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      HOW TO: 4-STROKE PISTON REPLACEMENT DONE RIGHT!

Steve_Moriarty

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About Steve_Moriarty

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    Arizona
  1. Great people to deal with.....some of the best prings in the industy
  2. couple things....... Its possible .001 off the cam might work but I wouldnt do anything like that until ive measured everything....there are specs in the book for journal clearance. Next is that the alum expands more than the steel when hot so clearance gets greater as it heats up....not that I would start it if its snug. Probably what happened is like mxer said.....overheat or lack of oiling smeared the aluminum. In the past Ive fixed this with a little lapping compound...320 grit or finer. Machining the cam would probably get you by but I worry about the overall shape of the journal and would rather see the journal get worked than the cam because after smearing like that its prob not as round as it used to be. Any questions on how to do this you can call me Steve 623-581-2900 Cycle Dynamics
  3. I have an 04 crf250r. I live at 1000' in Phoenix and will be going ro 7000' this weekend. Current jetting as follows 172main 4th clip 42 pilot 2 turns on fuel screw Any suggestions on what changes to make for altitude? Is there a rule of thumb like say 1 mainjet size for every so many feet? Thanks in advance Steve
  4. no updates for the 04 that I know of......06 used that crappy chain guide down at the crank. In my opinion its the tensioner thats the weak link.....ive seen bunches of the 06s grab that guide and break it off, then all hell breaks loose...the only way I can see the chain grabbing that guide is if the chain is not being controlled properly. As far as the cam spinning in the sprocket, we weld all of them if we happen to have the cams out. That said I dont think they spin unless something happens like say valves hitting the piston...then the extra forces involved on the cam cause them to spin. Be sure to replace valve springs often, especially if you like to rev the bike to the limit Steve
  5. I had this problem with once on the same bike after it blew up......It just kept jumping time over and over again....sometimes after 10 min and sometimes after several rides. We replaced the crank, cam chain and tensioner all in an effort to cure the problem, to no avail. I finally made a manual tensioner and set the tension on the cam chain as I do my drag motors.......6 months without a problem so far. When the motor blew up last time did you replace the chain? the crank is new so you know its running true......be sure you have a new chain and tensioner....they can be damaged in a way you cant see when you drop a valve......other than that you can box it up and send it to me and Ill have a look......but after past experiences Im not 100% ill find anything wrong. .004 off the head should not be an issue as far as clearance is concerned Steve Cycle Dynamics 623-581-2900
  6. .04mm off the head? or .004 thousandths of an inch off? Anytime you change that valve to piston relationship you MUST check the clearance. That said theres a few other things that could have happened. Cam timing could be a tooth off. Or the cam sprocket could have spun on the cam. Ive also seen them jump time on the Kawis for no apparent reason.......be sure you have the updated guide down by the crankshaft. If clearance is an issue, most aftermarket pistons offer deeper valve pockets than stock. Did it make the noise when 1st put together? if not id seriously look at cam timing....also be sure valves and valve springs are NEW along with retainers and keepers. Steve
  7. I stand corrected on the hotcam....It seems the 450 stg 1 is the only model that it advertizes more low end, all other models I can find do not. As for the fuel....its mostly corrosive to rubber. Here in the AZ heat u4 turns nasty pretty quick if left in the carb when not riding. It does gain a small amt of HP but will be lean with stock jetting. Out here we have seen some overheating with it too for guys that didnt take the time to richen up for it. Oxy fuels also raise combustion temps.....something we picked up on when rebuilding our racebikes top ends.....Rings and valves need to be gone through more frequently than say an engine running 110 sunoco. Dont blast me now.....we rebuild alot of thumper engines here, ( 5 or 6 a week ) And we race Motocross, Roadrace, and shifterkart race, and these are still just my opinions and interpretations of what we find when these things come apart. Steve
  8. The hotcam as advertized adds mid and top....thats also what weve found on the dyno. Oxy fuels are very expensive to run every day and are also pretty corrosive. The best bang for your buck will be any of the 13.5:1 pistons..JE, Wiseco or CP all work very well. Total seal gapless piston rings done at the same time add another HP and greatly increase ring and piston life. At this time a good competition valve job compliments the package nicely, be sure to replace the valve springs and valves. Done as a package this adds considerable power throughout the range and keeps the reliability of the stock cam... You can email me for more info cycle-dynamics@cox.net Steve
  9. Pull the large cap on the right side (8mm allen i think) and line up the two triangular arrows......much less confusing Steve
  10. 3% isnt too bad out of a cam change. Dont believe all these crazy numbers you see floating around this forum Steve
  11. I can get stainless valves......I can even have them made to order faster than that... Steve Cycle Dynamics 623-581-2900
  12. KW has been out of stock for months......and cant tell me when they will have more. WMR has excellent quality stuff even if its a little pricey. As long as the stock seats arent deteriorating they are fine to use. Check the guides for wear....they eat em up pretty quick Steve
  13. CV4 you have some good info there but I'm sorry it differs from what Ive been told. Two piece valves can be decent but again it depends on the workmanship and materials as to their quality. Its pretty common knowledge that the factories are using 2 piece valves and on top of that they keep failing in exactly the same spot. Ive got 3 apart at this very minute with the exact same failure. Notice also all the aftermarket companies making sure potential customers know that their product is 1 piece and not 2. I'm sure there are manufacturers out there that make a decent 2 piece valve....just not China. I worked for Total Seal for many years and we did engines for every class of racing including some WC testing......all the product we used were 1 Piece as far as I remember. As for KW, the only people I can reach on the phone are not older than 16 and know nothing about the product or when the next batch of valves will be in. They are out of stock of every common valve except CRF 450 stuff near as I can tell. They never return my calls and my orders are routinely lost (sigh). I like the product and the low friction coating they use but its hard for me to serve my racers that are all in a hurry with suppliers like this. The Ferrea valves are very nice quality and I would get springs and retainers from WMR......they have some really good stuff.....just a lil pricey. Thanks Steve
  14. We have been using kibblewhites but have found a new source. The customer service at Kibblewhite has been terrible and they havent had the popular valves in stock for several months. The KW valves are of good quality and all have run for very long intervals so far without needing so much as a shim change. WMR has them in stock but again are very pricey but of good quality. Ferrea has VERY good prices on Ti and stainless one piece replacements. Running stock valves is not a guarrantee of failure but from our experience i dont like the odds. Again the weight difference is very small and as long as you have the proper spring to control the extra weight its no problem. Titanium is very soft, even under the best of conditions they dont last nearly as long as steel. Ive built everything from full on superbike engines to Busch Grand national engines all using Ti valves and its the same issue......they are soft and tend to sink into the head over time much more quickly than steel. Steve
  15. I wouldnt do it....stock valves are garbage, the chances of a failure are too great. The problem is the stock valves are 2 piece and the extra seat pressure can pull them apart where they are fused. If you must run a ti valve WMR has 1 piece ti valves but they are very pricey. We run stainless in everything including serious race engines with no problems at all as long as you run an appropriate spring and the wieght difference is negligable. Steve