Hello everyone. I am a Brit living in the Philippines. 71 years old, had bikes since I was 16, never stopped, an addiction. Invited here for a job. Saw an NSR250 MC16 for sale. To me, a great price, UK pounds, around, 1,700. Unfortunately, I have only ever had it running correctly for short periods, its a hell of a story. When I bought, it had a flat spot, about 5 to 6,000. I decided probably worn needles. I bought a rebuild kit from cruzinimage. Japan company, but I assumed because of the low quality, must have been made in china. I fitted anyway, tried the bike, it wouldn't even pull away, it would just die, yet ran fine on the stand. I refitted all the old parts, and tried again, same. Coincidence, and some other fault?
At this point, I decided to check leakdown test. Centre seal and flywheel side seals leaking.
Removed and stripped engine, replaced all seals. Both pistons damaged, one with a chunk missing from the skirt. Rebuilt, checked leakdown test again, reinstalled. Just the same!! Wouldn't pull away, yet revved fine on the stand, and would start first kick.
I checked wiring, all connectors, cleaned all plugs and sockets. Went round everything with test meter looking for high resistance. Nothing, could find nothing wrong. I changed spark plugs many times, I fitted new coils. Just the same.
I could only think at this point, faulty CDI. I have spoken to Tyga and others who told ne the Chinese CDI's are fine, so ordered one. My bike was fitted with one genuine Honda, and one Chinese CDI that looked quite new.
So, new CDI arrived, assuming the Honda one failed with age, changed that one. Tried on the road, same. So then changed for the Chinese one. Yes, it worked, for the first time I am able to ride the bike......for a few days. Then same fault again. I still asked people are these Chinese CDI's OK, yes was the answer. ordered another. Arrived 4 days ago. I fitted immediately on receipt, no go, just the same. Doesn't matter which one I swap it for, just the same. I have even tried fitting my original coils back, all to no avail.
I can get it to pull away, misfiring and going onto one. As soon as I stop the bike, its back on two again.
I am quite patient, starting my days on BSA, Triumph and the like, but now at my wits end. Any good suggestions welcome. This story is condensed, its been even worse than this,

Two vids, one just running on the stand: https://www.youtube.com/watch?v=Tp-99BCAljA

On the road, it was hard to do, on my own and without equipment, so poor quality: https://www.youtube.com/watch?v=cX43o1NxG7Q

Thank you

Check all the plumbing around the carburrettors, ie air solenoids etc, i have seen this problem before, ie fine on stand, but wouldnt pull, if i remember correctly, it was johnymac who had this problem and it was related to the air correction system, i think it was either a pipe blanked off, which shouldnt have been, or vica versa, good luck with it.
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Proud Father of , 05 ktm 400exc supermoto 2018 honda crf rx supermoto

Admin: Moved to NSR250 Discussion for greater visibility.

Welcome to NSR-WORLD, "bigoperation"!

If you click the Member's Content link at the top of the page, you will be able to see our [translated] English Service Manual, which has a number of trouble shooters to try and help diagnose potential issues. The main body of the manual (the first 300 pages) cover the entirety of the MC16.

Also, in the Workshop section of the Main Site, is a generic electrical fault finding guide by Electrex USA, which many have found useful in the past.

It's always incredibly difficult to diagnose a problem online, and in almost 30 years of tinkering with NSRs, I've seen dozens of reasons why this can happen. I think you can take some consolation that when you swapped out one of the CDIs it ran cleanly, albeit temporarily. That would give me hope that it's nothing too critical.

I did note from the sound in first video that the bike is fitted with aftermarket chambers. Normally the first thing I say in these kinds of situations is "put everything back to stock", but realise this is almost certainly impossible where you are. Just be aware that there weren't a huge amount of aftermarket pipes for the MC16 back in the day, and if they are "local" chambers, or even adapted MC18 items, it could drastically effect performance. I've seen copies of TYGA chambers from both Indonesia and Malaysia, that were horrendous! The people who are producing the copies clearly don't understand just how critical every dimension is.

Lesviffer750 wrote:
Check all the plumbing around the carburrettors, ie air solenoids etc, i have seen this problem before, ie fine on stand, but wouldnt pull, if i remember correctly, it was johnymac who had this problem and it was related to the air correction system, i think it was either a pipe blanked off, which shouldnt have been, or vica versa, good luck with it.

The MC16 doesn't have the air correction wizardry of the later models, Les, it's rather simple by comparison. However, I would definitely ensure any hoses/breather tubes are clear and in good condition. Also the fuel tank breather.

I would be more inclined to use the OEM carb internals than pattern parts. I don't recall ever seeing an aftermarket carb kit for the MC16, and given that the needles are different in every single iteration of NSR, if the kit was meant for an MC21, or even 1988 MC18, they're likely to perform wildly different to the correct OEM 2QY/2QZ items, if at all. Try and keep everything as close as stock as possible, while trying to troubleshoot.

I look forwards to seeing more of your MC16 in due course. It looks great in "NSR-WORLD" colours! 😄😄
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Andy.
NSR-WORLD.COM

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Last edited by Andy on Fri Oct 08, 2021 6:10 pm; edited 1 time in total

Did you check/clean the filter in the tank?