Can anyone link me to some MC18 crank discussions? I have been searching through old threads, but i cant find exactly what i am looking for.

My Mc18 crank center seal is worn out and my rods are tired as well. Are the parts available?

Does anyone rebuild these cranks?


Sorry for the questions if they have been posted before, There are just too many threads to search to get the simple answer.

Dustin
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Dustin Boyd
www.cyclepathracing.com
Midwest Pirelli Race Support

HI,

check this link...

http://www.nsr250.net/forums/viewtopic.php?t=7806&highlight=

Cheers
Michael

The centre seal is no longer available but there is somewhere in OZ that is making a copy for about $90 AUS . I'll try and find the name for you.

Hutch hi,

What is OZ...? Country...?

Cheers
Michael

http://www.****.com/index.php?page=shop.product_details&flypage=shop.flypage&product_id=482&category_id=41&manufacturer_id=0&option=com_virtuemart&Itemid=26&vmcchk=1&Itemid=26

mixalisen wrote:Hutch hi,

What is OZ...? Country...?

Cheers
Michael

oz is australia

Thanks Grant...

I didn't know that...

Michael

mixalisen wrote:Thanks Grant...

I didn't know that...

Michael

No worries.

I apologize for my ingnorance, how can I tell a R2/4 crank apart from an R5 crank?
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Dustin Boyd
www.cyclepathracing.com
Midwest Pirelli Race Support

i have a 21/28 crank in my r5k 18 but you'll need to machine 2mm from the crank weights so that they'll fit the cases as they're smaller.

I have read that the 21/28 crank will fit with the machining, but will it work replace an r2/4?

And, I still need some info on how to tell the difference in R5 and R2/4 cranks.
_________________
Dustin Boyd
www.cyclepathracing.com
Midwest Pirelli Race Support

MC18 cranks came in two varieties to suit the R2/R4 (1988 PGM1) and the R5/R6k (1989 PGM2).

The difference can be seen in the photo but the biggest difference is the centre seal arrangement. The centre seal on the R2/R4 is a separate seal that sits beside the bearing (available from RGV spares here http://www.****.com/index.php?page=shop.product_details&flypage=shop.flypage&product_id=482&category_id=41&manufacturer_id=0&option=com_virtuemart&Itemid=26&vmcchk=1&Itemid=26

The R5/6 centre seal is an intergral part of the bearing and seals up against the web. Honda also put a thin Oring seal which sits in the thin groove you can see around the centre bearing.


NSR250 MC18 R2/R4 1988 Crank

[img


NSR250 MC18 R5/6 1989 Crank

[/img

All the bearings are available from mixalisen who has already posted here but the R2/4 bearings come with a pin now to stop the bearing spinning inside the case so the cases will require a small amount of machining to accommodate the pins (R5/6 already has the pinned bearings). The Japanese rebuild here http://88nsr250rsp.web.fc2.com/crank.html
shows the look if not a complete explanation.

The outer crank seals at both ends (and the middle seal for both the R2 and R5 MC18) are also available from ****** at RGV spares.



Comparison MC18R5/6 and MC21 Crank Webs



This shows why an MC21 Crank is too big for an MC18R5/6. As dunkenb has said you need to machine down the webs by 2mm as otherwise its a direct drop in with the same bearings, seals, and rod dimensions. Given the spacing I would assume that the later R5/6 crank would not fit into the R2/4 cases but have not had a close look at this


Last edited by geezagillard on Wed Feb 10, 2010 7:29 am; edited 3 times in total

****** at rgv spares will also rebuild all nsr cranks. Around $600au

Top info in this thread !!

A+++++++++++ work guys..
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Paranoia about failure will ensure nothing but failure to ever reach potential.



MC18 Race bike project..
MC21 Race bike..

So, this is my synopsis of all these threads i have been reading, correct me if i am wrong.

R2/4 Crank
Crank Bearings - two 83B569DA bearings and one 83B569AA bearing

Crank Seals - The middle seal is an ARS type (as the other two) FAJ8 51 68 5.5 GS A6 basically a 51x68x5.5 seal which neither Honda or ARS will supply.
Crank - 91201-KM4-003 – 25x38x8mm
Crank - 91203-KV3-003 – 36x68x10mm
Output shaft oil seal – Honda Part# 91204-mg3-003 (DIM 25x45x7)

Rod Bearings
Big ends (Pt # B1059) Wiseco
thrust washers (Pt # W5775) Wiseco
( They're not exact replicas but they will work)

Conrods- No replacement as of yet, big end 32mm, small end 19mm , center to center 104 mm and rod thickness is 16mm - All stock NSR rods are marked KV3

What you're left with when rebuilding the crank is new mains, big ends and thrust washers, but still the original rods and crank pins (part of the crank web). So if the pins or the rods are worn or damaged in any way then you're really wasting time and money by rebuilding as it'll never be like a new crank.
So, you need to either get the bearings, find a rod and a crank builder you trust (after confirming your crank pins are OK) or get a whole crank either new or 2nd hand.

Bearings from Micheal in Greece and seals for ****** at **** in Australia
_________________
Dustin Boyd
www.cyclepathracing.com
Midwest Pirelli Race Support