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Recommend me a two stroke mechanic/engine builder

Mario

Mario

Member
Joined
Dec 20, 2015
Location
San Jose, CA
Moto(s)
Track and dirty ones
Hi, I gave up on trying to get my two stroke running good. Time to throw money at it.

2009 KTM 200 XCW with 90hrs on the engine, trail riding. Did the top end and replaced all the engine seals while at it. Put everything together, set everything back to stock and it's been running rough since. Did all the troubleshooting I could do, still no luck. Ran out of patience.

Looking for a good mechanic and/or engine rebuilder and start again from the seals (leakdown), to checking the power valve, to redoing the carb and getting it running smooth again. I am OK if I need to ship engine out of state. Since this might be the last two stroke I'll ever ride in CA, I want this machine to run the best and last me a long time. Appreciate any recommendations you can send my way

Thanks
 
Is this the Mariano I met at the last PTT day? (I'm Rebecca's hubby). 2 strokes are pretty easy to work on (not as many parts involved!). If you did a reasonable job installing seals/rings I'd say it's not a motor issue. Likely carb/reed valve...or coil/ecu(cdi)
. PM me, maybe I could help you out.

Mike
 
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i heard it's really hard to do a valve adjustment on a 2 stroke because most people can't even find the valves?!?!
 
auntiebling said:
i heard it's really hard to do a valve adjustment on a 2 stroke because most people can't even find the valves?!?!
Click to expand...

Do these count? They are adjustable too :laughing

02kVkQa.jpg
 
kxmike said:
Is this the Mariano I met at the last PTT day? (I'm Rebecca's hubby). 2 strokes are pretty easy to work on (not as many parts involved!). If you did a reasonable job installing seals/rings I'd say it's not a motor issue. Likely carb/reed valve...or coil/ecu(cdi)
. PM me, maybe I could help you out.

Mike
Click to expand...

Hey Mike! Yes this is Mariano, did not expect to see you here! Say hi to Rebecca, I will stop by to say hi next time I'm headed north

I believe I did a reasonable job at installing all seals, all OEM and followed service manual. However I am not able to hold pressure for more than a few seconds. I read this could be source of engine sucking oil through the seal and running rich. Last resort I am taking the engine off, doing another leakdown and install new seals where I am leaking.

I did find the power valve needed adjustment (yes, there are valves in my two stroke, funny jokes here). I found a video on youtube showing that KTMs have an inspection port where you can see two notches denoting a range and a notch in the power valve. Manual mentions nothing on this. When I followed the service manual, it looks like I ended up with the valve stuck open. I did adjust following the youtube recommendation made a very slight improvement but not the main cause of running rough. I can confirm that the power valve works now.

Another thing I have done was adjust the float level but this one I am not sure I have done it correctly. I might get a extra float drain cap, drill it and install a clear hose to actually be able to see if level is correct and float is not leaking.

Last I did was adjust the needle position. Stock is 4. I went to 2 and started idling much higher (assuming mixture is getting lean) but still running a bit rough. Went all the way to position 1 and roughness went away but pretty sure I am on the very lean side, plus really doesn't make sense to be in that extreme position.

Running rough only happens when running at ~0-15% throttle. Once I open it fully, thing takes off full power. At very low throttle it feels like it is running very rich, plug comes out covered in oil, there is a lot of oil leaking from exhaust.

Two strokes are indeed very easy to work on, but making them work right seems to be an art I have yet to master...
 
Could be a leaking clutch side crank seal ...it will suck oil into the combustion chamber. It's possible to have a leak even if you put in a new one. If you can replace it without splitting the cases I would do that first. I also read somewhere ... that model had some carb float issues. Might look in to replacing the float and needle . The cdi could be going out as well. It could have a weak spark at low rpms almost fouling the plug....hard to diagnose without trying another cdi.
 
Clutch side is the side that is leaking. I changed that seal twice. I need to revisit this as the manual calls for one part, and AOMC lists a KTM part that supercedes the original part.

I didn't know about the carb float issues. I did change the needle and float. I will revisit this again.

Last one I will try is to get another CDI and give it a try.

Thanks for the help! Looks like I am going to be busy these coming weekends...
 
Pressure test before re-installing the side cover, and go over everything with soapy water to find leaks. Leaks can be from seals, crankcase half sealing surface, even base gaskets. I would pressurize it and soap it real good looking for bubles.
 
For pressure test, how much pressure do you put on the crankcase?

I haven't had the pleasure of having to do this. I don't even own a 2 stroke right now, but my psychic says she sees great pleasure, pain, joy, agony and suffering in my future so I guess I'm in the market for another.
 
seadog said:
For pressure test, how much pressure do you put on the crankcase?

I haven't had the pleasure of having to do this. I don't even own a 2 stroke right now, but my psychic says she sees great pleasure, pain, joy, agony and suffering in my future so I guess I'm in the market for another.
Click to expand...

Around 10 psi. It should hold 10 psi for 10 minutes or so. It's best to put pressure in with a hand pump. Using a compressor could potentially blow the seals out. Pressure testers can be made at home with either aluminum plates, or large rubber stopers for the intake and exhaust. You can admit air via a Schraeder valve (auto parts) on a block off plate or destroy and modify a spark plug. Even without a gauge you can put light pressure in, wait 10 minutes, and press the valve. If it hisses there is still air in the case. Wet side seal leakage causes transmission oil to be burned with the fuel, and dry side seals, case leakage, base gasket leakage cause lean running and can result in seizure.

Soapy water at all seals and seams will usually tell where the leaks are.
 
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seadog said:
For pressure test, how much pressure do you put on the crankcase?

I haven't had the pleasure of having to do this. I don't even own a 2 stroke right now, but my psychic says she sees great pleasure, pain, joy, agony and suffering in my future so I guess I'm in the market for another.
Click to expand...

A recent one done by yours truly

[YOUTUBE]eGzJz302XiI[/YOUTUBE]
 
So I went for the carb float this morning, and it looks like I didn't set it right the first time (even though I followed the manual). Set it a bit lower and runs much better. I really suck with carburated machines. I think I need to stick to fuel injected machines.... :(
 
A common mistake when setting float levels is to hold the carb upside down. It should be held horizontally and tipped until the float tang just touches the float valve. Upside down compresses the spring in the float valve and will give you a false reading. If no specs are available, I start with the bracket that holds the floats parallel with the carb body. A good place to start when specs are unknown.

I have the opposite problem. Carbs make sense, but I get confused by 4 or 5 sensors leading to a magic black box and 10 yards of wiring when things go wrong. :laughing
 
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Thanks for the info and video guys. Appreciate it.
 
Mario -

Sorry to hear about your struggles. If I were closer, I'd offer to give you a hand. I know you are relatively new to rebuilding two-strokes.... and can only offer you some positive reinforcement. If you can successful rebuild your four-stroke like you have previously, you will be able to get the two stoke done. It just may be trying your patience in the learning stage. In GENERAL they are easier.

I pressure test every two stroke motor I ever assemble, and they all eventually hold 6-8 psi for five or more minutes (many much longer.) I do this before assembling the stator/flywheel and primary drive gears so I can see what's going on, and track down any leaks with soapy water with a spray bottle.

Just my experience and opinion to tackle this first so you aren't chasing your tail with the carb. We have all had to redo main or PV seals, even base or head gaskets at some point. Heck, I had to redo a friends base gasket three times before it would seal on an engine I was helping him rebuild. Finally just took a good OEM spare out of my supplies to get it to seal vs the after market ones he had purchased. Sometimes you may have to replace the PV seals and cover gaskets as well as plug the vent hose (small bolt and safetywire.)

Good luck and keep at it. You've already successfully rebuilt a four stroke, you will get this one too. On a plus side, its a new skill you are learning.

If you decide to throw in the towel, I have heard decent things about 650 racing. Specializes in dirt bkes.
 
How are you blocking off the exhaust ports during the pressure test? I use those expandable rubber plugs with the bolt in them. They’re for plumbing, but no idea what they actually plug lol. How are you sealing the intake side?

http://vintagesmoke.com/product/2-stroke-leak-down-test-kit/

That’s what I’ve got and it works well.
Once you get that figured out, and only then, I would start on getting it jetted. You’re gonna have a helluva time getting it to run “right” if it’s leaking.

So, now it runs well above 15% throttle? Have you tried changing the pilot jet or adjusting the air screw? Those will affect low throttle settings more than the needle in my experiences, but my 2T is 45 years old lol.
Seriously though, get her sealed up correctly (10psi for 10 minutes or more) because you’ll chase your tail until you do.
Good luck!
 
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