don't know offhand but the other issue is matching pistons to cylinders. Can't recall the details but there are A, B and C cylinders and you need to match the corresponding piston. and just to make it interesting, i don't think the pistons are designated A, B or C.
There was a post on this in the last few years. Hopefully it will turn up if you search.
All NSR barrels are interchangeable, however the port timing differs between each generation (MC21 and MC28 are the same). But more importantly, you must ensure the RC Valve operation is correct. It's not as simple as just swapping barrels as the range of [valve] motion differs model-on-model.
It can all be made to work, but you need to be extremely careful with final setup. _________________ Andy.
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Apologize if i am hijacking this thread, but Andy, could you please elaborate on that? I have an MC28 engine installed but using the RC valves from an R4J and a PGM II. Should i just follow the set up procedure as per manual (make sure the valve matches top of the port when fully open)? Or is major surgery required?
You need to check the RC Valves are opening and closing correctly. I don't know how else to put it.
All the models have different length actuator cables, different sized valve flaps, and a different RC Valve control circuit/parameters. So you need to measure it all to ensure the sweep is correct. If the valves don't start and stop in the correct positions, at best it will affect power output, but at worst it could strain the servo motor and blow the PGM. Some combinations can be made to work, but some don't work at all.
We've see an MC16 with R5K barrels, heads, carbs, and expansion chambers struggle to make 50hp, and seen one done well that made almost 60hp. It's not as simple as just bolting bits on, even though technically they're [almost] all physically interchangeable. Not trying to pour salt on the wound, but we've even seen an MC18 with a mishmash of '88 and '89 bits that wasn't operating the RC Valves correctly and dropping 5-6hp.
It's the same with the HRC RS250R NF5. It's very easy to bugger one up by using the "wrong" year part that looks for all intents and purposes virtually identical to the correct item. _________________ Andy.
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The MC16E design intent was sound from day one, which is why it saw a 10 year production run, and was the basis of 6 years of customer GP motors. Compare that with the next best thing, the TZR/TZ, and you soon realise Honda hit the nail on head with the very first concept [designed in 1986]. However, each model is an evolution, including the R5/6K over the R2/4J, except the MC28, which is largely the same as the MC21 for the sake of this example.
The MC16 has small exhaust ports, and consequently matching small RC Valve flaps. The MC18 ports are significantly larger, so of course the valves are too, which obviously necessitates the use of a different controlling mechanism. The MC21 ports are similarly sized [actually a little smaller], but reshaped with matching RC Valves, so again require a change to the key components to actuate them. Bear in mind each model controls the sweep electronically, as well as mechanically. _________________ Andy.
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