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nigel cooper
Joined: 08 Aug 2012
Posts: 12
Location: Canada, Alabama,
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 Posted: Fri Oct 05, 2012 5:01 pm Post subject: Yamaha YZ250 anyone? |
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Hi Guys,
I`m new to the site and new to 250 on a kart.It looks like everyone is using a honda 250 rather than the yamaha yz250 that I have.This kart will not be racing-merely a winter fun project.It was previously being used and abused so I am doing a total complete rebuild,on everything.Only this engine is new for me.Is this engine ok for fun use? (I run rotax on my other kart)
A newbie question if you dont mind-
Why dont guys flip the piston,flip the cylinder head around 180 deg to place the intake at the front of the kart and the exhaust out the back with a custom exhaust?? it would not only look much better but take up less space ect ect like the genuine 125 shifter kart engines |
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Alan Lidke
Joined: 06 Jun 2005
Posts: 40
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| Posted: Sat Oct 06, 2012 6:01 am Post subject: |
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| Nigel, I have a vintage Barlotti shifter with an RD400 that has the cylinders turned around and worked fine. But double check the stud placements. I know some cylinder studs are not a totally square pattern to permit cylinder reversal without relocation of the stud holes in the crankcase. I think the front 2 studs may be a narrower pattern than the back two (or vice-versa). -Alan- |
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michael kranz
Joined: 10 Dec 2001
Posts: 30
Location: United States, Texas, plano
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| Posted: Sat Oct 06, 2012 2:35 pm Post subject: Yz 250 |
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| I ran the Yz and so did 2 of my teammates. The problems we ran into were the Ign rotor would brake, 4th to 5th gears failed and the studs for the cyl failed |
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Ian Harrison
Joined: 23 Nov 2006
Posts: 1671
Location: United Kingdom (Great Britain), Manchester
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| Posted: Sun Oct 07, 2012 4:01 pm Post subject: Re: Yamaha YZ250 anyone? |
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| nigel cooper wrote: | Is this engine ok for fun use? (I run rotax on my other kart)
A newbie question if you dont mind-
Why dont guys flip the piston,flip the cylinder head around 180 deg to place the intake at the front of the kart and the exhaust out the back with a custom exhaust?? it would not only look much better but take up less space ect ect like the genuine 125 shifter kart engines |
Hi Nigel
The YZ250 should be great for fun use. If you keep the rpms below 10,000, it will be fine in standard spec. If you are going to be up around those high rpm figures for long (long straightaways, etc.), you should add perhaps 2cc to the head volume and make sure that you change/inspect the piston regularly.
If the cylinder will flip and you can still align the transfer ramps between crankcase and cylinder, there is no reason that you can't do that as well. The rear exit exhaust is generally more efficient although the length can cause a bit of a problem. But if it's for fun use I would probably keep it as it is. There may be some issues related to piston thrust.
Having said that you could do this succesfully with the old 250cc Maicos.
If you are going to do any high impact stuff it sounds as though the box may be marginal from what Michael says and some HT cylinder studs won't go amiss.
Best Regards
Ian 
_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012 |
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