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Quimrider · 11-11-2008, 10:59 AM

motorhedfred,
first off I'm not trying to discourage you. I'd love to have a 300 or 350 to ride. I think it would take some serious machining and custom work to shoehorn a 350 piston on the GZ250 engine. Even supposing that you could simply replace the top half on the engine with that of a DR350 there is the problem that the DR350 engine has a 10mm longer stroke. 71.2mm vs 61.2mm. You would have to shorten the barrel by 10mm yielding you a 300cc engine. Comparing the bore of the DR350 to GZ250, 79mm vs 72mm. I think the best probability for an improvement would be if there's enuff meat in the GZ250 barrel to do a resleeve to a 79mm bore Which would yield a 300cc engine. An awful lot of work for maybe an extra 3-5 HP. I'm keeping an eye out for a DR350 engine to see if I can shoehorn it on the GZ250.

11-11-2008, 10:59 AM	#26
Quimrider Senior Member Join Date: Jun 2007 Location: Toledo, OH Posts: 198	Re: Convert your GZ250 into a 346cc!!! motorhedfred, first off I'm not trying to discourage you. I'd love to have a 300 or 350 to ride. I think it would take some serious machining and custom work to shoehorn a 350 piston on the GZ250 engine. Even supposing that you could simply replace the top half on the engine with that of a DR350 there is the problem that the DR350 engine has a 10mm longer stroke. 71.2mm vs 61.2mm. You would have to shorten the barrel by 10mm yielding you a 300cc engine. Comparing the bore of the DR350 to GZ250, 79mm vs 72mm. I think the best probability for an improvement would be if there's enuff meat in the GZ250 barrel to do a resleeve to a 79mm bore Which would yield a 300cc engine. An awful lot of work for maybe an extra 3-5 HP. I'm keeping an eye out for a DR350 engine to see if I can shoehorn it on the GZ250.
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