Flexer 25km vs. 45km. Differences

[granturismo]

Did you check your ignition for a pickup unit? Do or don't you have it on there?

Nope, no pickup unit
Removed the cylinder (A5) and piston (no window version), and installed an Airsal 50cc kit. Haven't tried it yet but guessing I need to up jet it... 10 steps maybe?

[shadowranger]

There's no need to upgrade your fueljet, only if your engine is running not smoothly. Every engine reacts different, try only by steps of 1 or 2 up or down. Check the colour of the ignitionselectrodes of your sparkplug if replacing is neccesary. At normal running and good fuel to air mixture it will be brown like coffe with milk. Check this after you have driven for apr. 2- kilometers at full speed and your engine is hot.

If it appears white/ grey it needs a bigger jet, if it's still black you need a smaller jet. 1-2 steps at a time. Maybe this workshop manual comes in handy. It's in english and it has some pictures of sparkplugs and the solution if engine misfires etc.

[granturismo]

It's not running at all Idle was ok, but when I pull throttle it dies. I had to cover 1/3 - 1/2 of the air intake with my finger, then it ran ok.

The original cylinder is very restricted and very sensitive. 1 step was huge difference. Anyways, I haven't changed the main jet since the largest one I have is already mounted. Need to buy some tomorrow. 55 is mounted now...

[shadowranger]

Check for air leakage around carburettor and intake. In many cases the airtightness of where the carburettor is mounted to the engine it leaks air inside, so your air-fuel mixture is getting more lean. That's why the engine runs better when you put your finger in front of the air intake, you make your mixture more rich. The same as putting a bigger jet in your carburettor to compensate the loss of mixture.

It's better to check for leakage and repair it than changing jets. You can do this by using deodorant or something else like it. If the engine revs change there is your leakage. Try to spray near where you expect leakage, but not into the air intake of the carburettor!

If no change in revs or running idle is noticed, you can change your jet. Please post your setup here so we can help you better with the jet size.

[granturismo]

No air leaks... so I don't know what is wrong right now

Current setup:
Flexer 2006 eu25
Low compression cylinderhead (one side is higher inside the dome)
Dellorto 14/12 (original 14/9)
Intake EU45
Bigger exhaust, chromed
Airsal 50cc kit.
Main jet 58
Front sprocket 26 (stock)
Rear sprocket 22
Top speed: 30km/h
Plug Chop is coffe latte brown

Old setup:
Low compression cylinderhead (same)
Dellorto 14/12 (original 14/9)
Intake EU45
Bigger exhaust, chromed
Original Tomos A5 cylinder with bigger exhaust port
Original Tomos Piston NO window version
Main jet 54
Front sprocket 26 (stock)
Rear sprocket 28
Top speed: 43km/h

A side note; my friends Quadro 2003 with 14/9 carb, same exhaust, same intake, 22 rear sprocket, does 55-60km/h.

[granturismo]

5kg compression.

[shadowranger]

Have you tried to put back the old jet 54, to see if it makes any difference? As far as i can see now from your setup postings the only big difference is the jet, cylinder (with custom/ window piston?) and rear sprocket. Maybe it's not neccesary to enlarge the jet to 58 because there's no real difference in carburettor so that you have to do that for the air-fuel mixture even though you've changed to a 50cc fast cylinder by Airsal.

What do you mean by "Original Tomos A5 cylinder with bigger exhaust port? Did you enlarge the exhaust of the cylinder or was this off factory?

[granturismo]

I tried 54 first. It died on throttle. Then also 52. Same result. So it didnt get enough gas.
Sorry I mean it was a Tomos original A5 cylinder and I made the exhaust port larger.

Right now I only have 5 kg of compression. I think eu25 has 6kg and eu45 is 9kg?

I hope its just to mount another cylinder head.

[ Post made via Mobile Device ]

[Ricker]

I have almost the same setup as you, with mainjet 51/53 it also doesn't work. Only with 49 and when it's warm.

Try even smaller.

[shadowranger]

Maybe a stupid question, but did you put your piston in the right way? I mean with the window towards the inlet valve. I find it strange that your "old" setup works with a 54 jet and enlarged outletport of the exhaust and now with a Airsal 50cc not. Did you change every seal between cylinder and engineblock and head? Did you turn every nut crosswise and with the right amount of torque? Normally if you can say yes to all questions i would prefer to change the sealrings from your crankshaft.

I don't know how much force it needs to push the kickstart down (as you say with 5 kg). Only i can tell by doing it by hand and i can push it down you need to replace them. When in doubt just replace them in precaution. So you elimintate one cause of why the engine doesn't run. Still i think it's an airleak.

[granturismo]

Maybe a stupid question, but did you put your piston in the right way? I mean with the window towards the inlet valve. I find it strange that your "old" setup works with a 54 jet and enlarged outletport of the exhaust and now with a Airsal 50cc not. Did you change every seal between cylinder and engineblock and head? Did you turn every nut crosswise and with the right amount of torque? Normally if you can say yes to all questions i would prefer to change the sealrings from your crankshaft.

I don't know how much force it needs to push the kickstart down (as you say with 5 kg). Only i can tell by doing it by hand and i can push it down you need to replace them. When in doubt just replace them in precaution. So you elimintate one cause of why the engine doesn't run. Still i think it's an airleak.

No questions are stupid Yes the window is facing the intake. Well, first I was running 53 jet, and after some porting on the original A5 cylinder I had to change to 54. But the airsal has better ports and a much larger exhaust port.
Every gasket is changed. They came with the cylinder. Except for the cylinderhead gasket wich is 1.0mm. Before I used a 0.5mm.
I think the compression is not measured in kg.. it's in bar. So its 5 bar. And I got help at a mc-store doing the test. They measured in the sparkplug hole.
Would be nice to know what the correct value of EU25 and EU45 has

Here is a pic of the A5 cylinder after my porting :

[granturismo]

@shadowranger: You were right. I had a leak at the back of where to exhaust pipe is connected to the cylinder. The Airsal has a different angle.. or actually, very different angle. Didn't see that when I first mounted the pipe...

I had to cut my exhaust in two pieces and fix with an empty coke can..... looks really awful
Sounds like a good idea to upgrade to a biturbo.... or something...... else

[shadowranger]

The only way i can think of why the angle of the exhaust is different to your original cylinder is that you bought an A55 cylinder instead of an A5 cylinder. It's known that those 2 cylinders have different angles of the exhaustport. Even though one has membrane and the other not (original) some people swap them without knowing it.

Maybe a Bi-turbo or Technigas (Reverse, Bullit or Circuit) for a A55 cylinder will fit properly, but maybe it's wise to check this with your local moped supplier. Otherwise you can bent the frontpipe a little to match the angle at the exhaust of the cylinder.

Btw, leakage at the back of the exhaust isn't the problem of bad running or idle-ing the mixture of air & fuel. Only noise and lack of power.

[granturismo]

It's 50cc Airsal Tomos a35 with reed valve, from here:
http://www.rijwielparts.nl/cubecart/ind ... oductId=57

I have an a52 engine, but looks like an a35 since I have a reed valve, and A5 cylinder. Maybe those two are different? From 2006 and newer there is another exhaust (for Flexer and so on), compared to the one Quadro has....
So maybe If I buy an A35 exhaust it will fit, bolt on?

[shadowranger]

Ok, i have understood you wrong. When you check the angle of your exhaust port it must be aligned with the ground (horizontally) to mount an A3(5)/ A5(2) exhaust. When you have an A55 exhaust port the angle is slightly angled so the exhaust pipe will fit at the exhaustport, but you cannot fit it to the back (pipe hangs to the ground or stands too much up).

Do i have make it more clear now? A3(5)/ A5(2) can have exhaust pipes wich start perpendicular to the ground, otherwise you need A55 exhaust. And look at the back if you need an euro 1 or euro 2 suspension (is this correct english?).

[granturismo]

But I don't understand. Did the angle change on the Flexer model? 2006- and newer?
This is how mine looks like:


Edit:: Started a new topic viewtopic.php?f=52&t=15258#p249085

[shadowranger]

And does the first part before the curve stay perpendicular to the ground when you only mount this to your cilinder? If yes, than it's the right, if no maybe the exhaust port is angled (like an A55 cylinder) and you need to , or bend this frontpipe, or buy an other exhaust that will fit proparly.

Could you post a picture when this frontpipe is mounted to the cilinder? And maybe a photo of the rest of the exhaust and the mounting at the rear?

[granturismo]

And does the first part before the curve stay perpendicular to the ground when you only mount this to your cilinder? If yes, than it's the right, if no maybe the exhaust port is angled (like an A55 cylinder) and you need to , or bend this frontpipe, or buy an other exhaust that will fit proparly.

Could you post a picture when this frontpipe is mounted to the cilinder? And maybe a photo of the rest of the exhaust and the mounting at the rear?

Nope, the original cylinder exhaust port is not aligned to the ground. Its an angle.. higher towards the front wheel. Comparing to a friends Quadro 2003 wich also has A52 block but this port is exactly horizontal, same as the Airsal on my moped.
So I will be ordering an A35 exhaust

[shadowranger]

Nope, the original cylinder exhaust port is not aligned to the ground. Its an angle.. higher towards the front wheel. Comparing to a friends Quadro 2003 wich also has A52 block but this port is exactly horizontal, same as the Airsal on my moped.
So I will be ordering an A35 exhaust

So now you have this Airsal cylinder wich has the exhaust port aligned to the ground or not? If your exhaust port is still angled (toward front) you need A55 exhaust.

I'm a bit confused. You say original cylinder has angled exhaust port. So why can you say that your Flexer has an A52 engine? In my opinion the only engine with an angled exhaust port cylinder is A55. But now with your Airsal it's proparly aligned to the ground? How can the frontpipe leak like in the picture? Or does it because your suspension at the rear has different measures (euro 2 instead of euro 1), eg. 2 or 1 hole.

[granturismo]

Original cylinder = Tomos Flexer 2006 = angle
Airsal cylinder = no angle (aligned to the ground)

I don't have the A55 engine. I got reed valves. Also A55 cylinder is alu-color. Mine was black (like A35).

My upgraded exhaust leaked because I was in a hurry, and didn't notice the angle difference between the two cylinders. Hence I got a gap after mounting it to the Airsal cylinder.