 05:37 PM   #72710
motolab
Beastly Adventurer
 
motolab's Avatar
 
Joined: Feb 2006
Oddometer: 2,044
Quote:
Originally Posted by deathu View Post
Thanks, do you happen to know approximately how much the plunger was extended at those 57.000kms? (I mean distance from the gasket surface to the tip of the plunger). Also I do not actually know how the automatic tensioner works, I presume it retains it's length when you remove it from the cylinder? Or does it extend fully when removed?


Another thing that concerns me is the piston. It seems to be in a relatively good shape, apart from the piston pin bores - they look sort of "eroded" although you can't feel any surface irregularities when driving a fingernail inside:



The piston pin I will replace for sure, but I don't know if the way the bores are "eroded" on the piston, justify replacing the piston as well. I don't have the instruments required to measure the ID of the piston bores. This is the first time I am opening an engine. It just seems to me as if aluminum from the piston was "transfered" to the piston pin:
The galling in the middle (that is where the pin runs in the small end of the rod) indicates an oil film failure, which is usually caused by detonation.

Regards,

Derek
motolab is offline   Reply With Quote
Old 01-09-2013, 05:42 PM   #72711
motolab
Beastly Adventurer
 
motolab's Avatar
 
Joined: Feb 2006
Oddometer: 2,044
Quote:
Originally Posted by deathu View Post
Also that photo highlights the worst looking part of the piston. Actually it looks better, and the measurements look good - only the bore thingie worries me.
I'd replace it because of the smearing in the pin bore. Also, that's a fair bit of carbon on top of the piston. I'd try to determine the source and and remedy that.

Regards,

Derek
motolab is offline   Reply With Quote
Old 01-09-2013, 05:45 PM   #72712
Thumper Dan
Gnarly Adventurer
 
Joined: Dec 2011
Location: Australia, Northern NSW
Oddometer: 305
luggage and dry bags

I'm slowly upgrading my DR for touring and i'm at the stage of getting a rear duffle bag. But i'm not sure to get a 40 litre or a 60 litre.

I would need to put into this bag: tent, sleeping bag, mattress (small) camping pillow , bike cover and some other odds and ends i'm sure will creep into it as well. I'm feeling a 60 litre bag should be a better size but I don't want it too bulky for the back of the bike.

I already have wolfman expedition bags but one side would be for clothes and the other will be for food and cooking utensils.

I've been looking at these on ebay: http://www.ebay.com.au/itm/OVERBOARD...#ht_3141wt_906

thanks -
__________________
Currently riding DR650 (2011)
Mods: Manrack, ebay 48 litre top box, grind header pipe; B&B bash plate; bigger/better tool compartment (pvc pipe) - Screens For Bikes Windscreen, TM40 Pumper Carb, Safari Tank, Seat Concepts, Oxford Heater Grips, Highway Pegs, Wolfman Expidition bags and racks, HDB handguards, Cogent Mojave rear shock, intiminators, GSX muffler/mod
Thumper Dan is offline   Reply With Quote
Old 01-09-2013, 06:22 PM   #72713
opium89
Beastly Adventurer
 
opium89's Avatar
 
Joined: Dec 2008
Location: Hutto, Texas
Oddometer: 1,136
Quote:
Originally Posted by motolab View Post
They are, but I would also make sure that they are genuine Mikuni items.I recommend checking for vacuum leaks.The most proper way to refer to the idle mixture screw (aka pilot screw) on a BST carb is as a fuel screw, as it does not adjust air and fuel simultaneously. There are things called air screws on carbs where you adjust the idle mixture by changing the quantity of air being bled into the pilot circuit. The reason this is important is that a fuel screw makes the idle mixture richer by screwing out and leaner by screwing in, whereas an air screw makes the idle mixture richer by screwing in, and leaner by screwing out. Fuel screws are usually on the downstream side of the slide, and air screws are usually on the upstream side (although I have seen occasional exceptions).That's likely to be happening because you're adding fuel to match the extra air that is coming in as a result of a vacuum leak.

Regards,

Derek
Thanks Derek. I also have highly suspected a vacuum leak, but if there is one I have been unable to locate it just yet...and not for lack of trying.

The bike is originally a CA bike, but being here in Texas, I went ahead and removed all the emission control stuff. For the record, I did plug the purge port along with the vacuum port on top normally used for the stock petcock. Bike has an IMS tank with a standard petcock. The only other hoses coming off the carb now are for the breather and there's one other one right below it that isn't attached to anything and runs up under the seat alongside the breather. I am not really sure of it's function. I am however aware of the fuel screw and it's function, just wanted to be clear to everyone what I was referring to.

I guess the next steps will be to take the carb apart one more time, measure the jets that are installed, and see if I can determine if there are any plugged orifices I still might have missed. I'm a little doubtful on the last one as I gave it a pretty good going through last time around.

I will also take a very close look around the airbox and maybe go as far as to remove it and the air boot and makes sure there are no leaky-leaks anywhere.

My initial guesswork has evolved around the throttle at 1/8 where the hesitation is taking place. This is really why the talk about the pilot jet has been bothering me.

I will report my findings. Thanks!
__________________
Tea parties are for little girls with imaginary friends.
opium89 is offline   Reply With Quote
Old 01-09-2013, 06:34 PM   #72714
Albie
Kool Aid poisoner
 
Albie's Avatar
 
Joined: Mar 2004
Location: Upstate SC
Oddometer: 8,273
Quote:
Originally Posted by Adv Grifter View Post
Excuse me? Hey Greg ... what about those pesky 10 years difference in age of these two bikes? And how many owners had your bike in those ten years?
And did you know a 5th grader can disconnect the stock speedo? I never trust it ... look at the bike, listen to the motor.

To me ... those ten years are easily worth the $1600 price difference.
Well, I wouldn't pay $1900 for a 96, but I sure as hell wouldn't pay $3500 for that '06. I got my '06 with 10K miles and about $750 more in farkles and a Zumo 550 GPS for $2800.
__________________
Good. Bad. I'm the guy with the gun.

Another day, another foot injury!
Albie is online now   Reply With Quote
Old 01-09-2013, 06:55 PM   #72715
C/W
Adventurer
 
Joined: Jun 2012
Location: San Francisco, CA
Oddometer: 89
Quote:
Originally Posted by Thumper Dan View Post
I'm slowly upgrading my DR for touring and i'm at the stage of getting a rear duffle bag. But i'm not sure to get a 40 litre or a 60 litre.

I would need to put into this bag: tent, sleeping bag, mattress (small) camping pillow , bike cover and some other odds and ends i'm sure will creep into it as well. I'm feeling a 60 litre bag should be a better size but I don't want it too bulky for the back of the bike.

I already have wolfman expedition bags but one side would be for clothes and the other will be for food and cooking utensils.

I've been looking at these on ebay: http://www.ebay.com.au/itm/OVERBOARD...#ht_3141wt_906

thanks -
In general, if you have a poled tent, the poles will determine the length of the bag. If you're worried about bulkiness, remember it's not the bag but the stuff you put into the bag.

I bought the Wolfman Medium Duffel. It's long enough to accommodate tent poles and big enough to hold tent, sleeping bag, small camp chair, & mattress with some room to spare. My decision was between the North Face duffel & the Wolfman. The Wolfman was waterproof & cheaper. In addition it has loops that you can strap things to.

There's plenty of cheaper duffels & dry bags that you can buy at Cabela's, WalMart, etc...just find one that fits what you plan to put into it.

Stick with 60L, if there's empty space just cinch it down.
C/W is offline   Reply With Quote
Old 01-09-2013, 07:07 PM   #72716
GSF1200S
Studly Adventurer
 
Joined: Jul 2012
Location: Austin, Texas
Oddometer: 975
Quote:
Originally Posted by Thumper Dan View Post
I'm slowly upgrading my DR for touring and i'm at the stage of getting a rear duffle bag. But i'm not sure to get a 40 litre or a 60 litre.

I would need to put into this bag: tent, sleeping bag, mattress (small) camping pillow , bike cover and some other odds and ends i'm sure will creep into it as well. I'm feeling a 60 litre bag should be a better size but I don't want it too bulky for the back of the bike.

I already have wolfman expedition bags but one side would be for clothes and the other will be for food and cooking utensils.

I've been looking at these on ebay: http://www.ebay.com.au/itm/OVERBOARD...#ht_3141wt_906

thanks -
I would go with the 60 litre and strap down. That said, you might consider strapping the tent behind the main duffel if your rack is big enough (I have a manracks BBQ rack, so it does for me). I have a thin and basically weightless rolltop bag from academy sporting goods to fit the tent into. That will give you more room in the duffel. Hell, I think I'm going to get a larger duffel and try to get my entire Alaska load in it. I pack very light, and my tools would be in a fender bag. My cameras and phone in my gl tankbag.
GSF1200S is offline   Reply With Quote
Old 01-09-2013, 07:14 PM   #72717
procycle
Beastly Adventurer
 
procycle's Avatar
 
Joined: Jun 2007
Location: Center of the DR650 universe
Oddometer: 2,045
Quote:
Originally Posted by motolab View Post
The validity of these statements depends upon whether the hesitation is in the 1/16-1/8 or the 1/4 opening range.
No. My statements are valid because this is the experience DR650 owners have when they decide to increase the pilot jet size (which was probably a quick easy fix on their last motorcycle). Instead of solving the hesitation they get a rich bog. My point is that using the pilot jet to try to cure the DR650 off idle leanness is running down the wrong path.

My statement is specific to the DR650 not a general observation about motorcycle carburetion and based on reading forum posts here and elsewhere regarding what actual owners have done to their actual bikes.
__________________
Clarke's second law of Egodynamics: "For every expert, there is an equal and opposite expert." - Jasper Fforde
www.procycle.us - Everything for your DR650 and lots of other great stuff!
DR900 Big Bore Stroker buildup
TurboDiesel Corvette - go to the end to start at the beginning

procycle screwed with this post 01-09-2013 at 07:51 PM
procycle is offline   Reply With Quote
Old 01-09-2013, 07:14 PM   #72718
NordieBoy
Armature speller
 
NordieBoy's Avatar
 
Joined: Dec 2006
Location: Kiwiland
Oddometer: 7,063
Quote:
Originally Posted by procycle View Post
Yes, yes, but you may be the only DR owner who has done that. Most expect a bigger pilot jet will cure a lean hesitation which is actually due to the needle. They end up with a rich bog off idle followed by the same lean hesitation they started out with.
It's cause I is smart.

NordieBoy is offline   Reply With Quote
Old 01-09-2013, 07:17 PM   #72719
procycle
Beastly Adventurer
 
procycle's Avatar
 
Joined: Jun 2007
Location: Center of the DR650 universe
Oddometer: 2,045
Quote:
Originally Posted by motolab View Post
The galling in the middle (that is where the pin runs in the small end of the rod) indicates an oil film failure, which is usually caused by detonation.
And you can be sure there is matching galling in the small end of the rod. Any repair that does not include replacing the connecting rod is going to have limited life/reliability.
__________________
Clarke's second law of Egodynamics: "For every expert, there is an equal and opposite expert." - Jasper Fforde
www.procycle.us - Everything for your DR650 and lots of other great stuff!
DR900 Big Bore Stroker buildup
TurboDiesel Corvette - go to the end to start at the beginning
procycle is offline   Reply With Quote
Old 01-09-2013, 07:22 PM   #72720
motolab
Beastly Adventurer
 
motolab's Avatar
 
Joined: Feb 2006
Oddometer: 2,044
Quote:
Originally Posted by opium89 View Post
For the record, I did plug the purge port along with the vacuum port on top normally used for the stock petcock.
Is the vacuum port o-ring in place underneath the diaphragm cover?
Quote:
The only other hoses coming off the carb now are for the breather and there's one other one right below it that isn't attached to anything and runs up under the seat alongside the breather. I am not really sure of it's function.
The smaller one on the right is a float bowl vent.
Quote:
I am however aware of the fuel screw and it's function, just wanted to be clear to everyone what I was referring to.
Accurate terminology helps with clarity. Inaccurate, not so much.
Quote:
I will also take a very close look around the airbox and maybe go as far as to remove it and the air boot and makes sure there are no leaky-leaks anywhere.
Vacuum leaks will generally be on the downstream side of the butterfly, which the airbox and airbox boot don't really have anything to do with. What method have you been using to detect leaks?
Quote:
My initial guesswork has evolved around the throttle at 1/8 where the hesitation is taking place. This is really why the talk about the pilot jet has been bothering me.
The high idle and rise in rpm when the fuel screw is opened indicate that the pilot jet is not likely to be at fault, or at least not solely.

Regards,

Derek
motolab is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 07:32 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014