KTM LC4 (640) Thread Index

[Lortdadu]

Originally Posted by enduro0125

Take some pictures of the cable routing and remember which throttle cable goes where.

This step is important for first timers!

I remember when I was assembling my LC4 when I purchased it when it had been used as a spare part box and it came in pieces; it took me around 3-4 hours to figure how all of the cables go to the carb and around the bike. I had never worked on an LC4 before, so, it took quite a while to figure it out.

Also

Originally Posted by Tonicu

By the way, I went this evening for a short ride without the snorkel at first and later on I removed that plastic bit that goes under the airbox side cover preventing air coming in from that side. The result was that without the snorkel the bike run worse than with it on. I more or less imagined it would be even worse without the plastic bit under the airbox side cover, and so it was. Mid-range performance was seriously affected, - apparently not so much at the end of the rev range - so I stopped and put the plastic bit back in place and then the snorkel. Now the power was "there" again, as it was before.

I'll post pics when the carb is off the bike, I'm curious about what the jets are and also what they should be without snorkel or with the opened airbox side cover.

I just saw this post, any modifications to the intake and outlet system on an engine will effect the type of mixture the carb will need to feed the engine to run well. Thus, allowing more air to enter the engine, you will have to equally allow the engine to gain more gas to balance out the mixture (e.g. change needle position, change main jet, etc..). It is vital, that before you do any modifications to the intake/outlet system, you must have a bike that runs well as it is. That way, you can always return to the position, where you bike ran well and start over with the modifications.

Work systematically as well. Don't change too many things at once. Like in this case, did your bike run well without the snorkel before you took the side cover off? When you say that the mid-range was affected, also realize, that the needle position affects the mid-range power.

[gunnerbuck]

Originally Posted by Tonicu

Thanks for sharing your knowledge. Things are as follows :
I've never taken a carb apart, the most "difficult" task I undertook was changing the rocker roller bearings after the inlet one seized, damaging the camshaft. It took me longer than expected, but I enjoyed doing it and I learned a lot of things doing it. After 5000 kms. the engine keeps running, so I'd say what I did was more or less right.
I'm not so sure about the carb, though. I'm pretty sure I might be able to take it off the bike and even dismantling it, but re-assembly is another issue, my lack of experience can cause a lot of trouble.
On one hand I'd love to learn how to do it - and at 40000 kms. - it is not a bad idea taking a look inside the carb, but on the other hand I'm more or less worried I could damage or lose that little spring, o-ring or whatever small piece that later on would mean it won't work.
So that's how things are. Shall I take the plunge or should I leave it for an expert to do it? "To be or not to be, that is the question", someone said,
Good advice, Daryl, Laramie - I wouldn't even think of taking the carb apart if it wasn't for your bible - Enduro, Dirty Sánchez. and Lortdadu. Daryl, I'll keep your "trick" in mind in case I'm far and away and I don't have a nearby internet access to cry out for help.
Cheers!

Has your carb ever been serviced in the 40,000 km ? If not you are likely looking at some worn out parts within the carb... I would think that your slide, slide guide, needle jet {emulsion tube} and jet needle will show some advanced wear... If this is the case then no amount of tuning will get the bike to run proper until the worn parts are replaced...

[enduro0125]

Originally Posted by gunnerbuck

Has your carb ever been serviced in the 40,000 km ? If not you are likely looking at some worn out parts within the carb... I would think that your slide, slide guide, needle jet {emulsion tube} and jet needle will show some advanced wear... If this is the case then no amount of tuning will get the bike to run proper until the worn parts are replaced...

My slide/and guide@22K




New slide/guide





Needle jet(emulsion tube) @22K



Needle was fine but my drain screw was not.

[Tonicu]

Took the carb off the bike tonight. It wasn't as difficult as I expected, but I'm quite worried about re-assembly; it's quite a tight fit - or so it seemed to me - and I presume it will take more time than taking it off.


I found the inlet boot from the airbox to the carb was "a bit" cracked :


Tomorrow I'll open the carb to take a look inside and see what I find.

I don't know if the carb has ever been serviced, so it's well worth taking a thorough look at it.

[Tonicu]

I finally couldn't wait.







No impact or drill to remove the bottom Philips screws here with me, so it'll be tomorrow knowing what size the jets are and how's the float, weight and o-ring.

[enduro0125]

Originally Posted by Tonicu

I found the inlet boot from the airbox to the carb was "a bit" cracked :

.

That explains alot of the lean symptoms,if sucking air.

Can't tell for sure from that picture but I'd bet your slide guide is worn.

[christian]

Make sure you have a filter on the air intake on the top of the carb
Sometime bike with the smog stuff removed have this left open. Bad idea

[gunnerbuck]

Originally Posted by Tonicu

I finally couldn't wait.







No impact or drill to remove the bottom Philips screws here with me, so it'll be tomorrow knowing what size the jets are and how's the float, weight and o-ring.

You will likely get the screws to come loose with a regular screwdriver, if not a set of needle nose vise grips will grab the screw heads for the 1/4 turn it requires to break them free...
The airbox manifold does look bad and will for sure need to be replaced, in a pinch you can patch it up with a urethane bonding agent such as aquaseal... This stuff is designed to repair waders and wetsuits but works fantastic for motorcycle botch fixes..

[Lortdadu]

By the looks of the top of your carb, it's about time you clean that thing!

If you have a compressor, you should clean all jets and ports inside the carb with pressured air. That way you can clean the ports effectively.

A few friends of mine have used carburetor cleaner sprays/fluids, personally I've never used them. My carb has never been so dirty that I would need to use such. I've used industrial alcohol to clean the carb with linen cloth and a toothbrush.

[dlh62c]

Originally Posted by Tonicu

I finally couldn't wait.
No impact or drill to remove the bottom Philips screws here with me, so it'll be tomorrow knowing what size the jets are and how's the float, weight and o-ring.

Your doing a great job!

Was the inline fuel filter present in the steel line of the carb?

daryl

[Tonicu]

After having children, planting trees and writing books, now I'm complete with the experience of disassembly/reassembly of a carburettor.

With the help of a friend we were able to remove the screws left, one of them with a screwdriver, the other with the impact one. Here's the result :
Daryl, it did have the tiny filter in the steel line of the carb. It had about 25% of its surface clogged with tiny small debries. Thanks for making me find it. I was looking for an usual fuel filter, not this type.
Idle jet is 45 (stock, I think), main 152.5 and the needle is at the 3rd clip ( counting from top, two more left ).
The idle jet was a bit dirty too, probably being the cause of the engine stalling from time to time.
I cleaned everything up with air pressure and then with alcohol. I didn't find any remarkable wear in the slide/guide. Lateral play is less than 0.1mm, so nothing to worry about I presume.
One thing, probably not very important, was that when removing the floats, the o-ring was sort of "stuck", and when reassembling I thought it would "fit" or make a click to enter a predetermined space. It didn't make that click as I was expecting. Maybe the o-ring was stuck and that caused I had to pull - lightly - the float to remove it.
I guess this is just held by the screws of the float cover, if I'm not wrong.

I'll wait for the inlet boot airbox/carb for reassembly. Will see if it works fine again.
Probably the engine was running lean due to the fuel filter and idle jet being quite dirty. A new plug will tell.

Anyhow, I've learned a lot thanks to you and now I can - with a fair bit of spare time ahead - understand the bike a bit more. Cheers for that.

[dlh62c]

Originally Posted by Tonicu

Daryl, it did have the tiny filter in the steel line of the carb. It had about 25% of its surface clogged with tiny small debries. Thanks for making me find it. I was looking for an usual fuel filter, not this type.

Good job!

Your well on your way.

The filter is easy to overlook. It does its job well.

daryl

[djchan]

I'm presently reassembling my 2002 LC4e as it's been in boxes for 3-4 years. I've been riding smokers and RFS bikes over that period. Now the big-boned girl is coming out of mothballs due to the sale of the RFS.

I noticed the o-ring seals on the waterpump are dried out from all that sitting. I'm also unable to find the waterpump rebuild kit I bought 3 years ago for the occasion. To add insult to injury - it looks like the rebuild kits are all sold out for this model.

Question - can I pull the o-rings, clean and revitalize, then reinstall?

Are these o-rings (large diameter, small thickness) available at an auto parts store?

Is it wise to reuse the other original parts, impeller and such, or should I look for a total rebuild before reassembly?

Don't really want coolant perking into my oil.

ps - wish the LC4 had the RFS system with a weep hole on the side

[gunnerbuck]

Originally Posted by djchan

I'm presently reassembling my 2002 LC4e as it's been in boxes for 3-4 years. I've been riding smokers and RFS bikes over that period. Now the big-boned girl is coming out of mothballs due to the sale of the RFS.

I noticed the o-ring seals on the waterpump are dried out from all that sitting. I'm also unable to find the waterpump rebuild kit I bought 3 years ago for the occasion. To add insult to injury - it looks like the rebuild kits are all sold out for this model.

Question - can I pull the o-rings, clean and revitalize, then reinstall?

Are these o-rings (large diameter, small thickness) available at an auto parts store?

Is it wise to reuse the other original parts, impeller and such, or should I look for a total rebuild before reassembly?

Don't really want coolant perking into my oil.

ps - wish the LC4 had the RFS system with a weep hole on the side

With the way the pump has been sitting idle for a long time I would replace anything to do with rubber within the pump, this would be the: double lip seal, the 2 bearings and the o-rings... If the pump shaft is not grooved then it will be reusable... Also look at replacing the paper gasket as well...

The Bearings{6001 2rsr c3} used in the pump are a common item and available through a bearing shop... These bearings are also used in electric motors and I was able to buy a 10 pack for under $15 by shopping around...

[skibum69]

wasn't there a Creeper valve check thread? I can't find it....anyone?