A few questions about tires, sporockets and suspensions

Hey all-

I've got a few questions about tires, sprockets and suspension.  I sent my bike to my mechanic for new tires and sprockets and a re-tuned suspension, but it rides terrible now.  It rode well before but I wanted the suspension a touch stiffer.  Paul and Karel have pointed me in the right direction, but I'm getting a bit confused.  Since it ran well before, I'll point out the before settings, the after settings and the stock settings.

Tires:
Before - Michelin Cross Competitions 90/90/21 up front and 130/80/18 in the rear
After - Dunlop MX-51's 80/100/21 up front and 120/90/18 in the rear.
Stock - Bridgestone M59 90/90/21 up front and Bridgestone M402 110/100/18 in the rear
Karel mentioned that the  new tires may be overinflated so I checked, and the front tire was ok, but the back was six pounds over. I understand what the numbers mean as far as width, depth and flex, but I don't understand what it means in real life.  How do bigger/smaller tires affect handling?  Which size would be best for somewhat tight trails?  MX? A 2008 KTM XC-W 250 woods bike?

Sprockets:
This one is easy because the before and after is the same - 13 tooth front and 50 tooth rear.  I looked in the owner's manual and I can run a 38, 40, 42, 45, 48, 50, 51, and 52 tooth sprocket.  What happens if I go up or down a couple of teeth?  Is 50 a good number for a woods bike?  What about an MX bike?

Suspension:
I think this might be the biggest culprit as far as poor handling goes.  I asked him to stiffen the suspension but I didn't understand how important the sag is.  I told him I weighed about 150 pounds but I think he just guessed because he never asked me to sit on the bike.  I checked the sag and it's 3.50 inches (there are 25.4 millimeters in one inch, 25.4 X 3.5 = 88.9 millimeters) I don't think that's a good number.   I looked at the receipt and it says 'serviced and turned down rear shock preload and front & rear compression and dampening'. So I can't just turn the clicker one notch at a time, can I?  I need something done to the front forks at the same time?  How do I find out the stock settings?

Thanks for your help.   At least when I bring the bike back I'll know what to tell him.  
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Hudson Valley NY
KTM XC-W 250

"If you don't have a dream, how can it come true?"

Your suspension is to stiff IMO. It should be about 4" or 100mm. You will most likely not like a 3 1/2" sag. Reset the sag first.
You can turn the clicker 1 at a time but set it back to stock ( what the manual says ) then go from there.  
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I love this dirt stuff.

Hair, Im glad you are gonna take it back to the shop Im sure they wont mind getting it right.

as far as the tires I would only run a 110 (width= first number in the tire size)
on a 250T

the sprocket sizing just depends on the track or trail, or what ever suits your personal prefference. adding a tooth or 2 on the rear makes the bike easier to ride in the tight stuff but makes throttle control more important (the bike will be more responsive) it also reduces top speed (in the woods im sure that isnt a priority)

dont forget the weight of your riding gear when estimating your weight.
good luck!  

Autismspeaks.org
Gilbert AZ
06yz144,05yz85,02yz85

I would agree that the tire is on the large side for a 250, but most important for a women your height is that the 120 will raise the back of the bike up a little. I doubt that radical wheelspin is an issue for you, so I think you could even go with a 100/100-18. It would spin a little easier, but would lover the rear of the bike a little. Again, that is good for you. Your bike should sag 35mm without you on the bike, and about 110-115mm of sag with you on it. If you are going to fudge the numbers, then make sure the bike sag of 35mm is correct even if the sag doesn't seem right with you one the bike. As far as the clickers go, the shock rebound (on the bottom of the shock) needs to be between 22 and 24 clicks out from all the way in. When you are turning the adjuster in, stop as soon as it gets hard, don't force the last click out of it. The adjuster on the top of the shock should be around 18 clicks out. The compression on the fork is the knob at the top of each fork leg. I'd start with 18 out there as well.
I thougt most KTMs had a 14-tooth front sprocket standard, but I could be wrong, and nearly everyone in your area puts a 13 on immediately. On point about the chain and sprockets that could affect the handling is the chain slack. To a regular mechanic a KTM chain should look like it is falling off. With the bike on a stand, there should be four fingers of slack in the chain. I check it by sliding my hand right up against the rear of the upper chain wear pad to check it. If you aren't sure, take the shock off. (Takes about one minute on a KTM -- just two bolts, but they are tight ones. Make sure the bike is on a stand, then put wood or bricks are something under the rear tire to hold the swingarm up until the rear axle is in line with the countershaft. That is the point where the chain is tightest, and it should have 3/4 of an inch of slack at that point.
You change sprockets because you want the engine to do something different, and hopefully better. For example, say you find you are riding two many trails in first gear. If you put a 52 on the rear, you could be in second on technical trails, and that would leave first as an emergency gear if you mess up. Or you might find that for the trickiest sections of your trail, first is too low, and second makes you clutch too much. A 51 or 52 might allow second to work easier, or you could go 48 or 49 and make first more usable. On a track the trickiest jump on the track might be overrevved in third, but fourth is bogging. You change gearing to have a gear pull right on that jump, then see if it compromised the bike on other parts of the track. Understand? I usually don't change more that one tooth at a time. If I am doing a fast race like Elsinore Grand Prix or a desert race, I might go up one tooth on the countershaft (front) and down one on the rear. That gives me longer power in each gear and more top speed, and I don't even need to change the chain adjustment. One tooth in the front is like 3.5 teeth on the rear sprocket.  

You guys are THE BEST!!
 
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Hudson Valley NY
KTM XC-W 250

"If you don't have a dream, how can it come true?"

the clickers just help speed up or slow down the damping reaction time,spring weights are what they are to stiff it deflects off of everything to soft gets wallowy even tends to bottom,i still say that springs need a few good rides to break in and soften up a bit i went bigger in the front and rear on my bike the rear is still good but im gonna get even bigger fronts the seem to have gotten a bit to squishy for me,i try to ride every type of terrain which is my biggest problem cause i need to set it up for a certain type and just deal with whatever else i throw at my bike,im no millionaire.  
im a legend in my own lunchbox

Hi again, I wanted to chime in on the fuel issue.  I too run clean gas with stabil, but the gas itself wasn't my problem.  It was the gas can.  There were little flakes of stuff in the can, that made their way into my carb.  That is what clogged my pilot jet.  I had to drain and rinse out my tank, and installed an in-line fuel filter just to be safe.  It was a new gas can and I am still stumped as to what the flakes were.  Anyway, it wouldn't hurt to take your bowl off, to examine the gas there, and remove your jets to make sure they are not clogged.  
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NW Montana
Where the pavement ends and the fun begins  
2005 KTM300exc
2001 Honda CR250
1978 Suzuki PE250

in line filter is the ticket cause i run fresh gas and still find unkown sediment in the bowl,this gas is garbage these days,ive been using sea-foam in my cars for years it works great ive just started using it on the dirtbike.  
im a legend in my own lunchbox

Oh, and here is what I am doing on the sprocket issue:  I ran it stock for the first year, then bought a 12 tooth front, to lower it for my technical trails.  This worked okay for the tight stuff but I lost too much top end speed.  So I went back to stock for the next three years.  I am pretty cheap so I wanted to wait until the stock sprocket wore down before I messed with the rear.  This summer I got impatient waiting and changed the rear sprocket to a 50 tooth, with a 13 in the front.  I've only ridden it a few times and I am not happy with the lower gearing at all!  I ended up pushing my bike up and out of a box canyon where I used to be able to ride out, because 1st gear is too low now, and 2nd is higher than my old 1st gear.  So my next move is to put the 14 up front, and try that trail again.  Of course everything was going wrong that day, my tires were overinflated and the recent rains had transformed my once fun trails into nightmare trials traps.  Everything was slippery to me that day.  I hope you figure all of this out, and can get back out there to enjoy your riding!  
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NW Montana
Where the pavement ends and the fun begins  
2005 KTM300exc
2001 Honda CR250
1978 Suzuki PE250

Thanks for the input spaz.  I think the springs should be broken in by now, no?  The bike has about 800 miles on it so far.

Hey Paul - what tires are you running on your 300?  One of the reasons the tire size was changed was because the 51's did not come in the old size.  Nor are they available in the 100/100 size.  Had I know how different the bike would be, I would have chosen a different tire!  Since the front tire is good, does anyone have any suggestions for a rear tire?  The stock tire that came on the bike (Bridgestone M402) is no longer available.  I ride mostly loose gravel, bedrock and some clay/loam.  What's compatible with an MX-51 front tire?

Hey Karel- I tried to find out what radical wheel spin is, but didn't get any search results.  One of the oddest things about the way the bike rides now is how the rear wheel just spins, especially on flat ground and loose gravel.  Even in first gear it kind of like fish tails back and forth and the faster I go, the more it fish tails.  I'm wondering if that's the radical wheel spin you're referring to (it's wheelspin and it's definitely radical!).  Also the XC has a stock 14 front sprocket - the XC-W is 13.  I think I'll stick with the 50 tooth sprocket for now until I get the bike back under control.    

Thanks for explaining all this stuff.  
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Hudson Valley NY
KTM XC-W 250

"If you don't have a dream, how can it come true?"

I run the 110/100 18 in the rear.  I am seriously considering buying a trials tire to use here because of all the logs, roots, rocks and mud I'm in.  I'll save the knobbies for the desert...  
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NW Montana
Where the pavement ends and the fun begins  
2005 KTM300exc
2001 Honda CR250
1978 Suzuki PE250

I meant what brand (Bridgestone M402's, Dunlops MX-51's, etc) tire do you have on the bike.  
~~~~~~~~~~~~~~~~~~~~
Hudson Valley NY
KTM XC-W 250

"If you don't have a dream, how can it come true?"

:
,ive been using sea-foam in my cars for years it works great ive just started using it on the dirtbike.  


I've never used Seafoam yet but I've used PB lawn mower tuneup and it's worked great so far.  Here's a link to seafoam and here's a link to pb blaster (you'll have to scroll to the bottom of the page).  
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Hudson Valley NY
KTM XC-W 250

"If you don't have a dream, how can it come true?"

yea the springs should be broken in must be to stiff,your gearing and tire choice might be the combo from hell its hard to make alot of changes at one time cause the smallest change on one thing can relect badly on so many others even things you havent messed with,and your lawnmower tu-up sounds pretty good ill try it out  
im a legend in my own lunchbox

okay, I took a look at the tires.  I noticed I have the Michelin crosscompetition S12 on the rear, and it's the 140/80 not the 110/100 I thought I had.  I ran the Dunlop 756 before this.  I liked the Dunlop 756, but I thought it wore out too fast.  Maybe some of my hillclimbing problems stem from this new tire size?  Like spaz said, I may have changed too much too soon.  I set the new sprockets and new tire up for the harescrambles race, and the bike hasn't run "normal" since.  I also had problems in the race with getting up one hill I nicknamed "the wall".  I failed to get up it on account of the too-low gearing.  On each lap I had to climb around the wall instead of go up it, two times after failing to make it.   I feel that the stock gearing would have been better for me there.  But maybe it was the tire size???  
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NW Montana
Where the pavement ends and the fun begins  
2005 KTM300exc
2001 Honda CR250
1978 Suzuki PE250