GPR Camp: Replica Racers

Recently picked up a blown 2009 GPR50. It's in bits atm. I also picked up a rebuilt TZR 125 bottom end.
My plan is to do the topend, get the engine to fit in the bike and just get it running.
Any tips on stator and general wiring would be greatly appreciated.
I'll probably run no powervalve until I can figure out how to wire one in.
Thanks x

Can I add pictures on here?

Welcome!

That may be a tricky swap...

How "blown up" is the GPR? You may want to go with a big bore top end if it's just the cylinder.

For photos, I've used the Imgur upload link at the top of the toolbar on the far right that looks like a "i". But it hasn't always worked.

Thanks for the interest. Im not having much luck with the image thing so i'll try again soon.

I know it's an ambitious swap but i think it shouldnt be too hard as the 50 and 125 share alot of parts.

My current concerns are:
-Making the engine fit with good chain alignment (Could I use the 125 cradle?)
-Making the radiator fit
-Wiring, mainly whether to modify the current harness or buy a gpr125 harness as I will need to run a powervalve.

Does anyone know a way of running a manual powervalve (e.g. no wiring needed?)

Thanks

Oh and the original engine is a d50b0 but its knackered. I have 90% of the parts to build an EBS050 Engine for it but ive had a 70cc derbi senda before and the power just wasnt enough for my riding style.

I have heard about these 88cc kits and supposedly i could mill the casings with a dremel but it all sounds very sketchy and expensive to me when i have a tzr engine anyways.

My concern with the TZR engine would be the powervalves. I'm pretty sure the Yamaha ECU controls the power valves, and there are servos and such involved.

I'm not familiar with the newer GPR frames, but I don't believe there is any way to swap to a 125-spec cradle.

As you mentioned, the countershaft alignment would be something to confirm before going all-in.

Yeah from what I believe, the GPR 125 had the late tzr/dtr electric start engine. Thats what ive got.

Im pretty sure I could easily redneck it to run off any old pickup coil and any old CDI (I know you're probably cringing behind the screen ).

As mentioned my concern is just the powervalve.

Im not sure but has anyone come across maybe a big bore kit that doesnt utilise a powervalve? Like an Athena 170cc kit that is just ported? Might sound silly but would be alot easier and I would still see good performance with the extra displacement.

raceraidan wrote: ↑

Mon Jul 28, 2025 11:27 am

Yeah from what I believe, the GPR 125 had the late tzr/dtr electric start engine. Thats what ive got.

Im pretty sure I could easily redneck it to run off any old pickup coil and any old CDI (I know you're probably cringing behind the screen ).

As mentioned my concern is just the powervalve.

Im not sure but has anyone come across maybe a big bore kit that doesnt utilise a powervalve? Like an Athena 170cc kit that is just ported? Might sound silly but would be alot easier and I would still see good performance with the extra displacement.

I haven't, but you could try 2strokeworld.net.