lean mix?

[norseman]

I posted about a couple little concerns after picking up my roadster after getting triples and a PC5 installed. I had experienced suction in the fuel tank ONLY at the first fuel-up after driving home (I've been checking diligently since and not had any other incidents).

I drove the bike home from the shop, about 1 hour, the day I picked it up. I drove out to my folks house on Sunday (it was cold, snowed just a bit), about 1.5 hours each way. I've been driving a good bit and had no issues, but for whatever reason yesterday while going out to visit family I got a scare.

I was doing about 75 (speedo said 80) on the highway and heard a loud backfire (like a gunshot) and the engine started running very rough, like it was missing a piston or something. I pulled over right away and turned the bike off. Remembering the warnings I had received about tank suction I opened up the fuel tank. There was absolutely no suction whatsoever, just a proper seal and no fuss. I started the bike up and drove just fine for another 30 miles or so before the same thing happened again. This time, before killing the engine, I tried rolling on the throttle a couple times gently. The engine picked up and rolled on, but remained extremely rough. Again, I stopped the engine, opened the tank (no suction) and started her back up. She ran rough for a few seconds then slowly eased back into that nice triple pur that I know and love so well.

Keep in mind, this was exactly the same drive I did on Sunday, when I had no problems. The biggest difference was temperature. It was about 10 degrees warmer yesterday than Sunday. Seems like that could have a significant impact and might account for the difference, but I'm not a pro so I'm just guessing.

Both times I encountered this issue I had been traveling for some time with relatively stable throttle, the first time at around 75 and the second time at around 65. I called the shop that did the work and they guessed it was a lean mix that slowly developed into a problem then manifest all at once. Possibly a combination of getting the extra air from the constant "high" speeds mixed with a slightly lean tune on the PC.

All I know is I don't want ANYTHING to hurt my Rocket. I want her to run smooth and happy all the days of her life. Hell I'm only getting the air and exhaust so she won't stifle with the stock bits! I'm already going to the shop ASAP to have the tank lifted and the vent lines double checked, but any additional theories would be very welcome. Thanks gents.

 

[dougl]

Was the PCV custom dyno tuned? If so, how could it be significantly lean? Are your MAP sensor tubes on tight?

 

[norseman]

I'm getting a jard exhaust put on as soon as it comes in (20th) so I'm waiting to dyno until those are on.

I don't mind dealing with a little lean until then, as long as it's not doing permanent damage to the bike. I would like to be sure there isn't a different, more serious, cause for the behavior.

Really, after coming back to this I'm realizing I shouldn't have run to ask here until after I'd been to the shop. I guess I'm just a worrisome parent.

Someday I'll learn when it's time to post, or you guys will just learn to ignore me

 

[atomsplitter]

Check your air temperature sensor hasn't fouled. The air mix is compensated by temperature. Easy check.

 

[TOMCAT]

Better safe than sorry mate .. always best to check if unsure

 

[norseman]

Well since I did ask, I might as well update.

The problem definitely seems linked to changing temp, and may be related to the engine running rich rather than lean. I have a fairly strong fuel smell with my exhaust and some white vapor at idle. This makes a lot more sense to me, since I've got the PC on with the "jardine and k&n" tune loaded but I haven't got the pipes on yet, so airflow isn't where the PC is expecting.

The O2 sensor is a good call. I will mention it when I take the bike in, just to verify it's working. My guess is that it IS working, and when it picks up changes in temp and O2 it's shifting the fuel mix to accommodate, but without the correct pipes it's throwing the mix off enough to cause the backfiring and roughness.

Pipes are supposed to come in early next week and I should be able to get them on shortly after. Hopefully I won't do any harm in the meantime.

 

[norseman]

I just wanted to wrap this thread up. It really did end up being a non-issue but I appreciate the support you gents chipped in anyway.

I took the bike to the shop yesterday and they loaded a leaner tune until I get the Jards on, and she's running smooth now. If nothing else I've learned a bit more about how to read the bike's needs and got some tips (like the O2 sensor) for troubleshooting in the future.

Cheers all!

 

[Idaho Red Rocket 3]

With a Dobeck Performance AFR Plus you can change your air fuel ratio yourself with the touch of a button on the AFR readout gauge it comes with. You always know what the mixture is. You can always have the right mixture for every occasion. I switched from stock exhaust to TORS and no problems what so ever. Very nice product.

 

[barbagris]

The problem definitely seems linked to changing temp, and may be related to the engine running rich rather than lean.

Interesting - Sorry I missed this earlier.

When I first put the PCV with Autotune on - I saw some very odd things like this if the ambient temperature rose above or fell below 20ºC.

For example If I put the bike "to bed" one day after a run in 25ºC temps - then the next run was (for example at 18ºC) it would run odd/rough or pop for a few miles until the Autotune rectified. Similar would happen gong from sub 20ºC to over.

As I progressively committed the A/T trim values - it's all become progressively far less sensitive to ambient temp differences. And in some cell zones the trim values have been as high as 40% LESS.

If you have a PCV - buy the Autotune - and load Hanso's AFR values. The A/T will compensate whether you fit Jardines or anything else.

 

[norseman]

Well this just happened on the highway and almost caused an accident. I am no longer running rich, show no signs of running lean, and 90% of the time the bike is perfectly fine... then suddenly, without any triggering event or change in conditions, I get a very rough running engine and frequent backfires. When I get the bike stopped and let it sit at idle, it eventually clears up and runs fine again. I am going to flood the PC connector with dielectric grease to flush out any water, but I don't have a lot of hope that will fix it. My **** pipes are still in the **** mail, as is the PC5 AT unit I ordered. I'm supposed to be riding all weekend with my dad and friend and now I'm worried about having trouble.