suzuki gn250 big bore kit any thoughts?

[jake47]

Hi first post here so be nice.
I have a suzuki gn250cc c 1992 , and have ordered a big bore kit from e bay from a chinese seller here https://cgi.ebay.co.uk/GN300-GN250-BIG-BORE-cylinder-Improve-performance_W0QQitemZ270514614149QQcmdZViewItemQQptZUK_Motorcycle_Parts?hash=item3efbed6f85 as you can see it states it ups the power to 300 cc.As ime not too used to working on bikes , well for some years anyway i wonder if anyone else has used the above and what are your thoughts.
is it going to be fairly straightforward to do the job or is it going to be a bike mechanic ? as cost is important i would like to have an attempt at doing the job myself but am a bit wary, could this kit do permanent damage and if so i suppose i could replace it with the original bore and piston etc.What do you think?

[27cows]

The GNs are very simple and easy to work on. Shouldn't be any problem putting the 300 kit on yourself. How the engine will then run is anyone's guess, though.

[smegballs]

If you read the item location its says its in Wuxi, China. The same place that made the dodgy bikes in the other thread.....

Also they give the stated power but where is the source or is it all made up?

I'd avoid to be honest but you have already ordered it

Its simple in theory but head will need to come off and so the cam will need re timing which if you haven't done before can be tricky.

Also your fueling will now be out so prepare to have fun dialing in the jetting, thats assuming the chinese piston lasts that long .

Good luck! Be sure to report back how it goes as it would be interesting to see how it goes.

[Minitwin65]

I too bought the 300cc kit and some race engine builder mates said it looks fine. It`s fitted and works ok but there is no power increase yet because it has not been re-jetted. They have a gearbox sprocket Dyno and will set it up for me soon. I`ll let you know how it goes.
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I`m very religious, every Sunday I get on my knees and thank God !

[Livefast123]

Judging by how much power the new Chinese 250's offer I wouldn't hold out much hope of a power increase as even though the barrel may be of OK chinese metal the quality of the porting etc is what makes the power along with the cc.

Job should be fairly easy apart from the cam/valves and timing etc.

Just bought a chinese piston to rebuild the NSR and TBH the quality is shi*t but it suited my financial circumstances and it works....so what if it lasts 1000 miles less than the Honda part.

Fair play to you though for giving it a shot and it'll be interesting to see how it comes out.
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Current ride - Yamaha MT-07

[Kickstart]

Hi

It is a 4 stroke so the barrel should be pretty simple. No porting to care about. Could be interesting to see what the compression lands up as.

As to a cheap piston in a 2 stroke, it isn't it lasting 1000 miles less than a stock one I would worry about, it is it lasting 1000 total at best. About the life expectancy of cheap pistons in my MBX125 many years ago (ie, they just about survived running in).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[hellbound]

Ok, this is handy, when it all goes wrong and your engine explodes I have a GN250 kicking around that I need shot of!
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May you always see the road rising up to meet you and your enemies defeated in the mirror behind.

[RatbikerNate]

I've had one of these GN300 barrel kits fitted to my bike for well over a year now, it's done about 15,000 miles now, many of which were hard miles across the most mountainous roads in europe and switzerland.

(My GN300 chopper and my mates sidecar in the Italian Dolomites 2011)
https://i245.photobucket.com/albums/gg50/RatBikerNotts/mongwayround2011/P1020697.jpg

About a month ago I had to work on the engine (bottom end had finally worn out after 60 odd thoudand miles) and to my supprise the barrel and piston were still in fantastic condition.

Based on actual experience I can recommend these kits.

Further information:

When running in the piston I used this method:

https://www.mototuneusa.com/break_in_secrets.htm

And I run it with standard airbox, straight through exhaust and a 135 main jet.

With uprated gears (17t front and 41 rear....if i remember rightly) it gives a cruising speed of 70, overtaking speed of 85, and better acceleration. Oh and delivers an average of about 85-90 mpg

[RatbikerNate]

[humanbeing]

That fleabay seller just resale this product, https://item.taobao.com/item.htm?id=89086236
IF u had pals in China / found reasonable agent u will save big money
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[croftys gamma]