Mugen ninja jx21

Old 12-07-2010, 09:04 PM
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Default Mugen ninja jx21

Just picked up a used jx with 4gals on it. Bought it because it was cheap and if it didn t work out I could make double of what I bought it for if sold for parts or a back up motor. Any how the motor seems to be in really good shape but don't plan on running it till I get advice. So here we go. Motor can hold it self for a while before cranking over. Also the owner said it's never been pinched. I can only take his word because it was a eBay sell. At 4 gals, what should or needs to be replaced? I know most will say they have to see it or depends on how it was ran but what would the advanced racer do after 4 gals besides sell it? Lol also what's the life of the motor(10gals)? And if I bought os vzb or speed vspec parts will they all work for it? Like a speed or vzb crank or p/s/r? Any help will be great. Thanks
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Old 12-07-2010, 09:24 PM
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If you feel the compression is fine the only other things that may need replacing are the rod and bearings. Taking off the backplate if you know what your looking for you should be able to tell if there is much rod slop. Hard to tell the condition on the rear bearing without taking it apart, if the front bearing seal looks to be in good shape just run it and keep and eye out for a buildup of dirt and oil by the clutch. These motors last a long time if you keep an eye on the rod, crank is coated and last a long time. Yes a Speed rod will fit.
The Os based engines will lose some compression if you get it hot so be careful. I have pinched some of these and the Speed 3-4 times and still ran great.

Rex
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Old 12-07-2010, 09:54 PM
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Ok let me see if I got this. When looking for slop where the rod connects to the p/s, if it's minor slop then replace it or run it till there is more slop? Reason asked, my lhs told me my GO has minor slop and to replace it after another gal but it's still running strong? Also if the rod blows before replacing, will this kill the motor? What's a temp that the ninja shouldn't pass to lose the compression ur telling me about? And last question, you said the crank is coated and will last a while. Lhs said it wears fast and after 4 gals it might be worn. Should I replace it along with a rod? I asked about the other os parts because eventhough they all fit, they at different prices. Rods are mostly 40 bucks but the cranks range from 50+ for a vzb and 150 for a speed or jx crank. Will the motor be weaker if I went the cheaper route with vzp parts?
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Old 12-08-2010, 02:25 AM
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i would only replace with ninja parts. the speed rod will be ok but its basicaly the same as the ninja. the vzb crank is junk! metal is soft and oil hole is in crank no good and wears out fast. speed crank is nice but not needed. iv got 3 ninjas 2 mod and 1 stock. every one has more thank 6 gallons on them and crank pins show no sign of wear.stick with the ninja sleeve. the vzb and speed are 3 ports wile the ninja is a 5 port. iv had the vzb and speed 2 and i like the ninjas more. as with any os based mill change front bearings when you get them. better to go ahead and do it than chase a air leak or spin a bearing in the case. ceramics are awful nice and can be found at a decent price. some prefer tko, or boca, i use avid hes a hell of a lot cheaper.
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Old 12-08-2010, 03:02 AM
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Originally Posted by swirlvike666 View Post
i would only replace with ninja parts. the speed rod will be ok but its basicaly the same as the ninja. the vzb crank is junk! metal is soft and oil hole is in crank no good and wears out fast. speed crank is nice but not needed. iv got 3 ninjas 2 mod and 1 stock. every one has more thank 6 gallons on them and crank pins show no sign of wear.stick with the ninja sleeve. the vzb and speed are 3 ports wile the ninja is a 5 port. iv had the vzb and speed 2 and i like the ninjas more. as with any os based mill change front bearings when you get them. better to go ahead and do it than chase a air leak or spin a bearing in the case. ceramics are awful nice and can be found at a decent price. some prefer tko, or boca, i use avid hes a hell of a lot cheaper.
Definately keep JX parts in it. The crank is dlc coated and should last more gallons than you would believe. I have speed cranks that have over 16 gallons and are still going strong. Unless it's been abused the rods last many gallons also, just check the play with the backplate off visually by rocking it back and forth at tdc. .002"-.003" is normal. Don't put vz-b anything in it. Done right it can be pinched a couple of times. They are great engines and perform very well. I'm sponsored by answer-rc and run their ceramics in all my engines except my werks since they don't make that size. I've had excellent service from those bearings and if you pm me i will give you a 20% off code for the answers. They have a nice front ceramic also. A JX with an EB Mods head button and a losi RE10 pipe is a stellar performer.
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Old 12-08-2010, 06:39 PM
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16 gals! Dang I hope to get that. All this info is great. I'm a rookie racing begn'er but I'm gonna move up to novice now and I hope this engine helps. I will order the avid bearings asap seeing that i need some for my rollers also. I'll order the re10 later after the holidays. I have the jp1,2,and 3. Which of those would be best for the time being? And where can I find that eb mods button or should I wait on that since I'm just a club racer for now? Again thanks for the help.
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Old 12-09-2010, 07:37 AM
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as for your pipes you curently have id start with the jp3. if your patiant you can look on here and come across a os 2060 and that there is the juice right there. great bottom smooth transition to mid with a screaming top, not to mention 10 min runtimes. i wouldnt really worry about the mod button, you will gain more with the better pipe
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Old 12-10-2010, 09:04 AM
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Thank u every for advice and tips. Motor was in great shape with clean bearings and no slop at all. I have never ran one tank of fuel through a fine motor. It had crazy torq at 190 degrees on a 50 degree night. But now the motor is r.i.p. After running it, I came in for a change of tires and battery, went back out, hit a tripple and it took off on me. No one could catch it. The rod went and taking everthing inside along with it. Sucks. Can't believe I didn't screw the battery box down. Well if anyone has a good pSR combo please note me thanks.
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Old 12-10-2010, 12:29 PM
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Originally Posted by Titian2010 View Post
Thank u every for advice and tips. Motor was in great shape with clean bearings and no slop at all. I have never ran one tank of fuel through a fine motor. It had crazy torq at 190 degrees on a 50 degree night. But now the motor is r.i.p. After running it, I came in for a change of tires and battery, went back out, hit a tripple and it took off on me. No one could catch it. The rod went and taking everthing inside along with it. Sucks. Can't believe I didn't screw the battery box down. Well if anyone has a good pSR combo please note me thanks.
Thats Sucks.
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Old 12-10-2010, 03:27 PM
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Originally Posted by Titian2010 View Post
Thank u every for advice and tips. Motor was in great shape with clean bearings and no slop at all. I have never ran one tank of fuel through a fine motor. It had crazy torq at 190 degrees on a 50 degree night. But now the motor is r.i.p. After running it, I came in for a change of tires and battery, went back out, hit a tripple and it took off on me. No one could catch it. The rod went and taking everthing inside along with it. Sucks. Can't believe I didn't screw the battery box down. Well if anyone has a good pSR combo please note me thanks.
dont feel bad it happens to the best of us just buy a new P/S/R make sure their no damage on the case. fix.
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