2018 Aprilia RS4 50 Euro 4 Upgrade Project

[Berkeley]

Hey thanks.

Yeah at the 9k run in stage. That part of things seem to be working ok.
Currently on a 90/42 jet. Tomorrow will check float level and make sure there's no air leaks.ie carb is on the flange but could be better.
By far not running right by the sound of it.

Tried with a 49/98 and at the higher rev range sounded horrible so went to the above setting.

Air fuel mix is about 1.5 turns out. Will Check plug tom. Speed idle is about half out

Still there seems not to be a good seal between the exhaust and the cylinder head port. Will have to sort that as well.
Will keep trying tomorrow

[jkv357]

Try turning the Idle Mixture screw in to see if it picks up RPMs and will idle.

I'm not a big fan of "free-revving" an engine (no load), especially up to those levels (9000 RPMs).

I'd much rather ride it moderately with varying load and moderate RPMs for break-in.

[Berkeley]

Hi Guys,

I completed the run in procedure. Bumping it seems a little easier, but no electronic start. When riding it goes up to 11k. It used to rev to 12.5k before whit the smaller 49cc head.

When revved in neutral it max's out at 11.5. running a 14/53 sprocket. I thought the 70 kit would give more power, seems quite tame.. Maybe the exhaust is too small for it and is hampering the performance? Tomorrow ill go out to check the top end to see how much of an improvement it has made.. Sounds a bit deeper/better.

Before I started running it today I took a look at the plug and looked fuel fouled. So I put the standard jet back to a 40. So 40/90 at the moment.

I fixed the leak at the exhaust port by cutting an O ring gasket (as was to big) inserted it and sprayed some copper sealant into it......seems to have worked.
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The float overflow nipple on the carb was hitting the top of the engine case it meant that it didn't fit properly into the reed valve manifold. I had to turn the manifold 1/4 of a turn which is a bit weird but now the carb does not touch the case bottom or sides and fits a bit better.

Can you buy more spacers for the reed value so the carb can sit right, couldn't see one on maxiscoot? Does the carb have to sit completely horizontal as at the moment its at an angle sloping fwd a bit.
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Here is what it looked like before:
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After a longer run here is what the plug looks like:

When I try to idle the bike is still stalls. It was better than before now dying at 2k as oppose to 5k. The idle can go all the way in and the revs wont pick up.

The revs didnt go up when i turned the air/fuel mix screw in as well.

[kaldis12]

It still looks waay to rich. The exhaust could be a reason for not revving but the carburation tune could be too. In theory bigger cc can make more power by revving more, faster. But its a littlebit complicated. If I remember that kit what you have revs to 12-13k but have waay more torque and power. Sometimes the max rev doesnt really matter. I wouldnt worry about that. If you tune the carb perfectly and have a good pipe then you shoul achieve better performance than the 50cc kit.

[Berkeley]

Yeah kal, its puts out more than the 50.. just expected a bit more .... maybe expectation?

I never tried going the other way with the jets.
Now it's run in a bit looks like it's still rich. This could be the reason for not idling and only working on the main jet when the carb is 1/4 open or more. I'll go down a jet size each and let's see.

For the carb fitting problem I found a spacer that wasn't malossi. ill see if this 5mm one from easyboost will do the trick

https://www.scooter-attack.com/einlasss ... 15-38.html

Thanks

[toratora]

MXS intake spacer

For right now having the bike run a little rich is desirable. So long as you aren't fouling the plug so much that it doesn't run.

It sounds like maybe the the carb slider isn't hitting bottom. If adjusting the idle screw makes no difference then likely the slide is above the screw. This is a mechanical adjuster that does nothing more than raising the slider. Try adding more slack to the throttle cable. You should be able to hear the slider hit bottom (not the throttle hit its lock, the slider in the carb—the will sound similar, and you actually want them to hit at roughly the same time).

There are a number of intake spacers. The main reason to not use one is the longer the distance from the carb the slower the throttle response. You should be able to turn the rubber part of the intake to create a slight left (non throttle side of the bike) angle. It's still going to be a little tight, but the CP is a small carb, and there should be plenty of room. Look through the Red Power thread for photos of how to set it up. The Malossi bike has a CP carb installed on it.

[Berkeley]

Hey tora,

So checked the carb slide and seemed good. Checked that it closed all the way when idle screw all the way out and there was a gap when it was all the way in.

Anyway slackened off the cable and tightened it until the slide want higher than the port opening.

Changed the main jet to a 88. Ran it again, still no electric start ( 13.2v)and still no idling possible. When i kept it at 3k I turned the air fuel mix screw in to about 1.5 turns out then it died. After the morning trying checked the plug and still looked rich ( same as before).
Im thinking that the pilot jet is too big at 40 but need to get some smaller jets as dont have them.. thinking what else is could be.

What you mentioned about the carb manifold and turning it.. thats what i did the other day to get it to fit better.

cheers

[jkv357]

When i kept it at 3k I turned the air fuel mix screw in to about 1.5 turns out then it died. After the morning trying checked the plug and still looked rich ( same as before).
Im thinking that the pilot jet is too big at 40 but need to get some smaller jets as dont have them.. thinking what else is could be.

If you think the Pilot Jet is rich, turning the Idle Mixture screw out (assuming it's an air-bleed) should make it leaner and run better.

Start turning it out and see if the idle improves. When you get past about 2.5 or 3 turns-out it means you need to change to a leaner Pilot Jet.

As tora mentioned, reasonably rich is fine for now.

How does it run as you take off and start to open the throttle? Can you post a video of how it runs and what it's doing? Might help get things sorted quicker.

Looking at the photo of the carb you posted above, I might be concerned that it's not sealing properly when sitting at an angle to the manifold like it is.

[Berkeley]

Yeah I think 2.5 turns out to 3 is about right at the moment for it to run (it's an air-bleed).

I have to bump it past 13 km/hr before it gets going. Seems a little tricky to get going but generally not too bad taking off and getting going open the throttle. I will do a video tomorrow as maybe you guys can pick something up.

RE carb Pic I posted. yes I agree with you, this was before I adjusted it and rotated the manifold. It now seats true on it, the same as what Tora suggested.

Would the reed valve be causing this issue of not starting and not idling? Just running through what's left to change/check, and go over.

This is the position of the carb slide when the speed idle screw is all the way out ( note that this was before I slackened off the cable this morning).
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This is it with the idle all the way in.
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This is the position of the needle clip at the 3rd indent up. This is the same as all the other needles I got in the original, and in the needle kit.

Would changing this position have an effect??
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This is the state of the plug after today.

Thanks

[jkv357]

I think you can tell more about how the carb is tuned from listening to how it runs as you are riding than from looking at the plug color. Is the compression ratio significantly higher than it was originally?

Is it a possibility that the ring is too tight and creating too much friction? When you shut it off does it wind down slowly or does it stop quickly? Can you look in the exhaust port to see if the cylinder wall looks good - without any scoring?

That could explain the inability of the starter to spin it over and the need to have high RPMs in order to stay running.

Hopefully not, but just something that came to mind.