g'day , i recently purchased a mc18 for the missus , currently she is in a sad state (the bike), i am looking to do a full tyga upgrade and am wondering if i put on the top end kit 300cc will i have to get the bottom end done ???? Also if there are other things to consider when doing a tyga job ???? i've been riding bikes now for 7 years but this is my first 2 stroke so the mechanic will be doin the engine work.....

Welcome Kimmy.

Any idea on the history of the bike? You might be best pullin it apart to check the bottom end before you splash out on power upgrades!
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Hello there!

The main thing to consider is; is someone who knows what they're doing doing the work?
If this "mechanic" doesn't know NSR250's inside out you'd be no worse off and learn a lot more doing it yourself, nothing on a 2 stroke is even slightly complex but NSR's have quirks and there's more knowledge here than probably anywhere outside of Japan.

Hunt back though the forum and there's been tonnes of problems with the 300's seizing, all traceable to poor setup and assembly errors, don't join them.

Also more than one person here has fell foul of taking their bike to an engine place/garage and they've made expensive mistakes (crank in wrong, wrong crank bearings used) or just plain annoying mistakes (sump plug not done up properly, bolts sheared off and not mentioned).

The '18 is getting on a bit now and that's it's weakness, Honda life the cranks at around 30,000kms and there is no such thing as a new mc18 crank.

It's not the best check but get the fairing lowers off and get the flywheel cover off (left hand side of the engine as you sit on the bike) it's the big bit of plastic held on by about six 8mm bolts, your flywheel will be bigger but you'll see this, now the round thing that spins when you push the kickstart, try to wiggle it, if you can feel any movement at all the 300 kit is the least of your concerns and unless you know of someone local who rebuilds MC18 cranks you'll be wanting to talk to Andy.

Well you did ask!!
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Please do not PM me technical questions, if you can't find it on the Forum start a thread

thanks for the advice so far , i'm not sure the exact history bout the bike but its done just ova 32 thou k's , i dont even know wot year it is, will it tell me on the frame no. ?? The mechanic i speak of dosnt exist at the mo as i was goig to do sum research as to who knows there way around a strocker , but if all else fails i was thinking goin to a honda dealership , surely they know about the bike their company built ..

The year is hardly relevent, they're all old and if that crank is 32000k old you would be less that wise to bolt a 300 kit to it.
The MC18 was discontinued in 1989, you can tell from it's shape to within a year R2j is 1988, R5k is 1989.

All NSR250's were Japan only, hence not elegible (until recent changes to the rules) to even be raced in the UK so there is zero tuning expertise and very little specialist mechanical knowledge outside of this forum
My local dealer whilst helpfull, friendly and willing to order any part number I'll give him has seen one MC28 ever (mine) and never had another NSR in the workshop. As another example I've been to reputable a 2 stroke specialist dyno and he's not known which way to cable the powervalves up on one.
Hardly the guy you want wielding spanners near your bike.
The problem is in the UK (if not Oz) the RGV250 was very popular, both it and the Aprilia RS250 were imported here officially and the tendancy is for "2 stroke specialists" here to actually be 90* RGV engine specialists. It may be different where you are but be sure.

Does the bike run?

And please, don't take this the wrong way but we try to avoid txt speak on the forum (wot, sum, ova) and slang as there are a lot of people here whose first language is not English and it renders the forum impossible to read for them, even the biggest correctly spelt English word can be looked up.
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first up, now i know about the text language i'll try to do my best , i am ozzy but migrated from england in 1988. Secondly yes the bike does run and has just come from a mechanic to get a roadworthy done (legal to ride on ozzy roads). the bike has got to see about 6 months before being turned into a tyga machine (two strock has always appealed to me ,I luurrvvee the sound of 2-strock moto g.p machines) on closer inspection the bike is an r2j. Yeah the rgv and the aprilia are more common on oz roads...
Fontyyy thanks for the insight !!!!!
happy new year to all !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

^^^^^^^^ to many new year drinkies for ME !!!!!!