I just purchased a 2002 KDX200.I've been reading your posts and you guys made me love it before i got it. I am 50 but feel 15 right now. Now I want to know every thing. What premix oil and ratio.I know this has a lot of preference but wanting to know. How much and what type of gearbox oil. My first water cooled bike, what kind of coolant? How about lowering it some, does anyone make a low seat? Do most stay with stock sprocket size?Any service manuals and owners manuals I can download.Thanks Bud in Illinois
Just got my first KDX
- Thread starter budpat105
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reepicheep
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- Apr 3, 2009
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I run 32:1 just for simplicity sake. I don't think there is any problem running 40:1, but you should pick what you want and jet accordingly. Changing the mix will change the jetting.
For the tranny, I really like the ATF type F. Nice and cheap, available everywhere, seems to clean like crazy and lubricate really well, and doesn't make my clutch slip.
For lowering it, I accidentally "lowered" mine. My tail section was badly damaged when I bought the bike (1/2 broken off, the other half badly bent). I fabricated some brackets and welded it back up, and lined everything square, but ended up having the tail section 1/2 to 1" too low. It makes a lot more of a difference then I expected, when I sit on a stock KDX it feels really tall (which is actually what I wanted), mine feels significantly lower. Havent had the tire touch anything yet. So you could heat up and bend down the tail section 1" or so. You will have to repaint the frame though, and the paint will never be as good as the powder coat. I expect you can get lowering links as well.
I geared down, but I am all woods riding and I'm a slow fat old guy :)
The commonly available illegally downloadable service manual is for an older model. Some bits the same, some different. I found the service manual (printed factory) on ebay. There is a third party online manual as well that is supposed to be good, I forget who but google will find it easy enough.
Congrats on the bike! Great pick!
For the tranny, I really like the ATF type F. Nice and cheap, available everywhere, seems to clean like crazy and lubricate really well, and doesn't make my clutch slip.
For lowering it, I accidentally "lowered" mine. My tail section was badly damaged when I bought the bike (1/2 broken off, the other half badly bent). I fabricated some brackets and welded it back up, and lined everything square, but ended up having the tail section 1/2 to 1" too low. It makes a lot more of a difference then I expected, when I sit on a stock KDX it feels really tall (which is actually what I wanted), mine feels significantly lower. Havent had the tire touch anything yet. So you could heat up and bend down the tail section 1" or so. You will have to repaint the frame though, and the paint will never be as good as the powder coat. I expect you can get lowering links as well.
I geared down, but I am all woods riding and I'm a slow fat old guy :)
The commonly available illegally downloadable service manual is for an older model. Some bits the same, some different. I found the service manual (printed factory) on ebay. There is a third party online manual as well that is supposed to be good, I forget who but google will find it easy enough.
Congrats on the bike! Great pick!
- Jul 20, 2009
- 417
- 0
Hi Budpat105,
Premix: 32:1 is factory recommendation and is a safe ratio.
Like reepicheep said ATF type F seems good and is not too expensive like some of the fancy oils. However if your seals are not up to scratch it will weep. Try it, if it doesn't leak or weep you are good to go. How much to use, manual specifies 700ml.
The coolant has to be suitable for aluminum radiators and I think it is supposed to be mixed 50/50 with water (I use distilled water).
The bike can be lowered by using different length suspension linkages (the thing that look like a dog bone). The originals are 112.5's (I think the length is stamped on them so just go have a look). If you doo lower the rear you will also have to lower the triple clamps on the forks to keep the overall bike geometry good.
I have kept the 47T rear sprocket on mine and I just change the front if needed. My first ride on mine was with a 13T front, but it was geared to high for the really steep tight slow stuff so I changed it to a 12T and I find it much better.
You can buy online manuals as a pdf, but I think they are dodgey. I bought one thinking it was factory one, but it turned out to be a home made photocopy of a genuine manual and it even had a couple of pages missing. Hmmm... I got ripped.
Premix: 32:1 is factory recommendation and is a safe ratio.
Like reepicheep said ATF type F seems good and is not too expensive like some of the fancy oils. However if your seals are not up to scratch it will weep. Try it, if it doesn't leak or weep you are good to go. How much to use, manual specifies 700ml.
The coolant has to be suitable for aluminum radiators and I think it is supposed to be mixed 50/50 with water (I use distilled water).
The bike can be lowered by using different length suspension linkages (the thing that look like a dog bone). The originals are 112.5's (I think the length is stamped on them so just go have a look). If you doo lower the rear you will also have to lower the triple clamps on the forks to keep the overall bike geometry good.
I have kept the 47T rear sprocket on mine and I just change the front if needed. My first ride on mine was with a 13T front, but it was geared to high for the really steep tight slow stuff so I changed it to a 12T and I find it much better.
You can buy online manuals as a pdf, but I think they are dodgey. I bought one thinking it was factory one, but it turned out to be a home made photocopy of a genuine manual and it even had a couple of pages missing. Hmmm... I got ripped.
reepicheep
Member
- Apr 3, 2009
- 670
- 2
Great points... for the record, I am at 13 front with a 48 rear sprocket I think. I wanted to go a shade lower, but I heard that 12 tooth and smaller fronts wear chains and the sprocket fast (because they are so small). Thinking about it, that is probably true on a street bike, but probably a non issue on a dirt bike... our chains are probably trashed by contamination long before they "wear out". Next time I put in an order I should pick up a 12t front. It would make the bike a lot of fun in the woods (where I normally ride).
bultaco4ever
Member
- Oct 14, 2009
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50 years old and you got your first KDX, eh? I'm 56 and just got my first KDX last Thanksgiving. I rode it up one block and back when I bought it, but not since... (winter set in here in the Rust Belt). I have spent the last month tinkering with suspension and tires. You've asked some good questions and already received some good answers. I'm reading and learning also. So, all you advisors...keep the advice coming!
bultaco4ever
Member
- Oct 14, 2009
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Last summer I visited an old friend who took my advice at the time and bought a brand new '90 KDX 200 twenty years ago. I had just restored an old Bultaco and took it over to show off. I rode his KDX and couldn't believe how nice it was. His KDX was the bike doing all the showing off. So, another buddy of mine, who is also 56, said he wanted to get back into dirt bikes and wanted some advice on what to get. I told him to do himself a favor and get a KDX. So, he takes my advice and gets a project '85 KDX 200 (air cooled, KIPS, and disc rear brake). He happily starts restoring it and I get really jealous. Two friends with KDX's and me with none. So, I couldn't live with myself til I had one. Found a nice '97 KDX 220 that needed very little. I think I'm happy now. Warm, spring weather is all I need now!
canuckhybrid125
Member
- Apr 8, 2009
- 11
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Im sure you heard this before,if you still have a stock piston in the 220 get it out of there.The piston skirt tends to let go.
bultaco4ever
Member
- Oct 14, 2009
- 149
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The PO said he just replaced it. Hopefully I'm golden.
bultaco4ever
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- Oct 14, 2009
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This thread started out with some fuel/premix ratio suggestions. Just wanted to point out that personal conversations with Jeff Fredette says that 50:1 Golden Spectro is what he uses. www.bultaco.com also suggests Golden Spectro at 50:1 for my vintage bike engines. I like the suggestion to jet your bike and be consistent with the ratio that you settle on.
reepicheep
Member
- Apr 3, 2009
- 670
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It might be interesting to do some math, and use tune the mix ratio to temperature to keep the jetting lined up...
Hmmm... 32:1 is 3.125% oil in the gas. 50:1 is 2.000% oil in the gas. So you could use the ratio between the two and compensate for density of air changes up to 1.12%. Cooler air is denser and needs more fuel, so run 50:1 on cool riding days, then 32:1 on hot riding days.
I googled up this air density chart:
http://www.engineeringtoolbox.com/air-temperature-pressure-density-d_771.html
At 30 degrees F, air is .081 pounds per cubic feet. At 100 degrees, it is .071 pounds per cubic feet. So between cold winter and hot summer, you have a 1.14% difference in density. So it's within reason. Run 50:1 in the winter, run 32:1 in the summer, and leave the jets be. That also gives you the "when in doubt, lubricate more" setting for the really hot summer days when you have more of a chance of overwhelming the cooling system.
Of course, all this assumes that oil doesn't burn, which I am sure is a wrong assumption. And kind of a hassle to keep track of what you are mixing. And one more variable to try and track for keeping the jetting straight, which is the last thing we need.
Hmmm... 32:1 is 3.125% oil in the gas. 50:1 is 2.000% oil in the gas. So you could use the ratio between the two and compensate for density of air changes up to 1.12%. Cooler air is denser and needs more fuel, so run 50:1 on cool riding days, then 32:1 on hot riding days.
I googled up this air density chart:
http://www.engineeringtoolbox.com/air-temperature-pressure-density-d_771.html
At 30 degrees F, air is .081 pounds per cubic feet. At 100 degrees, it is .071 pounds per cubic feet. So between cold winter and hot summer, you have a 1.14% difference in density. So it's within reason. Run 50:1 in the winter, run 32:1 in the summer, and leave the jets be. That also gives you the "when in doubt, lubricate more" setting for the really hot summer days when you have more of a chance of overwhelming the cooling system.
Of course, all this assumes that oil doesn't burn, which I am sure is a wrong assumption. And kind of a hassle to keep track of what you are mixing. And one more variable to try and track for keeping the jetting straight, which is the last thing we need.
bultaco4ever
Member
- Oct 14, 2009
- 149
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I've never heard of changing premix ratios to compensate for temperature and air density changes. I change jets to compensate for that. Oil only lubricates. Fuel actually helps 'cool' the piston when it gets in the combustion chamber. So, correct 'jetting' is more important than the premix ratio. I heard advice that says on a long downhill, where you're riding the brakes and keeping the throttle closed, that it is a good idea to pull the clutch in and blip the throttle to drawing in some needed 'cooling' fuel make contact with the piston crown. On a cold winter day when more oxygen molecules fill each space of cubic area in the combustion chamber you need more fuel to maintain the 18: 1 airl/fuel mixture. (I think it's 18:1) Adding more oil won't add more gas to the fuel mixture. I don't think changing the ratio will ever replace correct jetting.
Fuel contributes very little to engine cooling; not enough of it goes through the engine to carry away significant heat and what little does go through an engine does not have enough heat-carrying capacity to be significant. Ultimately, air is what carries 99% of produced heat away from an engine.
So, blipping the throttle on a long downhill accomplishes very little. At closed throttle, the engine is losing heat far more quickly than it is producing it and that tiny droplet of fuel that the blipping will put through an engine is insignificant. That "blip-on-long-downhills" theory has just enough truth to it to make it sound plausible, but in reality, after looking at the details of how it all works, it loses credibility.
Changing oil ratios will affect jetting, and as long as you stay within the min/max numbers, could be an easy way to adjust. However, if weather conditions change enough to require a jetting change, adjusting oil/fuel ratios probably won't give you enough change to be effective. Myself, I keep ratios constant at 32:1 and adjust carburation when required. At my age, I need to keep things simple.....
So, blipping the throttle on a long downhill accomplishes very little. At closed throttle, the engine is losing heat far more quickly than it is producing it and that tiny droplet of fuel that the blipping will put through an engine is insignificant. That "blip-on-long-downhills" theory has just enough truth to it to make it sound plausible, but in reality, after looking at the details of how it all works, it loses credibility.
Changing oil ratios will affect jetting, and as long as you stay within the min/max numbers, could be an easy way to adjust. However, if weather conditions change enough to require a jetting change, adjusting oil/fuel ratios probably won't give you enough change to be effective. Myself, I keep ratios constant at 32:1 and adjust carburation when required. At my age, I need to keep things simple.....
I use the blip for peace of mind... more for the oil it gives my moving parts than any cooling effect it may or maynot have
I sometimes don't pull the clutch in when going down hills and have the throttle shut too so an occasional blip makes me feel better about the "higher than TP rpm's"
I sometimes don't pull the clutch in when going down hills and have the throttle shut too so an occasional blip makes me feel better about the "higher than TP rpm's"
reepicheep
Member
- Apr 3, 2009
- 670
- 2
I blip the throttle going downhill so my riding buddies can follow the smoke trail and more quickly rescue my old, fat, stuck behind if things go really badly. ;)
:ride: :ohmy:
:ride: :ohmy:
- Jul 20, 2009
- 417
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Hmmm..... I have to strongly disagreemudpack said:
To blip or not to blip
On a hot day stand in front of a fan and spray a fine mist into the air flow, the cooling difference is substantial (yes I have done it, well kinda, I used to spray a fine mist of water into the air on hot days and walk through it). You are saying turn off the fan.
You talk about the air cooling the motor, if the throttle is closed there isn't a great deal of air or lubrication to cool anything, although I am sure your agrument is that if there is nothing to burn there is nothing to cool. My point is the engine is already hot and needs lubrication and we know lubricating the motor through oil in the fuel works and does NOT lead to seizure. In the end I have personally not know 'Blippers' to seize when off the throttle, but as has been stated many times on 2 stroke dirt bike forums "I was just slowing down when the engine seemed to lock up, can any one help? The answer always seems to be "you need to blip the throttle when off the gas", and I totally agree. Blippers of the world unite! Infact the next time I buy a bike I will be asking if the owner is a blipper ;)
