Re: Project: 500GP
 

Should make knee dragging breeze!

Re: Project: 500GP
 

Omg i didnt realise it was that small! Looks like a mini moto next to the SV hahaha so awesome


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Re: Project: 500GP
 

You should change the name of this thread to Grom II.

Re: Project: 500GP
 

The bike has been sat in the garage for nearly 12 months before I started work on it as I've been collecting parts (still have some to get), but its made it mark. Firstly the carb leaked as the float stuck and the fuel tap was on, that was an easy fix. The oil leak on the other hand, well it wasn't just oil, it was like an oil and petrol mix, but odd. I didn't really track the leak down it was coming from the engine on the left I think near the front I suspect a seal of some sort but with the lower still on I just stuck a tub under it.

Anyway time for a tour of the bike.

http://i153.photobucket.com/albums/s...pscsnlwkyd.jpg

The dash has a simple speedo and integrated lights on the left and a rev counter on the right. Trouble is that rev counter shouldn't be there. The YSR80 had a rev counter the 50 doesn't. The 50 engine and the 80 engine share a lot of the parts and is the same base engine. This base engine is also used in a number of other models including the RX and DT series as I understand it. And this bike had a RX50 engine fitted to it at one point. However the previous owner swapped that out back for the YSR engine that came with the bike originally. The rev counter will go.

http://i153.photobucket.com/albums/s...psszzbwn8q.jpg

From a distance the bike doesn't look to bad, but the paint has faded with time. There are chips on the tank but no dents and the nut pad is missing. The foot pegs are not original and they don't match.

http://i153.photobucket.com/albums/s...pssrcajmwf.jpg

The lower fairing is falling apart and that upper mount doesn't look quite right. The engine has been painted gold, but its been affected by the petrol leak. The frame has also been sprayed silver at some point, and not very well. There is overspray on bolts, the loom, and the shock so it wasn't stripped before the rattle can came out.

http://i153.photobucket.com/albums/s...psrw7vtwuq.jpg

Other than that there is the usual signs of wear and age. The ignition and petrol cap keys are different, and there is no kill switch on the right. The fork cap bolts have been attacked by the wrong size socket, but the brakes still work, the engine did run, and the gears were selectable.

http://i153.photobucket.com/albums/s...psn9haf7vc.jpg

Time to take it apart.

Re: Project: 500GP
 

The first step of any strip down is the removal of the plastics. The rear came of easy one bolt at the front and two at the rear, this revealed the battery tray and massive 6 volt battery.

http://i153.photobucket.com/albums/s...psmwynwita.jpg

With the seat unit off the tank was next. This showed me the lack of an airbox but a non-standard filter. It felt a bit loose, not the best quality. Also on display was more evidence of over spray and insulating tape holding the loom to the frame on the right.

http://i153.photobucket.com/albums/s...psv1sqywxf.jpg

The lower fairing didn't fight me but it did give up being a fairing, parts of it disintegrated around the mounting points. Not a huge problem as a spare lower was in the deal, but a shame none the less.

http://i153.photobucket.com/albums/s...ps3gwrvjy7.jpg

More bad news was found on inspection of the fuel filter. That crud implies there is a bit of rust in the tank. This may be a problem, but I'm working on an idea.

http://i153.photobucket.com/albums/s...psgef9ytbx.jpg

However all is not bad news as I noticed this little red box plumbed in. It feeds off of the alternator and intersects to the CDI. Its a Kitaco Rev Booster, and if I'm honest I'm not sure what it does. I suspect it itercepts a signal from the alternator and kills it off via a resistor to fool the CDI into thinking the engine is not reving as high as it is giving a bit more power. But if anyone knows different please speak up.

http://i153.photobucket.com/albums/s...psqjyycqzd.jpg

But good news only proceeds bad in the shape of the left fairing lower upper mount. I'm fairly sure that is not factory welding in play.

http://i153.photobucket.com/albums/s...ps4wyuu0od.jpg

And finally the front fairing surprised me as the headlight is mounted directly to the fairing and not the subframe. But after unbolting it only a plug was keeping the headlight on the bike with its gold painted frame.

http://i153.photobucket.com/albums/s...psxywng8nn.jpg

Re: Project: 500GP
 

Now I have a naked bike in front of me I can begin to remove the engine.

http://i153.photobucket.com/albums/s...pszxrf4lz8.jpg

And the first step here is the exhaust. Trouble is this one has a funny nut as standard that screws it onto the head.

http://i153.photobucket.com/albums/s...psjww1bzls.jpg

So out come the C-Spanners. Interestingly the only one that fitted was the Yamaha OEM part that I ended up buying for the steering bearings on the TZR. When I bought that I thought I'd never be using it on any other bike let alone not even steering bearings. I like tools.

http://i153.photobucket.com/albums/s...psrwrrxv8t.jpg

Onto the engine and the clutch cover. First it is the gear shift to remove.

http://i153.photobucket.com/albums/s...psb8erhsah.jpg

Before the cover can be unbolted and the clutch cover cable disconnected.

http://i153.photobucket.com/albums/s...psx15j7kdt.jpg

The oil pump was next. Open up the cover and disconnect the cable and pipes in and out. There was oil in the tank so that was drained into a tub via my hand and workbench.

http://i153.photobucket.com/albums/s...ps7j4q14ka.jpg

Next was the carb. Revealing the intake and the reed valves along with the boost bottle. I first encountered the boost bottle on my TZR125 (but that's for another day), no idea how it works, or why its not on the 250 so if anyone knows I'd very much like to understand.

http://i153.photobucket.com/albums/s...psjpndaroe.jpg

And finally the front sprocket nut. Or to be precise the front sprocket circlip. I'm impressed that a circlip can handle all the power being put out...

http://i153.photobucket.com/albums/s...psoym4rkp5.jpg

Re: Project: 500GP
 

And I almost forgot; the oil leak, I think I have found where it is coming from. The only candidate is what appears to be a drain hole from the alternator cover.

http://i153.photobucket.com/albums/s...pslfahj0i4.jpg

But this isn't an oiled cover, it should be dry behind the cover as behind the cover is just the crank cases. The only output from the crank case is the crank itself with the alternator on it. And using my experience from the TZR this is sealed into the crankshaft and separated from the engines transmission oil. I am concerned.

Re: Project: 500GP
 

Nice project, got to love a gag bike!

Re: Project: 500GP
 

Another great project thread SH - your patience to log it all amazes me. The boost bottle works as follows: when the reed valve shuts the intake charge still has momentum and it travels up the tube to the boost bottle and when the reed valve opens again it travels back giving a small boost. The revs it works best at are probably dependent on the length and diameter of the tube and the volume of the bottle.

Re: Project: 500GP
 

Awesome little bike loving the thread so far! [emoji106]


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