KTM 105sx trail bike

[strokemetwice]

I just bought a 2007 ktm 105 sx for the wife. Trying to make it trail worthy. A couple questions. 

Has anyone figured out a kickstand for the sx?

Has anyone retarded timing for more low end power?  

Thoughts on flywheel weight for this bike? 

Any other comments?

[wwillf01]

I don't have experience with that specific bike but have worked a lot with yz85,yz125 and KTM 150... If you are trying to make the power more controllable through the powerband I would add a flywheel weight... To me they do make the rpms rise slower but if the rider does not have the best clutch skills this helps a lot on mistakes... along with keeping momentum which is the name of the game for the small bore 2 strokes. Also a rekluse is very helpful and makes the ride much more enjoyable.... When my wife was on smaller bike making the ergo fit her body was super important.... I like to position the bars and controls to where it makes her keep her elbows up so there is not such an issue with arm pump... I added a promoto billet kickstand to the 150 sx don't know if they make one for the 105.... So I know as far as my wife goes she came off a mountain bike so the hand rear brake help a lot also for just the enjoyability of riding or coming down through tech type switch backs... I would assume like most ktms you should be able to get a switch that will mellow the power and give it more of a torque feel with the push of a button.
..

[seer]

Retarding the timing reduces bottom. You can try advancing but I'd be VERY carefull with detonation. 

 

 If you want to get serious have the cylinder decked and head cut to match. You can do some just with thinner base gaskets. 

 

 Lowering compression will mellow out the hit but will reduce bottom end.  Only do this by cutting the dome. Keep the squish tight. 

 

A smaller carb might be worth while. 

[slideleft]

Other than the frame, the XC has a tab for the stand the two XC/SX are the same.  Mine loves hers but we may go Lectron just to smooth things out.

 

[strokemetwice]

20 hours ago, seer said:

Retarding the timing reduces bottom. You can try advancing but I'd be VERY carefull with detonation. 

 

 If you want to get serious have the cylinder decked and head cut to match. You can do some just with thinner base gaskets. 

 

 Lowering compression will mellow out the hit but will reduce bottom end.  Only do this by cutting the dome. Keep the squish tight. 

 

A smaller carb might be worth while. 

Is the ktm 105 different with timing?  With big bikes like the yz250 retarded timing gives much more low end power. This bike was way far advanced to the point where it was signing off quickly. 

[seer]

2 hours ago, strokemetwice said:

Is the ktm 105 different with timing?  With big bikes like the yz250 retarded timing gives much more low end power. This bike was way far advanced to the point where it was signing off quickly. 

No it's not different. 

 

 The YZ was over advanced (adding bottom) and signing off on top. You retarded it and gained top end  rev. 

[strokemetwice]

From what I understand the 2 stroke timing is a bit different from 4 stroke. Everything i have experienced and read is that slightly retarding timing will smooth out the hit and give a broader rpm range and actually not sign off as quickly. Worked in all my yz's. Seems to have helped with the 105 too. Just going off what i have seen. Not trying to battle your knowledge.  

[seer]

1 minute ago, strokemetwice said:

From what I understand the 2 stroke timing is a bit different from 4 stroke. Everything i have experienced and read is that slightly retarding timing will smooth out the hit and give a broader rpm range and actually not sign off as quickly. Worked in all my yz's. Seems to have helped with the 105 too. Just going off what i have seen. Not trying to battle your knowledge.  

You are correct but in your original post you asked for more low end. I recommended advancing for that. 

[kcs]

My son has been on KTM 105s and now KTM 112 superminis for the past couple of years. He races an offroad series here in NC, so we are in the foothills of NC quite a bit. So bottom end is important. Jetting bike is something to look at. We used the stock needle in the number 2 position from top, 42 pilot and either a 115 or 118 main. I also geared the bike down a bit. Instead of 14-49(stock), I ran a 14-51 set up. Never needed a flywheel weight. They had made the 105's in the XC model and it came with a kickstand, so there are probably some on ebay. Simple bolt on. Another thing to think about is what 2 stroke oil to use. We found through trial and error that Lucas Semi Synthetic 2 stroke oil mixed at 40 to 1 worked best for us. Because he is racing hare scrambles, he is not on the pipe burning off any excess oil. The lucas has what I think they call a low flash point, so it doesn't build up clogging up your powervalve or silencer. With his 105 I was doing top ends about every 40 hours and could not believe how good everything looked. We still use that oil in his KTM 112 Supermini with Lynks engine and his 2017 KTM 150 with Lynks Engine. It just works for us and we are running race fuel. I buy the Lucas from Oreilly's auto parts. I also used ATF type F in the transmission, just changed it after every race or a couple of hours of ride time. Never had any clutch issues. I change them out once a year just because. Found that RMATV's tusk clutch pack to work the best. Plus they are cheap and last a long time. Also found that my son liked running bar risers, stock are 37mm and we used 47mm. Like I said, this stuff worked for us, but maybe it will give you some ideas. 

[strokemetwice]

On 5/28/2017 at 3:25 PM, seer said:

You are correct but in your original post you asked for more low end. I recommended advancing for that. 

Good point 

[strokemetwice]

On 5/28/2017 at 4:19 PM, kcs said:

My son has been on KTM 105s and now KTM 112 superminis for the past couple of years. He races an offroad series here in NC, so we are in the foothills of NC quite a bit. So bottom end is important. Jetting bike is something to look at. We used the stock needle in the number 2 position from top, 42 pilot and either a 115 or 118 main. I also geared the bike down a bit. Instead of 14-49(stock), I ran a 14-51 set up. Never needed a flywheel weight. They had made the 105's in the XC model and it came with a kickstand, so there are probably some on ebay. Simple bolt on. Another thing to think about is what 2 stroke oil to use. We found through trial and error that Lucas Semi Synthetic 2 stroke oil mixed at 40 to 1 worked best for us. Because he is racing hare scrambles, he is not on the pipe burning off any excess oil. The lucas has what I think they call a low flash point, so it doesn't build up clogging up your powervalve or silencer. With his 105 I was doing top ends about every 40 hours and could not believe how good everything looked. We still use that oil in his KTM 112 Supermini with Lynks engine and his 2017 KTM 150 with Lynks Engine. It just works for us and we are running race fuel. I buy the Lucas from Oreilly's auto parts. I also used ATF type F in the transmission, just changed it after every race or a couple of hours of ride time. Never had any clutch issues. I change them out once a year just because. Found that RMATV's tusk clutch pack to work the best. Plus they are cheap and last a long time. Also found that my son liked running bar risers, stock are 37mm and we used 47mm. Like I said, this stuff worked for us, but maybe it will give you some ideas. 

All very good points. I have found the klotz supertechniplate works great in my 2 strokes. Also has low flash point and smells delicious. Thanks for all the ideas!! So far just backing off the timing has helped a lot. It was crazy advanced and had a mean hit in the middle. 

[Shhhh]

On May 28, 2017 at 6:24 AM, slideleft said:

Other than the frame, the XC has a tab for the stand the two XC/SX are the same.  Mine loves hers but we may go Lectron just to smooth things out.

 

 

On May 26, 2017 at 11:03 PM, strokemetwice said:

I just bought a 2007 ktm 105 sx for the wife. Trying to make it trail worthy. A couple questions. 

Has anyone figured out a kickstand for the sx?

Has anyone retarded timing for more low end power?  

Thoughts on flywheel weight for this bike? 

Any other comments?

I have a 30mm Lectron for sale, it was on my sons 85.  Looking to sell, having no luck, and am negotiable on price.  PM me if interested.

[slideleft]

let me rum this past the Mrs.

[slideleft]

On ‎5‎/‎28‎/‎2017 at 6:19 PM, kcs said:

My son has been on KTM 105s and now KTM 112 superminis for the past couple of years. He races an offroad series here in NC, so we are in the foothills of NC quite a bit. So bottom end is important. Jetting bike is something to look at. We used the stock needle in the number 2 position from top, 42 pilot and either a 115 or 118 main. I also geared the bike down a bit. Instead of 14-49(stock), I ran a 14-51 set up. Never needed a flywheel weight. They had made the 105's in the XC model and it came with a kickstand, so there are probably some on ebay. Simple bolt on. Another thing to think about is what 2 stroke oil to use. We found through trial and error that Lucas Semi Synthetic 2 stroke oil mixed at 40 to 1 worked best for us. Because he is racing hare scrambles, he is not on the pipe burning off any excess oil. The lucas has what I think they call a low flash point, so it doesn't build up clogging up your powervalve or silencer. With his 105 I was doing top ends about every 40 hours and could not believe how good everything looked. We still use that oil in his KTM 112 Supermini with Lynks engine and his 2017 KTM 150 with Lynks Engine. It just works for us and we are running race fuel. I buy the Lucas from Oreilly's auto parts. I also used ATF type F in the transmission, just changed it after every race or a couple of hours of ride time. Never had any clutch issues. I change them out once a year just because. Found that RMATV's tusk clutch pack to work the best. Plus they are cheap and last a long time. Also found that my son liked running bar risers, stock are 37mm and we used 47mm. Like I said, this stuff worked for us, but maybe it will give you some ideas. 

the tab isn't on the SX its welded behind the foot peg on the XC.

[seer]

2 hours ago, slideleft said:

let me rum this past the Mrs.

"You're pretty... Can I buy a carb?"

[slideleft]

9 hours ago, seer said:

"You're pretty... Can I buy a carb?"

More like "you want a Lectron" LOL  and the answer is not now, wants a Beta 150rr first.

[michaelchristie207]

It should already be a goods woods hike I don't understand the hype about making the small 2-strokes "more woods friendly" I rode a completly stock yz85 besides prcircut silnecer in some crazy places and was better than all the kids and wife's with $2000's into making the bikes woods ready. Just ride it til she is as good as the bike can get. If she's scared of the bike or it is to much then a flywheel weight, jetting and maybe different tires