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300cc Big Bore Stroker Motor Rebuild Repair Kit

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Hi, my yz250f 06 just died. I need all the parts contained in this combo and it seems the less expensive route. I know it will gain more power at mid/low RPM and  loose some at the top. I can live with that. But my worries are about reliability and set up. My mechanical skills are 0 and dont want to go through a nightmare to make this thing work. Thank you for your help. 

 

http://www.ebay.com/itm/03-13-yamaha-yz250f-yz-250f-80mm-300cc-big-bore-stroker-motor-rebuild-repair-kit-/201338515799

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If your skills are zero then I suggest you get someone else to do it for you

Yes the work will be done at the shop. But I need to decide what parts install.  Thanks

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did you mean 315?  and by died...do you mean just the top end, valves, crank?

 

if you go with the 315 that is a stroker kit, which means you need to split the cases.  without changing the cams (leaving them stock, and I don't recommend it) the bike will be all bottom and some mid.  it will also feel heavier due to the longer stroke (but will still feel lighter than a 450). 

 

if you go with a 260,270,290 kit you only need to change the top end out (cylinder too of course) and the bigger the bore the more bottom/less top you will have if you keep the stock cams.  the bike will feel as light as it did as a 250 due to no change in stroke, but more power of course.  also, vibration will go up a bit.

 

when you change the jetting go leaner, not fatter.  its a common misconception when going to the bigger bore.  if you have a mechanic doing that for you as well, then he should be testing it out (ride it) because it will be trial and error.  those are the basics.

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I just want a reliable bike. I prefer more power at the bottom. and I dont want to spend 200 usd more to buy a Hot cams stage 2 either. Thanks!

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That combo is craving a 39-40MM carb and cams with more duration and lift. With the carb and cams you will gain power every where combined with your build. An exhaust that favors top end on a 250 will give you an increase also. Bigger air pump needs to get air in and out of the engine. You will need a smaller back sprocket with the increase in torque.

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If you have a 37mm on the bike now, a 39mm would work great, research exhaust systems for your year bike, look for one that improves mid to top end power on a stock displacement engine.

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If you have a 37mm on the bike now, a 39mm would work great, research exhaust systems for your year bike, look for one that improves mid to top end power on a stock displacement engine.

Thank you! I will take this route then. There is a set of Hotcams for oversized engines called Builder Series available for yz250f 06. Is that what I need? or the Stage 2 package. Here is the link:

 

http://www.hotcamsinc.com/ProductInfo.aspx?item_id=678

 

Thank you very much! 

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i built a Yz 310F after my cluch plates shattered and left a mess in the engine. i brought the parts from lukes racing and had a mechanic do the work including installing WR250F gearset for hill climbing. the bike was a animal. i recently sold it did 90hours on it and had no issues. i did not produce much additional HP but the torque was greatly increased and power broadened all the whole rev range

 

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i built a Yz 310F after my cluch plates shattered and left a mess in the engine. i brought the parts from lukes racing and had a mechanic do the work including installing WR250F gearset for hill climbing. the bike was a animal. i recently sold it did 90hours on it and had no issues. i did not produce much additional HP but the torque was greatly increased and power broadened all the whole rev range

 

 

 

Great to hear that. Thanks 

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