Lance,
finding a Derbi motor is somewhat rare, but as of now, it seems you have good timing. In fact, there is one ebay equipped with an electric start! Current start bid is $599 (good price). The posting is over today (8 hrs) from now.
cgi.ebay.com/ebaymotors/Derbi-GPR-50-Water-Cooled-Engine-with-Electric-Start_W0QQcmdZViewItemQQcategoryZ35618QQihZ015QQitemZ250014294947QQrdZ1250014294947.
at least get the contact info from the guy, as he may have other Derbi motors for sale in the future....or he may re-list this item since no bids have been placed yet.
I bought mine from a local seller (good timing as well) for $800. In total, was roughly $1500 to complete my conversion.
i200.photobucket.com/albums/aa210/YSRCali/YSR%2072sp/Yerbi-01.jpgHere's a list of other tid-bits to complete the project I had to purchase:
SP Metrakit pipe $279
Derbi mounting kit ( I can provide you a source for this kit)
TZM radiator $50
12v bulbs: turn signals, brake/tail, and head light
JDM headlight (imported) from JTrading (Jun) $35
12v Horn (used) from JTrading
41t sprocket (used) $25
13t sprocket (new) TCR
D.I.D. Chain (new) TCR
Aftermarket Clutch perch (adjustable)
Battery $35
Radiator hoses, copper fitting & clamps
Derbi Clutch Cable
Cost of materials to construct Harness (wires, butt & bullet connectors)
Misc screws & bolts (for brackets)
$100 misc brackets to mount/modify SP pipe
i200.photobucket.com/albums/aa210/YSRCali/YSR%2072sp/Yerbi-02.jpgAs for the harness, I made my own. You can purchase a GPR harness, modify the YSR harness or make your own as I did.
As for carb (Mikuni 24mm f/s), the carb was included in sale with the motor as it was pulled from a race bike.....one less item I had to purchase seperately.
I made my own (mickey mouse) brackets to mount my TZM radiator, for now. I plan to have quality brackets made soon. At this time, I am having way too much fun riding the bike, and no signs of any concerns of failure.
With my current gearing (13/41), 24mm f/s carb & Metrakit SP exhaust, TCR says the motor should produce approx 18hp. My top speed is approx 65 - 70mph. As to my guesstamation, I took the incraments between 40/50 mph on the YSR speedo, and added the markings with a Sharpy (low budget)
to equate up to 60 mph. The speedo needle peaks out on edge (left side) of the yellow turn signal light on the speedo, at max speed.
Moreover, I do have a suspision that my cylinder may be ported, but won't know until I do my first top-end rebuild (early 2007). Iv'e had the motor & running in the YSR since Feb of 2006.
I have contemplated whether to bump the motor with a 72cc SP kit, which will put it around 22hp, with top speed within the 80's, so it's been said. However, the kit is concidered a full race set-up which may require a little more attention (top-end maintanance) vs keeping the stock cylinder that obviously will have longer lif span. Besides, there aren't too many places I can ride the Yerbi to fully utulize the power of the 72cc motor, other than getting up to speed a bit sooner
Tbh, I am content with it's current set-up.
Being that the motor is water-cooled, gives me more confidence of riding longer because simply, it's water cooled (regulated tempurature). vs the downside of an air cooled, relies air cooling the fins of the cylinder casting (not efficient).
Being that the YSR motor only has 7 hp and a top speed of 50, maybe 55 mph w/ mods, it doesn't take much effort to get there. Furthuremore, the YSR motor runs it's leanest and hottest at top-speed. And if one holds throttle for long periods of time, it decreases the life of the top-end, hence top-end seizure. Again, the motor just can't keep itself cool at a regulated tempurature (efficiently) vs a water cooled motor.
Don't get me wrong, the YSR motor makes the YSR fun for speeds up to 45 mph, but not advised for more increased speeds (50 mph +).
The YSR motor is very reliable and fun on the track as well because most tracks are small and tight, which equates to "varied" throttle, which all 2-smoke motors love! Yes, you can pin it at full throttle at times, but you're not there for long periods of time to do any significant damage.....unless the motor is tired = due for a rebuild.
Also keep in mind, that top-end rebuilds are concidered routine. That is just the nature of 2-strokes. depending on set-up and how hard a person stresses the motor, which some require frequent rebuilds vs others.
Hope this info is useful.
