For the past few months (after I installed different mods including DAJs, Napa hose, Nyroc Mod & Twin Air filter), I have noticed that my P650 will occasionally backfire thru the exhaust (1 LOUD POP for each occurance)...its only seemed to happen after I hit WOT for some distance and then I let off the throttle. It was annoying to say the least. I was also having a different carb problem in that my motor would ocassionally surge/stumble at high speed (50 mph or so) while accelerating at WOT. I rejetted 2 sizes leaner than stock on my main jets and still had the backfire and surging/stumbling problems.

Today, I ran separate timed tests with my jetting at 3 and then 4 sizes leaner than stock on the main jets. The result was that during all of my testing this morning, I did not have a single backfire and the surging/stumbling at high speeds problem is gone too. For what its worth, my best recorded times and best seat of the pants performance was 3 sizes leaner than stock on my main jets (135 rr & 130 ft).

If any of you guys happen to have problems with a backfire after WOT & surging/stumbling at high speeds, then you might try going leaner on your main jets and see if that solves the problem. Not sure if this advice will work for everyone b/c my DAJs might act differently than carbs without DAJs.

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

How do the plugs look?

 

Haven't pulled them yet to see. Before I get around to reading the plugs, I plan to do more timed tests this afternoon (testing the Dalton Plain/White vs. the P700 stock primary spring).

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

Might want to check your plugs, you might be to lean?

 

You might want to check your plugs before any more testing. Otherwise you could wind up with a hole in the top of your pistons

 

BRENT... His plugs will likely be OK... it is hard to talk most people into jetting lean enough to get the Dial-a-jets to work the way they are designed... they will not work properly ( draw the extra gas mixture like they are supposed to ), if the engine is not lean enough... this is how they can claim increased fuel mileage, is that the engines demand calls for the extra fuel that the Dial-a-jet delivers, under less demand, the engine doesn't need the full amount of fuel, that the ( stock ), main jets are capable of flowing for the engine, during full demand... the result is increased performance, & better fuel economy... MIKEY... I'm betting that thing runs as good as it ever has, now that you have it adjusted properly... I have set mine to very lean, then make up the extra with the additional fuel the Dial-a-jet can flow, so that I can turn down the Dial-a-jet & be jetted correctly, to go to the mountains...

here is Thunder Products site, If anyone has questions about how the Dial-a-jet functions...

http://www.thunderproducts.com/dial_a_jet.htm

 

Mike W.,
Yep, its running very good right now! Right after I rejetted to its current main jet size this morning, I noticed that it started up very fast/easily - no choke needed! I'll have to wait until it sits overnite and see if it starts just as easily tomorrow.

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

Didn't know that about the dial-a-jets. I just didn't want to see him burn up his motor with some hard testing. Me, I would stilll look at the plugs, atleast the front one.

 

stock is WAY rich look at my profile and check out the A/F ratio it is near 9-1 which is incredibly rich
even after the muzzy i had to cut holes in the air box to get it to a respectible 12-1 which is a little rich but makes most power
i use a 138/142 and it works well using dynojets and No needle movement and adjusted the A/F screw 1.75 turns out no backfire and awesome fuel mileage