GPR Camp: Replica Racers

Hi folks,

ToraTora suggested I post this here, was having issues with the aprillia forum so hopefully this goes a bit smoother.

Am about to embark on a wee project for my daughter. It's a 2009 registered (actually seems to be a 2008 model) Derbi GPR 50 Belson, needing lots of TLC.



Stuff I know needs doing so far:

• Engine was hydrolocked, have stripped the head off and drained all fluids, but its still finding water from somewhere when you put it in gear and turn it over via the back wheel
• Oil tank had a fair bit of emulsified gunk in the bottom of it, and the filter and feed hose has some in too
• Exhaust was full of water, but otherwise looks intact. Seems to have an arrow back box on it, not sure if that's aftermarket/performance, need to figure out if it has been derestricted, and if it can be re-restricted
• Front shocks need attention, seals have failed on one and there's corrosion on the tubes
• Rear brake caliper is seized
• Rear brake pedal moves fine but no fluid coming out of the brake line to the caliper, even though there is fluid in the reservoir
• Front brake handle is flapping about, not putting any pressure on master cylinder. Not sure why yet
• Brake pads all round
• Front tyre is done
• Rear footrests missing
• Kick stand isn't fond of staying in the down position, and flicks up as soon as the weight is off it
• Fairing and tank has seen the wrong side of tarmac. Mostly intact but lots of scuffs etc
• Seat and ignition locks have some damage to them. Ignition lock seems functional still but would be nice to tidy it up

Are there any service manuals for these bikes, both engine and overall mechanicals?

Where's the best place(s) to find parts (UK based preferred)?

The biggest headache is presumably going to be the fairings - I doubt replacing them is going to be possible, and presumably the decals are also unobtainable?

Any hints/suggestions gratefully received, I've worked on plenty of cars but not bikes.

TIA.

Post some photos of what you have.

Tora tora can give you plenty of good engine advice, and there are a few options.

I removed most all of my stock stickers and had some basic logos cut from vinyl at a sign shop.

The kickstand is supposed to flip up when you pick the bike up. There are a few other bikes that did that back in the day, but not so many any more...

Will post some pictures, thanks. Had to upload them first.

Cylinder head, looking quite rusty, but it's all deposits from the coolant:



Managed to encourage the cylinder itself off:





Piston and crank. Note the water sitting on top of the crank. I don't really understand why it's still there, because I pulled the drain with the magnetic pickup and there wasn't a huge amount that came out.



The magnetic pickup had some debris attached, micro-filings though so presumably nothing to get too excited over.

Looking at the cylinder/block gasket, I'm hopeful that's the one that's failed?

Regarding the stickers, the bike is a limited edition, so I'd really want to keep it as original as possible in that regard. Hopefully a vinyl shop might be able to reproduce some of the damaged stickers if they are better on one side than the other, that's a good suggestion. I haven't gone through the fairings properly to identify all of the damage yet.

So engine wise, I guess I need some advise on how to proceed. Do I just replace the cylinder gaskets, piston rings and reassemble? Or should I be going further in at this stage?

Only additional information I have is that when I drained the gearbox oil, it was quite dark. It didn't smell burnt though, not sure if it would?

mace wrote: ↑

Tue May 08, 2018 5:21 am

So engine wise, I guess I need some advise on how to proceed. Do I just replace the cylinder gaskets, piston rings and reassemble? Or should I be going further in at this stage?

Only additional information I have is that when I drained the gearbox oil, it was quite dark. It didn't smell burnt though, not sure if it would?

I'll leave the engine advice to tora tora, but i'm pretty sure (ok, almost positive...) he's going to tell you to keep going with the disasssembly and a full bottom-end refurbish. That doesn't look good.

Just follow his advice and you'll get it.

Neat bike. Sad that it has been so abused but good to see it being brought back!

Just made it home. I think I'm on about 40 hours no sleep.

For this engine due to the condition I would open it up and put in new crank bearings, and a new crank too. For the top end you have lots of options as there are many great kits around for these bikes.

Another thing you should probably consider is looking for a bike in better condition. You could probably easily find a bike in much better condition for less money than you'll have to spend to fix the things we've been talking about. Keep this bike for spares, or maybe something to take out to the track.

Get some sleep!

I can't really afford to dump this bike at this stage. As it was, I had to travel to the other end of the country to even find one in this state, we don't have so many of them over here in the UK, and a lot have either been accidentally trashed because they are ridden by new 16 year old riders, or thrashed to death. This one I think is mostly the former. Its intended to be a starter bike for my daughter, so doesn't have to look A1, although obviously it'd be nice if I manage to tidy up the cosmetics. It does however have to be mechanically solid. Doesn't need any performance mods at all, just start, stop and go.

Am I going to need to buy specialist tools to break apart and reassemble the block/gearbox etc? That would definitely throw the budget out of the window, see the tools I'm talking about here:

http://www.pedparts.co.uk/bikes/aprilia ... &limit=12&

I caught a quick nap. Still tired though.

You do need some basic tools, but there's nothing super specific. There is an affordable puller for the flywheel, but even that can be removed with basic tools. I just did a tear down of the Red Rocket Euro3 engine. I'll be posting photos, but there's a really great video already linked on the site here in the tutorial/resource section.

And here's a Euro2 break down that's very similar.

Ah that video was really helpful, thanks. So is my engine the Euro 3? I notice from your DRP thread with the Euro 2 engine you talk about balancers etc. Do I need to concern myself with such things on the Euro 3?

Also note you went with an Airsal crank; presumably not much point in me going for that if the bike is to be kept fairly restricted?

I'm looking at the photos and video, and wondering if the crank case even has a drain plug? I removed the bolt in the side cover and the one underneath with the magnet, but are those purely for the gearbox? If so that explains where all this water is coming from (its caught in the crank case).