[HELP] AF16 swapped SE50 Elite Issues

[sdugasjr]

I have an AF16 swapped SE50 with a few issues that I can’t seem to get dialed.

My setup consists of : Malossi Crank, Polini Corsa, Naraku Intake Mani and Reeds, Arrow Exhaust and a Polini PWK 24mm w/ SSS Pod filter.

I’m on 120mj and 45 pilot currently on the carb and 40:1 mix ratio

The initial problem I was having was that I was getting a sudden idle surge of a couple hundred RPMs, so pretty substantial in my eyes, and I wasn’t able to go over half throttle without a lean style bog, no matter the jet size or air/fuel adjustment screw position. I chocked it up to an air leak somewhere (this was around the time I snapped a head bolt when trying to check torque so I ended up having to use Naraku head studs).

I then bought an entirely new bore with gaskets/pistons, the whole works. Went over every gaskets and re-hondabonded them all (including the new bore gaskets). I went ahead and put together a homemade pressure tester and immediately found a large leak from the crank seal on the stator side, I guess the guy who I had do them prior tapped them in too far onto the crank and they were leaking by, presumably folded over the lip on the seal as well. I had some help getting this replaced (did variator side right away as well, OEM Honda seals) and pressure tested again, it was holding air fine, no leaks.

Fast forwarding to bore break-in, I started heat cycles on a 120 main and 42 pilot on 401:1 Amsoil Dominator, seemed to be running fine, no idle surges, was having trouble with starting but, went back to OEM CDI box from the Stage6 one I had in there and it fixed that problem. Got all my heat cycles done and went for a test ride, no shrouds at this point, keeping a close eye on temps, didn’t let it go over 230 the first couple times out, then eased my way to 250, then the highest I got with no shrouds was 275. All was good, no surges bike felt great!

I got the bike back to my house (was at my moms at the time of heat cycling) put my shrouds back on and go take it for some more break-in riding, nothing too crazy just a few blocks down the road varying RPMs and coming back to the house and shutting off for cool down, temps never got over 280 I’d say. Did this a couple times and the last time it happened, I started surging again at idle, same as before, couple hundred RPM increments. For example, I have my idle set to around 1800-1900 RPMs, it would idle 1800 then I could hear it almost starve for fuel and drop to around 1700, then go up to around 1900 then back to 1800, in a repeating process. I was still on 42 pilot at this point, 1/2 turn out on the A/F screw, I evidently left my jets out at my moms house, so I just put the factory Polini 45 back in it and am now at about 1 1/8 turn out on A/F screw (seems super rich but that was my only quick solution at the time). Still surging after I ride it, it seems to be fine if I start it and just let it idle up to temp around 170s, but as soon as I go for a ride and it gets up into the 200s and such, is when it starts to surge.

I’m just about at my wits end, I’m not sure what else it could be. My only other option would be to pull the motor again and do another pressure and compression test and see what comes back. I’ve heard these D-Slide 24mm were hard to tune but I didn’t think it’d be this much of a hassle. This is currently my second one because I had this issue prior, thinking it was a faulty carb or something but now I’m not too sure.

About the only thing I have yet to replace is the vacuum petcock, but I am getting fuel at idle, I can see that via the fuel filter, so I’m not sure that’s my issue.

Let me know what you guys think,
Thanks in advance,
Sidney

[motormike]

Read through your post.
Can't say I have any advice, only that I understand and share your feelings.
Following so I can hear some opinions about why an engine "surges at idle".
It's an issue I've had with vehicles, and don't know what the typical cause(s) is/are....motor

[sdugasjr]

Read through your post.
Can't say I have any advice, only that I understand and share your feelings.
Following so I can hear some opinions about why an engine "surges at idle".
It's an issue I've had with vehicles, and don't know what the typical cause(s) is/are....motor

With my research and understanding typically an idle surge on 2 strokes (the article I read was specifically about dirt bikes, but I assume it translates into the scooter world), is usually caused by a lean condition. If I’m understanding it’s a lean condition on the idle circuit, like the pilot jet. But with the 45 I’m really rich and still "lean" so I don’t really understand what’s happening. I’m going to try to replace the petcock and see if that changes anything. Maybe something electrical?

[sdugasjr]

Anybody got anything to spitball? I'm all out of ideas.

[Meatball]

Air leak. Could be as simple as a top cap gasket on the carb. The D-slide carbs are simple to tune, especially the Polini PWK’s. Unregulated air entering the system would make the idle fluctuate as the mixture is all over the place.

[sdugasjr]

Air leak. Could be as simple as a top cap gasket on the carb. The D-slide carbs are simple to tune, especially the Polini PWK’s. Unregulated air entering the system would make the idle fluctuate as the mixture is all over the place.

I’m not sure where it could possibly be leaking from, the top hat on the carb is sealed tightly with their supplied gasket and leak down and compression readings come back good?? I can run it through all the tests again and report back.

[Meatball]

Could also be too fat on the jets. Try a 38/115and see if it helps the idle. I like to lean out the jets until I get heat issues and slowly fatten up to call it good. I always run the smallest pilot I can get away with for a snappy throttle. The trade off is tough cold starts.

[sdugasjr]

Could also be too fat on the jets. Try a 38/115and see if it helps the idle. I like to lean out the jets until I get heat issues and slowly fatten up to call it good. I always run the smallest pilot I can get away with for a snappy throttle. The trade off is tough cold starts.

I'll give it a shot, I replaced the petcock just the other night but it's been pretty cold so I haven't been able to get any riding in to see if it changes anything. I should mention prior to the entire rebuild of the rebuild, my temps never got over 300 even with the air leak from the crank seals. I was also really rich 1/8-1/4 throttle during that time too. I'll report back with results probably tomorrow, its supposed to be a little warmer.

[sdugasjr]

Just got an opportunity to take it out for a spin and seems like replacing the petcock did the trick, jetting and trans tuning will definitely be needed however, sounds like my main may need a bump up, sounds a little hollow on the top end. But most importantly, no idle surge it seems!