LC4e hiccup

[sss]

We are off the dirt and riding down the pavement yesterday toward Cheyenne doing 70 mph. The bike is fine. It vibrates; The pirelli MT21s vibrate; the Wyoming wind vibrates; it's fine. The group occasionally accelerates to 75. Somewhere between 72 and 75, under acceleration, there is a slight hiccup, a subtle vibration or brief loss of power. The bike does not slow down but continues to miss, vibrate, hiccup. The engine does not sound different, but I can feel that something is not quite right. Back at 70-72 mph the bike runs and accelerates okay.

Where do I start? Fuel system? My imagination?

[creeper]

Originally Posted by sss

We are off the dirt and riding down the pavement yesterday toward Cheyenne doing 70 mph. The bike is fine. It vibrates; The pirelli MT21s vibrate; the Wyoming wind vibrates; it's fine. The group occasionally accelerates to 75. Somewhere between 72 and 75, under acceleration, there is a slight hiccup, a subtle vibration or brief loss of power. The bike does not slow down but continues to miss, vibrate, hiccup. The engine does not sound different, but I can feel that something is not quite right. Back at 70-72 mph the bike runs and accelerates okay.

Where do I start? Fuel system? My imagination?

You start by posting this in the thumper forum where it's easier for folks to find it...

Anyway, a 2001 LC4E... so you should have a BST40 carb. Boulder to Cheyenne... so you’re at least at 5,000 ft. elevation. You live in Boulder so the bike is jetted for the elevation... I assume.

Done any work on the carb lately? Changed brands of fuel lately? Has the bike sat for an extended period of time?
Is your fuel cap vent line cleanly routed without any pinches or kinks? Same question... but for the fuel line.

When was the last time you checked your valve lash? When was the last time you checked your spark plug? Spark plug cap and wire connection... these can get loose and corrode very easily. Air filter clean?
Check the carb to intake manifold flange for loose screws and/or clamp. Still OK?

Remove the vacuum piston cap and check for loose screws, a damaged diaphragm, a gunked up piston and bore, a worn needle and needle jet. All OK?

Remove the carb and read this then check your float height, needle and seat condition and while your there, check to see that your main jet is tight and not clogged.
Any sediment in the float bowl? Pull the petcock and check the condition of the filter.

I've run out of things off the top of my head... maybe someone else will chime in with something I've forgotten.

Good luck,
C

[sss]

creeper,

Thanks for the reply. It is exactly what I was looking for.

Is it possible to move a thread or is it better to just start a new thread in thumpers?

I bought the bike just before Christmas. The bike started in Nevada, spent a few years in Wyoming and then moved to Colorado. The previous owner (#3) had it for two months.

I immediately checked the oil and overfilled it resulting in oil in the air box. I cleaned that up and cleaned and oiled the filter. I don't see new oil in the air box drain but I will check this again.

I pulled the spark plug. It is somewhere between tan and black (I need better light in the garage) but is not fouled.

It will take me a little while to go through your list. I am new to wrenching and am still in the process of setting up the garage and making space.

Thanks again.

[AceRph]

Over you go!

[sss]

Thanks for the move.

I gather that I need to ask the moverator to do this kind of stunt.

[creeper]

Originally Posted by sss

Thanks for the move.

I gather that I need to ask the moverator to do this kind of stunt.

Ace has "Johnny on the spot" relocated the thread… for your shopping convenience.

I don't know if you are aware of this SSS, but a vast resource of LC4 information that will be undoubtedly of great value to you in your quest to reach beyond n00bness is resting at the top of the Thumpers forum.

It's called the LC4 Index.

Hope you've enjoyed the show... remember to tip your waitresses and waiters. Goodnight.

C

[ChrisC]

I was on the ride w/SSS on Saturday and didn't notice him lagging behind much.

My '03 Hi-Flow is still has the OEM jetting and I can't fault the way it runs at altitude. My guess would be this LC4e has had it's main jet pushed waaay past it's OE 142.5. Maybe other BST massages, as well. I'd start by whippiing out the main jet and see where it is. Some folks really like monster mains, stoichiometry or not.....

[creeper]

Originally Posted by ChrisC

I was on the ride w/SSS on Saturday and didn't notice him lagging behind much.

My '03 Hi-Flow is still has the OEM jetting and I can't fault the way it runs at altitude. My guess would be this LC4e has had it's main jet pushed waaay past it's OE 142.5. Maybe other BST massages, as well. I'd start by whippiing out the main jet and see where it is. Some folks really like monster mains, stoichiometry or not.....

Using Dr. Wrongway Crackpots "Bigger is More Gooder" air/fuel ratio theories no doubt.

Came from Nevada?... Do ya' think? Naaaa, couldn't be... maybe.

[ChrisC]

Originally Posted by creeper

Using Dr. Wrongway Crackpots "Bigger is More Gooder" air/fuel ratio theories no doubt.

Came from Nevada?... Do ya' think? Naaaa, couldn't be... maybe.

I'm thinkin'.... "my jet is bigger than your jet", or "if this 165 is good, then this 185 must be reallllly good".....

[meat popsicle]

Originally Posted by ChrisC

I'm thinkin'.... "my jet is bigger than your jet", or "if this 165 is good, then this 185 must be reallllly good".....

Main Jet!?! We don't need no stinkin' main jet! We're Federales!!!

OK, your turn to quote a movie

[sss]

Thanks everyone.

I have been lurking for a while. It was this forum and the vast amount of conflicting information that led me to buy the ktm. I wanted something fun to ride and with a lot of support for wrenching. This is it.

Now I will study hard and work the oil and grease into my pores; Maybe some day I will be an expert.

[laramie LC4]

id check the emissions crap while i was at it. what you are describing sounds a lot like the vacume lock from a pinched line. check underneith the seat and see if im right...

as for jetting. i used to ride around cheyenne all the time. depending on the mods you have done to the bike (sounds like it may be stock) i would try a 152.5 main. i was running a 160 with a 47.5 idle but i had an open airbox and a full akrapovic race exhaust.

good luck,

laramie :cheers:

Sorry to hijack the tread, try this one on Meat!

"Its got KTM brakes and a KTM motor, its got a full tank of gas and I've got a half a pack of Cigarettes, Hit it!!! Its something close to that from the Blues Bro's. movie.

Originally Posted by meat popsicle

Main Jet!?! We don't need no stinkin' main jet! We're Federales!!!

OK, your turn to quote a movie

[sss]

This is an update.

The PO had removed the ISD2 muffler and the high flow side screen and mounted the stock muffler. I mounted the ISD2 muffler and the screen and adjusted the idle to the point where it would run. I can't reach the idle mixture screw but will have the carburetor out this week and maybe can fabricate a tool for the short term. I have ordered Loaded's screw and sent the check via a slow mule so will not see that for several weeks. Any assistance or guidance regarding this short term issue is appreciated.

I will also be working through this site to verify which vents/holes should be filtered and why that black plastic elbow is not hooked up to anything.

The main jet is 157.5.

When I removed the diaphragm cover I discovered black dirt/dust above the diaphragm. The area below the diaphragm appears to be clean. The slide has not been drilled. I will wait on this because it is pretty easy to get to and the mid-range response is fine for me. I may change my opinion later.

The slide is scored on the flat side.

The hiccup is gone.

I think (noob's guess) that the ISD2 is set up with a racing core. I will check this later and may go to a quiet core. I don't like a loud bike but the sound of this one is growing on me. Away from the bike it does not seem too bad. I also do not want to antagonize the neighbors.

The bike now has plenty of power; It easily accelerates from 70 mph and maxes out at 92-95 mph, but takes a few seconds to get there from 85 mph. There is some popping on deceleration and it is not consistent. Sometimes it pops and sometimes it doesn't.

Great bike. So far it is easy to work on. I am glad to not have to remove a lot of plastic before doing anything. The gas tank is so easy to remove compared to my other bike.

I have Flanny's Guide, Creeper's most excellent advice, a cold garage and a bike that I can ride while I enjoy wrenching this one.

Steve

[meat popsicle]

Originally Posted by sss

This is an update.

The PO had removed the ISD2 muffler and the high flow side screen and mounted the stock muffler. I mounted the ISD2 muffler and the screen and adjusted the idle to the point where it would run. I can't reach the idle mixture screw but will have the carburetor out this week and maybe can fabricate a tool for the short term. I have ordered Loaded's screw and sent the check via a slow mule so will not see that for several weeks. Any assistance or guidance regarding this short term issue is appreciated.

They make a special screwdriver for turning that screw; not sure if you can source it locally for a quick buy. Some folks can use a stubby screwdriver to get in there. Others used a ratchet with a flathead attachment to turn it. Those you should be able to source locally.

Originally Posted by sss

I will also be working through this site to verify which vents/holes should be filtered and why that black plastic elbow is not hooked up to anything.

Creeper did a little "how-to" on those carb vents (optional upgrades I believe); it would be good reading for you. but damn it, it's not in the index yet!

EDIT: dug it up: http://www.advrider.com/forums/showthread.php?t=114485

Originally Posted by sss

The main jet is 157.5.

When I removed the diaphragm cover I discovered black dirt/dust above the diaphragm. The area below the diaphragm appears to be clean. The slide has not been drilled. I will wait on this because it is pretty easy to get to and the mid-range response is fine for me. I may change my opinion later.

The slide is scored on the flat side.

The hiccup is gone.

but the slide is damaged? ~$35 to replace it.

Originally Posted by sss

I think (noob's guess) that the ISD2 is set up with a racing core. I will check this later and may go to a quiet core. I don't like a loud bike but the sound of this one is growing on me. Away from the bike it does not seem too bad. I also do not want to antagonize the neighbors.

take off the end cap and look in; if you can see the midpipe (straight thru) its the racing core. the baffles insert (quiet core) is about $60 as I recall.

Originally Posted by sss

The bike now has plenty of power; It easily accelerates from 70 mph and maxes out at 92-95 mph, but takes a few seconds to get there from 85 mph. There is some popping on deceleration and it is not consistent. Sometimes it pops and sometimes it doesn't.

The popping could be a leak in the exhaust, usually at the midpipe-can fit; common with the IDS2 since it doesn't line up well for all model years. If that is the case you can try to adjust the alignment or use something softer to fill the gaps; I have some stuff that seems to work - let me know if you need a bit.

Originally Posted by sss

Great bike. So far it is easy to work on. I am glad to not have to remove a lot of plastic before doing anything. The gas tank is so easy to remove compared to my other bike.

Steve

congrats on the fixes - sounds like you are almost there...