Question about 1991 Honda NSR 250 MC 21

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Hi there, I have a Honda nsr MC21. I have been told that my crankshaft bearings/seal has gone. The bike wont start, if I spray/leak a little fuel directly into the carbs, it starts like a dream. I was told that if you put about a cup of clean fuel into the left inlet into the crank and it seeps out the bottom cylinder exhaust port, the main center seal on the crank is gone and therefore the crank needs rebuilding? this is obviously an expensive procedure and dont want to do it unless i really have to. What are the signs of failed crankshaft center bearing seal? bike doesnt smoke more than usual, just really struggles to start and on occasion feels as thou its running out of fuel... otherwise it runs really well, around 60 bhp. thanks!

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Firstly two strokes obviously do smoke because they use a petrol/oil mix to lube the motor,have you noticed any gearbox oil disappearing because a worn crank seal would cause the engine to suck oil from the gearbox ?

Posted on Feb 03, 2015

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Difficult starting is a classic example of a faulty centre seal.The seals tend to harden up and leak after time and particularly with certain fuels.

Posted on Oct 24, 2013

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SOURCE: 1995 honda cbr f3 wont start

I would think about investing in a carb re-build kit.

Posted on Dec 22, 2008

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SOURCE: nsr 250 mc21 bike battles to kickstart

i bought a peugeot 306 gti6 the radio dont work it got 8 dots will i have to have it decoded

Posted on Jan 04, 2009

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SOURCE: NSR250 MC21 92 Not hitting power band, fine until around 7000rpm

Power valves on different 2 strokes operate differently. A yamaha version does a self diagnostic because its a cylindrical type, so cleans off excess carbon. The type that the honda uses is a butterfly type and so a diagnostics / cleaning action is not performed on start up, but does require cleaning @ the recommended service intervals. See NSR-world.com for further info.

Posted on Jul 01, 2009

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SOURCE: Hi,I just bought a 84 honda goldwing interstate.

The bike may be discharging the battery. you need to test stator output,voltage regulator,and the fuses. Does the battery need to be recharged to restart?

Posted on Mar 22, 2010

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SOURCE: fork seals gone on honda nsr 125

280 ml on the older models, and 320ml on the newer models.
1. you need to elevate the bike with a jack or something so the front wheel is off the ground.
2. undo the Allen bolt on the side of the fork, then proceed to take the main wheel socket bolt/bar out, so the the wheel comes off, the speedo drive will come off leave that hanging around lol.
3. take of the socket bolts attaching the brake caliper to the fork, dont leave it hanging secure it somewhere, so you dont damage the brake cable tube.
4.take handle bars off, one allen bolt on each one.
5. then unscrew the the 2 socket bolts that hold the folks on, if you follow the folks down you will see 2 socket bolts take them out. do the same on other folk.
6.then pull one folk at a time down, maybe tap it if its hard. and you will have the folk out in your hands.
7.unscrew the big socket bolt at the top of the folk out, but apply pressure, sometimes the bolt will fly off, so be careful.
8. take the big long plastic tube out along with the spring, and tip the folk upside down and pump it to get most of the oil out.
9.then go to the bottom of the folk and undo the allen bolt, when its moving around freely and not coming out put the spring in and push down and twist the allen bolt should come straight out.
10.pump it a few times and then you take the folk tube out completely and give everything a clean, it will be stiff when you get it near the top so get momentum and yank hard and it will pop out.
11. then the bottom pit of the folk that the tube goes into, if you look into it you will see the oil seal, take the cur-clip out and it should come out pretty easily.
12 give the folk tubes a rub down with fine sandpaper say 1000 grain or 800 grain, to get rid of little bumps, look carefully feel it with your hand, to see if theres any pitting, you will be able to see it, thats not good but make sure its not on the part of the tube which goes up and down the oil seal when compressed down.
13.put folk tube back in the bottom of the folk, then put spring in puch down tighten allen bolt.
14.put new oil seal on and push it down its best to use a oil seal hammer tool thingy, but if your careful you can tap it down with a hammer and something small and flat at the bottom, i used a bolt, worked well.
careful dont damage the oil seal.
15. put cur -clip back in, it should click, make sure its on the closest ridge to the oil seal.
16. put 280 ml, of oil or if you have a newer model 320ml, of fork oil in the tube, pump it a few times to get air out and oil to the bottom chamber.
17. put the spring back in and the long plastic tube, and put the top bolt on for now not to lose not to tight.
18. attach the folk to the bike again and same with the other one, make sure you align the little ridge on the top of the folk, with the top of the steering bar, the top steering the bar the folk go into last. its late lol getting confused lol. oh and when y0ou align make sure you tighten the bolts holding the folk in place.
19.then put the steering grips/bars back on and then tighten the top bolt tight cant remember the torque setting. then you know everythign from there. phew

Posted on Jul 20, 2010

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1 Answer

I put my Honda nsr 125 on a warm up after a warm up revved up then it cut &won't start back up , iknow the power valve servo has gone paid for one , has had new spark plug and air filter does spark


Hi Anonymous, and the usual suspects are:
1. Enrichner system plugged, not properly functioning or improperly operated.
2. Fuel overflow.
3. Restricted fuel supply.
4. Gas cap and or fuel tank not venting properly.
5. Plugged slow jet or passages.
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For more information about your issue please visit the websites below. Good luck and have a nice day.
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1988 1994 Honda NSR125 Service Manual Moto Data Project
http://www.vol-training.com/guides/honda-nsr-125-parts-manual.pdf
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Sounds to me like you should be checking the ignition coil and low tension coil for resistance
When it runs does it tick over, or does it stop when you let go of the throttle,
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2 Answers

NSR250 MC21 92 Not hitting power band, fine until around 7000rpm


not familiar with your bike but some bikes have electric controlled power band an some have mechanical.Electric ones usually do a quick self diagnostic on start up hope that helps

May 22, 2009 | 1992 Honda NSR 250 MC 21

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Whats under the engine case, what goes in each container?


2 stroke oil feels alot different than brake fluid and is usually blue or green ,where brake fluid is supposed to be clear but might be root beer brown in a 1991 bike. Stick your finger in and you'll find the one for oil....Good luck to you friend....Tim

Apr 25, 2009 | 2001 Honda NSR 125 R

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Nsr 250 mc21 low on power


you don't give much information on how the bike is running.  But most times when there is a performance decease it is best to clean the fuel system.  Spray some Gum Out or similar product( I prefer Deep Creep and Sea Foam) in the carb. then follow up with some in the tank.  Also change the fuel filter.
  

Jan 04, 2009 | 1993 Honda NSR 250 MC 21

1 Answer

Nsr 250 mc21 bike battles to kickstart


i bought a peugeot 306 gti6 the radio dont work it got 8 dots will i have to have it decoded

Jan 04, 2009 | 1993 Honda NSR 250 MC 21

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