daveh
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Post by daveh on Feb 1, 2022 12:08:25 GMT
Hello,
Just got myself a barn find 250NA from 1980. Been sitting (inside) for past 18 years, so a bit a project to undertake!
Mostly all together and engine looks sound from outside, but bike needs stripping down and first job is sorting out carbs so I can see how engine might run.
Also front brake piston seized in calliper housing. Won't budge so probably looking at replacement calliper section if I can find one or otherwise it's a whole new brake assembly.
First question if anyone can enlighten me please.... On the carbs (which are full of crud) which need a good clean and replacement jets, seals, etc, the idle jet needs sorting as rubber plug has perished. Can you clean this idle jet in situ or is it best taken out? I understand it is a press fit, so not so easy to remove if not neccessary.
Thanks.
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Post by Graeme on Feb 1, 2022 12:23:50 GMT
Hiya Dave, welcome to the forum.
From experience with the carbs, take everything you can off internally and ultrasonic if you can, let's the water flow.
Clean with gunk, elbow grease (Asda) agitating with a brush, that will break most of it down first before an ultrasonic.
You may be surprised how well the jets etc come up after a clean.
If you send them to me, I will ultrasonic for £25. You pay postage to and fro, only about £5 each way.
I don't dismantle the carbs, you do that.
Good luck with the rebuilding.
Lots of parts still out there.
Gee.
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stevegbr
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Post by stevegbr on Feb 1, 2022 12:29:42 GMT
Hello, Just got myself a barn find 250NA from 1980. Been sitting (inside) for past 18 years, so a bit a project to undertake! Mostly all together and engine looks sound from outside, but bike needs stripping down and first job is sorting out carbs so I can see how engine might run. Also front brake piston seized in calliper housing. Won't budge so probably looking at replacement calliper section if I can find one or otherwise it's a whole new brake assembly. First question if anyone can enlighten me please.... On the carbs (which are full of crud) which need a good clean and replacement jets, seals, etc, the idle jet needs sorting as rubber plug has perished. Can you clean this idle jet in situ or is it best taken out? I understand it is a press fit, so not so easy to remove if not neccessary. Thanks. one of our members wazzbo as done a easy follow guide on how to dismantle and clean, highly recommended if not sure how to. get your post to 20 and you can download the pdf. honda-superdream.co.uk/thread/6352/beginners-guide-stripping-cleaning-carbs |
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daveh
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Posts: 346
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Post by daveh on Feb 1, 2022 14:38:46 GMT
Thank you both!
Graeme, I might take you up on that. I'll see how the strip down goes.
Does that mean you would want the casings bare and also jets separate and you would clean all? I was planning to renew the jets, but maybe not necessary if they can be as good as new after ultrasonic clean?
Steve, I'll take a look at the guide.
Thanks again,
Dave.
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Post by Graeme on Feb 1, 2022 15:45:39 GMT
Thank you both! Graeme, I might take you up on that. I'll see how the strip down goes. Does that mean you would want the casings bare and also jets separate and you would clean all? I was planning to renew the jets, but maybe not necessary if they can be as good as new after ultrasonic clean? Steve, I'll take a look at the guide. Thanks again, Dave. Take the bowls and tops off, no need to separate the carbs, my ultrasonic can take a bank of 4. I can undo the internals in each carb. I can gunk it as well. Cheers. Gee. |
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daveh
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Post by daveh on Feb 1, 2022 16:37:01 GMT
Not sure I got my question answered about the idle jet (under the rubber boot).  Is it normal / necessary to take this out to clean as it is a push fit and not screwed in? Haynes manual says to remove it when servicing carbs, but I suspect they made a mistake as they don't mention it being a push fit. Unless I'm reading it wrong which is possible.  |
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Post by Graeme on Feb 1, 2022 16:46:13 GMT
Not sure I got my question answered about the idle jet (under the rubber boot). Is it normal / necessary to take this out to clean as it is a push fit and not screwed in? Haynes manual says to remove it when servicing carbs, but I suspect they made a mistake as they don't mention it being a push fit. Unless I'm reading it wrong which is possible. Sure it unscrews. I might have new rubber bungs, Chinese specials, but fit. |
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Post by Graeme on Feb 1, 2022 16:50:54 GMT
The rubber bung pulls out, the jet underneath screws out, it can be left in, but easy to take out.
Gee.
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Post by Graeme on Feb 1, 2022 17:50:58 GMT
The rubber bung pulls out, the jet underneath screws out, it can be left in, but easy to take out. Gee. This will give you an idea of a full carb rebuild kit, they are scarce and expensive in no particular order. For some reason, Chinese CB400N rebuild kits are seriously cheap, but the CB250N, very expensive...strange one. Gee.  |
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daveh
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Post by daveh on Feb 1, 2022 19:53:07 GMT
Gee,
Yes I have seen these and as you say quite pricey!
So does having the carbs and jets ultrsonically clean mean I should not need to buy new jets? I could then just get the seal kits.
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ian
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Isle of Man
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Post by ian on Feb 1, 2022 21:49:16 GMT
Hi Dave, welcome to the forum & good luck with the project. If the jets are the correct size they'll probably be ok once cleaned.
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Post by reversespin on Feb 1, 2022 23:09:42 GMT
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Post by tucksie on Feb 2, 2022 4:57:50 GMT
Hello.
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willy3pigs
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Post by willy3pigs on Feb 2, 2022 9:11:54 GMT
Hello and welcome to the forum. Having needed to overhaul my CM250 carbs last year, I can thoroughly recommend Gee's sonic cleaning service, you'll get a first rate job done there.. From my own experience admittingly only having worked on two sets of these carbs, providing nobody's been in there before and lost parts, or worse butchered the internals you should be fine using the jets you already have, and can just get away with just some new float bowl seals and rubber bungs, my recommendations linked below. The bowl gaskets supplied in some of the replacement kits swell when they contact unleaded which is a major pain if you're removing the float bowls in situ, as you'll struggle to refit them. The ones in the link are made of vitreon which won't do this. Also I recommend you change the float bowl screws to an Allen Screw type, they make it easier to remove the bowls in situ if you want to alter the jets without removing the carbs from the bike. Good luck with your project. Disregard the parts description these fit your carbs, and you'll have a pair of spares.. www.ebay.co.uk/itm/224340069671?hash=item343bb5cd27:g:fEYAAOSwsNlgHLRz&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5337683463&toolid=10001&customid=kz4qlj0djq02ylrr00003www.ebay.co.uk/itm/222477904913?hash=item33ccb76c11:g:KMUAAOSwwMJfzvnS |
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Post by grahamb on Feb 2, 2022 9:21:24 GMT
I got some of these last year ,
Gone up a bit in price but quality was fine.
item No 223689463153
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