I've found a HRC cylinder head conversion kit (inlc. waterhose).
The head has 'H' stamped on it.
Does this signify its a SE/SP head or an 'R' head?
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

i remember mine being marked the same as my sp,im going to garage tommorow so will have a look
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ive seen more tarts than mr kipling

Bare with me here.

A "H" head is for use with a R barrel not an SE/SP.

It's worth while though checking volume and squish and adjusting the head and or barrel to get the best setting before setting off with unknown volumes.
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If I have to take the carbs off once more...


Last edited by StephenRC45 on Sun Feb 22, 2009 5:53 pm; edited 1 time in total

Thanks. Bare with me now as well!

My 21R motor actually has SE/SP barrels ('L' mark) and currently 'H' heads , therefore 21R versions. Isn't this the lowest compression / largest squish volume combination?

So I was planning to get 2 rear SE/SP heads, to match the barrels for OE squish volume.

I am thinking on the right track?

Cheers.
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30


Last edited by RichG on Sun Feb 22, 2009 4:05 pm; edited 1 time in total

Yes you would be better getting different heads or swaping the barrels over. Of course heads are cheaper than barrels.
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If I have to take the carbs off once more...


Last edited by StephenRC45 on Sun Feb 22, 2009 5:58 pm; edited 2 times in total

All is now clear, thanks Steve.
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

Ok to fully clear things up

L is SP,
SP head has small squish (high compression)
SP barrel is tall (low compression)

H is R,
R head has large squish (low compression)
R barrel is short (high compression)

The best set up as long as you jet it well and keep an eye on it is a SP (L) head combined with a R (H) barrel.

So you are right. You are running the lowest compression/squish set up you can get.
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If I have to take the carbs off once more...

lol

I've been scouring my books to make sure I didn't put my foot in it, as I was sure there was something astray here!

Here's an official HRC note, back from the olden days when everyone wore grey and walked around very quickly!



As Steve says, you ideally want an H (High compression) barrel and L (Low volume) head combination.

It's very important to measure the barrels though, as not all barrels are created equal! The manufacturing variances and plating companies that machine a little off them all conspire to push the tolerances over the top! I wouldn't (and don't) personally run anything less than 97/98 Super UL for anything other than emergencies with the preferred setup, as it will be right on the boundry!
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Andy.
NSR-WORLD.COM

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Good info Gents.

Just one more question, do you know how much squish the VHM heads give (with the standard NSR issue inserts), relative to the SP 'L' and R 'H' heads?
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

Nope! Never needed them! You do know Steve's makes about 75hp with NSR heads?!

VHM's should be the same as a standard NSR head... that's the whole point! The inserts are machined to your specific requirements. They aren't NSR tuners, and I doubt they know anything about one other than what you tell them, so the "stock" inserts should be just that... stock!
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Andy.
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But they do put the plug SMACK in the middle, Elegy did ask me for a couple of heads to scrap so he could see if they could be centre plugged and I've seen a stock front head on Yahoo Japan centre plugged too.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread

Yes, the centre mount is the benefit for the most part - that and the O-rings.

The thing with the inserts really though, is once they are done and the bike set up, 99% of the time, for 99% of the population, they will never need to be touched again.

I'll put 50p on it that they probably aren't going to be significantly better than the top Honda head.
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Andy.
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The reason for my question about VHM heads was because VHM quote a specific part number for the NSR insert 'AE32069'. So I was wondering if anyone knew if that insert gave a squish as per the 'H' or 'L' Honda head?
http://www.vhm.nl/VHM/Cylinderheads/honda.htm
More curious than anything, as I'll probably stick with the Honda heads.
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

I would imagine it would be an SP insert, purely as I bet 50p that would be seen as the "performance" model by anyone why didn't know better.

I bet if you asked them they probably wouldn't know the difference between an R and an SP head, and if you asked "is the insert for an R, SE, or SP?" they would think there should maybe be 3 types.

This isn't a slating of VHM, far from it, but I really don't expect them to know the ins and outs of a 15 year old niche market stroker, or expect them to. If you told them they were for a 1989 NSR250R for example, I bet they wouldn't question you about whether it's an MC18 with different shaped barrels and advise you that they won't fit!

I think if you buy VHM heads you should either consider having the inserts machined yourself, or be prepared to do some careful measuring and set the deck heights up according to what they supply "as standard".

I'm not having a pop at you either Rich, it's just that the standard Honda stuff is bloody good, and people look for gains in expensive or later model parts where there really aren't any to be made over optimising the stock stuff*. The only bike that can really benefit from different parts is the MC16. Even the fitting of an MC21 flywheel to an MC28 is really an execise in spending time and money sourcing it rather than its rewards in performance, and fitting anything from an MC28 on another model is a real backwards move, despite it being the last "evolution" of the model!

*Of course, the MC28 is a proper anomally! That will benefit from parts from just about any earlier model! I'd love to see one with MC16 ignition and derestricted pipes! I bet it would put out 60hp then!
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Andy.
NSR-WORLD.COM

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I tend to agree Andy, in the day Honda will have spent many engineering hours perfecting the design of NSR parts + then employing top manufacturing quality.

I'm going to whip the barrels off my 21R trackbike, if the 'L' barrels are OK, I'll probably go with SP 'L' heads to reduce the squish. Forking out for another 2 sets of barrels (R 'H'), just after my 21SP rebuild is some step

I should have snapped up Dan's 2nd hand SP heads for sale at £30

If nothing else, at least I've got my head around the barrel / head combinations now. Thanks to you & Steve for the info.
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30