KTM 250 2 stroke

[Because Racekart]

So last year me and a friend did a homemade shifter kart build off of a chonda kart chasis with a 2s we picked out of 2000 ktm (spent ~1600). Anyway, when we got it the slave cyl on the clutch had been broken by a chain popping off. The guy we bought the bike from had included a brand new slave cyl with the bike. We installed it on the bike, still could not get the clutch to work and have spent hours and hours and hours (and hours) attempting to repair it with very little luck. We blew it off, built the rest of the kart successfully, attempted to repair the clutch again, couldn't do it. No one we have taken it to will work on it, so we are pretty much sol. We ran it without a clutch for a while, but it quit running after two weeks of fun. Realized we had water leaking into the crank case. And it is very difficult to use the kick starter now that it is in the kart, so we have been push/bump starting it since we've got it going.

Anyway, between spending ridiculous amounts of time trying to bleed the clutch, to ripping out the clutch disks mulitple times, and now pushing the kart back and forth 1200 times to try to diagnose the new problems, I think we have had enough. Recently, we have been weighing the options of just selling the engine, and whats left of the bike and putting it toward a new powertrain.

Would really like something of similar power (40-45 horse), cable clutch (or at least newer model hydraulic. My understanding is the 2000 was the first generation hydraulic for ktm so it had problems), and electric start if at all possible. Push starting is really not a problem until you are trying to diagnose mechanical issues.

Question is, do you think there is some engine/bike that I can accomplish this with for ~2k? Literally everything else is ready to go on the kart, shifter is built, radiator, engine mount, electric fuel pump, custom tooth sprocket, shortened chain, tensioner, etc. Was really hoping to stumble upon a complete 450 atv-enduro engine with e start for 1500 or so, but im not sure thats going to happen.


I can post some videos of the last time we ran it (about two months ago) as well.

 

[Desertduler]

So what are you using as a master cylinder? Are you using the stock handle bar master cylinder? How are you trying to bleed the clutch? I ask these questions because I have two KTM's and I am a Mechanic and I have worked on many of them and raced them.

 

[Because Racekart]

Yep. Using the factory master cylinder. We've bled it both from the master reservoir, by pumping and adding fluid before it got too low, then holding and opening the slave cyl valve, until no bubbles rose. Tried that many times, no success, So we went to a back bleed method. Borrowed a tool and pumped in through the slave cylinder back up until well after the master reservoir overflowed.

The problem is that the clutch will not disengage the plates. The best we could get was for the clutch to work by pulling the lever and revving it hard to break the plates loose. And even that only lasted about 10-15 min. Eventually you would be sitting still, and it would suddenly either start moving or stall, and progressively get worse until it did basically nothing.

So we pulled the plates out. They looked new and one was out of order. Fixed the order. Did note that the plates felt sticky. So we flushed the old fluid when we did this and changed it. Nothing.
And the last time we went to go play with the kart (blew off the clutch for a little while), it had been running strong a few days before but would not start despite not having changed anything. The spark plug was fowled (2 stroke problems i guess), drove to orielly bought a few more, Checked again, and had spark back. Wouldnt start still. Pulled the fuel line from the carb, hit the switch, had plenty of fuel, and the engine was turning over with compression.

Brought it back home, pulled the motor, decided we would give the clutch another go, pulled the plates again and noted that the gearbox oil was this time milky. Talked to a bike guru we know who said that we had water leaking into our crank case. Recommended we do a top end gasket set. Bought the gasket set, but have since then been preoccupied and left back for college.

Its getting over our heads really quickly, and I already feel a little odd pulling the top end apart on a motor that was firing excellently three days ago. And even if we do get it to fire again, we will have no clutch. At this point I am thinking it would be better to do the gasket change, try to sell the current motor for a few hundred, and look for another, preferably with e start, for ease of diagnosis in the future.

 

[Because Racekart]

Sorry for the rant haha. This is months of frustration built up over that thing haha. On a side note the thing is an absolute blast.

http://www.youtube.com/watch?v=YvG_pI3t3uE

 

[Desertduler]

Sounds like you bled the clutch correctly to me.I have seen the slave piston leak by the seal bleed off and dump brake fluid into the engine but you stated that the original owner gave you a different one than the one that came with the engine but was it new or used? Have you checked the overall length of the clutch push rod that disengages the clutch that the slave cylinder activates? As far as coolant going into the transmission I would check the engines water pump seal if it is bad or the water pump shaft bearing is loose coolant will leak right into the trans oil.Coolant in the oil can make the clutch plates stick together and the clutch will not disengage and one will think that the clutch is not working when indeed it is.Also this would not have anything to do with the problem you are having but make sure you use a oil in the trans that has a JASO rating that means that the oil is formulated for wet clutches do not use a oil that has friction modifiers such as some automotive oils that are multi grade energy saving with the API star on them.As far as changing the top end gaskets to keep the coolant from going into the oil none of those gaskets have anything to do with keeping the two liquids apart from one another this engine is not constructed that way the only other place that coolant could be getting into the trans besides the water pump seal there is a coolant passage that goes through the clutch cover from the water pump housing into the base of the cylinder and the gasket that seals the clutch cover also seals this passage that is the only other place that coolant could leak into the trans I would say that the water pump seal is your problem I have rebuilt many KTM's for my fellow Desert Racers and I have seen this problem first hand.
Regards,
Bret

 

[Desertduler]

As far as the plug fouling goes in hearing the engine on your video the engine is blubbering like the engine is cold and not up to operating temprature and if that is the case if you are running the engine for short periods of time the engine will not clear out and foul the spark plug and if indeed the engine is up to temprature and the engine continues to blubber like that you need to look at leaning the air fuel mixture out in order to get the engine to run clean.Also when a two stroke loads up and won't start because of an over rich condition you must hold the throttle wide open and have the choke is off and keep kicking the engine over until it starts and revs up this is common problem two stroke engines that are way too rich or get overdosed with fuel in some way and most people blame the ignition system when indeed the engine is just loaded up.

 

[Because Racekart]

Thank you very much for all your help. It is greatly appreciated.

Couple of answers to your questions. The slave cylinder is a brand new factory piece. When we picked up the bike he gave us the receipt to pick it up from the dealership.

We have checked to see how far the slave cylinder pushes both before and after bleeding, but have not measured it. If we have just bled it, and the clutch still has plenty of pressure, they will move what seems an adequate distance. This is the stage where we must rev to break the plates free. After a while, however, clutch pressure fades, and it does not push them as far. This leads me to believe we may need a master cylinder rebuild, or just buy a whole new one altogether, as I found this http://www.cheapcycleparts.com/prod...tem-replacement-lever-with-adjustable-plunger.

About the water, what you said about the water pump leaking coolant seems to make a lot of sense. There is a good chance we will be pulling that to check it as our very next step. I did not know that water could cause them to stick, but it seems that could very well be the reason they still try to stick even there is solid clutch pressure. So this would mean i have to change our clutch basket cover gasket, and this water pump seal (also gasket? o ring?) correct?

As far as the plug goes, there is a very high probability that the engine was simply cold, as we have only run it in about 5-10 minute max intervals thus far. Though it is possible that we currently have to rich of a fuel air mixture and the engine is loaded up. When we tried tried to get it started, it did not even sound as if it were trying to start however. No popping or anything, just the motor turning over as if it were not getting spark. (though we pulled the new plug, grounded it, kicked over the motor and made sure it was). Do these sound like symptoms of a loaded motor?

Also, after all of this, we brought it back to my dads shop and borrowed his compression checker to see if that were also a problem. It is an auto repair shop, however, so he was not sure if his compression checker would read accurately for our single cyl 2 stroke application. Anyway, on this compression checker, we kicked the engine and were only able to muster about 50 psi, although it is admittedly very hard to use the kick starter now that the motor is in the kart.

Again, can't thank you enough for your help. We are only 18/19, so it has been getting out of hand, but at least we are learning.

 

[Because Racekart]

however, it does appear that that clutch line attaches differently to our slave cylinder, Im not sure if that would matter.

our clutch line attatches from the top of the metal fitting like this, unlike the link.
http://i628.photobucket.com/albums/uu1/kenramirez-chs/IMAG0750_zpsf3997a7d.jpg

Though on a side note our clutch line is thicker than both of these pictures (might just be because it is braided)

 

[Because Racekart]

For that matter, the link seems too cheap. A new factory master cylinder will run me 209 without shipping

 

[Desertduler]

I believe that what they are selling on that link is just the shorty lever and not the master cylinder and the rest of the components.There is no way that they would be selling a Magura master cylinder,line and slave cylinder for that IMHO.In most cases that I have encountered with the handle bar mounted master cylinder is when they go bad they begin to leak out of the plunger and if you pump the lever you can get the clutch to disengage.Yes you will have to replace all of the gaskets and O-ring and water pump seal as you stated you can go online and find the parts you need and or a parts diagram for your engine at Munn Racing,Rocky Mountain Atv or any online parts store that sell KTM parts and and see they way that the parts are oriented in your engine in case you need some help this is exactly how you learn just don't be afraid to ask questions like they say there is no such thing as a dumb question and just because you are young that don't mean you can't take care of this problem we all started sometime and I am always learning something new and I will never know everything thats for sure keep us posted on what you find out and if you need help I will be happy to do that.
I would start by changing the water pump seal and gasket and while you have the engines side cover off dump as much oil out of the tranny as possible and remove all of the clutch plates out of the clutch basket and put them into say a metal container or old pan deep enough so all of the fiber plates will stack on one another and then soak them in clean oil say the type I stated before that has a JASO rating and when you get the engine all back together I would fill the transmission with oil and run the kart around for awhile and the drain the trans oil while it is hot and refill the trans again then you will be done with all of the internal work and then see if you need to do something about the master cylinder 50 lbs compression is low for this engine are you sure the compression gauge is acurate?
I don't know what altitude you are at but at say 5000 ft I would be looking for somewhere around 155 psi and more but then again I do not know what your squish band is set up is without measuring it.

 

[Because Racekart]

Okay, I'll give it a go and let you know how it goes.
We are almost at sea level. Houston

 

[Desertduler]

Ok,
When you get the side cover off PM me and I will go through some other things to look for while you have the clutch apart and I will give you some advice on how to clean the clutch plates prior to soaking them in oil and reinstalling them. Also there is a bearing that you need to check while you have the clutch apart that could cause you disengaging problems.

 

[Because Racekart]

Thanks, whenever I'm back in town I will give it a go.

Also, when we did our compression test, I do not believe we held the throttle open.

Read that you are supposed to. Could this make the difference between the 150 psi I should supposedly be getting to the 50psi it read? Obviously I could check myself when I get home, but it might be a few weeks (got engineering stuff to learn), so I figured I'd ask.

 

[Desertduler]

When you do a compression test you should always hold the throttle wide open in order to get a maximum pressure.I do not think that you will gain a 100 lbs by doing so because even with the throttle closed air will some what come into the cylinder through the exhaust port being that the engine is a two stroke and being as you are close to sea level I would say that you should have at least 165 and that would be the lowest reading I would accept otherwise I would tear the engine down and check the cylinder and piston rings for wear.When a engine has low cylinder pressure it will be prone to fouling spark plugs.