XR650L 2017 Honda XR650L - Stuck on power loss/engine skip

[Seth Rowley]

I have a 2017 650L... I ended up going with the DG "RST" slip on which I found that it does not fit my factory mid section and there is a ring that comes with it which a helpful member let me know it's purpose was for taking the spark arrestor completely out to run wide open (I haven't done that unless I need to??).  I put a FMF Power Up Jet kit into it, used the aftermarket needle and spring positioning the clip on level 3 from the top, smog block off kit, and I "think" I have desnorkled it by using the rubber plug from the smog block off kit into the bottom of the factory air box that I put an aftermarket high flow UNI air filter with the cage in.  The Jet kit, I used the bigger jet in the kit which I believe was a 165?? I may be mistaken as it's been a few months.  Any how, I ended up changing it out to the larger one as it was running too lean and not getting adequate fuel... Currently, the power loss is terrible comparing it to my last 650L which was a 2006 model and it was twice the power of this one.  Now... the license plate bracket is even melting from the pipe and rear fender in that area turning yellowish.  The engine skips fairly consistently at this point and very noticeable when holding the throttle consistent at the same speed.  It was getting hard to start, so I ended up pulling the spark plug and it was completely black!!  Obviously this means it is running rich?? Thinking I need to go back to the 160 main jet??  Also I put in the Amsoil high flow foam air filter and geared down to 14 tooth in the front with the regular XR sprocket.  I feel that I am in over my head so to speak with things that I have done and not knowing exactly where to start.  The exhaust was DEFINITELY LEAKING at the mid section where the slip on connects. I am tempted to spend more money which I would rather not if possible on purchasing the TM-40 carb, and the full FMF powercore system.    I used the exhaust high temp putty and also wrapped it with high temp exhaust wrap but very well could still be seeping out having a portion to do with the skipping.  Any suggestion would be so very helpful and appreciated.

Edited January 21, 2020 by Seth Rowley

[Shawn_Mc]

You've mixed and matched all the carb stuff with an aftermarket kit and stock jetting.

If the plug is black and sooty, it's indeed WAY too rich. That will cause excessive exhaust temps just like being too lean will. Why? All the unburned HCs (Hydrocarbons) will drag combustion temps right out of the engine and out of the exhaust pipe.

It was hard to start because it was carbon fouling the plug. More fuel only works when you've got more air to go with it. Opening up the air box and exhaust may allow the engine to breathe better, but not to the tune of 10-15%, and 10-15% more fuel will turn a plug as black as Hillary Clinton's heart.

Now, the main jet probably isn't the only culprit/perp in this heinous crime of hyper-richness. Reason being, I doubt you're running this thing WOT constantly, so the needle is way out the window wrong. The needle is the easiest thing to get wrong in a carburetor. It sets the fuel curve through 80% of the carburetor function, slide position wise. So if the needle is too steep, or too thin over all, or set way too high, the fuel curve is going to be way off the desired beaten path.

Consider this: You're trying to achieve an air fuel ratio of about 13.8 or 13.9:1 using typical pump gas that's 10% ethanol. 9:1 would be pig rich, like you are now. 15:1 is going to be lean and put you into a possible detonation range. Now, how wide is that window? Not very...

You seem to have made a classic mistake: making way too many changes at the same time.

Opening up the air box and putting a better, more open exhaust on the bike is going to help, but it's not going to require much more that one, maybe two sizes up in the main jet, maximum and possibly one or two spots on the needle if any.

Think about it like this; If you open up the air box to flow more air, more air going through the carb is going to pull more fuel past the same jet. The best way to describe this I think is like this. Say it takes (purely hypothetical numbers here) 10% throttle to move the bike at 30mph in 3rd gear. Now, you open up the air box. Do you think that at 10%, you were exceeding the original airboxe's potential air flow? I freakin hope not!! So, no change in that throttle position's fueling requirement would be necessary (unless it started out painfully incorrect). Now, you go 45 in 3rd, the throttle is at half. Are you exceeding the airboxes potential yet? I doubt it. Click to 4th gear, hang that throttle wide open...are you beyond the air boxes potential yet? Possibly, but you're also WOT. The needle isn't doing anything at that point. It's completely out of the way. That's all main jet.

My advice, put all the stock stuff back in the carb and make one change at time. If you buy a "jet kit" follow the directions in the kit. It may, or may not work for you, but typically a kit wont put you out in left field, which is where you are now.  A 4-6% change in fueling is HUGE.

Another thing a lot of people make mistake regarding is plug color. A four stroke plug should be relatively clean when it's running correctly. Not tan. Tan plugs are for two strokes, with oil in the fuel, or if you're running methanol.

 

 

[Seth Rowley]

20 hours ago, Shawn_Mc said:

You've mixed and matched all the carb stuff with an aftermarket kit and stock jetting.

If the plug is black and sooty, it's indeed WAY too rich. That will cause excessive exhaust temps just like being too lean will. Why? All the unburned HCs (Hydrocarbons) will drag combustion temps right out of the engine and out of the exhaust pipe.

It was hard to start because it was carbon fouling the plug. More fuel only works when you've got more air to go with it. Opening up the air box and exhaust may allow the engine to breathe better, but not to the tune of 10-15%, and 10-15% more fuel will turn a plug as black as Hillary Clinton's heart.

Now, the main jet probably isn't the only culprit/perp in this heinous crime of hyper-richness. Reason being, I doubt you're running this thing WOT constantly, so the needle is way out the window wrong. The needle is the easiest thing to get wrong in a carburetor. It sets the fuel curve through 80% of the carburetor function, slide position wise. So if the needle is too steep, or too thin over all, or set way too high, the fuel curve is going to be way off the desired beaten path.

Consider this: You're trying to achieve an air fuel ratio of about 13.8 or 13.9:1 using typical pump gas that's 10% ethanol. 9:1 would be pig rich, like you are now. 15:1 is going to be lean and put you into a possible detonation range. Now, how wide is that window? Not very...

You seem to have made a classic mistake: making way too many changes at the same time.

Opening up the air box and putting a better, more open exhaust on the bike is going to help, but it's not going to require much more that one, maybe two sizes up in the main jet, maximum and possibly one or two spots on the needle if any.

Think about it like this; If you open up the air box to flow more air, more air going through the carb is going to pull more fuel past the same jet. The best way to describe this I think is like this. Say it takes (purely hypothetical numbers here) 10% throttle to move the bike at 30mph in 3rd gear. Now, you open up the air box. Do you think that at 10%, you were exceeding the original airboxe's potential air flow? I freakin hope not!! So, no change in that throttle position's fueling requirement would be necessary (unless it started out painfully incorrect). Now, you go 45 in 3rd, the throttle is at half. Are you exceeding the airboxes potential yet? I doubt it. Click to 4th gear, hang that throttle wide open...are you beyond the air boxes potential yet? Possibly, but you're also WOT. The needle isn't doing anything at that point. It's completely out of the way. That's all main jet.

My advice, put all the stock stuff back in the carb and make one change at time. If you buy a "jet kit" follow the directions in the kit. It may, or may not work for you, but typically a kit wont put you out in left field, which is where you are now.  A 4-6% change in fueling is HUGE.

Another thing a lot of people make mistake regarding is plug color. A four stroke plug should be relatively clean when it's running correctly. Not tan. Tan plugs are for two strokes, with oil in the fuel, or if you're running methanol.

 

 

Thank you as this is very helpful information to help me understand more in depth and getting the issue resolved. I'll try this. Thanks again

 

[Oregon lightweight moto]

Any updates? My 650l did something similar and it was the Cdi box not advancing the ignition.

[Beamer1001]

You can't go wrong with the tm40 and changing the main jet is easy and done in less than 20 minutes. You just turn the carb to the side and remove the cap in the bowl. I have the DG V2 slipon and no problems whatsoever. With the 1 inch silencer you don't  need the spark arrestor. I changed to a larger silencer and put the arrestor back in. Don't want to start any forest fires. As I put larger silencers in I needed to increase the main jet slightly. Directions say to use high temp gasket sealer when putting the cap back on. I used it where it connects to the headers also.