Hi All
Hope someone can help please.

I have been getting a little bored as I am not allowed (following an Op.) to do any heavy work for a while and SWMBO is keeping a close eye LOL, so started messing about with a NSR250 MC21 Engine doing some small jobs as a starter.

I have a pair of Reed Valves (please see photos) that I was led to believe (my own naive belief) were for the MC21, however, looking at them more closely I’m not so sure as follows:

• one Reed Valve has 2 chamfers on the inlet edges and a Tab which the other clearly does not have. From what I can gather both Reed Valves on the
NSR250 MC21 & 28 all share the same part No. 14100-KV3-832 and none of them show a Tab ( including the MC16/18 ), any ideas please?

• they were both came with plastic blocks (please see Photos), are these fitted to meet some form of Restriction Laws?

• On inspection there are some gaps on some of the Reed Petals (at least 1mm). What would you recommend to replace Reed Petals with?

• When replacing the Reed Petals apart from renewing the locking washers on the Reed Screws, would it be recommended to use a locking agent on
screws like Blue Loctite 243?

Apologies one final question, is it prudent to use a Sealant on the Carburettor Insulator when assembling an old Insulator (the Insulator looks good and is not warped), such as, Hylomar/3 Bond?

Many thanks
Philip

OK, easy one (relatively) first... the reed cage with the tab is not an NSR250R cage, of any model variation. There are numerous Honda models that use a similar design and bolt pattern though, including some RS125R and RS250R, and even some CR125s. I'm pretty sure some of the European NSR125s use a similar cage too, as does the Asian market NSR150SP. I don't envisage any detrimental effects using it.

The plastic blocks are critical to performance, and deleting them will delete 90% of your throttle response! HRC also made a kit part. (See the bottom of this page: NSR250 tuning)

If you can get them, get OEM NSR250R reeds. Absolutely nothing wrong with OEM Honda, and we've never been able to measure any difference between them and carbon reeds on the dyno. Carbon may give a crisper throttle response in a minority of cases, but it's negligiable. They may be more easily available in some markets though.

We've never had any issues reusing the screws and spring washers. Honda don't specify using any kind of thread lock, and I expect the heads would likely sheer off (or round off) next time if thread lock was used on assembly. Of course, YMMV, and if you feel more comfortable using it, go for it!

There should be no need for any kind of sealant on either the inlet manifold or the reed cage gaskets. Always use OEM gaskets. I have never, and I mean NEVER seen a gasket set comparable to OEM Honda items.
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Hi Andy

Many thanks again for the sage advice, I couldn't have got it more wrong if I really tried lol!!

I have managed to locate some OEM Honda Reed Petals thanks, they state they are for the MC28 only, but given the MC21 Reed Valve shares the same Part No. to the MC28 I will get these.

Just as an aside though, I did manage to find some TYGA Fibre Glass Petals, but haven't managed to locate any Carbon Fibre Petals. Are these available or do you have to adapt other Reed Valves fitted with Carbon Reeds (just a thought)?

Many thanks

Philip

I stand to be corrected, but off the top of my head, pretty sure the MC28 reeds will fit all models. Actually, I'm pretty sure all the cages are interchangeable.

The HRC nylon inserts (commonly referred to as "stuffers") won't fit the HRC TT-F3 cages without modification, and the MC16/18 has "ears" on the inlet manifold that protrude into the reed cages, precluding the need for stuffers.

We used Aktive in the USA for carbon reeds for the NSR500Vs (made to order), and they used to do NSR250R reeds. If they no longer offer them, I am pretty confident they would make a batch. They were very inexpensive, I seem to recall, even for the made-to-order NSR500 parts, but that was best part of 10 years ago. Their website seems to be down right now, but Allens Performance are a UK dealer for Aktive. Might be worth a shout?

TYGA do their Hi-Flo kit, which includes HRC-style stuffers. Not sure if it's still available... you'll need to drop them a line.
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Andy.
NSR-WORLD.COM

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Hi Andy

Many thanks for the info very much appreciated.

I have left a message with Gavin at Jap4Performance about TYGA's Hi Flo Kit and emailed Allens Performance Ltd, so one way another will get it all sorted.

Take care

Phil