NX250 crankshaft repair

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doyar
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Registriert: Do Apr 02, 2020 11:13 pm

Re: NX250 crankshaft repair

Beitrag von doyar »

Hello. Looking nice. Is it possible to read the lower bearing marks? Could you please write them down for me, if possible? I would rather search somewhere for the Japanese proper one than use this item that came with the conrod. Or am I wrong..?
Cheers, Jarek
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scrambler
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Re: NX250 crankshaft repair

Beitrag von scrambler »

doyar hat geschrieben: Fr Apr 24, 2020 12:29 pm Hello. Looking nice. Is it possible to read the lower bearing marks? Could you please write them down for me, if possible? I would rather search somewhere for the Japanese proper one than use this item that came with the conrod. Or am I wrong..?
Absolutely not. Problem is, the lower bearing was never sold separately by Honda, thus the spare part number is not known. After some research I figured that the bearing retainer (of the early version, that is) was also used in the CLR125 CITYFLY 1998 and XLR125R 1998 (W) ENGLAND / MKH
The KW3 gave it away – the middle letters in the number code indicate the first model where a part was used and KW3 is the code for our NX250.
https://www.cmsnl.com/products/retainer ... qLCwplS_Tc

The Chinese bearing is 30x38x17,8mm with 17 rollers and the retainer is copper plated. As far as I know those retainers are usually silver plated, for better durability. The used original bearing has 20 rollers and the retainer shows signs of wear, it’s from my engine after 105.000km.

Bild

So it definitely would be a good idea to replace the Chinese bearing – it looks like the CRF250 has the same - https://motocrosspartsuk.com/honda-crf- ... 38-x-17-8/ - but original bearings come in three different roller sizes, so that the play can be adjusted to 1/1000mm precision http://forum.nx250.de/download/file.php ... &mode=view

Something else – the big end pin is to check if it’s like the origional. The caps must fit tight and on end there is a little hole, for getting extra oil for the primary drive and the bearing.

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doyar
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Re: NX250 crankshaft repair

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Wow! This is really a precious portion of highly exclusive knowledge unknown anywhere else outside this Forum! :shock: I will follow as close I only can. Thank you very very much, Michael! Great
Jarek.
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scrambler
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Re: NX250 crankshaft repair

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don't mention it ;) I never have done any work on the crankshaft myself so I only summarized what other people figured out. There are probably more points to consider, but a crankshaft expert should be able to figure it out. Some years ago there was a repair attempt by a metal shop which ended in a bended crankshaft. So I would trust this kind of work only to someone who really knows what he is doing.
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doyar
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NX250 strange engine sounds

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Hello friends. Instead of placing the new tread I decided to place my problems with the 'nasty sounds' from the engine here. Do hope it is a better way.
So, my problem are the nasty strong clicks from the upper engine. No matter cold or hot. No matter if engine works under the load (front wheel against the wall) or on idle. The clicks/cracks are irregular, irritating and frustrating. The engine had a conrod replaced for the Chinese one and new piston rings only a 1k km ago, hence my frustration. Valves clearances are OK, there are no metal filings in engine oil, so the next 'suspect' seems the valve chain tensioner/ valve chain, as discussed above in this tread. But those engine sounds of mine are different, they are like separate loud clonks or clicks. Here is the link to YT film (my 1st ever, I just became a youtuber!):
https://youtu.be/OyXJxw3u3KY
I would appreciate if anybody could share their experiences or opinions on this issue. Thanks in advance.
Cheers from Lodz, Poland.
Nikolajsen
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Registriert: So Mai 16, 2021 3:56 pm
Wohnort: Denmark

Re: NX250 strange engine sounds

Beitrag von Nikolajsen »

Hmm, new piston rings, but not piston?
Could it be the piston that is worn, and therefore sometimes is "banging" the lower part of piston against the cylinder wall.
Yamaha XTZ 1200, 2017
Honda NX 250, 1988
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scrambler
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Re: NX 250 strange engine sounds

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Hi,
sorry to hear that. I'm bad in judging engine noises - but it does not sound like a loose cam chain, that's more of a rattling noise that changes when you pull the throttle. It also does not sound like a worn out conrod bearing, but I would not rule out the option that the chinese conrod is part of the problem. That clicking sound could be - if I would have to guess - a problem with the spocket of the cam chain on the crankshaft. Sometimes it is missing a tooth or like in this case all theeth are worn out.

ps. I merged these posts with what was written about the conrod issue. Maybe you have a bit of info and pics how the exchange of the conrods was done?


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doyar
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Re: NX250 crankshaft repair

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Hello NX-brothers :D
Thanx for all your opinions and thoughts. I may be (as usual) far too enthusiastic, but it seems the reason in this case was... the cam drive chain tensioner! Just take a look on my 2nd ever YT 'movie': https://youtu.be/7DSLCOQ0z0A
All the nasty noises are gone. I am going to change the tensioner for the new one and see if this really was the cause. Cheers!
Jarek
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doyar
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Registriert: Do Apr 02, 2020 11:13 pm

Re: NX 250 strange engine sounds

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scrambler hat geschrieben: Mo Okt 11, 2021 7:51 am I merged these posts with what was written about the conrod issue. Maybe you have a bit of info and pics how the exchange of the conrods was done?
Unfortunately not. I ordered it at the local 'small engines repair shop', have it changed, balancedand and returned. So no pictures :cry:
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Garfield
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Registriert: Mi Okt 14, 2020 8:19 pm
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Re: NX250 crankshaft repair

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Hey Jarek, the engine indeed sounds much better now !
Did you notice anything on the old cam chain tensioner ?
I know from experience with a VFR VTEC that even if the cam chain tensioner seems perfectly fine, it can be worn.
MfG, Arvid, Niederlande.
Suffering severely from the N+1 virus. N is currently 7, including a NX250
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