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introduction and MC21 track bike project


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simonmc18

 
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Joined: 01 Nov 2016
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introduction and MC21 track bike project

Wed Sep 13, 2017 10:29 am » Post: #1 » Download Post

Hello everyone,

This is my first post here, thanks for welcoming me in the community, I thought I'll write a few words as an introduction. I am 30 years old, live and work in Bangkok, Thailand. Appart from a Honda NC30 that I refreshed and use for "touring" (understand rip it), and a Grom I use for commuting, I have a MC18 R5k (R2J engine) which is step by step being transformed into a R6k, and a recently acquired MC21 that I want to use as a track bike. This is the latter I want to start a thread on now. The purposes being to give updates on the progress of the build, ask for advices and opinions, share ideas as I myself enjoy reading about other's problems and solutions.

I got the bike from a local friend that knew I wanted to run a 2 stroke on the racetrack, and he had a cheap bike for me. I didn't know much history of the bike, except that it came with an engine that needed rebuild (it had already been rebuilt in the past), MC18 cylinders, no sign of seizure, was a runner though taking forever to start due to what I believe was a leaking center seal and low compression. There is a dry clutch and track bodywork that belong to a local racer before, the flywheel seems to have been machined but no crack, the carbs are MC18-2 and look worn out, it runs PGM2 (easy to derestrict), sports a ZXR400 front end, NC30 front wheel and disks which should give stronger braking and stiffer suspension. The rest is standard. My objective is to build a reliable track bike with a fresh motor and a handling that gives confidence so I can focus on improving my riding at the local circuits.

I have not ridden the bike yet since the bottom end makes a uninspiring rumbling noise, and the tires have cracks all over. First step after confirming the motors starts was check the condition. I made a leak tester and compression tester thanks to MattTyga advices and a machining shop. Step two was stripping the engine to evaluate with my modest experience the level of "damage". I didnt find any alarming issue, but the crankshaft needed a lot of attention. Center seal was gone, O-ring missing, left and center bearings dead. The clutch has seen better days but may well be usable. I decided I wanted to run the MC21 cylinders for better cooling and possibility to use the VHM heads.

Having the engine appart is a good opportunity to throw a lot of money at it (!) and try to get it back as good as new! For this, being located close to Tyga came in very handy since they can source all the necessary parts new. Matt will work on the crankcase & cylinders to make sure everything flows as it should. The cases have just been sent for modifications and we are sorting this out. It will get a completely new bottom and top end, to start from new with a motor i can trust.

During the past few months I have had the bike I also could source a number of components for it. There is for now:
- Rear NF5 wheel (4 holes brake disk)
- MC21 cylinders as mentioned earlier
- HEL brake lines
- HRC ignition coils
- new shorty spark plugs & caps
- Ohlins rear shock is on the way

My plan is to have this set running well, so then I can start adding up the chassis mods.

This is where I am now, I'll keep trying to post updates and my questions as they come (if not answered elsewhere on the forum).
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Andy
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Wed Sep 13, 2017 3:01 pm » Post: #2 » Download Post

Welcome to NSR-WORLD, Simon! Well, welcome to your first post after almost a year! Wink
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Lesviffer750
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Location: Hampshire
1992 Honda MC21SE
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Wed Sep 13, 2017 7:19 pm » Post: #3 » Download Post

Nice little project, keep the piccies coming, dont go too mad on the tuning if you want to keep it nice and reliable, i'm sure Matt will advise you wisely on this.
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ian_gt

 
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Location: West Sussex, UK
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Thu Sep 14, 2017 7:51 pm » Post: #4 » Download Post

Hi Simon, thanks for the introduction. I was living in Bangkok for a while (in fact my MC16 track bike project is still there - in boxes - in storage with a couple of other bikes).

I found Tyga very useful for parts and had quite a few deliveries of bits for the '16 and also the MC21 that I have in the UK. I think it was wise to get Matt to look at the engine - there are very few people I'd let work on my engines, and as the 250cc NSRs were grey imports there aren't many about, and presumably not much expertise.

There are a few Facebook groups for NSRs in Thailand and some of them list spares for sale. I did import a few bits to Bangkok from Japan but it proved quite expensive in the end.

Anyway good luck with the project, look forward to seeing how it comes along!
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