Aprilia Rally project nightmare

Hi all

So my little project bike is driving me up the wall....

Bought a 2001 rally a/c at Xmas as a toy and gradually working through its many faults. It hadn’t run for 8 years but was cheap and ran ok apparently back in the day.

Fitted new 70 kit, 17.5mm carb, street variator and belt, derestricted cdi, new std Reed, new filter, plug etc. Only thing not done is exhaust.

I’ve got a set of jets, started at the 90 jet which came in the carb, gradually back to a 72 which seems to run best, and after a short run the plug is nice and brown.

Problem is, it does about 28mph and is hellish slow on pick up.

Any idea where I go next with it? Is the exhaust likely to be restricted?

Cheers guys and gals

 

One of my zips did this and it was because the rollers were too heavy. It stops the engine from reving in the powerband. It could also be the exhaust restricting the mods you've done.

 

Will try the rollers thanks but thought once the bike hits the maximum extent of the rollers it should carry on revving? I was messing with these until I realised the carb was a more serious problem so replaced that. It's literally fighting to get to the powerband but can't quite get into it properly. I can't understand how a 70 with big carb would struggle so much to make power.

 

With mine it would hit 15 20 no problem but would struggle as if it wasn't in the right gear if it was a manual. Changed the rollers (4.5g if i remember correctly) and it reved higher and kept it in the band and it flew to 30+ no problem and kept going. Might be your exhaust/ jetting though as you've moded it. Mine was pretty much standard so a lot easier to diagnose.

 

Will give it a whirl thanks

 

So, ped definitely better with lighter rollers, slow to pickup initially but then hits power and goes ok. Hit about 40, still accelerating but then cuts out completely. Starts easy on kick or button.
Think I need to play with jets some more but it feels like it's run out of fuel, well actually like it's seized but it hasn't.
I'm thinking float bowl emptying, any suggestions?
Thanks

 

Things to check for fuel starvation would be the operation of the vacuum pet cock (if it has one, I know piaggio do), float height or the needle being stuck, blocked or partially blocked Bets or passage ways. Some times if there is no airfilter or element it can lean it enough to not run correct. Tbf I'd want to try a different carb just to rule it out as I have had bad carbs before. The bike would rev freely on the stand and up to a certain point when riding but would bog as soon as I hit a hill or anything that wasn't flat. It's due to there not being enough fuel to burn the mix and the engine runs very lean and hot as a result. Chances are as you have modded it it's due a bigger jet to cover the extra cc especially when riding WOT. You need to adjust the oil pump usually aswell to cover the 70 or premix instead. I've seen a couple of scored up 70 kits in the past.

 

All makes good sense mate thanks. It's a new carb, up from 12mm to 17.5mm, jets I'm playing with but 74 at the moment seems to rev ok and make some power although working my way up to 76 probably (std pipe). Fuel valve is vacuum type and already replaced. I'm going to take the fuel filter out and go direct to see if any different. Plug colour looks ok if a little hot. Just the cutting out opposite which I didn't expect.
What do you do if racing with a 21mm carb? Must use far more fuel!
Air filter is a polini pad in standard air box.
Cheers

 

Tbf if you've gone from a 12mm to a 17.5mm carb and a 70cc kit with a insert filter your probably drawing in way too much air at full throttle. Mines a similar engine but a 50cc sports pipe and malossi insert filter and runs best on 58/60 main. Another thing to look for because you must of had the float bowl off is maybe it is leaking. Near every time I've took one off the bowl has warped or the ring won't seal. Either sand the bowl down on a flat or get a new seal.