I've been chasing what I think is a common f4 problem: idle stumble. Mine only happens when hot with the fan running. If I trigger the fan at low temp and unplug the fan at high temp the problem goes away.

I've replaced the battery
I've replaced the reg/rec with a Mosfet
I replaced the fan.

I think all that's left is the stator. I'm getting an ohm reading of ~1.4 at operating temperature and ~2.4 at room temperature. The bike does charge correctly just a bit off idle: I get ~14v. At idle it's in the high 13s until the idle stumbles--during the stumble it's low 12s. I'm not sure of the latter is a cause or effect.

Would you consider an ohm reading of 1.4/2.4 a bad stator? The manual says 0-1ohm at room temp is normal, I'm not sure if 1.4 could be considered close enough.

Also: are electrosport high output stators a good choice? If I'm replacing I'm going high output.

thanks,

-morgan

 

I can't speak for the stator itself but I had the exact same symptoms (idle issues when fan kicks on especially at a stop light, lurching/nearly stalling on roll off when it happens, noticeable performance drop). I replaced the RR a few days ago with the Electrosport one.

It seems to perform better at idle now. I'm still keeping an eye on it because it seems to be a common symptom on the F4 that doesn't always have a single culprit or end all fix. In my case it always seemed to be on a day where the outside temps were 80+ F and after riding for a good 10 miles or so before it happened.

 

Yeah, my impression is the problem is due to a combination of a weak charging system combined with generally aging components.

I'll be curious to hear how it works for you. My problem is sporadic but I can almost always repeat it by riding in stop and go traffic after getting the bike fully warmed up.

I looked around and didn't find any other options so I ordered the electrosport stator from Murry's Cycles (www.murrayscustomcycles.com). I hope this resolves the issue, I'm looking forward to having the bike "back."

 

Yep I'll keep you posted, should be giving it a good test ride to validate the fix once we get up past 80 here in Ohio later this week. That RR should, from what I have read, produce a charge at a much lower rpm than stock so hoping that helps both our cases.

Heads up on the Electrosport RR, it comes with two new, longer bolts that work with the existing nuts for the old RR.

 

Sounds good. FWIW I bought my Mosfet R/R from roadstercycle.com. He sells a bracket and hardware that adapts to the stock mount points. It's not a cheapest option but I didn't want to play ebay roulette. I didn't know about electrosport at the time.

-morgan

 

Curious me decided to ride out to grab some groceries this evening (residential drive that gets me up to 45mph, max). It was about 83F out and I got it up to temp right before the needle on the coolant temp hits the middle point and kicks the fan on. I got a good 10 miles in like that and had zero issues. Purposely sat at a couple stop signs (no traffic) waiting for the fan to kick on for a second so I could take off like I was stuck in traffic with the fan running. Can't say I noticed any hesitation and idle seemed to be steady.

So maybe it's fixed? I checked the battery with the bike off after I was home for about half an hour. Read 12.85 so it seems to be charging fine.


I take that as I sign I should do some more through testing this weekend on a road I can get up to proper speed on for a more extended period of time. Such a shame I'll have to do all that riding...

 

That's great, hopefully that cures it.

I installed an Electrosport stator last night and went for a 30 min ride downtown. There was no traffic but lots of lights. I think my problem is better but still there--the idle still wanders when it's hot and the fan is running but it seems less apt to stall. I did have a stumble off idle once or twice.

Tell me this: with the bike at full operating temp and the fan on for more than a few minutes how consistent is your idle? Does it stay steady or does it move up and down a bit? How many miles are on your bike? This bike was out West and then down for a few years with gearbox issues but my memory is it always idled perfectly. Maybe this is just how they are--this is the densest place I've had this bike.

thanks,

-morgan

 

My idle without the fan is staying steady at a 1400 rpm and doesn't show as much variance as it did before. When the fan kicks on it does dip slightly maybe down to 1250-1300. It does feel better than before and was a little nerve racking when it kicked on in traffic a few times yesterday because I was expecting bigger problems.

It's a 2000 and has 9,100 miles on it now. I bought it with about 7,700 back in April this year. I am still seeing about 12.8 ~ 12.9 volts post riding so it is charging for sure. The battery got put on a charger last night just to make sure I topped it off for longer riding this weekend.

 

Our symptoms are similar, interesting. Let me know how your weekend ride goes.

-morgan

 

Put ~160 spirited miles in this weekend and one long, stuck in traffic ride back from work yesterday. I have to say I really might have fixed the issue. After the top off I really don't notice the drop, if any, in idle when the fan kicks on. Everything seems more responsive and I have not had an issue with stalls at roll-off. I think replacing the RR and making sure the battery was topped off all rolled into the fix.