June 28, 200521 yr If you compare the three 4 strokes up close it is obvious which one looks "Thrown Together"! Nice job on the Scorpa and the other one!
June 28, 200521 yr 5 titanium valves and 249cc .. is this gonna be underpowered. ??? Also, it does look heavy in the engine department so what do you think the weight will come out at ? If it does 70kg or better then it will be impressive. The exhaust system is slick.. really like this idea.. no more burnt legs Edited June 28, 200521 yr by Webmonkey
June 28, 200521 yr 5 titanium valves and 249cc .. is this gonna be underpowered. ???Not if its anything like the YZ250F that it is based on! Those things can really haul!Those titanium valves cost a fortune tho when you have to renew them!!
June 28, 200521 yr Adjustable handlebar clamp. Adjustable footpeg position. Recycled Aluminum. Thicker disks, but more slots. 5 valves. I don't even know how many the others are using. Interesting stuff. I'm keeping my valve lathe at the ready and wondering what size/angle seat cutters I'll be using in a few years.
June 28, 200521 yr I'm keeping my valve lathe at the ready and wondering what size/angle seat cutters I'll be using in a few years. Charlie, Valve grinders must be just like ties, if you keep them long enough they will come back in style. You may want to figure how to how to hook a computer to your valve lathe. Ciao Doug Wilson
June 28, 200521 yr I'm keeping my valve lathe at the ready and wondering what size/angle seat cutters I'll be using in a few years. You shouldn't need them with a Yamaha...... I ran a YZ426 for nearly 3 years in H & H and enduros and when we finally stripped it to put a new cam chain in we found it didn't need it. The engine was still like new inside. Couldn't fault the quality of it. Being a Yam fan for many years it's going to be hard to resist this Scorpa, especially if Mr Birkett is involved in it's development. Should be one heck of a clubman bike.
June 29, 200521 yr Yeah the valves should be more than ok in a trial bike, I only mentioned them before cos in the 250F MXer the engines take a LOT of abuse and some people do neglect the valves when they should be checked regularly. The results can be erm very costly
June 29, 200521 yr Ooh I also gotta say that the Scorpa really is kinda growing on me now! First impression for me was'nt that great but now it does look quite good
June 29, 200521 yr Adjusting the valve clearance will be a chore. Shim and bucket design and all. Got the same set up on my Kaw trail bike. Yamaha seems to be winning the valve system reliability war at the moment. It's a nice looking bike.
June 29, 200521 yr I realize the shim and bucket thing is superior, but wouldn't something adjustable (the old adjuster and stop nut, or something on an eccentric that can be adjusted) be a little more kind for us 2-stroke folk? What do you do if you don't have a local dealer? Take 5 measurements, place an order and wait for your shims to show up in the mail just so you can do a bit of routine maintenance? I'm not slagging, Yam or Scorpa...I'm sure they'll all be the same.
June 29, 200521 yr be a little more kind for us 2-stroke folk? What do you do if you don't have a local dealer? Take 5 measurements, place an order and wait for your shims to show up in the mail just so you can do a bit of routine maintenance? Pretty much.... yeah!
June 29, 200521 yr I can honestly say, that YZ426 I had never needed the shims doing once, so I wouldn't worry too much as the trials engine won't take anywhere near the punishment of the YZ.
June 29, 200521 yr Seems like quite a bit of discussion is going on about the top end maintenance and durability of the Yamaha engines. Since 2001 I have owned three 250 Yamaha 4-strokes, a 2001 and 2003 YZ250F and a 2005 WR. I still have the 2005 WR250F. The 2001 I put the most time on, riding 28 Enduros and about 20 Hare Scrambles, not to mention practice time. Each of the hare scrambles are 2 hours and the Enduros are as long as five hours. Even off road on an MX bike, the preferred throttle setting is
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