yamarilia

[chris the rat]

Had my first short ride today on it!!! Works fine, some tuning to do but hopefully next weekend will allow some more riding.

[petros67]

Here you go......



Nice bike !!!
Think rear end is quite high though.

Petros

[crazydiablo]

Beautiful bike. Thats exactly how I want my bike to look. What front end is that. Give us more specs of the bike.

[peterz84]

Appears to be Aprilia rs250 front and rear ends with rs250 wheels.

Nice bike

Pete

[chris the rat]

Thanks for the comments, (and the working picture...) Both front and rear are as stated from an Aprilia RS250. Front just almost bolted itself on by itself. Used tapered bearings and two spacers and that was about it. The rear was a little more work. The dogbones=? two plates between the swing and the lower shock attachemnt are 5mm longer than original aprilia, maybe I will make them anouther 5mm longer but since the rear is a little soft it fixes itself when I sit on it. Also the bike is leaning away from the camra against the garage (since I havent fitted the sidestand) and the camra is low so it looks worse than it is.
Regarding the rear hight I have also done some work with the spring. Information I have so far is that the original RD spring rate is 85N/mm(475lbs). The Öhlins shock I mounted had a spring of 100N/mm( 575lbs). I found this to soft so I ordered a new spring at 140N/mm(800lbs) but it still feel to soft. Am aiming at about 200N/mm (1150lbs) as correct but it just that this feels like a very very hard spring. Have done a ton of measuring of sag and even made a excel sheet that can calculate movement for differnet rates. Anyone have any experience from other conversions. The aprilia swing is about 50mm longer so this would require a hard spring than standard but I dont see it making all that much differance. The shock has about the same stoke and the bike also moves about as much as original.

[Evans Ward]

Beauty and tastfully done!! Whose pipes are on it?

[chris the rat]

Pipes are Kennys Mick abbey design, Sound great! Trying to find a local tuner that can help me with jetting. She runs a bit rich but for now thats OK as pistons and rings are new. Had the engine apart and put in a fresh crank in. Everything else looked fine despite 25 years of use. Yamaha!!

[RuZty]

Chris, keep in mind the spring rate is a function of the suspension linkage rate. This is why a CBR600 can run a spring twice as stiff as an R1 and still have a similar ride. If you duplicated the Aprillia geometry then close to that rate should be good. Also remember that the shock is valved for a given spring rate, if you double (or more) the rate then the damping is way off.

[chris the rat]

Well the linkage is a mixture of RD and aprilia.. Which is why I have nothing to compair to. The shock is very similar to RD original in length, stroke and upper attachment point, the lower arm (between the frame and the lower shock point) is stock RD, the dog bones are 5mm longer than stock Aprilia and the attachment point on the swing is stock aprilia. I beleive the stock RD has a spring rate of 85N and since I have about the same stroke in the shock and same movement on the wheel ( same leverage) I can't understand why I would need such a different rate. But facts speak for themselvs when measuring the sag with and without rider. Maybe I should trust the facts and leave the theory...?

[bmp776]

mm sounds wierd to me also, looks like a moment equation to me? because the swinger is 50mm longer in theory you would need proportionally more force in the spring to counteract the extra leverage the swingarm would have as opposed to the orginal.