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Dave Hopkins

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  1. Dave Hopkins

    2003 450sx wont start...

    Full compression on the engine would be about 200PSI, the automatic decompressor lowers it to 115PSI to allow easy starting. If yours has 50 PSI one of two options; 1: compression tester is not sealing, or 2: Engine is dead!
  2. Dave Hopkins

    new intake port for dungey replica head

    Question Ron, on the heading of the post, has KTM changed the ports on the Dungy rep, or. are we looking at one head guys porting work.
  3. Dave Hopkins

    2012 350xcf valves

    I work on many dirt bike heads, the DelWest brand is by far the best Ti is used in KTM as well as Husky at least in the Italian engines of a couple years ago. They are delicate, do not like Bronze guides, combo KTM had in the 450SX in 03-05, it is a big no no to lap them or clean the carbon off with a wire wheel, glass beads etc, I use an Ultrasonic cleaner, takes several days. The DelWest valve typically does not cup like the steel unless a bunch of dirt gets past the filter and as such the valve clearence usually does not change. If your hearing noise its more likly the tensioner, let me explain, the hydralic tensioner yours oil pressure to extend the tensioner tight against the chain, then it has a little bind up thing inside to try to keep it from retracting. Every time the cam follower goes over the nose of a cam lobe the cam trys to run ahead so rather than the chain pulling the cam for a moment the cam is pulling the chain. If there is any slack in the chain this becomes a big jerking action which beats the chain to death. Would not be an issue if you had oil pressure all the time. Ever dropped the bike on its side and it continues running. Do you think the oil pump is picking up oil? Not! This is why I made a simple adjustable tensioner which you can see at djhcyclesport.com
  4. Dave Hopkins

    KTM 450 EXC-R starter clutch

    yes you need a puller
  5. Nice drawing but, is that from Mikuni? 2 stroke Kehein? On the FCR MX carb the bottom drain tube has two functions; 1: as in the drawing to drain the carb such as for storage, and 2: It has a by pass passage that goes from a verticle tube inside the bowl that goes up to above the float level straight down past the drain screw to the hose, this lets a small amount of fuel out to help prevent flooding the engine if the bike is leaned way over such as when a rider drops it. JD came up with a plan several years ago that I have used ever since to put a loop in this line so less gas is lost here
  6. Dave Hopkins

    250 port and cam desighn

    Interesting your earlier coments on intake ports too big. 99% of my work is on the bigger bikes and on the RFS engine 2000-2002 had a modest intake port, in 03 the intake got bigger, in theory this was to fit the 41mm carb that became available on SX in 03 but in reality they lowered the entire floor of the port, the bikes where never the same, old head clearly had more torque, never been convinced the higher RPM power changed?
  7. Dave Hopkins

    06 sx-f 250 standard carb settings

    Trying to recall, pilot I am almost certain was a 42, some run 40, some run 45, Needle, I recall the third letter was an E, (that is taper) 5th letter may have been an R (that is the diameter before taper) the others letters first is an O on all that fit this carb second is just the material it made from, not criticle, 4th is distance from clips to start of taper, it matters but we can adjust around any of them. Main I am thinking 175 The big thing that needed changing on them was the accelerator pump, many ways to tweek it, simple route is the pump diaphram from a Honda, Note in 07 they started drilling the carb for a leak jet, it was 08 before they fitted a jet to it
  8. Dave Hopkins

    06 sxf 250 keeps stopping

    2006's where plauged by the gas cap! Need to take the cap off & apart, if there is a black plastic ball bearing in there toss it!! Make certain the cap can vent freely both in AND out! Some people add those little check valve things in the vent hose, that his a huge no no!
  9. Dave Hopkins

    2006 KTM SXF 250 Valve Problem?

    All of the 250s have Del West Titanium valves, expensive and the best there is, these valves MUST be run on iron guides! The "problem" and it was not minor was 2003-2005 450SX & SMR which had the same brand/construction of valves but on Bronze guides, Bronze guides are excellent with steel or Stainless Steel valves but do not get along with Ti, life expectancy on those was about 15 hours, then the right intake failed. Why the right? The accelerator pump washes the oil off the stem when the valve is open. This isuue was fixed with the iron guides that all 250s had and all bikes with Ti valves have had since 2006, is not an issue on any of the steel valve models
  10. Dave Hopkins


    What cause the brake to get air in it? Parked wrong! Bike MUST be parked, stored with the right handlbar higher than the left! Normal side stand bike leaning left this takes care of itself, block it up level if the bars flop left your good, flop right and the master cylinder is lower than hose going over the headlight/number plate and your screwed. Also coming into play the SX models have a minimul length hose, this helps, an EXC has a longer hose to get over the headlight and this becomes a big issue!
  11. Dave Hopkins

    2005 RFS rebuild

    RE the locking lever is an arm that is under the clutch side cover under the lower rear of the clutch, it has a ball bearing in a roller tip that rolls over a star wheel as you shift gears. the ball bearing has been known to fail, this part was updated at the factory June of 07, so a few of the last 07s got the new part, its $10 and will save a nightmare if it fails, not only ruins your day but leaves tiny balls running thru the bottom of the trans, order 77034024044
  12. I don't know what the mini grooves are but difference between red & blue is in the OD of the needle before the start of the taper. My recolection is red is .1082" and blue more like .1074"
  13. Dave Hopkins

    Changing to the OCEMR on the KTM 520

    520 had the FCR carb, be carful as most of the input you get is going to be from folks with the FCR MX carb that KTM went to in 03, idle circut is different Idle I have always had sucess in that carb with a 48, 45 will just make it harder starting Off idle, the R needle is perfect, stay with the OCEMR Mid, I would have to have the needle in hand to confirm where to put the clip, IF you have a dial caliper and a 1 inch micrometer, set the mic at .104", slide the needle into the mic untill it sticks, measure up 2.6" and put the clip there, done! Main, anything in the range of 158 to 162 works,
  14. Dave Hopkins

    350SXF - Race Bike Build

    The most significant things you can do is a Ti rear spring and 2 ply tires!
  15. Dave Hopkins

    piston sizing

    I think he meant 94.96? which is 100th of a mm bigger. I stock & use the Woosner piston (better replacement) and their 2nd step up is .25mm larger, what I find is if the bore has enough wear to use it the bore is worn to the max. I would also question, does it need a piston? Typically the OEM piston outlast 2 sets of intake valves, where are you on valves?