What are the differences, if any, between an SP motor (MC21) and an SE or R.

If there are differences are there any disgusting marks/numbers on the outside of the motor to check?

Mike
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The SE and SP are the same.

The R has different heads and barrels, and of course a different transmission.

So long as you use R heads and barrels together on an SE/SP bottom-end, there is no performance difference. Do not mix SE/SP and R heads and barrels though. It is OK [although less than ideal] however, to run SE/SP on one side, and R on the other. Just don't mix the heads up.
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Andy.
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Thanks Andy.
The reason for my query is that some time ago I purchased an 'SP??' motor. Noodle is an R and I wondered if I should put the SE/SP engine in.

Are there many external differences between the R and the SE/SE motors?

Mike
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..anybody?
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External differences are cylinder and head markings, plus the obvious dry clutch. You won't differentiate between an SE and SP motor though.

Hi, thanks for that but 'what' are the different markings so that I can check both engines.

Mike
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Since I am not a walking NSR encyclopaedia like Andy, click on the links in the left, one of them will talk about model differences.


Last edited by nxrsr20 on Thu Nov 01, 2012 8:44 pm; edited 1 time in total

Wet clutch models have "H" cast into the heads and barrels. Dry clutch models have an "L".
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Andy.
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Ahhh Thanks. Wasn't too difficult now was it!

Mike
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http://www.nsr250.net/forums/viewtopic.php?t=3077
http://www.nsr250.net/forums/viewtopic.php?t=9090
http://www.nsr250.net/forums/viewtopic.php?t=2544

No, not hard at all!
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Andy.
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Oh dear.

Consider me Fully chastised!

I'll get me coat, and float level adjustment tool, and be on my way!!!
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Basically if you can live with the lack of rattle (from the clutch) and the engines are in good condition you won't be able to tell a difference at all.

Anyway I think I'd strip the other motor and swap the gearbox/clutch (not a big job) and keep the spare barrels head and crank for a rainy day before I swapped a whole motor I'd never started for another I knew worked fine.

The R barrels are shorter, the R heads have a similarly larger volume, effectively when the motor is built the head gasket on the R motor it located 0.2mm lower.
In theory the dry clutch should give more power, but it's not a measurable amount.
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Thanks Fonty but here is the dilemma...I had already put a dry clutch in 'Noodle' during my rebuild. The motor that I purchased some months ago has a dry clutch and has 'L' on the barrel castings. SE/SP as purchased (hopefuly).
Noodle ALSO has 'L' stamped barrels but had a wet clutch. Eekk!!

I'm not really worried either way but it's a bit weird. One thing that I am worried about though...whoops, that's for another post I think as I'm about to go off topic slightly and I'm already in Andy's bad books already. (Place relelvant emoticon here!!)

Mike
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Hobbit210 wrote:
Noodle ALSO has 'L' stamped barrels but had a wet clutch. Eekk!!

Why? All it means is that at sometime the motor has been apart and the barrels changed.
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..thought that must be the case!
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