Super Dio ZX AF28 and other Dio scooters

[Wheelman-111]

Greetings:

This is difficult to explain. I had the 35/180 combo in F4 and temps were always under or at 350. Installed back in F3 (Nikasil 78 stock crank, CT Mani TM26 and PG Long) and it was Way rich. Idled at 200 and smoked like a badly-tuned Jawa.

I'm down to a 20/170 and still feel it's rich. (recent events have made me leery of leaning too quickly...)

Did you perchance remove the reed stoppers from your Stage6? What RPMs is it turning?

[sanjuro]

I don't have an rpm gauge installed yet. Regarding the reed stoppers they are still on there since I didn't touch that assembly other than installing it.

I'm eager to see what the bigger jets will do. The last long ride I did, the bike performed beautifully at the latter stage. I suspect the hotter engine temps/40slowjet/180main setup indicates I was running lean since it performed better.

[sanjuro]

I ran the 45 pilot and 190 main jet this morning, and the bigger jet is awesome on the take off. My top speed sucks though and it feels like I hit a dead spot right at 40 mph.

The temps at idle were in the 310F range and at 30-45mph the temps went to 600-700F.

I think I have a lead on why the temp is going that high. I saw some fresh oil/gas mixture right below the exhaust flange on the bottom edge. I figure an air leak there would cause the high temps. Opinions?

[Wheelman-111]

Greetings:

Wait! Is that your new-fangled EGT Gauge? Nobody knows less about those than me, but I have read that 700-800 degrees ain't all that high. MadDog once posted his gauge was in the 7s too. I believe he was using a CHT but bolted the probe under an exhaust stud nut. If this is all true, you should be good.

Your Jet numbers still sound awful high compared to what F3 has been running for over 1000 miles. I had a 15 pilot for most of it, admittedly now too small. Ran strong with a 150, but a 160 was in there when F3 was temporarily retired from duty. Now with a 170 and noticeably softer on top.

[sanjuro]

Yeah, the 190 jet seems like it's totally killing any topend. My EGT probe is installed on the top side of the header about 3 inches away from the exhaust flange. I'm going to check the plug and change out the exhaust gasket after lunch.

Here's where I thought the temperatures were supposed to be:

Edit: I feel stupid, I think the temps below were referring to a CHT gauge reading vs an EGT reading.

I always keep an eye on temps and haven't had it ever go above 400F, usually 350-380F when wot for long distances.

Is 400F+ dangerous territory? What is the highest temp you'd want to be cruising at for hours at a time?

On normal or mildly modded bikes, yes this is playing on the edge of danger. On modded bikes it's a little more complicated because it depends on the quality of parts, jetting, oil ratio, oil type (Castrol 2t vs Castor 927 which are nothing like each other) will all play a role at whether the engine will survive in the long run.

250F to 300F is about normal for most normal bikes, with brief spikes into the 325F range is fine.

350-400F are usually for the modded bikes that are running Castor oils running no less than 32:1.

In normal street riding that is around 20-40mph, the temps should be around 250-300F.

If you intend on holding the throttle wide open for miles and miles, you'll need to start thinking about jetting the bike so that the temps stay around 300F. This usually means you'll be jetting big (main jet) in order to allow the fuel to keep the temps down. Bikes tuned this way will tend to be a little lazy feeling when you zip around town short distances like we do in Hawaii where we hold it open WOT for only 15-30 or so seconds before we need to slow down, only to repeat it over again.

My personal bike has a 72cc Polini Corsa (stock stroke) ported for midrange power (street riding). My temps sit at around 200-250F in speed zones ranging 25-35mph. It jumps up to about 300F when I cruise it at 50mph and spikes to 350F at wide open under load, but never goes above it.

[Wheelman-111]

Greetings:

See my previous post, but my understanding is that EGT and CHT are very different animals. The spent gases will light a stogie off the header, but you wouldn't want the head to get anywhere near that hot. 700-800 degrees is OK for the exhaust gas/header. The Ruima Danger Zone for the bore begins at 350 in my own experience - with the exception of the 78cc Nikasil, which seemed to tolerate 450-degree off-throttle spikes.

The 65cc Polini and Malossi bores I've run in Flash I and II were in-between. The former stayed around 300-350, the Malossi saw 400 on a multiple occasions. Neither had any damage on inspection.

[sanjuro]

700-800 degrees is OK for the exhaust gas/header.

Hmmmm. When I had inspected the piston through the exhaust outlet, it looked great. So hopefully, I can go back down on the main jet. I'm thinking of keeping the 45 pilot on there, but wish I had a 42 slow jet to test out.

[Wheelman-111]

Greetings:

I've got that 35 you can have...

[sanjuro]

Greetings:
I've got that 35 you can have...

Haha, no, it's cool. I think the 40 was spot-on, and the 37.5 wasn't as good. Maybe a 42 might be better.

[Wheelman-111]

Greetings:

If you had a CHT I'd suggest to watch the gauge when you let off the throttle after a WOT run. With a small pilot it'll jump up from 300 or whatever to over 350.

With the 35 Pilot in F4 the behavior stopped, but it rich-burbled a lot before RPMs rose. EliteDio may have had a point about chamber pipes making it all but impossible to jet the midrange, particularly with high compression.

[sanjuro]

I just finished putting in a new exhaust gasket and put my carb back to the 40 slow jet and 180 main jet. I'll report how she runs this evening.

[sanjuro]

Wow, had a scary ride this evening because I thought I was going to run out of fuel and neglected to bring an oil bottle with me.

As-far-as the testing goes, cruising at a constant 40 mph the EGT read around 750-760F and at 50 mph it hovered around 800-810F. It ran cooler than I thought it would, and the highest temp I saw was 825F. Idle was in the 320-350F range.

This bike totally wants to lift the front end up a foot or two off the ground if you're mid-turn.

So, one gallon of gas only got me 43 miles, and I had a tiny amount left. Here's the top speed that was on a slight downhill:

[bakaracer]

what was the egt at that speed?

[sanjuro]

When I looked down at the gauge it read 825F.

[bakaracer]

now do a plug chop to see what it looks like.just to confirm the egt