just picked up a 2003 wr450 with a blown motor. Id rebuild it but it exploded top to bottom. Any idea where I can get a motor? There is one on ebay buts a 2007 not sure if it would work.
Posted November 18, 2013 - 07:21 PM
Could I run a yz motor on it if I decided to go that route or would that require modification?
Posted November 18, 2013 - 08:53 PM
It will work.
Any year Wr450F motor will work, pre 2012.
Fascinating. I suppose it's possible, but using an engine from a WR later than '06 would tend to complicate the swap somewhat. '03-'06 WR450F's and '03-'05 YZ450F's were first generation 450's, the Gen1 engine. The oil tank is external, using oil lines to connect it in the traditional dry sump manner.
The '07-'12 WR450F's and '06-'09 YZ450F's are the Gen2 engines. They're still dry sump engines, but they have the "oil tank" located internally in the forward section of the crankcase. They also eliminate the external manifold that feeds the top end and transmission; that's internal, too. The first snag with the newer engines is that the cylinder is more vertical than the Gen1, so at the very least, you would need to fabricate top engine mounts, if not rework the rest. Next is that the more vertical cylinder mounts the carb at different angle, and moves it farther rearward, causing air boot problems.
As to whether one can use a YZ450 engine, yes he could, BUT remember that the only way to use an electric starter on a Gen1 YZ450 is to use the crankcases, crankshaft, and electricals from the WR. In this case, it doesn't sound like some of that at least is usable. The Gen1 YZ450 was also a 4 speed, so you'd need to switch out the trans to keep your 5 speed. The YZ has a completely different electrical system, though, sharing only the coil in common, so it's a good idea to get the harness and CDI with it.
On the other hand, the '03-'05 YZ450 engine will be more available (simply because more were sold), and probably cheaper, and if all you want is to get the bike running, then it might be what you're after. It will bolt directly in, but remember about the electricals.
Posted November 18, 2013 - 09:17 PM
Appreciate the response you sure know your 450's .. Sounds like the best option for me is going to be new cases a crank and a new head. This way I can keep the electric start and 5th gear and I know what I have... Thanks again