Messing with my Aprilia Cup

Previous owner of my RS250 Challenge Cup routinely used 100LL. I assume that’s what you mean by “avgas.” I’d recommend you run any high quality fuel that you can routinely get that fits your budget. It’s a pain for me to get 100LL where I live. So I either buy 5 gallon pails of Sunoco Standard at the gas station 10 miles away or I fill up at the race track when I’m there. Thankfully, both Summit Point and NJMP sell Sunoco Standard. It ain’t cheap. But it works for me. I don’t ride enough to worry about fuel costs. It gets lost in the noise relative to all my other expenses.

 

Yep, 100LL. My buddies have a hangout at a local airport. Direct sales are a non-starter but they have a work-around.

They're fans because they have bikes that might get ridden once/yr or less and 100LL lasts forever.

 

It last a while. Not forever. It’s similar to many race fuels that don’t have ethanol in that regard. There is usually a range depending on whether it’s stored “under ideal conditions” or not, and whether it’s remains unopened in its original container or not. But generally speaking, 1-2 years is usually fine if well cared for. But always read the fine print for your exact fuel.

100LL is generally more consistent than typical pump gas for automobiles. But it’s exact composition can still vary somewhat depending on the fuel supplier, geographic region and time of year. Most petrochemicals are made in batches. Depending on the fuel and the specific performance requirements, they usually have a range of acceptable values. Race fuels tend to be more stringent in terms of consistency. But that can vary also. Remember the Fresh N Lean Progrrssive Attack Performance Yamaha fuel controversy in MotoAmerica Superbike in 2023?

https://forums.13x.com/index.php?threads/fresh-and-lean-attack-using-illegal-fuel.384141/

 

I use a 50/50 mix of avgas and ethanol free 93 octane in both my bikes, a vintage Ducati single and an aircooled Rotax single.

I have been told that neat avgas burns slower and therefore doesn't produce the same power as gasoline of the same octane rating, don't know how true this is.

I can get it easily from the local airport where I can drive straight up to the pump and pay by card.

 

Av-Gas or 100LL is perfect for any machine without an O2 sensor.
It's just pure leaded fuel, no bullshit, regulated, tested and checked along with the holding tanks
every 6 months, up to a year for remote locations, worldwide.
They say 3-5 years stored properly in normal climate..
Round here (Mid-Atl), NAPA's and Southern States Co-Ops carry Sunoco and/or VP.

 

Engine in last night. I think I have all the parts I need to make some noise. Planning to start it on pre-mix with the oil lines disconnected to make sure the pump is working.

I was happy to find that the engine cradle fit almost perfectly. Just a light nudge to make a few holes line up. It was way off after the initial welding because I didn't leave the frame with the fabricator.

 

Change your coolant kids.



Might make some noise today.

 

Hahahahah. Yeah, sure...



Pipes are mounted, don't hit each other, and are even almost straight. Only took about 1.5hrs. Clutch side buttoned up. Kickstarter rotates the assembly.

New coolant lines 'fit' but several needed to be trimmed to get things in the right spot so all the parts fit back together.

Having a 2nd complete bike to refer to has saved me more trouble than I expected. I initially had the coils reversed and made some poor routing choices with various cables and hoses.

 

Really looking like a bike now

 

Making smoke and noise.



Started it with pre-mix in my little aux tank and the oil lines disconnected. Good thing, because the pump is not doing anything. I'll do a better prime before I get worked up about it.

Warmed it up to 60C and shut it off.

 

Wish there was smell-o-vision!

 

Happy to see it running!

 

Just a caution. I don't know about Aprilias but some two strokes have some of the pumped two stroke oil going directly to the case crankshaft bearings. Engines that do this should not be ran on premix unless modifications are done for a path from the transfer ports to the crank bearing.

Modifications are probably not needed if ALL the two stroke oil goes to the intake track. That would mean the engine is already set up to guide some atomized intake fuel/oil to the outboard crank bearings.

 

The engine does pump oil directly to the bearings, which is one of the reasons I want to use it but people apparently do just fine with premix in these engines. I even mentioned it to someone who works for Aprilia and was around back in the day. He had never heard of it being a problem. Go figure.

I'd be interested in Steve's take on this. My MK1 came from a friend of his and it was pre-mix so I'm guessing Steve hasn't seen a problem with it. I got sick of it pretty quickly and switched back to the pump after about 1000km.

 

Looks like you already know about this, good deal.

Suzukies I have raced have pump oil going direct to those bearings. I have heard of people running them without mods and I have seen the "transfer port to bearing mod" on them. A long time suzuki mechanic who also built race engine's told me it was needed on the Suzukies. My rz350 puts all it's oil into the intake track so obviously the bearings get enough. I run it on premix only. I have also heard of folks removing the inner bearing shield to enhance exposure to the fuel/air as it passes by.

 

And now for something completely different.

PROTECT TRIBAL TWO STROKE KNOWLEDGE!

 

And by protect I mean carry it forward.

 

Nothing exciting but some ring-ding-ding. Third run. I have no idea how I'm going to get this thing ready for the dyno. If the weather was better, I could get away with a little neighborhood riding to at least put some load on it or bring it to an big parking lot.

I'm not sure the pistons are getting warm enough to even qualify as a heat cycle. Honestly, I'm not sure how important that is these days. Back in the day, Kevin Cameron once explained that if you heated a new piston in an oven, it would come out misshapen. A heat-cycled piston would not.

Oil pump is primed and the old crap has been pushed through.

 

Do you have a temp gage on your bike? Each bike is different, but when putting new pistons in my bike, I'd do 3 heat cycles up to 60 deg. C and then let it cool down completely.
It was then ready to go. The loading on the engine, is to get the rings to seat. But the 3 initial heat cycles is to get the pistons to match up to the cylinders.

 

Well, damn. That's exactly what I've done. The video was the 3rd run.