2008 KTM 50 sx engine/clutch HELP NEEDED PLEASE - KTM Forums: KTM Motorcycle Forum
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post #1 of 10 (permalink) Old 05-07-2019, 09:37 AM Thread Starter
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Thumbs down 2008 KTM 50 sx engine/clutch HELP NEEDED PLEASE

Ok, so I bought my son a 08 ktm50 sx. When I purchased it the guy told me that the person before him put in a ďbeginner clutch". I though nothing of it because honestly my knowledge is limited on these bikes....
Well we got it home and the bike ripped, it was great. It shredded up our steep hill on the track easily and my son loved it.
I changed the fluid in it, the guy gave me a bottle of asmiol ATF fluid so I just stuck with that since it worked so well. I added 225cc even though I only got out 175cc. Fast forward to it running good riding every day for about 1 week the bike starting struggling to make it up our steep hill, it felt like it was overheating so I adjusted the air fuel mixture screw on the carb.... that helped with it a little but you could tell it was slipping big time up the hill so I had him pull it in for the night. That weekend we went to our local track that is flat and the bike ran great, no issues for about 3 hours damn near of straight riding. After that I got home and started researching stuff about the clutches because I want my son to be able to ride my full track at home..... the guy I got it from gave me a bunch of the beveled washers and a clutch puller a bunch of other crap so my dumb a** thought hey ill pull this thing apart real quick to fix it so he can ride the full track a few days before he has to go home to mom.
so I drained the oil, I only got 110cc out of the motor even though about 6 rides (probably 4-5 hours run time) ago I had put 225cc in it. Now my son is 4.5 years old.... his killing it but he does have at least 2-3 tip overs every ride but from what I could tell there isnít anywhere for the clutch oil to come out other than possibly the crank seal????
The bike does have a little smoke coming from the exhaust (doesnít seem excessive for 2 stroke), but it does have oil running down the back of the muffler. There isnít any restrictors or anything in the exhaust it does have a spark arrestor installed.
Iím running at 50:1 because I was told thatís what the bike always been at....

So I pulled the clutch found out that it actually had the mini adventure clutch springs installed instead of the beveled washers.... I found the stock configuration and ran that. OD of the clutch was 81.58mm, my stacks of washers was .5815 for all three. The bike needed damn near half throttle to engage but boy did that thing take off when it did engage. The bike was squirrelly everywhere shredding and tearing the track up. The rear wheel was breaking loose with a brand new tire on good dirt. So I though ok cool he will get used to it and gain control. Well the thing shut off while he was hauling butt on our track..... I took it back in, defiantly have a little scoring on the piston... so know Iím looking up top ends.... the bike had 30 psi first kick on the compression gauge but then I couldnít get it to go past 110psi after multiple kicks.

It still starts and actually seems like it runs fine so I decided to continue to play with the clutch. From what I was reading it was saying that if you want the clutch to engage faster (at lower RPM's) to remove a .5mm flat washer.... and if you donít have any .5 mm shims in it to remove a set of double washers..... I converted the bike from HH (()) (()) (()) () B and went to HH (()) (()) () () B. Now you canít even start the bike without the wheel moving. Was I supposed to replace the removed bevel washers with flat washers???

Everyone Iíve talked to said these bikes are a constant struggle but after they are dialed they are great for at least a bit. My son came off a PW50 since heís jumping now and his suspension was shot of his pw. I figured this was the best route to go since heís really into racing and loves it/wants to do it but now I feel like a POS because he canít even ride. Every "Moto Dad" just says I feel your struggle and a few old times said F that bike just by a crf50 itíll run for ever and you donít have to do anything to it....

Any help with the bike would be appreciated tremendously.....
Thanks for reading my novel.
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post #2 of 10 (permalink) Old 05-07-2019, 10:46 AM
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post #3 of 10 (permalink) Old 05-08-2019, 04:23 PM
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Common issue

Welcome to the KTM Forum!

These small rocket ships love to scream! First one we got (a 2004) I had started it where I bought it and it did run well. Next day we went to the track for a racing day. I put the bike on the stand, started it but could not get the rear wheel to engage. After some trying I asked another dad whos son was riding well on same bike. He came over, started our bike and revved the bike and the backwheel was turning. "All good" he said. You need to get them to 8 - 9 thousand revs before the clutch engages... I had never owned a bike that would do anything close to that!! So once we understood that all went well.

Saying that, we also learnt that the clutch needed dismatling and cleaning after every race day to keep it working as it should.

You can adjust when the clutch grabs by playing with the washers (as you have found). You find info re the setups and more if you read some of the threads above. If you still are stuck after that come back and we will try our best to guide you through it.

.................................................LET THE BRIDGES I BURN LIGHT THE WAY!
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post #4 of 10 (permalink) Old 05-11-2019, 10:44 AM Thread Starter
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Originally Posted by Axzon View Post
Welcome to the KTM Forum!

These small rocket ships love to scream! First one we got (a 2004) I had started it where I bought it and it did run well. Next day we went to the track for a racing day. I put the bike on the stand, started it but could not get the rear wheel to engage. After some trying I asked another dad whos son was riding well on same bike. He came over, started our bike and revved the bike and the backwheel was turning. "All good" he said. You need to get them to 8 - 9 thousand revs before the clutch engages... I had never owned a bike that would do anything close to that!! So once we understood that all went well.

Saying that, we also learnt that the clutch needed dismatling and cleaning after every race day to keep it working as it should.

You can adjust when the clutch grabs by playing with the washers (as you have found). You find info re the setups and more if you read some of the threads above. If you still are stuck after that come back and we will try our best to guide you through it.

Yeah I read that in some paperwork that the guys had printed out, but the owners manual I have is saying 4500-5000 rpm. This is the air cooled 50, is the air cooled supposed to be 8000 too or just the water cooled? From what I understand after 08 they changed it and went with water cooled ....my manual tho it says Ktm mini and mini adventure, it shows only spring assembly for the clutch.... that’s what confuses me so much, is the water cooled 50 supposed to have beveled washers and not engage the clutch until 8000 rpm.
While my “bastard year” 08 air cooled ktm mini sx is supposed to have clutch springs/ engage at 5000 rpm ??? It just throwing me for a loop because he gave me beveled washers from the previous owner and then he also said “it has a beginner clutch “
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post #5 of 10 (permalink) Old 05-13-2019, 06:47 PM
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Originally Posted by kmf987 View Post
Yeah I read that in some paperwork that the guys had printed out, but the owners manual I have is saying 4500-5000 rpm. This is the air cooled 50, is the air cooled supposed to be 8000 too or just the water cooled? From what I understand after 08 they changed it and went with water cooled ....my manual tho it says Ktm mini and mini adventure, it shows only spring assembly for the clutch.... thatís what confuses me so much, is the water cooled 50 supposed to have beveled washers and not engage the clutch until 8000 rpm.
While my ďbastard yearĒ 08 air cooled ktm mini sx is supposed to have clutch springs/ engage at 5000 rpm ??? It just throwing me for a loop because he gave me beveled washers from the previous owner and then he also said ďit has a beginner clutch ď
Sorry for the confusion. The first KTM we ever had was a 50cc aircooled... it lacked power to take my boy up the hills and he needed to use his feet to push so we do not conside that a MX bike really... (see pic of bike). The water cooled ones come in 2 versions: The 50 MX Mini (Think this one also was called Adventurer at some stage) and the 50 MX. The MX Mini had springs in the clutch, the 50 MX uses the washers and was the one I was referring to initially. I have no experience with the clutches with springs in sorry but they would engage earlier and softer than the washer one that tends to be like a on/off switch...
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post #6 of 10 (permalink) Old 05-13-2019, 08:33 PM Thread Starter
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Quote:
Originally Posted by kmf987 View Post
Yeah I read that in some paperwork that the guys had printed out, but the owners manual I have is saying 4500-5000 rpm. This is the air cooled 50, is the air cooled supposed to be 8000 too or just the water cooled? From what I understand after 08 they changed it and went with water cooled ....my manual tho it says Ktm mini and mini adventure, it shows only spring assembly for the clutch.... that’s what confuses me so much, is the water cooled 50 supposed to have beveled washers and not engage the clutch until 8000 rpm.
While my “bastard year” 08 air cooled ktm mini sx is supposed to have clutch springs/ engage at 5000 rpm ??? It just throwing me for a loop because he gave me beveled washers from the previous owner and then he also said “it has a beginner clutch “
Sorry for the confusion. The first KTM we ever had was a 50cc aircooled... it lacked power to take my boy up the hills and he needed to use his feet to push so we do not conside that a MX bike really... (see pic of bike). The water cooled ones come in 2 versions: The 50 MX Mini (Think this one also was called Adventurer at some stage) and the 50 MX. The MX Mini had springs in the clutch, the 50 MX uses the washers and was the one I was referring to initially. I have no experience with the clutches with springs in sorry but they would engage earlier and softer than the washer one that tends to be like a on/off switch...
Ok, yeah mine is the sx mini, from what I can tell the sx and sx mini use the same motor but I think the only difference is clutch springs vs washers, more suspension and a foot rear brake... either way I just ordered new top end, new crank seals, and new clutch springs. Figure I could always shim the washers to make it hit a little higher in the rpm, I just don’t want to burn up another top end... the bike was running great , but they always do right before they blow up lol. Hopefully this new top end and clutch springs will make it shred again, he had no problem making it up our steep hill the first day he road it... if not I’ll work on his corner speed so he carries more momentum!
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post #7 of 10 (permalink) Old 05-20-2019, 02:29 PM Thread Starter
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OK so after the worst set of crap from amazon around i finally got the bike going and this is what i delt with....

what i found out. 08 and older is actually a beta motor, if the bike is are cooled ( like my 08 sx mini) then the clutch should engage 4-5k rpm. if the bike is water cooled like all the sr models or new sx mini 09 and up KTM motors the clutch will have the bevel washers instead of springs and engage at 8000 ish rpm.

Replacing the crank seals!!!!
guide the lip of the seal, i learnt this on my 3rd $25 seal after talking to a local mechanic, its was frustrating.....

Amazon top end kit
we will see how long it lasts.... it does say it carries a 1 year warranty but i will defiantly buy something better next time. the kits was only $80 but the head had wrong size domes (i ended up just using my stock one), the crank rod needle bearing was incorrect size(bought new oem one from ktm dealer), the shaft rod that mounts through the piston to the connecting rod was at least 2 times as thick and heavy (so i used my stock), the ring gap needed to be set by a file...

clutch kit
even after new springs and the 1mm + .5 mm shim washers that came with my new springs.... i required a additional .5mm shim ( i of course figured this out after fiddling with the carb and a million other things since i refused to take the clutch back apart for the 5th time.)
needless to say after raising and lowering the needle c clip i ended up shimming the springs the mention additional .5mm and the bike started ripping around the yard up and down the hills no problem.

Carb.
the guy i bought it from had changed out the main jet from a 70 to a 65. so i put it back at 70. i know the main is only really the topping on the cake.... while i was hunting the problem with the bike down ( ended up being the mentioned clutch needing the additional shim) i raised the c clip on the needle from the 2nd of bottom to the 2nd of top. the bike is running great around the yard and i will be throwing a new spark plug in it today or tomorrow to much sure its not running to lean. the old plug wasn't fouled but it was very dark, my new plug that had 20 minute of testing on it was very dark before i lowered the needle.. we shall see what the new plug looks like.

i had been having problems with the bike dying as it was going down my steep hill, i think its because half the track is up hill and half well... is down hill. i believe it was loading up since sometimes its took 3-4 good kicks to get it going and then clear it out. hopefully lowering the needle and a fresh top end will keep it from dying but we shall see.. non of the jets were plugged...

Has anyone else had a problem with the bike dying going down hills? if so what did you do to fix it????
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post #8 of 10 (permalink) Old 05-21-2019, 01:04 AM
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Nice!

You are going down the track most of us have been. We spent hours playing with these small things and learnt from our mistakes! (I did not think they made the air cooled ones past early 2000?).

Re the engine dying when coming down the hill:
- Make sure your airfilter is clean and oiled up. Depending on what kind of terrain you are on you can get away with one airfilter/day or have to change them between each race...
- Check that the float in the carbi closes at the right place. Depending on how steep the hill is it could have a bearing on how much fuel gets in to the inlet. Do you have same issue on more flat terrain?
- Again re the clutch: It is an ongoing battle. You will find the "sweet spot" for the clutch, but as the bike is used there will be buildup between the small washers and it all changes. I took the clutch apart after every race day and gave it a clean up... my current lady friend (now since 11 years) came for a visit the first time when my youngest son had just started racing the 50's. She spent that evening sitting in a chair in my workshop having a drink or two watching me sorting the clutch... She stayed, she recon I am a keeper...

Keep up the good work!!

.................................................LET THE BRIDGES I BURN LIGHT THE WAY!
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post #9 of 10 (permalink) Old 05-21-2019, 08:16 AM Thread Starter
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You are going down the track most of us have been. We spent hours playing with these small things and learnt from our mistakes! (I did not think they made the air cooled ones past early 2000?).

Re the engine dying when coming down the hill:
- Make sure your airfilter is clean and oiled up. Depending on what kind of terrain you are on you can get away with one airfilter/day or have to change them between each race...
- Check that the float in the carbi closes at the right place. Depending on how steep the hill is it could have a bearing on how much fuel gets in to the inlet. Do you have same issue on more flat terrain?
- Again re the clutch: It is an ongoing battle. You will find the "sweet spot" for the clutch, but as the bike is used there will be buildup between the small washers and it all changes. I took the clutch apart after every race day and gave it a clean up... my current lady friend (now since 11 years) came for a visit the first time when my youngest son had just started racing the 50's. She spent that evening sitting in a chair in my workshop having a drink or two watching me sorting the clutch... She stayed, she recon I am a keeper... [IMG class=inlineimg]/images/KTMforums_2015/smilies/tango_face_wink.png[/IMG]

Keep up the good work!!
Yeah all the adventures were air cooled and then from what I was told the 08 sx mini is the first year of the sx mini. If it’s a air cooled motor like my 08 sx mini/any adventure they actually come with the springs in the clutch rather than the bevel washers.

It has a new air filter and I just cleaned everything with the carb.

Yesterday he rode it and the bike had plenty of power to rocket him up the hill. It seemed like it was running a little hot (I forgot to bring my heat gun out to check it) but it didn’t load up at all, didn’t loose any power at any point just ripped all around the track.
I only had him go down the “big hill” 3-4 times.... he was struggling a little so I just kept him on the top half of the track... his clutch seems perfect, carb seemed perfect. It only died one time and it’s cause I tried dropping the idle a little lower because it seemed a little high, but there was no clutch drag so I just set it back to where it was....

What oil is everyone running? I picked up the motorex kind the dealer says it takes but I’m wondering if there is something equal without the $20 a quart price tag...
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post #10 of 10 (permalink) Old 05-22-2019, 04:47 AM
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Yeah all the adventures were air cooled and then from what I was told the 08 sx mini is the first year of the sx mini. If itís a air cooled motor like my 08 sx mini/any adventure they actually come with the springs in the clutch rather than the bevel washers.

It has a new air filter and I just cleaned everything with the carb.

Yesterday he rode it and the bike had plenty of power to rocket him up the hill. It seemed like it was running a little hot (I forgot to bring my heat gun out to check it) but it didnít load up at all, didnít loose any power at any point just ripped all around the track.
I only had him go down the ďbig hillĒ 3-4 times.... he was struggling a little so I just kept him on the top half of the track... his clutch seems perfect, carb seemed perfect. It only died one time and itís cause I tried dropping the idle a little lower because it seemed a little high, but there was no clutch drag so I just set it back to where it was....

What oil is everyone running? I picked up the motorex kind the dealer says it takes but Iím wondering if there is something equal without the $20 a quart price tag...
You have the gearbox oil and the 2 stroke oil that you mix in the fuel. We also initially used the Motorex stuff, but now use fully synthetic Castrol Power 1 Racing 4t 10 - 40 in the gearbox and Castrol Power 1 Racing 2t to mix in the fuel.

.................................................LET THE BRIDGES I BURN LIGHT THE WAY!
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